Sirion autoX build random questions

Projects builds and rides
1

OK guys new to the Dai scene, seems like this is the place to be.
So I’m an Aussie living in germany, mechanic by trade, looking to get into autoslalom (also known as autoX or motorkhana depending on where you come from)
Here in Germany there seems to be a lot of the sport awd sirion’s (102 PS motor) getting around, quite a few available for less than €1000, so this seems like a good entry point for me.
I can get OEM parts through work for ridiculously cheap, and I can do all the work myself.
Goal is to have one road registered for the purpose of driving to and from events so I don’t need to worry about trailers, tow vehicles ect. help keep costs to a minimum.
Would be nice to squeeze a bit more power and better handling out of it without spending crazy amounts of money.
So here come the random, bizarre and stupid questions.
Naturally intake and exhaust would be first on the cards, some of those Malaysian headers I have seen people talking about here, and a full exhaust. Just wanting to know if its worth going 2.5" or if that’s overkill?

Next I would be getting better springs and shocks for it, not a prob, there are a few options available here in Germany. But looking at swaybars, I’m hoping the rear can be doubled up or does anyone know if there are any other cars that have heavier swaybar with similar dimensions that will fit easy enough? Same for the front? (It would be cheaper for me to find a heavier swaybar from another car that fits or double up in the rear than it would be to buy aftermarket)

Next, anyone know what the AFR is like with these on standard tune? I would imagine these cars would be geared towards economy and the mixture would be pretty close to stotch? Thinking there might be some gains to be had by increasing fuel pressure by say 5psi or so.

Because the car would be for slalom racing in tight courses I would like to increase the rev limit by a few hundred. If I have a course with a straight for example that’s too short to shift to third but if I stay in second I’d hit the limiter it would be nice to have a few hundred extra rpm up my sleeve; so I’m curious if anyone has over-clocked an ECU on one of these? (Also why I’m asking about the AFR, if its already close to stotch over clocking the ECU could result in a lean mixture)

Also thinking of using a pot to modify the iat signal to give it a bit more fuel and a few degrees more timing. Anyone had a go at this?

Has anyone used a bee*r rev limiter on a dai or know if its compatible? (Not looking for bang bang its just a cheap option for launch control)

Any gains to be had by adjusting cam timing?

I know the comp on these motors is already high but has anyone shaved the head to increase comp? Any gains to be had here safely while staying with 98ron and factory tune?

What’s available in the way of under drive balancers and lightweight flywheels?

I think that’s about it for stupid questions… for now :slight_smile:

Other mods would be stripping the interior, strut brace, and since I’d have no back seats I’m thinking of fabricating a X-brace for the rear to bolt onto the 4 seat belt mounting points. And of course some better tyres/bigger rims. (If someone could recommend a good offset that gives a bit of poke, would be appreciated)
Hope I don’t get scalded too bad here, just looking for people who have done similar mods who can comment and share there ideas and experiences :slight_smile:

2

You have missed perhaps the most important item. An LSD will be essential. I guess you want the extra rear sway bar to make the thing turn, go with a higher rate rear spring - it will be right when you are lifting a rear wheel in corners. Some externally adjust Konis - not Malaysian rubbish. Hydraulic handbrake is essential. You’ll need to end up with a single brake line going to the rear or else there are a couple of really expensive master cylinder options either from AP or Subaru STI gpN. Next, as you realise look into the softset (at least front) race radial tires you can get onto it. Std brakes won’t cut it. At least fit the best cold pads you can get.

I’ve won Khanacross here outright years ago in under powered cars but with the suspension really well sorted. Just started doing them again and my last Khanacross I placed top 1/4 field in a NA Subaru wagon (my tow car) beating a heap of huge power cars. Soft tires, good brakes and handling really helps to keep corner speeds high. Once you have the chassis sorted and some experience with the car then turn up the wick.

3

Yeah I understand I should be focusing on handling first and foremost but the problem I have here in Germany is TÜV (registration) when I buy aftermarket parts if they don’t come with a TÜV guteschein (similar to an ADR approved certificate is aus) then I can’t get the car registered, I might get lucky finding coilovers that are compliant but with things like a hydro hand brake I have absolutely zero chance of getting rego. Without rego I would also end up in a different class and I’d be racing against the big boys straight away. I like the idea of having an LSD though, whats price and availability like for the sirion’s?

