Boost Creep Issues

[Sparky206]

I've been having an ongoing issue with boost creep for a while now, replaced a few things and just cant get it to hold a constant boost level.

Car is an R33 series 2, has the following mods:

- FMIC

- 3 inch turbo back exhaust

- Now has a hi flowed turbo, but did the same thing with stock turbo

The issue is that the car will hit stock boost level as the wastegate opens at about 2500rpm, at about 4000rpm the boost will start rising again, to about 10-12 psi by redline. This is running a vacuum hose straight to the wastegate, adding a boost controller just moves the same symptoms to a higher boost, i.e. starts at 10psi then creeps to 15.

Things i have tried/replaced:

- Replaced wastegate actuator

- Replaced split dump pipe with Bellmouth

- Pressurized the vacuum hoses to 5 psi to check for leaks

- Installed a 2.5" restrictor plate just before the muffler

Interestingly the only thing that worked was installing the 2.5" restrictor plate, this had it holding boost levels either off the wastegate or boost controller, but obviously id rather not use this as a band-aid fix. Previous owned said it had started creeping when the exhaust was installed.

I've checked the operation of the wastegate with a compressor and it seems to be working fine. The fact I've replaced it aswell would suggest its not a problem with the wastegate operation.

Bit stumped on where to look now so any suggestions would help

Cheers

[3LGODZILA]

im guessing it has a de-cat pipe? if so put a cat in there

does it have the standard ecu?

[lachlanw]

you sure its plumbed up right ? and you didnt use the factory hose with the restrictor in it did you ?

what are you using for a pressure source

[Pal]

mine had the same. was using a restrictor plate till i got some bigger injectors and then took out the plate and let it go to 15 psi safely. also tune has a bit to do with it. i think it was running to rich and getting high exhaust gas flow. as i said, put bigger injectors in and a proper computer and it will go away. mine did

[lotsalag]

if its done it all the time(even with the old turbo) it kinda sounds like a tiny boost leak somewhere, in the signal line perhaps. maybe just replaces any sus looking vacuum lines or maybe all the ones u can see.

vac hose is cheap, and most of the standard stuff would be well shagged by now anyway.

keep us posted either way.

where is ur pressure feed for the actuator picking up from?

[rob82]

If the gate has insufficient diameter to bypass the exh wheel then you will get boost creep. Have you tryed wiring the gate open and seeing if it still creeps.

I've seen alot of aftermarket wastegates that crack at there preset level say 10psi but aren't fully open until around 30psi. Have you tested your wastgate movement vs input pressure.

[Sparky206]

Thanks for the replies guys, to answer your questions.

Yes i have a Hiflow cat installed

Im nearly positive its plumbed right, although this is the first ive heard of the factory hose having a restrictor in it. Heres a pic to clarify (with boost controller installed, currently it has the black hose straight to wastegate)

As for tune it is currently running the stock ECU, but im ready to get toshi to tune it, but i really wanted to get this sorted before i get a tune as it would probably be hard to tune with such a varying boost level.

I've given the car a run to redline with the wastegate arm disconnected, and as expected the car sat on 0psi the whole way

Thanks again for the replies so far

Edited June 27, 2010 by Sparky206

[lotsalag]

Black hose to the wastegate?! me thinks the way in the pic is the correct way to have it installed

Those boost controllers r very touchy and sensitive to set. Does it still have the spring and ball inside it too?

If the gate has insufficient diameter to bypass the exh wheel then you will get boost creep. Have you tryed wiring the gate open and seeing if it still creeps.

I've seen alot of aftermarket wastegates that crack at there preset level say 10psi but aren't fully open until around 30psi. Have you tested your wastgate movement vs input pressure.

I immediately thought this too, but it was doing it with the old stock turbo as well apparantly. Sounds like an issue unrelated to the turbo itself imo.

U may try leaving the wastegate full open on the dyno and see what happens, but often if it cant spool down low, it will barely get moving up top either.

On the dyno try disconnecting the actuator rod off the actuator arm completely, hold the wategate flap it full shut with a long screw driver/lever and then at about 3000rpm let it go slowly so it can get full open by redline, hopefully then u can see if its still creeping at all.

U sure the actuator rod isnt fouling/binding on something and stopping its full range of movement(unlikely on a skyline)?

[Sparky206]

Black hose to the wastegate?! me thinks the way in the pic is the correct way to have it installed

Those boost controllers r very touchy and sensitive to set. Does it still have the spring and ball inside it too?

