Loving this thread!
A question on the rear brakes - if they do not contribute a lot to the overall braking effort, what is the driver to replace the drums with discs?
There is a guy here in Adelaide who is retrofitting Prelude 282mm front rotors onto a YRV and hence no doubt would fit on a Sirion with appropriate wheels to go over them. Surely larger fronts > rear disc conversion?
I’d love to know more about the high compression pistons. Were they a custom order?
Ditto - and if you don’t go down the aftermarket ECU, how is it all going to be controlled?
E85 fuel?
Would also like to know about the Supercircuit Header 4-2-1 could you let us know if its good and how you went about getting it.
I’ve got a set of the 4-1 and 4-2-1.
Very simple; hit them up on Facebook and dealt with Frank.
Paypal the money, they made them and the showed up. I can unwrap the 4-2-1’s as they’re not on the car for pictures of welds etc. They’re decent quality, you could spent some time cleaning up some bits if you were chasing the 10/10ths. Otherwise they bolted up fine to the Sirion’s K3 and stock exhaust, good clearance to the engine mount and the factory exhaust bolted upto it, after I took a few mm off the factory donut that mates the front pipe to header. Even with the factory header-back exhaust, it’s changed the note from ~4k rpm and upwards.
To be a little vague here on the exact sizes and type drum vs disc in a single stop application, “comparable” items will have the drum out perform a disc - in a single hard brake application. A drum gets more bite. The shoe/linings actually dig in (I’ve driven semi-trailers and wow it’s amazing how well 40t will stop with drums - but not so good down a long long hill). The better modulation though goes to the disc, so they provide more control through the different levels of pedal pressure. Then there is the far superior benefit of cooling with discs. A performance drum will have heat fins like an early Corvette or the rear alu vented items on 240z or 260z for example. To do track work a drum brake set up needs big scoops in the backing plate to channel air in. If you run out of brakes on a track (or anywhere they are pushed hard - with the exception of failures of components or running out of fluid) it typically falls into “pedal goes to the floor - so fluid has boiled” or “pedal is rock hard - so the pads have overheated”. A pad or brake shoes asked to work beyond its thermal capacity will vent a gas. As the gas comes out it works a bit like a hovercraft stopping it contacting the disc rotor and hence no friction. Drum brakes gas up really easily since the lining go almost all the way around the circumference of the braking area and there is almost no venting of gases. Drums lock up well, so are used on many modern cars for handbrake mechanisms and are cheap (hence why the are still used on the rear of crappy cars like the current (2018) Holden Barina Spark CD), but because of the better all round performance stopping and cooling they have found there way onto anything half decent front and back, which includes many new semi-trailers.
While the front may need to provide 80% of the braking, those dinky little drums may only be doing 10% of the work (we did say a drum can work well but it has to be of a comparable size, which the rear on a M100 are only 180mm). This could mean overloading the front such that it is doing 90% of the work. If we upgrade the rear and take some load from the front to get the perfect balance of 80/20 then it is worth it. Better balance, better modulation and less chance of the rear over heating.
Can you over heat the rear? Some people may only begin to get the rear hot when the fronts overheat and “go away”. I found it easy to overheat std rears as I am a left foot braker. It is not recommended for the road (it may be illegal in some places). However, I’ve done this all my life in comp and daily driving. Dad had a mini (and a VW which I began driving up the back paddock from 8yrs - picture Dad putting 5litres of petrol in on a Sat arvo and letting me go on a 10acre thin strip of land till I ran out of juice) which unlike his VW or GTR XU1 (never got to drive the later - I should have asked, sigh!) would not oversteer - that was unless you planted the accelerator and brought the brake on hard mid corner (had some grunt for a mini as it had a David Vizard head and big carb). The mini turned out to be wicked fast by left foot braking. It was slow if you fanged the tail with big brake jabs but fast if you modulated the pressure as it would pull the nose in. The trick was, and still is, to do your braking concentrating on left foot perfection, don’t worry about using gears to slow yourself down, do worry about being able to change into the gear you need to accelerate out of the corner (yes without the clutch action), be back on the throttle lightly before the appex and begin to bring up the throttle while on the brake through the apex and where you might normally be rolling on the throttle - the throttle should already be full and you roll off the brake to accelerate straight ahead. So back to thinking about the affect on the rear brakes, this left foot action can get them hot. Yes it puts a lot of stress on everything, but done right it’s why I love front wheel drives. It’s also how I drive my awd, and I believe it to be beneficial in picking up fractions of a second in Khanacross. I’ve driven turbo cars where it helps keep the turbo spooled. And it can help on a rwd simply because of the reduce time moving feet between pedals. There have been a few rwd cars where I had to, like in a Formula Ford where there was no room to move your foot from clutch to brake because the steering column fouled my big fat feet and the clutch was only depressed at take off to stop (sometimes you just flick out of gear).
