Sams Polo 3.0

[sambb]

and these guys go right through the Yaris chassis - cnr weights, supension, alignments, brakes etc

Toyota goes Back to the Future with the GR Yaris GR-Four | fullBOOST - YouTube

[seangti]

Thanks Sam and Gavin, sounds like porting the exhaust manifold may be the smartest move for me, followed by review of tune. I think I have a spare manifold here, so to source someone to port it. It's the low and mid-range I'm thinking to address, the turbo doesn't really engage without a reasonable level of acceleration and slow to boost. WOT power is fine, more would be nice and can be done (only ~16 psi atm), but more linear power and throttle response is the goal (which admittedly is difficult on boosted cars).

[sambb]

The other thing you could do Sean is bit by bit increase the diameter of the inter cooler piping. The steel pipe across the back/top of the engine is 2/1/4 in but then once they drop down around the crank pulley etc they are nominally 2inch but when you look inside the pipes at the click joins etc they are actually more like 45mm. That can be done bit by bit without breaking the bank and should yield some better breathing.
Do you have a forge IC or SEAT?

[sambb]

Sean I have a spare exhaust mani (the one that was gasket matched). Its spoken for at the moment but due to our lockdown there'll be a wait on getting it to the guy who wants it. If that falls through for any reason I'll let you know.

[sambb]

for any of the guys who have cut the dome off their strut towers to allow adjustable top access, heres a good trick to cover the hole and make it look factory.........provided you have spare dead headlights. The black flexible cover that goes over the globe access hole on the headlights fits perefectly over it as a factory looking dust cover.

[sambb]

so after finally getting the MCA fronts corrected so that I could fit them up, I moved onto the back MCA's. They were untouched in the accident and had just been waiting to go back in once the front was stiffened up to match.
This time I thought I'd check everything properly. After adding up the fully compressed heights of all the platforms, shims, helper springs etc and the working spring I calculated the fully spring bound length between bottom adjustment collar and the chassis. I then fitted up the dampers without the springs and jacked the beam to check that the damper length/bump stop position was correct. It turned out it wasn't. The springs would have been coil bound and the bump stop was only starting to be active. So I had to wind the base adjuster down to lengthen the damper body. This increases droop and pushes the top of the damper body closer to the bump stop. Once I got it so that the bump stop was fully compressed and the spring was a safe distance away from being coil bound I fit it all up.
Thats where the problems appear.

Basically to get the damper body length correct to prevent coil bind, you end up introducing so much droop that the main spring whilst still connected to the helper is not captive over the adjuster. Now I could spin up a cone shaped aluminium guide to fit into the end of that adjuster cup to get around this, but the other fundamental thing wrong is seen on the damper shaft. The cable tie on the shaft shows how much shaft is taken up in droop and how much is available for bump. After taking it out for a test drive the insufficient bump travel can be seen here:


the tell tale cable tie has been pushed to just below the bump stop. While it wasnt going to coil bind and throw me off the road it was only a smidgen off really hardening up in a nasty way. Once out on a circuit pulling much bigger cornering G's and then riding up an outside kerb, this would definitely be going well into the stop.
SSSSssooooo whats the solution. It seems that the keeper arrangement coupled with a low ride height really restricts travel. I could increase ride height to gain travel but then the springs would fall clean out at full droop, and I need it to operate at that ride height.
advice needed!!!

[simon k]

go ghetto like me.... cut down honda springs and old seatbelts as droop limiter straps

[sambb]

yeah the more I think about it, its going to have to be droop limiters. No body makes 8kg springs that are wound like H&R or KW 'sport springs' where they are designed to coil bind at one end when the car is on the ground - ie long enough to be captive at full droop yet stiffen up when on the ground. There's only the short main spring/helper spring arrangement for twist beams that I can see. So you're kind of snookered. The short springs you need to get a good enough rate are really prone to coil bind because you have to run the car arse down which gives you next to no bump travel. You cant run a taller say 180mm (up from 150mm) main spring either because to keep the ride height you want you couldnt run helpers and these would fall clean out of the back at full droop.
Yeah I think I'll have another look at verifying the coil bind vs bump stop setup. Maybe if I set it up so that it coil binds literally a mm after the stop is taken up ie no safety margin, then i'll eek out a bit less droop hopefully keeping the springs from unseating. If there's not much to be found there yep i'll be digging around under the house for old seat belts to make droop limiters like you did.
I will make cones to fit into the top of the spring seat cups to ensure they reseat smoothly. I hate the fact though that with that much sliding of helpers, the divider and the main spring up and down over the threads on the cups every time you jack the car that the threads are going to be minced soon.

[sambb]

In the pic you can see that under where the MCA rear bolts to the car in the wheel well, there's a whole assembly on the shaft for the damper adjustment which moves the bump stop down the shaft eating into travel. Comparing it to the KW damper that came out it has less shaft available. Admittedly when i removed the KW's there was no bump stop left. There were fragments of them up in the dust covers etc they had been obliterated and perished so it was running with no shaft stops. So it could be that the bump stop that was meant to on there was a long cone style or was even designed to have the long factory one transferred across onto it before installation. If so that may have brought the KW shaft travel out to the same length as the mca. But on the face of it the mca setup does appear to compromise available shaft. The lower stop position would normally be a non issue but I want its bum on the ground which is showing this up.

[sambb]

I think I want to do this. On my beam you could run the links out to the bottom damper bolt. The mid beam point could be clamped/bolted on initially to test its viability. It could be used to adjust toe very easily and also help fix that toe position over the usual operating ride height. At the extremes of travel though I'm sure you'd have to be careful that it wasnt having an adverse effect on toe or camber gain. Not something I could ever figure out but I'd love to hear from anyone who has run it or has knowledge of it.

[sambb]

here's a shot of one on an early golf. Good pic as it shows it with a rear ARB fitted too. Seems like a lot of unsprung weight to add when the only real gain over shims is the ability to adjust rear toe easily BUT toe adjustment is a biggn

1976 VolksWagen Golf Mk1 Track Car Build Project - YouTube

[HaydEn]

How much toe adjustment would there really be?

After all you’re just loading up a fairly solid structure (rear beam) If I recall those types of toe arms on MK1’s were to increase rigidity rather than adjustment


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[sambb]

Dunno. I was watching a vid where a common setup on rally mk2 ford escort (solid live axle RWD) that use the Atlas rear end uses links that tie back to the front of the diff casing to adjust toe by pulling on the live axle assembly. So I reckon a twisty twist beam would be plenty pliable enough to pull or push a couple of mm each side for adjustment in comparison to that. I've emailed SCCH to see if they did it just to lock in their toe or actually be able to adjust it.
On the Polo you'd have to make plates that would fit onto the bottom of the spring platforms to get the link low enough to clear the spare wheel well. They'd look like upside down strut brace mounts basically. If the additional weight was going to become an issue then I'd probably pull my finger out and go to an 'inside the beam' RARB to get the weight back to where it was.

[HaydEn]

If you could get close to where you want to be with washers or shims, then use the bars to force the beam to get the last 1mm or so, that would be awesome.

I just don’t think you’d be able to adjust the beam that much. Only my thoughts, no evidence to back up what I’m saying.


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[sambb]

me neither ha ha. It would be very cool to have the car on the ground on slide plates and just turn the rods and see an easy toe change. That'd be great but things never come that easy.
Still waiting to get my wishbones welded to take wishbone mounted drop links. Having to go into northern beaches ISO has sort of slowed things. I'm no welder so i'll leave that for a pro but the toe rods I can definitely wrangle now that i'll be back in a workshop and have a spare beam at home to build on.