I immediately thought this too, but it was doing it with the old stock turbo as well apparantly. Sounds like an issue unrelated to the turbo itself imo.

U may try leaving the wastegate full open on the dyno and see what happens, but often if it cant spool down low, it will barely get moving up top either.

On the dyno try disconnecting the actuator rod off the actuator arm completely, hold the wategate flap it full shut with a long screw driver/lever and then at about 3000rpm let it go slowly so it can get full open by redline, hopefully then u can see if its still creeping at all.

U sure the actuator rod isnt fouling/binding on something and stopping its full range of movement(unlikely on a skyline)?

Black hose to the wastegate is to bypass the boost controller and just run it off the wastegates pressure. Its useless running a boost controller atm as it just creeps and hits R&R straight away.

Ive checked the wastegate operation with a compressor and the arm has a full range of movement.

[Pal]

i went through 6 months of all the things you went through Sparky. its not your turbo setup, i ported my wastegate hole up a extra 4mm and still did the same thing. u need a better computer and sort out the tune.

[lotsalag]

Almost outta ideas here, last simple thing u can try.........

Get a "new" piece of vac hose, hook it up a known pressure source, why is it not near the turbo outlet as usual(?) u sure that hose to the plenum isnt teed off to something else.

Still sounds like a small boost leak in the ressure feed or similar to me.

Good luck

[Sparky206]

i went through 6 months of all the things you went through Sparky. its not your turbo setup, i ported my wastegate hole up a extra 4mm and still did the same thing. u need a better computer and sort out the tune.

You were able to tune yours out?

[lotsalag]

Computer/tune?!

The standard solenoid isnt even hooked up right?

R33 boost normally tapers off at the top end, not the other way around.

Have u had the car at an experienced workshop yet, or even on a dyno? maybe ur boost gauge is the problem. lol

If its doing ur head in so bad, take it to an experienced shop.

I know u replaced the actuator, but maybe theres a small hole in the diaphragm, does it hold pressure ok when pressurised?

[SWITZER]

buy a proper ebc

[Pal]

You were able to tune yours out?

yes, mine would spike to about 17 psi, even removing my boost controller it would go to 14 psi. as soon as i got the injectors and power fc fitted, i could tune it down to 11 psi no problems, i got a highflow turbo as well. i may be wrong but you have all the same problems i had, i even changed my split dump to a bellmouth but nothing changed, everyone was saying ,check the actuator, check for leaks, but in the end it was the tune, a rich tune will cause extra gasses in the exhaust spooling up your turbo beyond what your wastegate can handle. once it is leaned out and ignition sorted it should go away

my saga

http://www.skylinesaustralia.com/forums/Ov...ml&hl=boost

[lotsalag]

Ive never ever heard of or seen rich mixtures causing higher boost or better spool.

Only thing to do with fueling i have seen help spool/response is a stuffed fuel pump causing dangerously lean mixtures.

[Sparky206]

Computer/tune?!

The standard solenoid isnt even hooked up right?

R33 boost normally tapers off at the top end, not the other way around.

Have u had the car at an experienced workshop yet, or even on a dyno? maybe ur boost gauge is the problem. lol

If its doing ur head in so bad, take it to an experienced shop.

I know u replaced the actuator, but maybe theres a small hole in the diaphragm, does it hold pressure ok when pressurised?

The standard solenoid isnt even being used, all i have is a vac line hooked straight into the wastegate, so its seeing the same presure as the boost guage. The boost guage is working, i can feel it hit R&R as it hits about 12psi.

The diaphragm is inside the actuator? so it would have been changed when i changed the actuator

[Toshi]

The standard solenoid isnt even being used, all i have is a vac line hooked straight into the wastegate, so its seeing the same presure as the boost guage. The boost guage is working, i can feel it hit R&R as it hits about 12psi.

The diaphragm is inside the actuator? so it would have been changed when i changed the actuator

We'd probably be able to identify the reason if you try running your car with a remapped computer. So why don't you just come in first?

[Pal]

Ive never ever heard of or seen rich mixtures causing higher boost or better spool.

Only thing to do with fueling i have seen help spool/response is a stuffed fuel pump causing dangerously lean mixtures.

i may have had the rich /lean mixed up. either way. it was causing the boost creep

[RRob]

Pull the actuator rod off and take it to redline see what boost you get by limiter. Also your boost source should be out of the cooler pipe just after the turbo. Not off the inlet manifold like it is.