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Andy

Turbo Squareback - 20 year refresh

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Jake

Looks sweet in that pic, the only thing I'd be personally worried about is a stone or something ploughing through the oil cooler or air filter as the fogs are fully cut out.

Polo's like this need to be in mags more imo.

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Andy

Air filter isn't directly behind the open fog lamp orifice, it's just above it, so should be okay. Oil cooler is behind the radiator grille - it's the catch tank that's behind the other fog lamp recess.

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harris.racing

Yeah spoken to some actual people instead of reading the net gravity centre seem quite good, especially Porsche wise so :)

Iv found the 86c to be quite toe sensitive, can massively alter steering feel but it's a trade off with speed as you can gain a really positive response steering feel but then at speed it's shit and not stable at all lolz

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MartinB

The ultimate sleeper now looks even better!

Well done :)

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Andy

Thanks for all the positive comments!

Just got this back from Centre Gravity after a lengthy geometry setup on both mine and Yoof's Polos. Was an educational trip as well as a productive one. I don't profess to be a chassis expert, so please take the following in that context!

Interestingly, although the damping I'd set on the Gaz coilovers was out by a country mile - and my spring rates are on the hard side, my DIY geometry setup wasn't too ridiculous. String, spirit levels, rulers and measuring tapes can get you to a decent position if you've got a flat surface - though I think some luck and a straight shell also help!

Ride Height

I'd set my ride heights myself, turned out FR and FL were the same to the nearest mm, and RR and RL only 1mm out. Time with a metal rule and coilover C-spanners paid off. The car isn't low, but I'd set the ride height as a compromise between aesthetics and suspension travel - biased towards the latter, as last time I checked cars were for driving. Feedback was that suspension travel is good.

Dampers

The car was put on a damper dyno, to check the damper effectiveness. Data from this, coupled with a test drive, enabled CG to significantly alter my randomly-guessed damper settings to something sensible.

Weight

Total car mass, with >3/4 tank of fuel and full washer bottle was 841kg. I have a full interior, no spare wheel, but things like interior rubber mats etc. in the car too. Put it down to half a tank of fuel, and it'd pretty closely match the official G40 weight. Not bad considering massive radiator, intercooler, big heavy exhaust etc. So far so good!

Most places won't touch the rear axle on the Polo, as the computer tells them it's not adjustable. This isn't the opinion of CG thankfully... I'd bolted on a straight-looking G40 rear axle, and aligned the brackets based on the original marks in the underseal. It appears that on a straightish car with a straightish axle that this is a decent place to start.

Rear Axle Before

Camber Left -1°52'

Camber Right -1°29'

Toe Left +0°12'

Toe Right +0°18'

So, it had some negative camber at the back - as most Polos that are straight and have been lowered will have. It wasn't even both sides (remember 60 minutes in a degree, not 100 - so 52' is nearly 1°) but not horrific either.

Toe out is, I believe, desirable to a certain extent on the rear of a FWD track car, as it helps the rear to grip mid-turn and aids turn-in. However, for a road car you don't want the rear to be too lively - predictable and controllable is the aim of the game.

So therefore there was scope to improve...

Rear Axle After

Camber Left -1°29'

Camber Right -1°30'

Toe Left -0°01'

Toe Right +0°07'

As my axle and chassis seemed to be straight, no tweaking on the axle mounts was required - just Eibach shims behind the stub axles.

Rear cambers are now very even, and toe much more appropriate for a road car.

As most geometry setups reference the rear in one way or another, it's important to get this right! Then it was on to the front end - really the whole point of the exercise, as with a Stage 3 frame and adjustable TCAs there's a lot more to setup than on a stock Polo.

Now here is where things are interesting, as I'd previously set camber and toe using some borrowed gauges, then taken it all apart and fitted Gaz coilovers, but I kept the TCA and compression strut lengths the same. This meant that on rebuild I had a starting point.

All I'd done on the rebuild was leave the TCAs as they were (I no longer had a decent way of measuring camber), measure the wheelbase to set compression struts (a crude way of setting castor) and got out the string and measuring stick to attempt to set the toe roughly parallel. The results were surprising!

Front Axle Before

Castor Left +2°15'

Castor Right +2°17'

Camber Left -1°23'

Camber Right -1°18'

Toe Left +0°16'

Toe Right +0°16'

Positive castor of around 2 degrees is what we're aiming for, so the 'setting wheelbase' method I'd used seemed to be acceptable here!

Camber is presumably a product of the TCAs staying the same length from when I borrowed kit to set it up last time - and a dose of luck. This amount of camber is not bad for a road car either.

Toe was set to toe-in, though I was aiming for parallel. Not bad for the old fashioned 'string method' though. Definitely some luck in getting it equal both sides.

So the aim was for improvements, but bearing in mind changing any one parameter affects the others, this is a highly iterative process - and hence time consuming. With string etc. it's all possible to do, but would take weeks and bore me to tears. The objective was to keep similar camber and castor to what I had, but had a touch of toe-out. Adding this toe-out aids turn-in, but also is supposed to assist traction, as under acceleration the front wheels have a tendency to toe-in on a FWD car - so a bit of static toe-out means your wheels end up closer to parallel when you put your foot down.

