How to get car to boost quicker

[Jacko]

Ok. My city doesnt boost until about 4000rpm and doesnt reach full boost (15psi) until around 5000rpm which is where there is a fuel cut, ignition cut, boost cut or something like that.

How do I make the boost come up earlier and also get it to boost quicker? I dont mind if I only run 10psi.

[Colza]

4000rpm is very high. You should be making boost before that. Check the turbo for excessive shaft play (take off the intake hose and see if you can wiggle the shaft from side to side or back and forward). Does the car smoke when you start it up and when you come on boost? There could also be a leak in your intake system somewhere, but id say that is unlikely if you can get up to 15psi!

Without an exhaust or a pod filter, you should not be able to get up to 15psi unless you have a boost controller tucked into there somwhere. If you have a boost controller, turn the boost down till you dont hit fuel cut anymore. If you do NOT have an exhaust and a pod filter then you should check if your wastegate is working. Check the hose to the wasegate actuator for leaks. Check to see if the diaphragm inside the actuator is still sealing properly (suck on the hose and see if the diaphragm is leaking air). Could also be due to cam or ignition timing too retarded.

Thats all I can think of at the moment, try that for starters  ;D

[si]

Keep in mind he's running the GT17. But as colza said, turn the boost down, especially if the car is running like sh!te. Keeping the boost up could just make ur problems worse.

Have you had a compression test done on the car?
Would be good to find out what the previous owner did to the beast. It does sounds like the turbo has copped a bit of a beating maybe.

[James]

If my memory serves me right thats a little bit higher revs than the revs everyone elses GT17s spool up at, could be many things as colza said but it is a much bigger turbo than standard and you wont get it to spool too much lower than 4g on that engine. If you want the awesome quick boostin citys are renowned for sell that turbo and the manifold to me and ill get you a nice reco stock one in return ;)

[Colza]

Its a GT17? whoops ::)

I agree with Bigelboe on that selling the turbo thing...

[Jacko]

Well I could sell the whole car to all of you guys and you can just fight out who gets what  :P

[Colza]

Jokes I only said that cos Bigelboe doesnt have a car so it would be mine it ends up on ;D Keep it man, make it B ;D ;D S T

[JohnT]

Jacko

We're running a GT17 on our car, and it boosts well before 4,000. Couple of things to think about

Is the boost gauge actually telling the truth? I know that if I've been out to 2,500 or so with an open throttle, the blow off valve will let go with a nice loud "whoosh" when I back off the throttle, so there is boost there at those revs. We get serious readings on the boost gauge by the time we're at 3,000 or so.

Is your manifold design suitable for the GT17? We're running a near equal length custom manifold, with the GT17 getting pretty evenly timed puffs of exhaust gas as each cylinder fires.  If we're not seriously on boost until 2,000 plus, with that manifold, then a longer / less effective manifold would cause problems.

Having said that, the car does drive best at high revs, but if you do some work on the engine you can drive between 2,500 and 7,000 rpm at most times anyway. And at those revs with an open throttle you're making just a bit of boost.

John

[Jacko]

Yeah, ive got an autometer boost gauge. i think its telling the truth.. anyway even when it comes on it feels as if the turbos not working properly. it doesnt put you back into your seat or anything. quite pissy really.

[Jacko]

Ok I think the reason it boosts late is just because BIG intercooler + TINY engine + BIG turbo (small but twice the size as the original hehehe)

[city_cabriolet]

Funny how when we were all talking top vs front mount, (nearly) everyone said "you shouldn't see any significant lag between the two". Of course that's considering the standard turbo... but it's all Air Volume, and it does make a difference.

Longer pipes (thicker too) and much larger IC = more lag + BIG turbo on small engine = even more lag.

BUT when it's over the lag, it's gotta go like a bat outa hell!

[Jacko]

If it was working right  :P

[JohnT]

I checked out the boost versus lag yesterday, on boost from 2,500 with a GT17 - and decent boost at 3,000 (all with open throttle as our gauge in post throttle)

Only about 1lb at 2,500 rising steeply to 10 plus at 3,000 (and we're dialled back so max pressure is 10 or so at the moment)

We've got a lot of pipe work and intercooler - yes that does make some lag, but not huge. Sounds like you have a crook turbo bearing?

John

[Jacko]

Damn thats bad news, is it fixable or do I need to replace the turbo? And how hard is it to fix? Any tests I can do?

[Charles]

Jacko, you aren't by any chance running bigger injectors or raised fuel pressure are you. If so that can make the car fall flat on it's face and take for ever to boost, too much fuel is used on cars running high boost to give them a safety margin and cool the exhaust temp and combustion temp (but only after the car is boosting).

The other thing I would check if you happy with your fuelling is your timing. Sounds like it may be retarded somewhat. Be careful here, and slowly slowly.

Manifold design can make a big difference but generally anything will flow better than the typical city log type manifold.