Daihard forums FAQ's (sort of a wiki)

I was given permission to share this on daiforum so i brought it here also. Considering we are the evolution of daiforum. I think it should be fine. (this was copied and pasted from files I had kept as I have lost my password to daihard and cant get back in lol

Daihard FAQ - http://dairally.net/faq/

Postby grog » Wed Oct 16, 2002 4:13 pm
OK guys, this is what i’ve got so far… http://dairally.net/faq/

Anybody got anything to add… Ohh, i do know it needs a clean, but i’m just looking for info at the moment…

And last time, i got plenty of responses, but no infomation. If your gonna surgest things, give info…

  1. What PSI does the fuel cut com in at.
  2. What is the Difference between the CB80 & CB70
  3. What are the different CB engine models
  4. What are the different H engine models
  5. What are the different engines from the Miras
  6. Where do i plumb in a Boost guage.
  7. How do i fit a BOV.
  8. What is better, a Pumb back BOV or a atmosphere one.
  9. Who should i get to work on my car
  10. Im thinking about turbocahrging my H?-E engine, where should i start?
  11. What are the TPS readings on the CB-80 spose to be
  12. How do i do a compression test on my Engine
  13. How do i do a Vacume Diagnostic test on my engine.
  14. Any info on putting a CB-80 in a G11 Shell?
  15. I have a CB-60 and want a little more power, what’s some simple mods?
  16. Why are Pushrods Bad.
  17. I want to build a 200Hp CB-80 Motor, What do i do?
  18. What’s bad about putting big wheels on my car?
  19. What turbo should i run
  20. I have a carbie problem, who should i see…
  21. I’m replacing my headgasket, what are the Torque settings and bolt sequences for the Headbolts?
  22. What are the Fault Codes on a CB-80 GTti and how do I bring them up??
  23. SOme basic Diagnostics
  24. GTti Oil Recommendations by Matt Slade
  25. More of chas’s useless info.
  26. CB23 to 61 valve timing allignment.
  27. Gearbox Info.
  28. Chas’s “Basics of cams 101”
  29. Ru’s info about temp Vs. ignition timing.
  30. Chas’s info on BOV’s
  31. Chas’s info on Exhaust backpressure.

  1. What PSI does the fuel cut com in at.

The Fuel Cut on a GTti comes in at 12.5 psi

  1. What is the Difference between the CB80 & CB70

The CB-70 was the Japanese Domestic Market Engine which ran a slightly different EFI system and an Oxygen Sensor, the CB-80 is the international engine which doesnt run an oxy sensor

  1. What are the different CB engine models

This is just an educated guess.

CB-22 Single OHC Carbie N/A 993cc Leaded Found in G10 Charades
CB-23 Single OHC Carbie N/A 993cc Leaded & Unleaded Found in G11-G100 Charades
CB-50 I think some wreckers call a CB60 a CB-50
CB-60 Single OHC Carbie Turbo 993cc Leaded Found in G11-G10x Charades
CB-61 Single OHC Carbie Turbo 993cc Unleaded Found in G11-G10x Charades
CB-70 DOCH EFI Turbo 993cc Unleaded Found in G10x GTti Charades
CB-80 DOCH EFI Turbo 993cc Unleaded Found in G10x GTti Charades
CB-90 Rumoured to be Fuel injected 1L N/A (If anybody can give more info, let me know)
CB-100 Just like the CB-50, some wreckers call a CB-70 or CB-80 a CB-100

  1. What are the different H engine models

This is just an educated guess.

HC-C Single OHC Carbie 1.3L Found in G10x-G20x Charades
HC-E Single OHC efi 1.3L Found in G10x-G20x Charades
HE-E Single OHC efi 1.5L Found in G20x Charades
HD-E Single OHC efi 1.6L Found in Detomaso Charades & Applause’s
I think i’ve left out a few here, so fill me in.

  1. What are the different engines from the Miras

I Have no bloody idea, and dont realy care…

  1. Where do i plumb in a Boost guage.

Basicly anywhere where boost is pressent, I have a t-piece in the hose going
from the plenium to the Fuel pressure regulator, and it works a treat there,
showing boost and vacume.

  1. How do i fit a BOV.

The hose that controls the Piston in the BOV needs to see both boost and vacume, so
i’d plumb it from the hose going to the break booster, but make sure it before any one
way valves. The point where the boost will vent from shoud be somewhere just before the
Throttle body, that way, there is little air moving backwards when the valve opens.

  1. What is better, a Plumb back BOV or a atmosphere one.

Since the CB turbo engines use a MAP sensor insted of a Air flow meter
it is possible to use a BOV that vents straight to the atmosphere, just be
warned, if you do go the atmosphere route, never (and i mean never) drive near
marc or his house, as you will be risking life and limb.

But more seriously, My own theory on the matter is, since the air is compressed
therefore heated, some of that heat will be disapated, and when the BOV activates
the air expands again, that air will be colder than ambiant (I could be wrong on
this but nobody has ever questioned it) So you now have nice cold air, why waist
it, why not use that waisted energy and make your car go faster.