4

Also brakes would definitely be on the cards, looking at some slotted rotors and quality pads. Is the awd 4 whhel disc brake or drums in the rear?

5

No idea on the AWD discs as we don’t get that variant here. Typically the choice is to go with Appluase rear discs, however, the the piston size is really small (note MX5 rears are same casting and you may find ones with bigger bore). I have the Appluase rear discs with a 0.625 hydro h/brake and my 600kg is a bitch to slide. Bigger calipers are on the way.

6

Yeah I havnt had a look under one yet, not sure what to expect… I would imagine IRS and 4 wheel disc. Still hunting for one though all the good ones ore in south Germany and I’m living in the north, hopefully one pops up nearby otherwise I’ll have to make the drive

7

If I need to make the rear disc conversion what’ll I need? I guess a complete applause rear end would be best to scavange backing plates, caliper mounts ect. yeah?

8

In Queensland certification of parts is only an issue if you want to get rego, sell something on or get pulled over for inspection. Surely Koni dampers or Bilstiens would be certified? Of use a certified external leg and build your own. As a mechanic you’d find a way to pull a Koni strut insert apart and put those internal bits into the std Sirion strut. Surely springs don’t need certification or at least such would not be something checked if the spring was black. A good externally adjustable Kon and the right spring rate will be better than 99% of the coil overs out there.

I’d be slicking up you handbrake cable and modifying the leverage at the drum/disc - or else hiding a double hydro master cyl under the carpet with sneaky plumbing and have it actuated by the std h/brake.

Looking forward to hearing how it all goes.

9

I can get a set of H&R coilovers with certification for around €1000 but that’s starting to get out of my price range :frowning: (that’s approx $1500 aud) or I can go with KAW or einbach which would be similar to king springs for half the price.
What’s the go with these koni inserts, could you please elaborate?

10

For motorsport you at want to at least be able to have external bump adjustment. Most Malaysian stuff that has adjustment is not linear through the clicks and often the shocks are not matched and the quality of all the parts and tolerances are not a patch on a Koni. It is hard to predict what one click of adjustment will do let alone two or more clicks. Aside from the very first position and the last Konis are reliable/predictable in what the adjustment does. They are also rebuildable and with some experience you can rebuild them yourself and tune them a bit even with change of oil viscosity. The other beautiful thing is that you can use the internals of them and place them into something else. Here is a picture of standard Sirion leg that I have shortened, lowered the spring seat, moved the bracket down the leg and am about to install the insides of a Koni into (was from a MkI Suzuki GTI).

The strut seen it the bottom of the image is completed. Half a coil was removed from top and bottom of each spring also. Result was 80mm lower and vastly improved handling.
To get into something better than a Koni you might get a Bilstein to work (but not many are adjustable). Otherwise the only things better are going to something like a Penske or MCA both of which will be about $3000au a corner installed.

I don’t sell Koni but I have been through the mill with KYB, Tien, Tockico and a heap of other rubbish that cost me time and money.

check this out, might be some help or a better explanation on shocks/dampers

http://farnorthracing.com/autocross_secrets6.html

11

OK just to clarify, you disassemble the sirion’s strut and fit koni internals to it? Its just when I did a google search for koni inserts it looked like they were a blank strut that you’d weld your mount and spring seat directly onto. Also after you have a strut fully disassembled like in your photo how do you go about charging it again with nitrogen?

12

Another question, obviously when a strut is assembled the spring is already somewhat compressed, so how do you go about working out the location of the spring seat for the right about of preload on the spring?

13

These are twin tube non-pressurized. So no nitrogen.

Yes they look like a blank insert. The insides get pulled out of this and put into a factory leg after its internals have been removed. There are diff diameters and diff lengths. If you have lathe there is some leeway to shorten them further - a little.