Some began reading this might not have gotten as far as you - well done. I may have stated things already known or there may be this to disagree with. The info here is my experience and that learnt more recently with my L200. I might also point out that my L200 has a single brake line to the rear which has a brake bias valve and then a hydraulic handbrake plumbed inline after that. The rear discs went in before this and were “better” than the Sirion drum with Sirion wheel cyliders which were a step forward from L200 std rears. The bias valve allowed even better braking. I have built a brake pedal with drive adjustable balance bar which does away with booster, this should provide even better feel and tuning. One day I’ll get back onto my build and the thread update. Thanks for reading so far through (sorry for the hijacking of the excellent thread)
That was a really good read @Mr_Gormsby and while I don’t have heaps to contribute than from what you have said I can say that My latest trip to lakeside earlier this year.
My move has Sirion front brakes with rsr Sirion low springs on Suzuki wagon r struts and the rear Applause disc brakes with Suzuki swift coils (2.5 springs cut off). The wheels I had were a 14x6 with just a street Formoza tyre. There was negative camber in the front wheels with both sides as equaled as possible with a spirit level.
What I found was this setup gave me far better braking going into into corners and could get on the brakes much later than a lot of other cars on track. I also didn’t feel like I was going to flip on my side like in the previous track day (Mira low king springs all round) I felt like the weight transfer back to rear was spot on for Lakeside Park. The biggest thing was cornering was so much better. While everyone would leave me on the straight I had no problem being all over the back of them through corners. It was such a shame we were not allowed to pass anywhere but the straight.
I have now raised my rev limit from 5500rpm to approx 8000rpm thanks to @Mick for helping me out with the ecu mod so hopefully that may get me a little more on the straight. I will be taking my spare ecu just in case it fails.
that’s one of my doubts @TPG … I thought I would try RON 97 fuel + an octane booster, in addition to giving a little more fuel with a SAFC2 but I think the way is an aftermarket ECU.
@b_hoves Buy them at a Malaysian store. I found them as Piston Shop on Facebook.
They have many things for k3-ve and k3-vet. It took a while to arrive but everything OK.
In theory the pistons are plug and play, I still have no progress in the engine to confirm this.
Been enjoying reading this thread - I too have also been looking at ways to overcome understeer on my 91 Charade.
Hello World!! … I live again …
I must confess two things; first, that the last date I was unfaithful because the little sirion was not ready yet, so I participated with a toyota celica 1977 with atmospheric engine and solex carburetors (which make a really orgasmic sound)
Here some pics…
Second, I was scared to death that everything we had been preparing for the car not worked. At least until today, it’s working. 
Well, I tell you a little bit. We disarmed the engine with a little fear, I had never participated so much in car racing, I didn’t know how the engine was going to come out, fortunately the engine came out in good condition, without much to do.
We send it to the rectifier for review and work. We take advantage of preparing the cilinder head a little. 
Taking advantage of that it was all disarmed we sent to make double clutch press (standard disc)
well, with everything in our hands we build the engine with a lot of faith, maybe too much …
The engine didn’t turn, it was as if it were hitting a valve … ok, we will have to disarm it again and see what happens. 
I must have said a million expletives at that minute, I was really angry.
Once disarmed we realized that what was coming was the head of the piston with the head cilinder (another million expletives came out of my mouth).
After a while we decided to lower the cilinder head by the sides of the combustion chamber, according to our calculations we would solve the problem.
We were right, with that everything worked without problems. In theory the pistons were plug&play but for some reason, this was not the case. Fortunately, it was not a big disaster. 
Before mounting the engine, we hardened the rear engine bracket and reworked shift lever bushings, then assembled the engine.
The installation of the header was much simpler … really plug&play (beautiful the header)
And the moment of truth arrived … it broke or it split …
The engine started at the first, soft, somewhat noisy …the rear support does not let the engine move transmitting vibrations to the interior.
The header began to change color, but it was beautiful … after the adjustments of a newly rebuilt engine we should go to a test.
the clutch … it was very very hard, uncoupled a little slower but coupled immediately, I think it’s something to get used to.
I did not want to accelerate it for fear that the VVT would crash the valves, little by little I was gaining confidence until I reached 7,500 rpm with success. I do not hear it detonate (maybe I have a bad ear), I’m using gas 97 RON, but I think for racing needs something better.