  1. Who should i get to work on my car

Anybody but Rigoli…

  1. Im thinking about turbocahrging my H?-E engine, where should i start?

You want to build a good motor you first need to make it bulletproof. Now there are a few problems that the daihatsu 1300, 1500 and 1600 motors have with them. The first is the main one. That is the block. The design of the cylinder sleeves is not very good. You see because there is no cylinder wall bracing whatsoever, under turbo conditions( high boost conditions 20psi and up) you get cylinder distorsion. This is when all the load generated by the high boosting causes the sleeves to move around( head gasket problems). This can be remedied in one of two ways. The first is the less cost effective way which is to dowel the block. This is when dowels are inserted in the water jackets around the cylinder sleeves holding them in place. Cheap and affective. The second option is one of great cost I can vouch for that. This is when using the AutoCad thingy on the computer they design a block brace. Now instead of just locating the sleaves in spots like the dowels do the block brace completely surrounds them locating them 100% to the block. To mantain coolant flow up to the head there are special drillings for water to pass.
The next stage in the bottom end is the rods. from factory these are pretty piss weak. Mind you they can handle 15-16psi with a good tune and no detonation. These will set you back between 1400-1500 bux. These must be made of good grade billet steel. For other applications apart from turbocharging you can run alloy or titanium if you want to acheive very high revs. The alloy items have a way short lifespan as they have the ability to strech. Argo are the people to use here. You can’t beat Aussie made.
Next will be the pistons. Usualy forged high silicone content. Two top people in Aus machine these. You have to tell them what size dish you need as this will play a major part in your final static comp ratio. Specialised Piston Services(sps) and Australian Performance Engine Parts(apep) both located in melbourne.
what else? good idea to o-ring the block. You definately need to drill out and retap the bolt holes and fit custom arp head studs and nuts due to the fact that with the high boost I have experienced head bolt strech. This is all custom gear, and costs, and also takes time to get. Along with the head studs you can get bolts for the mains. Oversized of course.
Now the block has to be deburred, all the rotatingand reciprocating masses have to be balanced and blueprinted etc. That should give you a bottom end that will be able to handle 30psi with out a problem and realistically put out a power figure of 300 horses at the wheels depending on turbo spec.
As for the rest of the motor there is so much you can do with the head depending on how you want to chase your power, how you want your car to drive and so on. Usaully with a turbo you don’t have to go to drastic with the cam. A good set of one piece steel valves machined to suit is a must as you dont want the valve head dropping off. Stronger valve springs also. There is no need to go for double valve springs either.
Head gasket should be metal(copper) no more than 80 thou thick. Make sure you use a good sealant( I use threebond high temp sealant) and not too much either. Stay away from the oil gallery.
The rest of the motor is the ancillaries. You need a good fuel pump anything from a VL Commodore turbo bosch pump and up. After my engines last build I believe that there is still some power hidden in the injector positions. So Grog here is one of those trial and error tips. Eight injectors mate. My next set up will to use four 145cc(standard injectors) in the standard locations. Then on the rear of the manifold the section that faces the firewall on each runner as far away from the head as posible I will weld in an injector boss and fit 4 550cc injectors. Fitted further up the runner it will in theory give you a different type of power. Much better top end. Just one of my theories that I have read in books and will try on the new motor, accompanied with a new turbo. These injectors will be staged and each injector will have its own injector trim table. You see the time and money that I will spend doing this after the end result could tell someone and they will have it a whole lot easier. So feel privelliged.
Then apart from little things like moding you distributor to run four coils, running different spring rates in your oil pump, baffling sumps the rest is pretty easy. I hope you and heaps of other people on the board has learnt or picked something up from this. If I missed something that you may want to know like with intercooler plumbing for every 90 degree bend that you have you need a straight section that is 3 times in length to pick up the air speed again. That is one area that Ufo’s car has a bit of an edge over mine.
SORRY UFO BUT SOMEONE HAD TO TELL THEM. Don’t worry they don’t know all the tips. We will keep therest for ourselves.

  1. What are the TPS readings on the CB-80 spose to be

According to the manual, the TPS should read as follows:

Between Terminlas…Resistance (Kohm)

1-4 … 4.25-8.25

1-2 … 15-35

3-4 (with throttle
valve fully closed)… 3.5-10.3

3-4 (with throttle
valve fully opened)… 0.3-6.3

  1. How do i do a compression test on my Engine

Compression Test : this is fairly simple and tells
you the static pressure efficiency of your compression chamber.

Step 1 Beg, borrow or steal a compression gauge that’s fairly accurate.

Step 2 Unplug (or remove wires on +ve) the low voltage side from the ignition coil

Step 3 Unplug fuel cut solenoid on carby (there’s an inline connector).

Step 4 Remove high tension leads from spark plugs and clean out recesses with degreaser to prevent dirt getting
forced into gauge.

Step 5 Remove all spark plugs and connect gauge to first cylinder to test.

Step 6 Have a mate sit in the car, with foot flat on accelerator pedal and crank the engine, while you check the maximum pressure on the gauge. It should only take a few motor revolutions.

Step 7 Your readings should be 1225 kPa at best and 1029 at worst. If the readings are low pour a small amount of engine oilin the bad cylinder through the plug hole, crank the engine momentarily to spread the oil over the rings, then put compression gauge back on and retest.

Step 8 If the pressure rise with the oil is muchhigher than the initial reading your rings are shot. If there isn’t a significant rise your rings might still be shot, but the valves or head gasket are also routed (aka rooted).

  1. How do i do a Vacume Diagnostic test on my engine.

Vacuum Diagnostic

The vacuum test will tell you heaps about the
engine: bad valves, bad rings, bad ignition, bad timing, etc

You need to put the engine back to together for these tests. The vacuum readings are taken from the manifold so:

Step 1 Find a connection point, like the fuel canister line or brake booster.

Step 2 Beg, borrow or steal a vacuum gauge (they’re fairly cheap from car accessory places)

Step 3 Connect gauge and start the engine and let idle

Step 4 observe the gauge needle: It should be steady and somewhere between 14" and 22" Hg (mercury column).

Step 5 if the needle is fluctuating 1" - 2" Hg then you’ve probably got bad leads, bad dizzy cap, faulty coil, bad plugs or something else in the ignition giving problems.

Step 6 if the needle is fluctuating 3"- 4" Hg then you’ve probably got dicky valves (sticking, burnt or rockers over adjusted). For example the guage fluctuates between 14" and 18" Hg. If the needle fluctuates 13 -15" Hg it indicates weak or broken valve springs. For example between 10" and 25" Hg.

Step 7 if the needle floats aimlessly 4" - 5" you have a fuel problem.

Step 8 if the needle drops sharply to about 10" or 12" Hg before rising back to the general vacuum, then you have a head gasket leak on one of the cylinders. If it drops much more than 10" Hg you have a blown head gasket between cylinders. For example it may fluctuate between 7" and 20" Hg.

Step 9 a steady low idle speed reading (less than say 10 " or 12" Hg) indicates leakage through brake booster, manifold gaskets, etc. If these are ok then it also indicates late valve timing and/or bad piston rings

Step 10 give the throttle a quick blip and the gauge should drop to about 5" Hg and rise up to about 23" Hg before settling back to step 4 reading. If it doesn’t you have problems

Step 11 gradually increase the motor speed to about 3000 rpm. The vacuum should be the same as in step 4. If it is lower the exhaust system is probably clagged and needs to unrestricted.

  1. Any info on putting a CB-80 in a G11 Shell?

This was supplied by oakleaf, taken from the old madcow board.

profile | email posted 08-14-99 8:13 AM
Daft Question how hard is it to put the GTTi
Motor in a G11 Shell??? and what parts do I need.
I have access to an engine & injection system
Will the G11 gearbox mount straight on???
Will a G11 turbo manifold & turbo fit???
Hey I hav’nt bought anything yet but need a
little help here

profile | email posted 08-14-99 11:31 AM
Would you belive I am doing this conversion right now? It is a relatively straight forward conversion. You need the engine and complete loom. Efi fuel pump, I belive a suzuki swift or Daihatsu Applause brake booster (to clear the head of the engine as the G11 booster is too long) and a stronger clutch plate.
The engine itself mates up to your original gearbox. Use the clutch plate off the G11 however and the pressure plate off the GTti engine. It bolts up to both the front and back engine mounts but the driver’s side mount needs a 90 degree bracket made as the engine mount does not reach the body.

The wiring itself is quite simple and only requires seven or eight wires to be connected from the Gtti loom to the G11 loom. The wiring diagram is available from MRT Australia. As mentioned before swap the brake boosters and install an efi pump near the fuel tank. Should be sweet. Fingers crossed.


profile | email posted 08-14-99 2:58 PM

your G11 exhaust will bolt up to the dump off the cb80 (GTti)…You will break gearboxes though, guaranteed.!!!

