Huge Boost Creep... Big Turbo Lag

[Kryostaisis]

hi all, my friend and i have hit a big problem with his R33 Gtst, its got a highflowed turbo, 3inch exhaust, intercooler, boost controller, safc, fuel pump, fuel reg, pretty much everything you need.

the car comes on full boost at 3000 or just over, and then as soon as it hits around 4-5000rpm, it just climbs all the way to 14psi, even with the boost contrtoller removed and having a boost line from the acutaltor the intercooler pipe, it still does the same, but as soon as it hits 6000rpm, a big rush of power comes, so fast that you dont have enough time to change gears before it redlines.

we've put it into the mechanic, and hes trie regapping the spark plugs, changed the cat, cahnged the actuator, changed the silicon hoses, some vaccum lines, replaced the hiflow with a stock turbo, and it still has the same porblem, sounds like its just blowing air but we are really stumped. occasionally when we retune the computer or change something small it would hold boost for a day or so, but then it would just happen again the next day.

its very frustrating, we have spent over 6 months trying to figure out whats wrong with the car and many thousands of dollars trying to replace parts and tuning and inspections and all to no avail, there are still stock coils in the car but they are fine. afm is fine. actuator is fine and turbo is fine.

we havent tried a compression test yet, ive been told it might be a manifold gasket....??? who knows...

can anyone help????

ps sorry for the long post, and help would be much appreciated

[Craved]

sorry but this doesn't even make sense to me

"the car comes on full boost at 3000 or just over, and then as soon as it hits around 4-5000rpm, it just climbs all the way to 14psi, even with the boost contrtoller removed and having a boost line from the acutaltor the intercooler pipe, it still does the same, but as soon as it hits 6000rpm, a big rush of power comes, so fast that you dont have enough time to change gears before it redlines. "

what does it do between 4K and 6K ? lose boost? spike? lose power not boost?

got a dyno sheet with a boost or AFR map for this issue?

[nuffin_werks]

have you checked the actuator for leaks and the actuator lever isnt sticking or hitting anything?

You also havent told us what your stock or actual boost level is? 9psi - 10psi ?

Are you sure you have the right hose hooked up on the actuator . Remember there is two hoses from the stock solenoid and they need to be around the right way.

just some suggestions, hope you sort it out mate.

ron

[Kryostaisis]

we only wanted to run stock boost...

there is a greddy profec b installed, its supposed to be sitting at .5 bar, but

after it hits 0.5bar at 3000rpm it just climbs/creeps all the way to 1.0bar at 6000rpm.

between 4000 and 6000, the power has been varying, two things have happened:

before the safc was detuned , boost would come on to 0.5 bar @3000rpm and then while it climbed up to 1.0 bar there was a huge flatspot between 4500 and 6000.

we since then have detuned the safc, but there is still a flatspot just not as noticeable and with less power.

weve replaced the actuator for a new one, no leaks............ so it rules that out

we have tried using the stock solenoid, that didnt work

we also tried just feeding a line from the actuator stright to the intercooler pipe(theoretically it should be sitting at .5 bar) but that didnt work either

............so it rules out the EBC

air fuel ratios are good, the dyno sheet only shows power and torque

any ideas???

Edited February 3, 2006 by Kryostaisis

[BHDave]

A couple of questions and a couple of ideas/suggestions:

What actually happens above 6k? Does boost increase rapidly above the 14psi you have stated or does boost stay stable and the car just all of a sudden has a spurt of power?

And does it build boost to your base pressure (which i am assuming is 7psi) by 3k, then stop, then start building again after 4 or does it just slowly build right the way to 14psi?

Your ebc will be doing nothing to help at this stage. you're trying to run boost at a level lower than the actautor can do by installing something that bleeds air out of the system.

And i'm assuming you are still running a stock r33 actuator and have blocked off all the unused factory hoses and are only using the boost signal off the factory position (which is on the cool side piping?).

By running the stock actuator on an aftermarket turbo you have no guarantee of stock boost levels. The whole rb25 actuator has a 7psi spring arguement is a bit simple as you are talking about a spring with a spring rate and a preload and a diaphram with a certain area and volume.