Front Axle After

Castor Left +2°15'

Castor Right +2°06'

Camber Left -1°22'

Camber Right -1°25'

Toe Left -0°09'

Toe Right -0°09'

These might not seem like drastic changes, but they involved cutting down one of the TCAs to get the right amount of adjustment, so weren't done in 5 minutes - and required adjusting all aspects of the front end, not just the steering arm!

So, nice numbers - but ultimately this is all bollocks if it doesn't drive very well. The test drive was an eye opener.

Conclusions

I need to do some miles to decide whether spring rates need softening up, but the work done to arrive at the current damper settings took the car from utter shite to tolerable. Now this is a toy car, so tolerable ride comfort might be acceptable if the handling benefits are there...

I've gone from a soggy -40mm FK kit with no ARB to 325lb/200lb front/rear springs with no ARB - so it's no shock that body roll is massively improved. Damper settings were critical to making the car driveable with these spring rates though. If I can live with the ride quality, then I won't be bothering with an ARB - roll is much much much better now.

Conveying how the car now feels to drive is difficult, as this is more subjective and less science. Turn-in is improved - but was okay before from what I remember - definitely better now though. Mid-corner stability and traction are greatly improved, and the rear end likes to follow you round a bend now instead of staying put. This is a big improvement for a FWD car.

I'm going to see how I get on with the front toe-out, as I've always had it set parallel before - so need to get some miles on to review this. I like the turn-in improvement it brings, and certainly traction is better, but I still need to get used to the slightly more active steering you get as a result. No bother though, CG will happily tweak if required in the future.

Before the setup I could throw the car around, but not with the confidence that the chassis balance now inspires. This surprised me, as I've owned this Polo for 13 years, so know it pretty well. It's still no sportscar, but it's an awful lot better than a 20+ year old shopping trolley ought to be! I now need to put miles on the car, and contemplate further tweaks to optimise.

Three words probably sum up what I think this exercise achieved - confidence, balance and control.

Review will follow in due course from Yoof once he's had his car back out on track. His setup was more involved due to track orientated nature of the car, additional adjustability, and what's presumed to be consequences of his Oulton crash on the rear of the car.

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harris.racing

Nice write up mate, makes sense to me.

I think people massively under estimate the effect of where the wheels (the only thing on the car in contact with the ground) are pointing.

Damper settings for yours will probably be a lot different to mine anyway with the spring rates you have, IMO mines under damped in compression on the front, but nothing I can do about that without pulling them apart. Intreaged to go for a drive in it, really need to pay attention to the chassis on mine, its going to have a bit of a chassis alteration when I change engine I think, make the handling better suited to a track, a compromise for the road obviously, but like you say - a toy..mine was a daily previously.

Might pop round next friday evening if youre about?

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MikeyMK

Well executed build, great looking motor inside and out, looking like it could've been done by a whole specialist team at VW. Only, then it wouldn't have been RHD..

Congrats on the bab, btw baby.gif

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Andy

Thanks for all the positive comments again guys!

Took it to the Pod last weekend, ran a 13.4 @ 104.5mph, but only did 4 runs as it was so busy. On a quieter day when I can get dialled-in to the car more I'm confident it can go quicker as my 60ft times weren't great.

Pretty pleased with the time regardless though, as it beat my previous PB, and only setup was swapping the front wheels out for slicks - kept the full interior in and left the suspension in its road setup guise.

Currently trying to track down the cause of some handling discontinuity when on full-throttle, one of my rose-joints is shagged so need to replace that, but will go over everything else to check all is well. With that sorted I can then make a call on whether to go slightly softer on my spring rates or not.

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harris.racing

Sounds good mate - good time also considering you only had 4 runs, that's only just about long enough to get a feel for it let alone do much useful lol.

Did Yoofy run his too or?

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Andy

New rose joint on to replace the fooked one, and adjusted/trimmed the rear gearbox mount to try and give a bit more clearance around the gearbox. Need some time for a road test to see if the rose joint has sorted the handling out.

Also ordered some softer springs so I can experiment with ride vs handling trade-offs.

Oh, and put some mapping time into my own car for once. Now has half-acceptable AFRs on what, but more tweaking to do.

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mark_crox

How is this going now? Any updates?

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Andy

Only just seen your post Mark! Been a bit busy with other stuff of late, but have done a bit to the car this year.

Tried some softer springs, which are better - but I want to revisit the geometry settings and look for a bit more caster. Have an ARB that might fit too, but need more time than I've got at the moment to get stuck into that one.

Also playing with different throttle body types to get a more progressive response, as the 3F item I use only gives about 30% throttle for 70% pedal input.

Oh, and I've built another turbo to try as well. Just a different trim K03 to what I had before, but hopefully will spool a little earlier and make the same boost more efficiently.

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herrod

Awesome read! Great to see long time members still going strong. This has got me craving another!

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jonny s

amazing colour build the lot ....

any updates?

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Buxton

whats happened to this? any updates?

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G40NUT

Vow! Read the whole tread tonight. Made me realize that I really need to get mine up and running

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