If you get a GTti fuel pump it will go into the G11 fuel tank as the mounting bracket bolts onto the fuel pump…

You also need 3/8th inche (I think from memory someone ask Kent as he’s in the middle of it!!!) fuel line and return…

The applause brake booster needs to be used and will fit straight in as mentioned above…

It’s only marginally harder than pulling the old engine out and puttiong it back in, almost the easiest angine swap possible…

Also Note that you need to get the front and rear mounts off your CB60 and fit them to the block of the CB80 (they bolt straight on)…

  • Damian

profile | email posted 08-14-99 3:02 PM
oh and no using the G11 turbo and manifold is a bad idea, not that they would fit as the manifold is different but the turbo is far far far too small…
The IHIRBH5 on the CB80 993cc is also available in various configs. on engines up to 1800cc whilst the smaller CB60 turbo hardly flows enough air for the SOHC

  • Damian

profile | email posted 08-15-99 5:18 PM
In question to your comment about the fuel lines being 3/8 inches thick is that necessary? I have friend who just did his and has had no probs with the std G11 turbo lines while running 17/18psi.
Also which part of the exhaust will bolt up to the Gtti exhaust. The G11 5bolt dump straight off the turbo or the 3bolt flange at the bottom of the dump?


profile | email posted 08-15-99 9:50 PM
Both, the ‘cat’ which is the crappy excuse for a dump on both the G11 and GTti is the same except that the GTti has internals and the G11 doesn’t…so use the G11 one…This reduces costs when you do it…the 3 bolt flange @ the bottom also bolts up as it’s all the same, bonus eh???

With the fuel lines I guess it’s better safe than sorry, I’ve heard some say they haven’t used bigger (like your friend) but all that I’ve spoken too properly about it recommend using bigger lines…(they’re cheap anyway)

I guess you can have the mixtures setup on the dyno and check it out…

profile | email posted 08-16-99 9:51 AM
Thanks for that dude…definate money saver there. I’ll check out that fuel line thing later on. As I’m on a budget at the moment I’ll go with std ones and let you know how I fare.


profile | email posted 08-16-99 12:53 PM
damn this all sounds very familiar! LOL
Fuel lines : 3/8 lines are the best … I have a mate with GTti who didn’t change his and they are fine …but my line of thinking makes it a good idea if using an EFI (40psi) pump you might as well let it have all the Pipe it wants to use… will work out better in the long run if you want to run high boost and need more fuel … I think you’ll find the pump will last longer as well.

The Clutch issue… depending on how much grunt you want … you can get away with runnig a G11 clutch plate and a GTti pressure plate. but if you want to run some real boost you will need a pretty beefy clutch as the torque of these motors will s*** a standard clutch on high boost like its a peice of paper! I will be running a 180mm Tri rotor Brass button Clutch plate (with the G11 centre) and a 180mm Double diaphram Pressure plate. But then a again if you are running just standard boost and ECU you should be fine… I hope to have some pics of all the clutch bits and peices, including specs on my website soon…

Booster: the 1990 applause booster will fit straight in… you will need to change the brake lines a little and bend the “lip” on the firewall up a little, but it looks quite neat and doesn’t look “dodgy” at all.

I hope I haven’t scared anyone off about all this … its a quite straight forward conversion to do really!

there are a few other things like a different side mount (side of the head - strut tower) and intercooler mouting etc … but these are pretty easy to take care of.

  • Kent

profile | email posted 08-17-99 9:53 AM
In regards to the applause brake booster. Do I just want the booster or master cylinder or both? Coz I just went to buy my booster and the bastard was only going to give me the booster and wanted extra for the master cylinder.


profile | email posted 08-17-99 10:03 AM
NoPSi: You will need the complete brake booster and Master cylinder (including fluid resevoir etc) as this has the shorter cylinder and allows for the larger head on the Twin Cam! you should be able to pick a complete set up for $100 to $150 or there abouts … if you get one for $100 you doing pretty well! The 1990 applause booster has an identicle Stud/mounting pattern on the fire wall.

  • Kent

profile | email posted 08-17-99 10:06 AM
Damn dude that was quick reply. Thanks for that. Yeah I got told $85 for booster then he wanted an extra $65 for cylinder…what a ripoff!


profile | email posted 08-17-99 10:42 AM
Yeah … I live on this site … LOL
hmm sounds like you need to find a new wrecker I paid 135 plus freight for mine … keep looking! you’ll find one …

  • Kent

  1. I have a CB-60 and want a little more power, what’s some simple mods?

First, Tee off the boost line on the carby hat and connect a tube to the secondary actuator. You can also remove the secondary spring if you want but it will use more fuel. This will stop the ‘flat spot’ experienced before the secondaries open. Then, go to a Motorcross shop and buy a Unifilter for a bike. Fit this straight on the end of the turbo. Ditch the factory filter. - Cost: About $20 - $25

Second, remove the factory boost controller on the carby “hat” and buy a second hand Blow off valve off an RX7, Supra etc. (Denso) and fit it in this location. Cost - About $25 - $50

Third, If budget permits, buy a second hand intercooler off a Supra or MR2. Fit it in front of the radiator. Turn the Compressor housing on the turbo 90 degrees to reduce the pipe length. - Cost: About $150 for the intercooler and about $30 for some tube and bits of radiator hose.

Fourth, Up the Boost!! Use a bleed valve or piece of tube with some small holes drilled in it in the wastegate boost line. You really need a boost gauge to test this. Run between 10 and 15 psi and it should last a while. It might pay to increase the secondary jet at this time. Go to the wreckers and get a secondary jet off a 1.3 Corolla. These are the same carby but have larger secondaries. - Cost: About $60 for a bleed valve or $1 for a piece of tube with holes drilled in it.

These mods are exactly what I have done to my car. performance increase is amazing. The biggest improvement was from fitting the Unifilter and the secondary carby mods (apart from increasing the boost!) Should drop quarter mile times into the fifteen’s. Fast enough to scare lots of bigger engined cars.

  1. Why are pushrods bad (By rauidah)

Right then,

Pushrods are bad as the valvetrain is heavy and so consequently can’t be revved.


Pushrods are bad as the valvetrain is flexible so aggressive camshaft profiles can’t be run.


This means that Pushrods are bad as we can’t run at higher engine speeds to make power. This means that specific horsepower is poor.

This means to make more power we just throw capacity at the problem.

This means that when we don’t want ALL the power the fuel economy is shocking.

Pushrods are bad as they result in inefficient engine designs. However, they are dirt cheap and simple (no complex head casting).


A big V8 shoves you along as it makes loads of torque at low speed. Moderate power.

A smaller engine makes less torque but makes it at a higher speed = same power. Result equal performance. However, you only need a small engine to do it. This means that fuel econ is better.

Psychologically, however, the smaller engine feels like its working harder. Despite the fact that both engines are making the same power…

That’s where all this torque myth comes from. Forget torque just think about power.

Low end torque is just power produced at a lower speed…



  1. I wanna build a 200Hp CB-80 Motor, what do i do.

I want to build a Group A GTti Motor??