With half throttle is another car, much more torque. With the pedal fully open stays a bit, maybe detects detonation, maybe it lacks a larger acceleration body.
For now I’m still in the process of testing, but this month I have two races. One on October 13 and the next on October 21.
I still have things to do, but this is what I can tell you until now!
a hug!
Looks fantastic!
Please share more information about the clutch and engine mount… I am very curious 
Great work. Love to read and see what you are doing.
The double diaphragm clutch is only one solution to more clamping force. As you have a lathe you can modify the pivot location and end up with the needed clamp force and a light pedal action. If I can find an old pressure plate I’ll pull one apart and show what to do (have had a big clean out and tossed lots, normally I’d have a heap).
Great write up again. This is with the high compression Pistons??
I see you went with the SuperCircuit headers! So far they’ve worked well for me, and I agree they “colour up” quite nicely with the heat.
Amazing work. Building the K3 I wish I was able to when I had a Sirion. Watching with lots of interest.
Hi!
Regarding the clutch, @Mr_Gormsby is right, it’s a solution to give more clamping force, as a result the gears changes go slower but they pull more, I think it’s a solution to not place a ceramic clutch because the press give more force and the disc skids less … only it’s a little uncomfortable until you get used to it.
I’m also interested in what @Mr_Gormsby says, hopefully you’ll find the old press so you can show us how it’s done.
Regarding the engine mount, it is nothing more than a lathe work, replacing the original material with a harder one, in my case i used one that here in Chile they call “tvinil”, it’s like a hard plastic, but it can be made from different materials like rubber or polyurethane.
@TPG You are right, this is high compression pistons, even in the testing period…
I’m going to take the minute to maybe ask something crazy … since the ECU of the Sirion is only read, it will not be possible to replace it with one of a Toyota engine (2NZ-FE), change the Wire Harness and remap this ECU? the operating parameters must be similar.
The 2NZ-FE ECU is write-read so if there is software to reprogram, on the other hand, with the ecu of the k3-ve2 there is only the way of the aftermarket ecu.
What do you think, will it be posible?
I can think of no reason why a Toyota ecu would not work. Great idea so long as you can write to it yourself. Some of that stuff you cannot write to “live” or while it is running. Perhaps you know who all that works anyway.
Hi guys,
I come with my post update…
Finally the race on October 13 was suspended so I only participated in the race on October 21st.
It was an entertaining date, the car was a 10 and I won in the category.
If you remember, the categories are established by time, from GT1 to GT6. Where GT1 is 1:07:00, GT2 is 1:05:00, GT3 is 1:03:00, GT4 is 1:00:00, GT5 is 0:57:00, GT6 is 0:54:00.
At the beginning of the year I was participating in the GT1 category but in the last races I had access to GT3 although far from the objective times (1:04:48x)
Well, apart from what has already been said about the engine changes, for this race ichanged the rims. Moving from Sport 185/55/R14 tires to Semi-Slick 195/50/R15 tires.
I also paid attention to some of the recommendations of @Mr_Gormsby by placing rubber stops on the rear suspension. However, I returned the front configuration to my lowest and harder setting.
The issue of suspension I have to sit down to work on, but I already have an idea. Hard spring rear, soft spring front but lower than the original ones, front camber between -3 ° and -4 °. hard shocks rear and soft shocks front.
i’m worried about the caster … today I have 3 ° but I must hope to reach 6 ° … but I have no idea how to do it.
In spite of everything, the car looks much more stable in the corners, although I think the tires do a lot of the work.
Here are some photos and videos of how it looked on track
Returning to the performance of the car … honestly I thought it would be more noticeable, the car was faster and won the category with a time of 1:03:1xx, 1.3 seconds faster than the previous time, I feel that learning to handle it can reach 1:02:5xx but no more from there.
This is a comparison of the previous best-time against the actual best-time, in general what I see is that the car turn faster and I think this is more effect of the tires than the engine itself.
Well, in spite of everything I can’t complain, very happy for the first place. Also my family went to see me and my eldest son wanted to go up to the podium with me
Finally to tell them about the ecu, in the end I bought a piggyback, that is coming somewhere in the world, I hope that the change in the engine is more noticeable once it is installed. Here is the website for you to see
See you later.
Great to see you on the podium with your son. Well done.
Have a look through my build thread. Find the pictures of the front sway bar mod. Should get you one or two reg more castor. Also the pics of the strut tops, if orientated to move rearward you get more castor.
Car is looking great. Love the wheels. excellent constant improvements and congrats on the win!
