Sirion AWD conversion/ autocross build

I’ve thought about a few of your problems, and here’s what I came up with:

About the strut tops:
There is a ridiculous amount of parts that are interchangeable between the Cuore, Sirion and YRV. I know there are adjustable strut tops available for Cuores, in both camber and caster. Eventhough they’re mostly from Malaysia, they do exist, so they may be available closer to home as well. I wouldn’t be surprised if you can use those for a Sirion. I happen to have a YRV donor car atm, so I could compare those struts to the stock ones from an L7 (I’m driving on BC coilovers myself).

About the rear axle:
Now this may seem a bit extreme, since you’ve put a tonne of work into your AWD swap so far, but maybe it’s worth thinking about FWD. Obviously, AWD gives you more traction, and it makes sense why you did the conversion. However, I’m wondering how much you actually gain from the AWD system. You know the car best, so maybe this doesn’t apply to your car, but these are my thoughts:

FWD means a torsion beam rear axle (in case of the Sirion). The obvious advantages compared to AWD, are less drivetrain losses, less weight, and a simpler construction. But that may not be enough to make up for the traction disadvantage. I think the biggest difference will be the handling. When cornering, the outer wheel will gain camber and toe out, which will result in the car wanting oversteer more (which might help with those tight corners). Relatively though, because it all depends on the rest of the car. On top of that, you can put a swaybar on the rear axle. I’m not sure if all Sirions got one from the factory, but I know they exist. Anyway, that’s another option for adjustability.

What I’m trying to say is, that although you would lose traction (especially from the start), you might be able to gain some time because of the decreased weight, decreased drivetrain losses, and improved handling. I’m guessing you’ve already thought about this, but it might help.

If you want to go independent, I guess you’d have to get the rear suspension from a Charade G200 or Gran Move, as they have independent rear suspension. I don’t think it’s worth the hassle though.

Edit: I might have used the term ‘torsion beam’ incorrectly. Should have been ‘twist beam’.

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YRV left, Cuore L7 right


Cuore L7 left, YRV right

There appears to be no difference between the two struts (apart from the springs). Today I got the chance to compare the two, so I thought I’d share it, in case you needed to know for the strut tops!

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I appreciate you taking the effort, unfortunately it doesn’t help me. I maybe wasn’t clear when I was explaining it, I built custom strut tops with uniball pivots, which move the top of the strut inwards and rearwards to increase camber, castor and spread. There is still some room to increase further, but I don’t have the motivation to cut the steel plate by hand.

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Ah yes, I misunderstood that. I thought they were fixed in place, instead of movable. My bad!

Did you read my other post about the rear axle as well? I’m curious about your thoughts :slight_smile:

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If it were to go FWD, just about anything will work in the back provided everything points in the right direction and the spring rate and damping is right. Trailing arms instead of a beam axle may not really produce any reasonable benefit. The beam can be bent to get the needed camber. And to get the weight transfer to the front the rear needs to be stiff and wheel travel limited. A tiny tiny sway bar could be added but should only be there for track day adjustment. To go to the effort of fabricating something for the back an unequal wishbone rear would be a better thing. Where I am such mod’s put you into “sports sedan” which is a wild category here. In fact, that was one minor reason for dropping my work on the Mira. I really wanted to run proper radius rods on the front. But that one mod put the Mira into a catagory in which it would never be competitive. To start with the minimium wieght is around 800kg. Another thing with dropping the progress was that I wanted to run GSXR600 pistons and could have ened up with a 1100cc ejve but for the price of custom rods I could buy a Hyabusa engine. All the while I was running out of working space. Enouhg of hijacking this thread.

Mick you can bend the rear diff housing to get perhaps up to half a degree neg camber. A quarter of a degree neg each side should be safe. I’ve worked on a few live axle rear-wheel drive cars with CVs inside the axle housing, wedges and rod ends for camber and toe. You may have seen this sort of thing already as it is a mainstay in highly modded Ford Escorts.

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First update in a while :slightly_smiling_face:

I got the rear shocks finished up, also had them on a shock dyno before installing the new lower mounts, just to see how my valving actually was.

Blue is left and red is right. The difference was concerning at first, but after disassembling and inspecting everything to install the new forks, I found the left side had a noticeable amount less oil in it compared to the right. Im pretty sure this my fault from the first assembly.

The bump adjustment has a small influence on the very low speed area, and the rebound adjustment has an effect on the whole working range from low speed through to high speed, nice to know. The rebound is also pretty hard on the shocks, but I’m sure it’s a good thing as the rear axle is pretty heavy.

I also did some playing around with the front geometry, some more info can be found here

I only installed 10mm spacers, the bolts were too short to test any more than that. The results look promising, and longer bolts have been ordered for further testing.

I have been working on setting up a small mobile workshop with all my trackday gear, here are a few pics of how it’s looking so far

https://youtube.com/shorts/IBoJd3MdhJg?feature=share

I finished my tire pyrometer and had a chance on Sunday to test it out at the first race this year. Seems to work pretty well :sunglasses:

Speaking of the race on Sunday, the weather man said it would be raining the whole day. I decided to take semi slicks, turns out it was super sunny, and the other guys were on slicks.