14

I do a heap of measuring with springs in and out while the car sits on a trolley jack. Write it all down. I really want to know travel extents of the wheel and of the strut. From this you can calculate the percentages as to how much strut movement is as to wheel movements. It gets moved up and down to simulate the extents of travel. Sit it at desired ride height on stands without springs. For what you are doing I’d seek to keep about 70mm of travel before hitting the bump stops and same in drop. At all costs the front wheels must stay on the ground and you don’t want the strut hitting the bump stop. Should any of this happen you are taking away traction. Speaking of the front standard spring rate is an excellent place to start. Rear spring rates will prob need to go up quite a bit. To see if more rate makes a difference make some wedges or chocks to go inbetween the coils. Blocking a section of spring will stop that part working and increase rate. Go for a short drive, but make sure those things are well and truely attached. I use hard wood with holes drilled for jumbo zip ites. Anyway, spring seat gets lowered the correct percentage of ride height lowering - that is until it gets to within about 5mm of the where the inner edge of the tires you will run are and with any camber adjustment at max neg.

Did that make any sense?

15

Yeah think I got it.
So quick question, if I ordered a set of lowering springs with a better spring rate (say 30mm lower) then in theory I could use the standard legs as is just swap out the internals with koni inserts (provided I have the 70mm travel each way as you’ve described) and this would give me adjustable struts while maintaining the factory look of the stock parts so I can fly under the radar when it comes to rego while also lowering the car without cutting and welding mounts and spring seats?

Does koni make a set of inserts with the right dimensions fit the sirion’s legs without modification? (Don’t have access to a lathe)

If I get the info on spring rate could you recommend which inserts to use? (If seen some of your posts and topics on this site and looks like your a very knowlegable guy)

16

Also when thinking about this some more questions come to mind, first of all when you say 70mm travel from ride height to bump stop, and from ride height to full drop this would be measured from the wheel or from the strut?
Next, when making these measurements you would take the measurement of ride height while the spring is in the car, then measure the travel without the spring in the car, only the strut, yes?
So how would you take into consideration if your using a stiffer spring how this could affect the upward travel? I mean the travel would be there but there would also be a point where there isn’t enough force to compress the spring any further resulting in less upward travel than anticipated? (I hope you can understand what I’m trying to explain, I can picture it in my head but maybe not explain what I’m imagining so well)
Sorry for 101 questions, I just want to really understand everything before I get elbow deep and realise I’m in over my head.

17

Also it would be awesome if you knew of any cars that have springs with a better spring rate that would fit on the sirion struts, I can get OEM parts a hell of a lot cheaper than aftermarket parts.

18

Rate and height are different things. You can have a 30mm drop with same rate. At guess front rate prob around 150lb/in. There are online calculators for getting an approx idea on this. Some calcs just do closed end springs but you want to find one that does open end spring calculations.

Yep, std leg with Koni is the goal.

The easy route for you is an insert that bolts in. You see, many modern original struts are sealed and will require the top being cut off - does yours have big nuts on the top or do they seem to be welded or crimped? The new insert is slide in and held in place via a bolt that goes up through a hole drilled in the bottom. The outer casing of the Koni has some small impressions in the casing at the top which make it fit tightly. Not optimal but better than std. There may or may not be an insert that works.

The better route which needs more problem solving is pulling the insides out of an insert. You will be able to use a bigger diameter unit since there is no need to allow for the outer shield/casing. I could explain this further but let’s establish if the top of your struts have a nut or not? To give you an idea on what to use it’d also be useful to know at least the outside diameter of your leg. Pic of you car too so I can be absolutely clear on the model.

19

You’ll have to take a stab at what cars might have something similar and start measuring to find something that has the same open end diameters and work from there.

20

Ok, I’m starting to get a pretty good idea of how to go about this, thanks!
Here is what I’m looking at buying, they are a fair way away from where I am living, at the moment I’m holding out on buying in case somthing comes up that’s closer to where I live.

The first 2 are awd with 102ps and the 3rd is fwd with 102ps but already has eibach springs and a sports exhaust and these have been certified for TÜV.

https://m.mobile.de/auto-inserat/daihatsu-sirion-allrad-sport-winterreifen-mp3-elek-fenst-rauenberg-gewerbegebiet/240241963.html?ref=srp

https://m.mobile.de/auto-inserat/daihatsu-sirion-1-3-awd-4x4-euro-3-struppen/237936983.html?ref=srp

https://m.mobile.de/auto-inserat/daihatsu-daihatsu-sirion-1-3l-lenningen/243512751.html?ref=srp