I went to the workshop on Saturday to see how the GTti was going with its rebuild!
The cage looks sweet, BUT

While the Sti was getting some new stoppers I saw my motor totally striped in the engine room, only to see the number 2 piston split in half (top to bottom) with a busted con rod and crank! Ouch! 5 years on the road and 2 years on the track have taken it toll.

So I want to know from probably the UK guy. What can be done with these motors’s to get some real HP out of them with reliability? (I think in the UK the GTti was group A spec) here in Aust it only got to be a Group N beastie for the rally team’s so there’s not too much know how in the engine department here.


Brad Mifsud
Registered User
Posts: 2487
(9/17/01 1:04:01 pm)
Reply even

Ross Mackenzie?


Registered User
Posts: 542
(9/17/01 1:25:26 pm)
Reply Group A

The car’s at NRG…
I dont pay for labour(the car is sponsored by them), so why would I go to someone else …
Plus Nick has built plenty of race car’s but not a daihatsu. We could look at it as another turbo motor and go from there, but I want to cut a few corner’s with a bit of know how on what a GTti motor like’s and dislikes before we start


Brad Mifsud
Registered User
Posts: 2488
(9/17/01 1:46:58 pm)
Reply I mean

call him and ask for some advice, not build it for you.

he usually gives it freely and is helpful!!!

He has raced the things so he may be of some help!


Registered User
Posts: 544
(9/17/01 1:56:43 pm)
Reply Oh

I see sorry
But Ross never raced them in group A spec’s
can’t you read ?
I will email him anyway

btw, got your email

Registered User
Posts: 63
(9/17/01 8:26:41 pm)
Reply Re: Oh

one set of custom billet steel i-beam conrods, on set of forget pistons and ring set, balanced and nitrided crankshaft, o-ringed block with copper head gasket, aftermarket computer that is tuned by someone who an idea not no idea and some other little things along the way. keep an ye on oil, water and exhaust temps. that is if you want reliability.

matthew slade
Registered User
Posts: 395
(9/17/01 10:49:04 pm)
Reply Group A

You can spend a fortune and have parts made, however this is not necessary. The Group A cars here, UK, could run 200bhp quite happily on relatively stock motors. I own an Ex-works Group N car at the moment and I have also owned an Ex-works Group A car previously. I have stripped them both and compared them, there were not many differences, it is predominantly done by the ECU.

I have just had a new CB80 short race engine built and we did the following:

Standard pistons, slightly skimmed for compression
Standard rods, balanced end to end
Standard crank, balanced (never lighten a CB80 crank!)
Standard balance shaft, balanced
Considerably lightened flywheel, balanced
Paddle clutch balanced
Uprated coverplate, balanced
Mig wire rings to each cylinder to prevent head gaskets blowing.

I have had a hybrid turbo made and fitted an Omex ECU, it is expected to produce 200bhp when the head is done.

The Group A cars ran an LSD and a close ratio gearbox too. The group A cars were rally cars and not race cars and essentially achieved their power from the ECU.

I have a set of homologation papers that I am slowly scanning, it is a very large document and will take some time for me to complete, when it is I will get it posted for general information.

matthew slade
Registered User
Posts: 397
(9/18/01 2:24:50 am)
Reply Homologation Papers

FYI the Group A FISA Homologation Number for the G100 is A-5344 and homologation was valid from 01/10/1988. You might be able to track a set down from FISA or indeed from the ‘Japan Automobile Federation’, they prepared all of the paperwork.

Registered User
Posts: 546
(9/18/01 12:06:13 pm)
Reply matt

Thanks mate,
Look’s like another beer for you when you come over to sunny aust!

80% of what you said has being done so I will just make sure its all balanced!
btw, you said never " (never lighten a CB80 crank!)"

Why?..mate there bigger than a WRX crank!

have you done any major work to the head?

thanks boy’s

1 Like

matthew slade
Registered User
Posts: 398
(9/18/01 6:13:06 pm)
Reply Re: matt

You will see when you get the crank out that Daihatsu have already lightened it and balanced it a little. When you map your engine you will be able to rev it like a motorbike engine and a lightened crank will just snap, my race engine builder refused to anything other than balance the crank. If you want reliability don’t lighten the crank.

When you have the crank balanced, have balanced on its own, then with the lightened flywheel attached, then with the clutch and coverplate attached. This will guarantee a very smooth engine.

I haven’t done my head yet, but all it will require is a port and polish job, don’t be tempted to fit larger valves. I wouldn’t waste any money on cams either, stock ones will do fine.

matthew slade
Registered User
Posts: 399
(9/18/01 6:19:47 pm)
Reply Crank

You will see when you get the crank out that Daihatsu have already lightened it and balanced it a little. When you map your engine you will be able to rev it like a motorbike engine and a lightened crank will just snap, my race engine builder refused to anything other than balance the crank. If you want reliability don’t lighten the crank.

When you have the crank balanced, have balanced on its own, then with the lightened flywheel attached, then with the clutch and coverplate attached. This will guarantee a very smooth engine.

I haven’t done my head yet, but all it will require is a port and polish job, don’t be tempted to fit larger valves. I wouldn’t waste any money on cams either, stock ones will do fine.

Registered User
Posts: 547
(9/19/01 3:03:08 pm)
Reply GTti donk’s rocks!

there you have it people’s just buy a GTti…looks like they come built of the factory with all the good gear! unlike those silly detom’s…
you need to do head work. pistons, bottom end, valves, etc to make those silly buz boxes move! pfft!


Registered User
Posts: 1455
(9/19/01 3:09:03 pm)

Re: GTti donk’s rocks!

The reason the STi’s crank is thinner is that the boxer engine is inherrently more forgiving when it comes to cranks, so they dont need huge ones

matthew slade
Registered User
Posts: 404
(9/19/01 6:11:39 pm)
Reply Re: GTti donk’s rocks!

And they don’t rev into 5 figures.

come at me
Registered User
Posts: 28
(9/19/01 10:55:34 pm)
Reply Re: GTti donk’s rocks!

how about the pistons??? they are only semi forged aren’t they??? i was thinking of puting forged pistons in my spare motor and working th f#*k out of it…
if i am going to put them in would 40 tho oversized be ok?
i want her to handle big boost…and have no worries


matthew slade
Registered User
Posts: 406
(9/20/01 8:05:54 am)
Reply Re: GTti donk’s rocks!

Forged pistons are not essential but always good for large boost, improved compression is also a must for reliability.

Be careful with oversized pistons, the waterways are very close to the cylinder bores, you could induce a weak spot, you will probably find that the block will only need a hone.

come at me
Registered User
Posts: 29
(9/20/01 10:35:58 pm)
Reply Re: GTti donk’s rocks!

Thanks, one question how much can these motors really take??? are bolt on gear the way to go???

Sometimes I dream about reality,
Sometimes I feel so down.

Hey, Bobbie Marley,
sing somehting good to me.
This world go crazy,
it’s an emergency!

