Boost Dropping At High Rpm...

[MattMR2Turbo]

Hi all.

Before I start, here is my car spec:

'94 Rev3 turbo

Custom Exhaust with decat

Apexi Induction kit

Uprated leads

Bailey dump valve

Boost gauge and bleed valve

Right, I'm currently running my car with a bleed valve. I know this is a poor method of altering the boost levels and I will be changing to a grainger valve shortly. But, at the moment I'm running 1.0 of boost and acceleration through the gears is very good. However I do find that acceleration at higher speeds (100mph+) is not as good as I'd like it to be.

I had a race the other night with a Vauxhall Calibra V6 which surprisingly put up a very tough fight. I managed to get up the side of him at 130mph but it was extremely slow going past him

I have noticed though that my boost levels drop at higher rpms, mainly after 5k revs. I think it drops to something like 0.8 BAR. Could you tell me why this is happening and if this could be what appears to be slowing me down at higher speeds where I would need higher revs to keep the acceleration good?

If I was to get a grainger valve, I understand that if I set the boost level to say 17psi, it would stay there as pressure is only released from the valve at the desired level before it goes to the actuator?

Cheers

Matt

[Jimlad]

the actuator may have gone slightly soft

[MattMR2Turbo]

Hmm <_<

Am I right in thinking that this won't happen with a g-valve though?

[Jimlad]

the actuator is a part inside the turbo. If it has gone a bit soft, the only thing that will fix it is a new one/uprated one.

But it might not be this... only a suggestion.

[dj_davo]

also dont underestimate the calibra!

my last car was a cavalier v6 and i touched 150mph on quite a few occasions. fast cars, and what a sound

[MattMR2Turbo]

I did underestimate it and what a shock I got! One of my mates has put that V6 in a Nova, just waiting for it to get back from a bodyshop. That should be an animal

[pizza boy]

my last car was a cavalier v6 and i touched 150mph on quite a few occasions. fast cars, and what a sound

Well I can verify this...my m8 at work has a black bone stock Calibra V6 which we usually race on the M74 after work on the way home and it DOES NOT EVEN COMPARE..and please note this was BEFORE mods when my car was bone stock back in sept. We never have a a 'good race' I toy with him or toast him...we both know the Turbo is much much faster .

You should get your car RRd Matt its the only way youll know exatcly whats up and bleed valves are known to give extra lag. You might have a combo of problems..RR it and find out. Your rev3 100% should have left him trailing..it shouldnt have even been close whatsoever.

But yea the V6 sounds brilliant..like a beast and at £1.5-£2k Calibra V6s are bargains nice cars. And yea its pretty shocking but ive been in the car with him and he took it up to 150mph too..but the rear end was swinging it felt so damn dangerous!

[MattMR2Turbo]

Yea I know that, that's why I was so gobsmacked!

I can regularly beat Subaru's, 300ZX TT's, and just about keep up with M3's...

Maybe this one wasn't standard though?! Or maybe it wasn't a V6 at all?!

I'm going to a RR day soon, but it's just a run and printout but I'll see what happens there first.

[Dame]

Yep I borrowed a V6 Calibra for a weekend some years ago (had a mate at the garage), and hit 150. Very fast cars, and do sound lovely :)

[MattMR2Turbo]

So how does your Unichip control the boost levels Pizza Boy?

[dawesy]

i dont condone doing this as its not that safe fut you can "tweak" the pre load on the actuator by bending the mounting plate outwards a bit this has the effect of holing the wastegate shut a bit longer but go too far and you'll endup with over boost. id get a proper boost controller firs and see if it cures the problem

[jondh]

The ct26 runs out of steam after around 5,000rpms unless you have it upgraded...the exhaust portion of the turbo is just too restrictive. It is fairly normal to loose some boost at higher rpms on a stock turbo. Especially when you pump up the boost to ~15psi.

[MattMR2Turbo]

It's the rev3 turbo (C20?), so is that the same?

[jondh]

oh...thats right. You've got a c20b.

Honestly i'm not positive, but i'll check into it. the c20b is better than the c26...

[pizza boy]

So how does your Unichip control the boost levels Pizza Boy?

Not sure m8.All I know is that its been custom mapped carefully and safely within the cars boost+cooling limits.

Another concern is your car is running super rich too cos I remeber you postin a bit ago how your gettin constant flames. Your fuel consumption must be %$(ed needlessly..your car is chuckin in extra fuel and not using it for power instead igniting it out your tailpipes... waste of good optimax. Get a diagnostic done from an RR it will reveal problems you didnt even know existed, like Jimlads soft actuator...he didnt know until it got RR'd.

[MattMR2Turbo]

Yea ok, I think that sounds like the next step for me. I don't think I'm getting flames as such, just a 'pop' on hard gear changes.

From looking at your results I think I'm gonna save and get a Uni chip TBH