Still managed to score 2nd place though :smirk:




Sorry it was soo long since my last update, I will try to post more regularly now that the racing season is in full swing :v:

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I’ve had a bit going on since the race at Diepholz…

I’ve always been a bit disappointed with the big semi slicks, the rims are super heavy, the tires too, it’s too hard to get temperature into them, it’s a lot of unsprung mass, and so on.

So I decided to sell them and go all in on another set of 13’s, with a set of proper rain Tyres.

I went straight for a set of the Renault Twingo Shmoor rims, I didn’t want to experiment, and I know these will fit over the Copen brakes. A bit of a clean up and a fresh lick of paint and they are looking nice :sunglasses:

I then got in touch with my guy in Italy and ordered a set of Formula 3 Pirelli Rain Tyres to go on them

I quite like the color scheme, my girlfriend hates it though :joy:

I had a race at Bremerhaven and unfortunately the rain Tyres hadn’t arrived on time, so I went with slicks. Ended up staying dry, but I had a pretty average day. Ended up in 2nd in one of the race’s, but only first place got a trophy as there weren’t enough entrants in the open class on that day. First place went to a guy named Tony Tute, who normally completes on a national level. His front suspension alone was worth more than my whole car :pensive: Unfortunately I don’t have any photos, still waiting for the photographer to post them online.

Between runs I was logging my tire temps, which were unfortunately pretty low. I also brought to my attention that I was running too much toe in, good to know.



I spent a lot of time assessing videos of previous races and talking to a lot of different people, and decided to stiffen up the front a bit. The suspension frequency at 2.5 Hz was a bit soft for the slicks, and now that the semis are gone there is no need for a compromise. I ordered a pair of 70N/mm springs for the front, and added a rubber spring travel limiter to the rear to more or less remove the function of one coil.

I also decided to address something that had been bothering me for a while, the front control arm to swaybar bushes. I had already installed the upgraded items from Siberian Bushes, but there were still pretty soft. The movement that occurs in this area causes big geometry changes, so I figured I’d have a go at addressing the issue.

A member on the Facebook page shared a .step file of the original bushes, and I used this as a base to design a mould for casting some replacements.


Those were the first attempts, I had some problems getting air bubbles out of the moulds, and after some test fitting I had a pretty good idea where I could add extra material and reshape the bushes for some improvement.


The second attempt, happy with the shape, and almost no air bubbles. The mould design was optimized again, and this time a full set were cast using Polyurethane with a shore 90 rating (same hardness as power flex black series)




They are asymmetrical to help reduce lateral movement, and there are two different sizes. The thinner ones go on the front side of the control arms, and the thicker ones on the rear. This moves the ball joint forward, increasing castor :sunglasses:

All of the improvements got a good testing at the last race in Oldenburg. The car handles much nicer now, and I managed to take home a win and a 2nd, and some of the fastest times for the day.

Currently sitting in first place for the championship :muscle:
I will add some photos from Oldenburg and Bremerhaven once they are available online.

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Congratulations with your championship lead. Your car looks great with those wheels! When are you going to make and sell your bushes? I need a set!!!

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Those are some cool new mods!

What tool do you use for measuring the tire temperatures? Tires can cool very quickly, so to get a good idea of what temperatures your tires are reaching, you’d need infrared sensors in the wheel well and monitor them while driving (especially while cornering).

Keep up the good work! :smiley:

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I measure the core temperature with a k-type thermocouple needle. Measuring with infrared you really have trouble with them cooling too quickly. The core temperature remains consistent for at least a few minutes after the run.

This is a device I designed myself that can log the temps to an as card

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Is the excess toe problem perhaps from sway bar flex as it performs radius rod duties?

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I actually was running like 1° or something ridiculous. I adjusted it back to 0 and during the lunch break at the last race gave it a few mm toe in to get some better temperature coverage.

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@Rallynrace I can send you the file for the moulds if you wanna have a crack at casting them yourself.

I could also do a set for you cover the material and postage cost.

I plan to uninstall them at some point and inspect how they are going, but so far it’s looking good.

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Thank you Mick,
I am busy rebuilding the rally car at the moment and I am around 3 or 4 weeks away from building up the front suspension. My Post Code in the UK is B49 5PP. I can send you funds through Paypal or direct, please let me know.
Best regards,
Trevor.

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https://www.instagram.com/mickeywilkinson/

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Been a hell of a journey guys. Big thanks to the OG‘s @Mr_Gormsby @evilhighway @b_hoves @FrAsErTaG and everyone else on here keeping the forum alive.

I am pretty hyped, and looking forward to improving the car even further for next season :grin:

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Mick your fantastic write ups on what you are doing certainly helps keep things alive. The forum is like an animal that has to keep being fed and taken for walks etc

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Congrats on the 1st place! This build has been a pleasure to watch. The skills, knowledge and ingenuity you’ve shown is nothing short of amazing.
Looking forward to seeing where you take the car next!

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well done mate 1st place and 10th overall. Congrats!.
As Mr G and b_hoves has stated your write-up’s knowledge and the willingness to share it all here is and help other’s. It is the people such as yourself that do this help keep this forum alive. Well done! and thankyou for being a part of it.
I look forward to what you are doing next. I love your electronic technical knowledge also.

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