  1. What’s bad about putting big wheels on my charade?

The first reason that going so big is wrong is basically because tyres/wheels have to work with the suspension:

As the suspension moves through it’s travel, various things happen to the susp. geometry: The main problem that going so low in profile gives is that the tyre no longer has sufficient sidewall flexibility to take care of the camber change that occurs during normal suspension operation. This means that as the camber changes, the tyre ends up running on it’s edge rather than the tread of the tyre being flat to the road. This can (and does) mean that you end up with LESS rubber on the road during hard cornering where you need it most.

The classic example of this is watching a lowered Escort Cosworth with rubber bands launch off the line: The rear suspension of the EsCos is the same as that on the donor Sierra, namely semi trailing arms. These have a particularly bad camber change during bump travel. This means that the tyre is completely on it’s inner edge. This is made worse by the fact that during launch the weight transfer make the rear squat more causing further camber change. You can see the skid mark gradually become thicker from 2" out to the full tyre width as the launch progresses. These muppets actually believe that their traction problems derive from the monster boost they’re running rather than their choice of tyre/wheel. The really laughable thing is that they (esp RSOC Muppets) think they know more than you when you developed the goddamn thing in the first place!!! Hehe!

The above is not true of race cars as they 1) don’t have McPherson strut/semi trailing arm/other cheap nasty road suspension compromise and 2) have incredibly stiff springs and barely roll during cornering.

Finally, and yes, there is more: to allow suspension to work properly we want the lowest unsprung weight possible. This is not achieved by hanging 17" of styling off each corner and then expecting good traction on a bumpy road. The lightest (and cheapest) wheel tyre combination for a G100 Charade is 185/60 cut slick on a stk steel rim. Stylish? Poss not. Effective. Certainly and you’ll drive circles round your mates on their rubber bands. I take it you didn’t see me lapping Silverstone last year on this setup?

  1. What turbo should i run

Compressor Selection

When using the formula’s below, you will need to use compressor flow maps and work with the formulas until you size the compressor that will work for your application. Compressor flow maps are available from the manufacturer, or do a search on the web, you’ll find that they are readily available. On the flow maps, the airflow requirements should fall somewhere between the surge line and the 60% efficiency line, the goal should be to get in the peak efficiency range at the point of your power peak. In this article I will walk through an example as I explain it, once you understand it, you can get the the formula’s in the Sizing Formula’s tech article for quicker reference.

Engine Airflow Requirements

In order to select a turbocharger, you must know how much air it must flow to reach your goal. You first need to figure the cubic feet per minute of air flowing through the engine at maximum rpm. The the formula to to this for a 4 stroke engine is:

(CID × RPM) ÷3456 = CFM

For a 2 stroke you divide by 1728 rather than 3456. Lets assume that you are turbocharging a 350 cubic inch engine That will redline at 6000 rpm.

(350 × 6000) ÷ 3456 = 607.6 CFM

The engine will flow 607.6 CFM of air assuming a 100% volumetric efficiency. Most street engines will have an 80-90% VE, so the CFM will need to be adjusted. Lets assume our 350 has an 85% VE.

607.6 × 0.85 = 516.5 CFM

Our 350 will actually flow 516.5 CFM with an 85% VE.

Presure Ratio

The pressure ratio is simply the pressure in compared to the pressure out of the turbocharger. The pressure in is usually atmospheric pressure, but may be slightly lower if the intake system before the turbo is restrictive, the inlet pressure could be higher than atmospheric if there is more than 1 turbocharger in series. In that case the inlet let pressure will be the outlet pressure of the turbo before it. If we want 10 psi of boost with atmospheric pressure as the inlet pressure, the formula would look like this:

(10 + 14.7) ÷ 14.7 = 1.68:1 pressure ratio

Temperature Rise

A compressor will raise the temperature of air as it compresses it. As temperature increases, the volume of air also increases. There is an ideal temperature rise which is a temperature rise equivalent to the amount of work that it takes to compress the air. The formula to figure the ideal outlet temperature is:

T2 = T1 (P2 ÷ P1)0.283

T2 = Outlet Temperature °R
T1 = Inlet Temperature °R
°R = °F + 460
P1 = Inlet Pressure Absolute
P2 = Outlet Pressure Absolute

Lets assume that the inlet temperature is 75° F and we’re going to want 10 psi of boost pressure. To figure T1 in °R, you will do this:

T1 = 75 + 460 = 535°R

The P1 inlet pressure will be atmospheric in our case and the P2 outlet pressure will be 10 psi above atmospheric. Atmospheric pressure is 14.7 psi, so the inlet pressure will be 14.7 psi, to figure the outlet pressure add the boost pressure to the inlet pressure.

P2 = 14.7 + 10 = 24.7 psi

For our example, we now have everything we need to figure out the ideal outlet temperature. We must plug this info into out formula to figure out T2:

T1 = 75
P1 = 14.7
P2 = 24.7

The formula will now look like this:

T2 = 535 (24.7 ÷ 14.7)0.283 = 620 °R

You then need to subtract 460 to get °F, so simply do this:

620 - 460 = 160 °F Ideal Outlet Temperature

This is a temperature rise of 85 °F.

Adiabatic Efficiency

The above formula assumes a 100% adiabatic efficiency (AE), no loss or gain of heat. The actual temperature rise will certainly be higher than that. How much higher will depend on the adiabatic efficiency of the compressor, usually 60-75%. To figure the actual outlet temperature, you need this formula:

Ideal Outlet Temperature Rise ÷ AE = Actual Outlet Temperature Rise

Lets assume the compressor we are looking at has a 70% adiabatic efficiency at the pressure ratio and flow range we’re dealing with. The outlet temperature will then be 30% higher than ideal. So at 70% it using our example, we’d need to do this:

85 ÷ 0.7 = 121 °F Actual Outlet Temperature Rise

Now we must add the temperature rise to the inlet temperature:

75 + 121 = 196 °F Actual Outlet Temperature

Density Ratio

As air is heated it expands and becomes less dense. This makes an increase in volume and flow. To compare the inlet to outlet air flow, you must know the density ratio. To figure out this ratio, use this formula:

(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio

We have everything we need to figure this out. For our 350 example the formula will look like this:

(535 ÷ 656) × (24.7 ÷ 14.7) = 1.37 Density Ratio

Compressor Inlet Airflow

Using all the above information, you can figure out what the actual inlet flow in in CFM. Do do this, use this formula:

Outlet CFM × Density Ratio = Actual Inlet CFM

Using the same 350 in our examples, it would look like this:

516.5 CFM × 1.37 = 707.6 CFM Inlet Air Flow

That is about a 37% increase in airflow and the potential for 37% more power. When comparing to a compressor flow map that is in Pounds per Minute (lbs/min), multiply CFM by 0.069 to convert CFM to lbs/min.

707.6 CFM × 0.069 = 48.8 lbs/min

Now you can use these formula’s along with flow maps to select a compressor to match your engine. You should play with a few adiabatic efficiency numbers and pressure ratios to get good results. For twin turbo’s, remember that each turbo will only flow 1/2 the total airflow.