If boost just slowly builds all the way to 14psi then you have the same problem as a lot of guys who complain about excessive lag on aftermarket turbos, just you are thinking about it a diferent way

What i would suggest (don't worry it wont cost thousands) is get a new aftermarket adjustable actuator. It has a heavier spring and you adjust the boost level by playing with the preload by shortening the arm. I'd accept the fact that you probably wont be able to run as low as 7psi and set your actuator (remove the ebc temporarily) for around 11-12 psi by shortening the arm until its a few mm shorter than the stocker and then stretching it over the wastegate pin.

This is the first step in trying to get stable boost as opposed to me telling you to run more than you want. Once you have installed the actuator and have good boost response and it's stable, then it's time to start reducing the preload in small increments, and then when you get it back to a point where you're happy with the stability and the boost level for day to day driving, then reinstall the ebc and stat messing around with higher boost levels.

bit of an essay there but hopefully it helps some.

And it all assumes the problem is the actuator rather than wastegate creep! That's a whole nuther issue that needs the turbo out again

[chrissso]

Some really quick suggestions. - pretty much what BHDave said but with one new one.

1, Get a new actuator.

2, use a more resrtictive intake.

3, make your wastegate hole bigger, or go external.

[Kryostaisis]

"And does it build boost to your base pressure (which i am assuming is 7psi) by 3k, then stop, then start building again after 4 or does it just slowly build right the way to 14psi?"

it builds it up to base pressure and stops momentarily, alsmot asif it starts to build up when the engine is under alot of load, if that makes any sense to you guys. as soon as it gets under "load" say aat 3500-4000rpm then it would slowly build up to 12 to 14psi, its very random to where it builds up pressure to

thnks for your help so far guys

[R31Nismoid]

Who hi-flowed it?

[paulr33]

get a real ecu

[Kryostaisis]

gcg hi flowed it, the turbo is fine, we even put a stock one back on and boost still crept, the wastegate actuator is fine. checkd all hoses and piping there are no obvious leaks.

a ecu is not something we want to look into as it is a lot of money to risk to fix the problem.

[R31Nismoid]

drop the exhaust

then see what happens

[Kryostaisis]

why the exhaust?, i started to happen last year till now, before then the car ran fine. weve replaced the cat with a hi flow one, and the problems still occur.

ill give it a go anyway, but i doubt it will do anything

[R31Nismoid]

either that ot you have a leaky/split hose (if it was ok before... which is pretty important detail) then something has changed.

[Kryostaisis]

any other ideas?

[Kryostaisis]

any help?

we have noticed something odd, when the car is revved through the rev range when the car is in neutral, it feels rough around 4500 - 6000, rough as in you can feel the engine vibrate a little more than normal, hard to explain.

another thing, when the car wasnt driven for 2 weeks we took the car for a ride again, but the boost was smooth and was holding at 0.55 bar and the car pulled all the way through the rev range. but only after half an hour worth of driving boost began to creep again leading to the flatspot

does anyone have any ideas? even two mechanics i have taken the car to now are stumped and have run out of ideas

[black_tx5]

it sounds like the ebc isnt setup properly. ive seen the same thing happen on my mates 180sx. try fiddling around with it.

[Kryostaisis]

we have disconnected the ebc and sent a line from the wastegate actuator to the intercooler pipe, so theoretically it should be at stock boost, but it isnt.

so the ebc is completely fine

[Craved]

have you tried a STD turbo to see if it tries to peak .. i noticed you said the turbo was fine... but after 6 months i would be willing to change the turbo over to test it out...

if a std turbo works to std boost, then it would be the turbo thats faulty..

[Kryostaisis]

yeah, we have tried to std turbo, it does the same thing but on a lower scale(ie boost only creeps to .8bar)

[discopotato03]

If it were me I'd be checking exhaust manifold pressure as you already know what boost pressure is . Provided there's no actuator signal leaks you could check the integral gate bypass flat/flap valve to make sure it actually opens as it should . You could try disconnecting the actuator rod from the gates lever arm and see if it still boosts - it should not . I have heard of tales of less than well manufactured dump pipes restricting the valves travel and this can defeat its ability to open/bypass so it cannot control turbine and therefore compressor speed .

If all else fails and you can narrow it down to the turbo (IF) , there is a slight chance it has the turbine housing off an RB20 although the chance is slim .

Always try the simple tests first , can save a lot of time effort and money .

Best of luck cheers A .