Liam's Z4C race car project

[enuff_zed]

Just watched the video.

'Probably the most successful club racer'
'Brilliant tactician'

Well done God!

[thornad]

Hi Liam,

Killer thread, a joy to read.
How are you getting along with the GAZ Mono coilovers?
Some Z-Cars racers said they are terrible and that the spring values seem to be completely off.

I bought a 2004 E85 Z4 (M54 engine) race car built for the Z-Carts series (but never raced) using the GAZ Mono kit, and it has almost no rear compliance. I do have a 3.73 diff with LSD, but still...
I can go into oversteer way too easy with a bit of lock and just 1/3rd throttle in 4th gear in the dry (on MTF ZTR tyres 215/45/17). The rear also seems very rigid when pressing down on it, even on the softest settings.
My rake seems to be pretty high too, the rear being about 25-30mm higher than the front.
Alignment is Camber 3 degrees front, 2 degrees rear, and toe 0.2 degrees (or 12 minutes, or 2mm) toe-out in front, and same amount but toe-in in the rear (for each wheel). Stock roll-bars.

So I was really wondering how did you manage to do so well on them? Or did you have any issues not mentioned in the thread? Did you have to make changes to the setup?

Thank you,

Adi

[Liam22]

AFAIK, the ZCars series ran the GAZ Gold dampers (not the monos).

I very quickly changed the spring rates so I'm not using the ZCars setup at all. Whoever spec'd the ZCars spring rates didn't know what they were doing. I went stiffer, but also changed the front/rear delta. I run the damping at about half-way on the front and 3/4 on the rear.

My ARBs are M3 CSL front and M3 cabriolet rear.

Rake is about 5-10mm higher at the rear.

Alignment is parallel front (+0.5mm, -0mm) and as much toe out as I can get at the rear.

Camber is similar to you, but I don't have my setup book to hand.

Tyres are 225 front and 255 rear (17") Nangkang AR-1 at ~21-22psi cold.

[thornad]

Many thanks for the prompt answer Liam, I really appreciate all the info.
I'm pretty sure it's the Monos, at least this is what I have on my car, but not sure about the spring rates.

http://www.dropbox.com/scl/fi/n2pea4lz4 ... jrn8k&dl=0

What do you mean you changed the front/rear delta ?

And if you don't mind, what springs rates (and length) are you using? Do you have the GAZ product number ?

[Andrew J]

I was travelling down south for a holiday back in March and completely forgotten I'd taken this picture. If I remember rightly we were on the A43 so potentially a Silverstone day? Anyway, car looked ace, proper mean!

[1536Z4]

Found this on You Tube . You have another admirer Liam . Any updates for us ?

[thornad]

Sorry to be a pain Liam, can you please tell me the actual values you went for the spring rates in the end ?

Thank you,

[Liam22]

It's been a while since an update but the Z4 is still going strong.

Found a bit more power over the winter by removing the MILVs and fitting an AFE induction kit. I was skeptical about the induction but my tuner thought it was the bottleneck and he was right.

I tried 2 options:

1. Home-made 3D-printed adapter to fit a K&N cone filter to the top-half of the OE airbox. This was worth +3bhp
2. AFE - this was worth +6bhp

20240303_111631.jpg (195.98 KiB) Viewed 360 times

So we're now at 273bhp (flywheel)

Maybe now the MILVs will help - I dunno. They're back on the shelf. BTW, refitting the OE intake lifter supports is a lot more difficult than fitting the modified ones! It was sketchy…

Enjoyed a 1hr15min race at Brands Hatch GP circuit at the weekend. Playing with the big boys in Porsches, M3s and TCR cars. The little Z4 held its own pretty well. Almost got fastest lap (class B) but a poor finishing position as the car wouldn't restart after refuelling. Went 3 laps down but had great battles all race.

https://www.youtube.com/watch?v=CXAFED95ebY

[axelleveau]

Cool update Liam

There is a thread running on the forum talking about MILVs as well. Both this and your thread got me thinking that someone has got to try the MAF + Throttle delete and run 3D printed velocity stacks with a remap to make all controls rely on the Valvetronic It should be possible to make a big airbox and filter to go alongside those trumpets similar to a N54 box

[Liam22]

There is a thread running on the forum talking about MILVs as well. Both this and your thread got me thinking that someone has got to try the MAF + Throttle delete and run 3D printed velocity stacks with a remap to make all controls rely on the Valvetronic

I just saw that discussion (reminded me to show up here more often!) and MILVs do seem to be a polarising topic.

I'd been toying with the idea of using a N53 cylinder head to get a lighter top end (no Valvetronic enabling higher rev limit) and direct injection. But that's probably an awful lot of work and experimentation for modest gains.

[axelleveau]

I'd been toying with the idea of using a N53 cylinder head to get a lighter top end (no Valvetronic enabling higher rev limit) and direct injection. But that's probably an awful lot of work and experimentation for modest gains.

I would guess the direct injection will not help much for top end? From your current dyno, would you benefit from more revs at red line or is the engine laying over? If the second then I would work on helping air flow rather than pushing revs, hence the crazy idea of ditching the intake manifold completely and going for an N54 style airbox. As you are on a budget, a set of 3D printed velocity stacks bounded on some airbox volume (maybe large PVC pipe ) which gets filtered by a cone filter could work

[1536Z4]

As you are on a budget, a set of 3D printed velocity stacks bounded on some airbox volume (maybe large PVC pipe ) which gets filtered by a cone filter could work

It`s already being developed by Raimund and 22 RPD tuning https://www.e90post.com/forums/showthread.php?t=2063463 .

[Liam22]

Well, wow! I only need another 15bhp to get to my class limit...

[Mr Tidy]

I loved your video Liam!

Brands GP circuit is fantastic - Indy is nothing special IMHO.

Maybe you could share your plans for this year with us. I'd love to give some support to an E86, and nearly did last year at Donnington but sadly you left early.

[Liam22]

Maybe you could share your plans for this year with us.

It's all a bit ad hoc at the moment as life and work gets in the way! I only entered BHGP with less than a week to go.

Next one is Cadwell Park, 21st July.