Last updated 12/28/02
Turbo Type ----------- Approx flow @ pressure
Stock Turbo ---------- 360 CFM at 14.7 PSI
IHI VF 25 ------------- 370 CFM at 14.7 PSI
IHI VF 26 ------------- 390 CFM at 14.7 PSI
T3 60 trim ----------- 400 CFM at 14.7 PSI
IHI VF 27 ------------- 400 CFM at 14.7 PSI
IHI VF 24/28/29 ----- 410 CFM at 14.7 PSI

========= 422 CFM max flow for a 2 Liter at .85 VE pressure ratio 2.0 (14.7 PSI) 7000 RPM =======

IHI VF 23 ------------- 423 CFM at 14.7 PSI
IHI VF-30 ------------- 435 CFM at 14.7 PSI
SR 30 ----------------- 435 CFM at 14.7 PSI
IHI VF-22 ------------ 440 CFM at 14.7 PSI
T04E 40 trim -------- 460 CFM at 14.7 PSI

========= 464 CFM max flow for a 2.2 Liter at .85 VE pressure ratio 2.0 (14.7 PSI) 7000 rpm =======

PE1818 -------------- 490 CFM at 14.7 PSI
Small 16G ------------ 505 CFM at 14.7 PSI
ION Spec (stg 0) — 525 CFM at 14.7 PSI

========= 526 CFM max flow for a 2.5 Liter at .85 VE pressure ratio 2.0 (14.7 PSI) 7000 RPM =======

Large 16G ----------- 550 CFM at 14.7 PSI
SR 40 ----------------- 595 CFM at 14.7 PSI
18G ------------------- 600 CFM at 14.7 PSI
PE 1820 -------------- 630 CFM at 14.7 PSI
20G ------------------ 650 CFM at 14.7 PSI
SR 50 ---------------- 710 CFM at 14.7 PSI
GT-30 ---------------- 725 CFM at 14.7 PSI
60-1 ----------------- 725 CFM at 14.7 PSI
GT-35R -------------- 820 CFM at 14.7 PSI
T72 ------------------ 920 CFM at 14.7 PSI <— Note you would have to spin a 2.0 L engine at about 14,000 rpm to flow this much air.

IHI VF 25 ----------- 395 CFM at 18 PSI
IHI VF 26 ----------- 400 CFM at 18 PSI
T3 60 trim ---------- 410 CFM at 20 PSI
IHI VF 27 ----------- 420 CFM at 18 PSI
IHI VF 24/28/29 – 425 CFM at 18 PSI
IHI VF 23 ----------- 430 CFM at 18 PSI
IHI VF-30 ----------- 460 CFM at 18.0 PSI
AVO 320HP -------- 465 CFM at 17.5 PSI
T04E 40 trim ------ 465 CFM at 22 PSI
IHI VF-22 ---------- 490 CFM at 18.0 PSI
SR 30 --------------- 490 CFM at 22 PSI
Small 16G ---------- 490 CFM at 22 PSI
ION Spec (stg 0) - 500 CFM at 19 PSI
PE1818 ------------ 515 CFM at 22 PSI
Large 16G --------- 520 CFM at 22 PSI

========= 526 CFM max flow for a 2 Liter at .85 VE pressure ratio 2.5 (22 PSI) 7000 rpm =======

========= 578 CFM max flow for a 2.2 Liter at .85 VE pressure ratio 2.5 (22 PSI) 7000 rpm =======

HKS GT2835 ------- 580 CFM at 22 PSI 400 hp
MRT 400 ------------ 580 CFM at 16 PSI
AVO 400HP -------- 580 CFM at 17.5 PSI
MRT 450 ------------ 650 CFM at 19 PSI
AVO 450HP -------- 650 CFM at 20.0 PSI
SR 40 ---------------- 650 CFM at 22 PSI

========= 658 CFM max flow for a 2.5 Liter at .85 VE pressure ratio 2.5 (22 PSI) 7000 rpm =======

HKS GT3037 ------ 670 CFM at 22 PSI 460 hp
PE 1820 ----------- 680 CFM at 22 PSI
20G ---------------- 695 CFM at 20.0 PSI
HKS GT3040 ----- 710 CFM at 22 PSI 490 hp
AVO 500HP ------ 770 CFM at 22 PSI
SR 50 ------------- 770 CFM at 22 PSI
GT-30 ------------- 790 CFM at 22 PSI
60-1 --------------- 800 CFM at 22 PSI
HKS GT3240 ----- 830 CFM at 22 PSI 570 hp
GT-35R ----------- 880 CFM at 22 PSI
T72 --------------- 1000 CFM at 22 PSI <— note you would have to run a 2.0 L engine at >40 PSI boost to flow this much air

Conversions used where there was control over conversion factors:
1 HP approx equals 1.45 CFM

1 CFM approx equals 0.0745 lb of air/min

0.108 Lb/min approx equals 1 hp

1 Meter cubed/sec = 35.314 CFS = 2118.867 CFM

1 KG/sec = 132 lbs/min approx equals 1771.812 CFM

power coversions:
1 PS = 0.9859 HP = 75 Kgf m/sec
1.3405 HP = 1 KW
1 HP = 746 watts

  1. I have a carbie problem, who should i see…

In Sout East Queensland Australia, i would recomend, Ian Stewart.
In the UK doddy Recomends http://www.carburetters.co.uk/frontofshop.htm

  1. I’m replacing my headgasket, what are the Torque settings and bolt sequences for the Head? (from Mike)

Loosen in the sequence over 2 to 3 stages
(suggest 1/4 to 1/3 turn on each one)
with 1 being the head bolt nearest the driver and 2 being furthest away

for those with manuals section 5 page 56 top of page

Refit in the sequence

with 8 being the head bolt nearest the driver and 7 being furthest away

First Tightening 4.0 to 4.5 Kg-m (29 to 33 ft lbs)
Second Tightening 6.0 to 7.0 Kg-m (43 to 51 ft lbs)

Engine manual section 5- Page 56 top of page

  1. CB-80 GTti Fault Codes

First find this connector under your bonnet,

its to the right of the engine in the space under the pipe from the intercooler to the throttle body, it will be just hanging loose in there not connected to anything, Short the two Brown wires:-

Fault Code Instructions below After shorting the white connector, switch the ignition to ON position and check the instrument cluster.
The number of times it blinks indicates the fault codes.
The two pins to short are the top left one and the bottom one.
The following method is used to output the codes: 0.5s on, 0.5s off per code, 2.5s gap between codes and then 4.5s gap before repeating all stored codes.
S/C = short circuit
O/C = open circuit
1=number of flashes per code

1: Normal
2: MAP (manifold pressure) sensor or turbo
3: Ignition eg output s/c or o/c
4: Water temp sensor
5: A/F trim (AKA mixture pot) ONLY on NON-CAT applications like GB
6: Distributor
7: Throttle position sensor
8: Air charge temp
9: Vehicle speed pickup (In speedo head)
10: Starter (may be set by bump starting)
11: Switch error eg idle switch off or A/C on during diagnosis.
Engine should not be running or A/c on

Fault codes 1, 10 and 11 do NOT set MIL (Motor inspection light)

CB70 Codes to follow…

  1. Basic Diagnostics… By Chas…

Testing Air/Fuel Ratio

Take out the air filter;
run engine at idle;
slowly blank off the carby throat with some stiff cardboard;
if engine rpm increases the mixture is lean, if it decreases it is rich, if it stays stable with throat almost blanked she’s scmick.
Repeat for 1500 & 2500 rpm.

