ZS VVC track car project

[Supercharged_Z]

many moons ago i used to say that the zs did not need a diff. My supercharged ZS generally did not wheel spin at all on track.

When I purchased the VAG ZS, it became apparent that I was probably mistaken. The ability to plant your foot knowing the tyres will not light up was mental. IT would literally drag you around the corner.

However, that was a 300bhp 300 torques mental turbo car, part of me wonders if i could of floored it in the supercharged zs at the same time as the vag zs on a corner and because the supercharged zs was down on power and torque. While I want to say yet just to argue for the sake of it. I generally believe I couldn't, the way the quaiff diff worked was just unreal.

You know what your doing for sure, but don't dis credit a quaiff or even a type B if it comes up cheap enough.

[Mark S]

yep, if the car had torque, or if it was to be used in racing, a diff is a must.

From experience, the type B just doesn't cut it.

Not tried a 'quaife', but had similar diffs in other stuff, but they are not a patch on a well sorted plate diff.

I am a big fan of plate diffs, but I wouldn't buy a used one, they need setting up properly and bedding in properly and there's often a reason why there for sale.

Totally agree, if it was a big budget project, a carbon plate diff would be the only choice.

[talkingcars]

I am told the torsen A was better than the b but more fragile - personally I've never tried any diff in a car, just in my 26t crane truck.

[petet16]

Yes, the type A had a habit of shearing the bearing journal off the l/h side

[p_b82]

I guess for the lighter and much lower torque generating VVC, the dif is not as critical, but (rally_)Matt runs the quaife on his ZR 160 rally cars (even if they did start life as 25's on the paperwork). Although he did switch to a custom one a friend of his built - although I am not sure if he switched them on all the cars.

I found personally with the diesel and the huge slug of torque they generate, the quaife on the road was one of the biggest differences I found, as I have to be be being really stupid to get the car to understeer now - with the change in suspension, that limit is now even higher than it was before.

Short of driver tuition, the diff is Matt's honest opinion for the gaining the biggest jump in laptime over a 'standard' car/setup if you were to do just the one mod to it.

Either way - really good post, glad to see that you have got what you hoped to get out the car and long may it continue

[ZS Phil]

As always, thanks for such a lengthy reply and advice.
I am gathering an understanding of roll centers, roll axis, bump steer etc and appreciate that a "slammed" car isn't necessarily best unless the suspension geometry is compensated for.
I plan to get under the two cars (one currently standard, one lowered significantly) and get measurements to establish where the roll center is on the standard car and exactly how lowering the other one has influenced this.
Once I have quantified it I will then make the decision of compensation (with stiffer springs) or to try and correct (with extended ball joints of appropriate length relative to the planned drop in ride height).
Unless you know of any working diagrams to save me measuring?

It's actually very interesting once you start digging into the theory behind these things isn't it.

I'm sorry to say that I went against your word and got some GAZ coilovers but for the money I paid, I just couldn't pass them up.

They do need a refurb though and some stiffer springs (they came off a 1.8). I was thinking of running the 325 lb/in currently on the front on the rear and getting some 550 lb/in to run on the front.
They normally come with 425 / 225 for the 180 so the above rates should give a slight proportional increase in stiffness without going silly. What do you think?

Originally Posted by Mark S

the twin pot accord type R brakes (300mm) and I use a 300mm disc I get machined up.

Were they the 300mm accord type r 5 stood discs you had re-drilled?

[Mark S]

Originally Posted by ZS Phil

Once I have quantified it I will then make the decision of compensation (with stiffer springs) or to try and correct (with extended ball joints of appropriate length relative to the planned drop in ride height).
Unless you know of any working diagrams to save me measuring?

They normally come with 425 / 225 for the 180 so the above rates should give a slight proportional increase in stiffness without going silly. What do you think?

Were they the 300mm accord type r 5 stood discs you had re-drilled?

Yes, you need to look at the 'big picture' of the car, avoid doing the easy stuff and leaving the difficult bits, it all works together.

There is software available to help simulate chassis, if you are OK with 3D cad software or xyz axis then it could be an interesting project, I wouldn't get too hung up at this point, lower it no more than 10mm and go testing.

No re-drilling, I got them machined up.

springs! Why not fit something like a 425-450 all round as a start point then test it and see where is best to go?

[ZS Phil]

It won't be with CAD, good old fashioned paper and a sharp pencil to make scale drawings. By the time I've learnt how to use CAD, I could be finished!

Who did you get the blank discs from?

Only trouble with getting the accord type r discs re drilled is the center bore is too large (70mm instead of the required 64mm). There are other 300mm honda discs with the correct 64mm center bore however they are then too thin (25mm as opposed to the required 28mm). Either way its a compromise so getting some "blank" accord type r discs would be best then get the 64mm bore and 4x100 studs drilled.

[Mark S]

I don't use a 28mm disc, the calipers weigh enough without adding extra weight to the discs.

I wouldn't recommend a narrower disc to the majority, but for those savvy enough to monitor pad wear they are fine, anyone with a decent maintenance programme of a track or race car will be changing their pads way before they hear the grinding of metal!

The discs I use cost me about £110 a pair by the time they are machined up correctly. Bit of a faff but the finished product is good.

Its easy to get hung up over a lot of things, a big budget project would have a bespoke braking system, a budget project needs a functional and safe system and maintenance after every track.test/race is essential at any level.

[ZS Phil]

Fair enough, seems logical

You got a contact for the disc supplier? There is a local machine shop I can use to do the rest.