Help Get Above 19psi

[rtune]

I've an engine from Ben @ racepace on 2530s., with the included actuators..

Car won't hold more than 19psi currently, at which point it punches out 310 awkw

I think it should go to 25psi or so and would like to see that.

Things tried:

* remove airbox (got to 310kw, but, no more boost)

* pod filters (ditto .. and currently installed)

* big exhaust cam (holds boost better at 19 but no more power)

* remove cat (no more power)

So at this point we're thinking of running the car sans exhaust to see if

that eliminates the problem. Just to see. If so, I'll be a customer of a

custom exhaust. I think it is really close to being done, but can't take

it if 19 is the limit, I'd feel the 2530s are being wasted.

But before plunking down that $3k for an exhaust, what else could it be?

And, a supplementary question. Is the racepace dyno a 2wd only? what does

a car there do on unfriendly 4wd dynos elsewhere? (this is the excuse from the tuner:

car is great, you'll see much higher than 310 on a 2wd dyno, or croydons dyno).

I want to know that to calibrate my expectations, so to speak.

But mainly .. is the problem most likely to be back pressure? This is what Ben

says it is, but he doesn't have the advantage of seeing and touching the car

although damn I wish I'd started with him in the first place.

[R31Nismoid]

If you have not dropped the exhaust yet - you certainly can't rule it out - and it's what i would be suggesting to do first.

2WD, 4WD - not a lot of difference from all reports of various users, certainly not 50kw which is about what you are down on a benno motor (roughly)

[rtune]

If you have not dropped the exhaust yet - you certainly can't rule it out - and it's what i would be suggesting to do first.

2WD, 4WD - not a lot of difference from all reports of various users, certainly not 50kw which is about what you are down on a benno motor (roughly)

yeah, so Ben tells me.. says 375 should be easy and even 400 with more tune work.

but the exhaust is critical.

my tuner is skeptical and I feel is trying to end his bleeding by selling me on ending the job here.

last thing sydney tuner said was that maybe the head doesn't flow enough..

and he wants to try trust type r bov..

[R34GTFOUR]

have you pulled the boost lines off to the actuator? Just to see how much boost they can make.

What boost controller are you running? What exhaust does it have at the moment?

[rtune]

have you pulled the boost lines off to the actuator? Just to see how much boost they can make.

What boost controller are you running? What exhaust does it have at the moment?

boost controller: latest HKS. It has compensation programming to keep things flat if

necessary, but can't cope at 7800 when the boost just dies in the ass if its heading

for north of 19psi.

current exhaust: ganador ti, 3.5". I suggested trying something else super loud, but

they couldn't source one to try, all the available ones foul on the rear diff.

He didn't want to free boost it, he was scared. haha.

[R34GTFOUR]

Scared haha, he's on a dyno, he can ease on the boost and keep it under control.

If it was me, i would be running open boost just to see if it will go above 19psi, If it does then you know its more boost controller/actuator related.

Cam timing dead on?

[rtune]

Scared haha, he's on a dyno, he can ease on the boost and keep it under control.

If it was me, i would be running open boost just to see if it will go above 19psi, If it does then you know its more boost controller/actuator related.

Cam timing dead on?

inlet is a vcam, and exh cam gear was adjusted, if I had more ability to

ask intelligent questions about the cam or tune I'd be trying to do the tune myself!

yeah well now I have two plans to ask him to try.. open boosting, and drop the exhaust..

one or the other.. both seem like 20 minute experiments to me. Thanks.

not keen about mucking around with more aftermarket crap. Getting tired of it.

[R31Nismoid]

Just drop the exhaust - to he honest when the car was removed - it should have been done then... full run no exhaust.

Not take out the cat and bolt the exhaust back on...

[GTRNUR]

Have you pressure tested all the piping from the turbo's to the plenum by blocking the pipe from the twin turbo pipe with a plug and clamp, and then pumping up the entire inlet manifold and intake plumbing by connecting an air compressor hose to one of the vacuum lines (like the line to the fuel pressure reg).

Running 25lb you should be able to pump up to at least 35 and not hear any leaks. Doesnt matter how good quality your intake plumbing is, or how careful you have been with assembly. If you over tighten a clamp or if something isnt aligned and assembled just right you will bleed boost. Just make sure you close the bonnet when you do the test. You can launch the pipe plug a fair distance if it blows out at 30+psi, with enough force to put it through someone's windscreen. You can hear and track down most boost leaks at only 3-5psi very easily.

[rtune]

Have you pressure tested all the piping from the turbo's to the plenum ..

may have to try this because the jury just returned a verdict with

the new patented design "invisible exhaust":

"330 kw and 23psi midrange .. but boost falls off after 7500rpm .."

so .. the actuators (although why if they can hold 23psi mid range do

they not hold that at the end, what is the difference from their perspective?)

or a boost leak either through the stock bov or the piping (although, again,

what is the difference between 8000rpm and 5000rpm from the perspective

of the bov or the intake at constant psi)

maybe this head doesn't flow well, after all .. not flowing enough air is definitely

a cap to power (and therefore boost). Or the stock coilpacks?

[GTRNUR]

If it were the head not flowing enough it would still achieve the boost level your after and the pressure drop would be between the plenum chamber and the combustion chamber inside the head. That is the only area that inadequite head flow will present a pressure drop. The 3" pipe that feeds the plenum is more than large enough so thats not the restriction.

As a general rule I wont even bother trying to tune a car without pressure testing the entire setup. Makes a massive diference in response and overall tune not having any leaks at all. The HKS piping and front mount setup I had on my R33 GTR didnt seal at all well until it was tweaked and pressure tested a few times. Also, how the engine twists under acceleration will effect plumbing seal too.

[mad082]

what intake pipes are you running from the turbo to pod filters? are they rubber or steel? if rubber, could they be sucking closed a bit at high rpm?

the other thing is, what sort of intercooler are you running? it may be a restriction at high rpm. might be worth putting a boost gauge before the cooler piping and 1 after it to see what sort of drop you are getting across it.

what manifolds are you running?

[rtune]

Success!

turned out that the trust BOV type-r fixed it .. the stock bov leaks at 19psi+

Now it can hold flat at 25psi, and is doing over 380kw at that level

so we're done, (but it will need the big exhaust).

Who knew.. Stock bov can't handle the pressure...? I wonder if it is in poor shape,

don't people post that the stock gtr bov is usually fine?

I thought after-market bov's were just bling, or for huge hp.

so the summary of mods are:

racepace (but stock) engine and head, with just oil mods/big sump

stock intake plenum and n1 manifolds

apexi intake (will have to be airboxed)

greddy intercooler

2530s, midori dumps and downpipe

trust bov, spitfire coilpack

big exhaust cam (made more midrange), v-cam intake cam

fat exhaust

hks evc

f-con vpro

big clutch

Edited June 23, 2009 by moneypit

[R31Nismoid]

They can handle the pressure - your ones must have failed mate.

I ran 24psi daily (through a SINGLE GTR BOV, not two), and i know others than have run 35psi+ through two... that was 550rwkw+.

No need for aftermarket ones if your stockers are working fine - which yours were not - i'd have replaced them with another stock set personally

[rtune]

They can handle the pressure - your ones must have failed mate.

I ran 24psi daily (through a SINGLE GTR BOV, not two), and i know others than have run 35psi+ through two... that was 550rwkw+.

No need for aftermarket ones if your stockers are working fine - which yours were not - i'd have replaced them with another stock set personally

maybe so, or however it is fastened was leaking, and the act of replacing it solved that problem.

I'll be keen to take a look at it, to see what might be visible.