PCV Test

The postive crankcase ventilation valve syphons oil fumes into the carby for burn off. If it clags the engine no like it, so:

Start engine and idle;
remove hose from PCV and block the hose end with your thumb;
if rpm drops more than say 50 -60 rpm then its ok;
if it drops less than 50 rpm the PCV needs o/haul.

Air Filter Test
Take out filter;
drop one of the vaccuum hoses off and start engine and idle;
put filter back in while idling;
if rpm drops your filter not so good…replace.
Dropping a vacuum hose off leans the mixture so a dirty or restrictive filter will have a measurable impact.

Equalisation of Cylinder Power

Start engine and increase idle speed to about 1300 rpm with the fast idle screw;
using electrical pliers and or rubber gloves remove each spark plug ignition lead and ground the end to the engine;
replace each lead as you go before removing the successive lead;
note the rpm change each time;
check for the difference in rpms between cylinders;
if they are about 50 rpm apart she’'s ok;
if there are one or two that noticeably didn’t drop the rpms around the others they are the ones with bad leads, plugs, compression, etc.

  1. GTti Oil Recommendations by Matt Slade
    There are many things to consider, it is important to understand the condition of your engine and the mileage it has covered. Oil should be changed every 3,000 miles in a CB80 if you want a good running long living engine.


If your engine is old and the stem seals are worn etc, then I would use a semi synthetic oil. If your engine is in good condition then I would use a good quality synthetic oil like Mobil 1 Motorsport (not Mobil 1, there is a

Ideally you want a synthetic oil with a rating of something close to 10W 50

According to the Manual use 2.7 Litres when oil is only changed, When oil and oil filter are changed use 3.1 Litres

  1. More of chas’s useless info…

When sizing inlet valves the magic velocity figure not to exceed is 0.6 mach or speed of sound, as the volumetric efficiency starts to tail off noticeably…

At say 30°C the speed of sound is about 350 m/s.

If you take the inlet valve of the CB23/60/61, the full open to air flow area is 0,00026425m2. So using a rule of thumb 1 l/s/kW:

the CB23 is 0.038 m^3/sec air and therefore has a velocity of 143 m/s or a mach factor of 143/350 = 0.410

the standard CB60/61 would be 50 l/s so the mach factor would be about 189/350 = 0.54

So if you push the CB60/61 to 80kW the mach factor becomes 0.86 the volumetric efficiency will be dropping of very rapidly.and will require a cam profile change to delay the closing of the intake valve. An higher lift cam might be the go here as the valves are pretty close to hitting the piston crowns as stock.

The exhaust valve has to follow the intake valve and should not exceed 80% of the valve opening area otherwise the power will drop off due to less restriction to backflow when the piston passes TDC. The CB23/60/61 has an area ratio of 0.84 so there is a case for 5% larger inlet valves in the chase for higher power and volumetric efficiencies.

More interesting than Richie Benaud don’t you think?

Poste Script

Of course you could run the calcs using swept volume at max power revs, but I’m too lazy to do that…well no I’m not :- 76mm bore, 73mm stroke at 5,500 rpm and 35mm valve is 0.39 mach index with 0.8 VE (NA) or 0.49 with 100% VE (turbo).

Rubbery figures at its finest

Another interesting bit of information is the way the power/torque curves for the three 1 litre motors track each other:

From the limited data I have the curves appear to track each other from 3200 rpm upwards of 6500 rpm.

Using the CB80 as the baseline and formula for power kW = (N-M x RPM)/9549 there is a fairly constant offset through the range:

CB23 = 60%
CB60 = 82%

So I have been asking myself if the pistons and stroke are the same, what could be the contributing offset differences in torque/power?

A twin cam is good for flowing and high revs, but probably has increased valve train losses and extra mass;

The valve opening and closing angles are different;

The GTti has a better flowing turbo (6 psig CB60 and 8.5 psig GTti @ 4000rpm), intercooler? and slightly lower CR;

The GTti has fuel injection and electronic ignition;

The rest are fairly minor things like combustion chamber design, etc

Has anyone here actually dynoed a standard GTti to see if the 74kW is real or hype?

  1. CB23 to 61 valve timing allignment.

This is for the single overhead cam three pot:

On the driver’s side of the engine is a black plastic cam belt cover. It is a two piece construction. The top piece is held on by four screws, two plainly visible at the top, a third also visible about 150 mm down and a forth also about 150mm down, but hidden by the water pump pulley. You should be able to use a ring spanner and fingers to get all of them out (even the difficult one).

Once the cover is off you will see the cam sprocket and belt.

To check alignment…

Make sure the the battery negative is disconnected, so I don’t get the blame for you losing fingers. Make sure the handbrake is on and a brick or something (mother in law) behind a back wheel to stop the car rolling while in neutral.

Locate the stamped dimple on the outer rim of the cam sprocket;

Locate a small cast projection that looks like a penninsula on the lip where the plastic cover was at about two o’clock position;

Locate the number one cylinder lead position on the distributer cap (it should be the one closest to the carby);

Take off the dizzy cap so you can see when the rotor is pointing to where the number 1 lead is normally located;

Put car in neutral and with a ring spanner on the bolt head holding the drive pulley to the crankshaft, rotate the motor clockwise while keeping an eye on the dimple (on the cam sprocket);

Once the dimple is aligned with the cast penninsula (use a straight edge or ruler to ensure the centre the of the sprocket, the dimple and penninsula are aligned), check to see the dizzy rotor is pointing at number 1 lead position, then look for a dimple on the flywheel;

The dimple on the flywheel (located between the engine and gearbox) can be seen through a small square portal on top of the bell housing. It is not TDC, but an 8° BTDC mark for your ignition timing. TDC is about 22mm away from this mark (anti clockwise);

So if you rock the engine (rotating back and forth with your ring spanner)you should be able to find the flywheel dimple, imagine where TDC is and have that imaginary point aligned with the notch in the small square portal.

If all the planets are in alignment then its sweet. In not you will need to loosen off the belt tensioner and start skipping the belt to get it right.

Please note if you don’t trust your eye to find TDC, take out number 1 spark plug and put a long straw down the hole to measure the piston height. When you rock the motor you will soon discover the highest point, by the straw protrusion length.

Note 2 if you really want to go to town you can strip off the drive pulley and everything else around the water pump, take off the lower plastic housing to reveal the drive sprocket that has its own alignment dimple and casting projection (=TDC). I prefer my method.


  1. Gearbox Info

This is all the gear ratios from all std daihatsu gearbox’s.With this you can make a close ratio box for anay daihatsu.

GTti box
1st 3.090
2nd 1.750
3rd 1.23 or 1.25
4th 0.917
5th 0.750
final drive 4.643

1st 3.090 (34/11)
2nd 1.842 (35/19)
3rd 1.230 (32/26)
4th 0.846 (32/37)
5th 0.707 (29/41)
final drive
CB23 4.500 (72/160
CL11 4.933 (74/15)
CB61/CL61 4.642 (65/14)

1st 3.090 (34/11)
2nd 1.750 (35/20)
3rd 1.250 (35/2
4th 0.916 (33/36)
5th 0.750 (30/40)
final drive 4.266 (64/15)

Charade G200 1.3

1st 3.181
2nd 1.842
3rd 1.250
4th 0.864
5th 0.707
final drive 4.266

charade 1.5

1st 3.09
2nd 1.750
3rd 1.250
4th 0.864
5th 0.707
final drive 4.266

1st 3.752
2nd 2.182
3rd 1.428
4th 1.00
5th 0.665

now i have been told if you use the gears out of a G202,G200 and a gtti box you can make a close ratio gear box useing std parts.I guie around the corner from me works with daihatsu and has made 1 fore his car and its unreal.Rospen also make the box.They use 1st,2nd and 5th from a G102 and GTti box and custom make 3rd and 4th from there group A rally gear sets.ratios are as folowed.

1st 3.042
2nd 1.842
3rd 1.450
4th 1.180
5th 0.917

these kits cost alot and i think you can use gears out of one of the box’s as i have listed.All gears out of aney daihatsu will go into aney daihatsu gearbox caseing.

The ownly thing that has crossed my mind is,
The gears out of a GTti box are a little wider than all the other gear sets there for makeing them a little stronger.so if you cross all these gears 1st 2nd and 5th will be a little weaker than 3rd and 4th.I dont think this will be a prob as i was hooting my car around with a std G202 box for 1 year and had no probs but its still a thort.

  1. Chas’s basics of cams 101.

Duration = D Lobe separation angle = S

D(short), S(narrow) = stump puller
D(short), S(wide) = trailer puller, torquey up to about 4000 rpm, need headers
D(midrange), S(narrow) = hill climber, power band from idle to about 4000 rpm
D(midrange), S(wide) = riceburner and daily drive, power band up to 6000 rpm +, needs headers, intake runners and some head work
D(long), S(narrow) = Drag car , narrow power band up around the 10k rpm range, rapid torque, needs low final drive ratio and close ratio tranny
D(long), S(wide) = Zeekmobile (or Adam’s Dad), pro street, no brakes, high end power band, shakes like a drunk club patron in the hands of Darryl

  1. RU’s info on temp Vs. ignition timing.

We advance the spark, the combustion occurs earlier so more work is done on the piston = more power. Since the amount of energy in one chamber full is constant, the more work we do on the piston the less gets passed out the exhaust port so the EGT is LOWER for a more advanced spark.

Retarding the spark, means combustion occurs later so less work at the psiton (less power) plus more wasted energy = higher EGT.

This can be used to give more boost but if youaren’t transferring the results to the piston then the engine runs less efficiently. Since we have to keep things cool to prevent cracking we actually end up running too rich to cool things down again.

All this torque of optimum fuelling EGT is nonsense. A turbo engine will be run far richer than optimum (approx 5%CO 0.85 Lambda) in orderto keep things cool.

Remember kids you’re calibrating to optmum TORQUE not EGT. EGT is only an indicator and a limit.

Hard limits to tuning a turbo engine?

  1. Knock
  2. EGT limit
  3. Max cylinder pressure
  4. Compressor shaft speed
  5. Ignition limit

In practice you keep reatarding the spark as you increase pressure until you can’t add enough fuel it keep it cool. At that point, you either reduce compression ratio, reduce restrictions, add RON or add cooling.

Let me clarify a few things: advancing the spark increases the temperature in the combustion chamber but as this results in increased work done on the piston plus more heat transfer throught the walls, the end result is that the EGT is cooler after the exhaust valve opens.

Det is a result of pressure/temperature in the charge plus the surface temperature of the combustion chamber hence advancing spark increases tendency to det. Some fuels will det less than others irrespective of detonation: eg Elf Turbomax is only just over 100 RON but lets you run a WRC car a 2bar boost against 11:1 compression w/o det.



  1. Chas’s info on BOV’s

Tedium is the expert on fans, having written a thesis on axial fans, but I will give it a crack in lay terms having been involved in the design application of fans.

The wheel doesn’t actually stall as in stop, it is a term used to describe the loss of flow or pumping due to a shutoff or high head condition. You may find the compressor wheel actually speeds up and is sent into the choke region. Fans and pumps tend to require less input power as they do less work. On axials the blades actually start to cut the air. On prop fans the slightest upset and they stall (stop pumping). Turbo compressors are more a mixed flow style impellor that combine the advantages of axial and centrifugal fans.

If you have ever listened to an air compressor, you will note that when it turns off the relief valve gives a short vent due to a surge spike created when the velocity pressure is suddenly converted to static pressure (amongst other things).

The surge hammers the compressor blades and in turn its bearings. The air is now stalled and building a high pressure up against the throttle body. At this point a phenomenom called stall flutter starts where impellor the tips are buffetted causing stress on bearings, the blades, etc. A large heat build up also occurs around the blades as the mechanical energy is converted. It is not uncommon in our industry to see a pump that has been left shutoff boiling the water in and around the volute.

Now if you have one of those cheapo desk or pedestal fans you may have noticed if you have it too close to a wall, the noise pitch rises and the air flow reduces significantly. Even when you pull it away it takes some time for the air to start pumping again, akin to a standing start as opposed to a rolling start. While the turbo compressor wheel is not a prop it still exibits similar behaviour. As I understand it, this is the primary reason Porsche hit upon using a recirculating bypass valve in the first place.

Obviously its pointless putting a mismatched bypass valve on. And I would hazzard a guess a lot of the negative ideas about them is due to the upping of the standard boost without considering or knowing about the setpoint and range of the bypass setup.

CHas’s info on backpressure.

There’s lots of factors involved in so called backpressure and torque, but backpressure is a misnoamer association as it is really describing the system resistance at various gas velocities. The significant factor is the velocity the exhaust escapes (and the scaveging effect it has). If the exhaust piping is sized for high revs then the velocity must be lower at lower rpm. Conversely if the gas velocity is high at low revs it will be much higher at high revs and therefore the “backpressure” will increase as will the choking effect.

If you have low velocity at low revs the exhaust gas will hang around the exhaust port like a stale bottle of piss and mess up the exhausting of the cylinders.

Burnt valves can be the result of bad seat contact or insufficient contact face. If the valve faces are too big there may be insufficient contact pressure and on leaded engines this was a problem because leaded fuel has a low combustion swirl and the valve contact faces tended to build up with carbon and lead deposits.

The valves will burn with lean mixtures, but to say the carby models got