Help Me Bring My Boost Down

[georgeonboost]

Hi guys,

As gay as it sounds, I need to turn the boost down on my R33 GTR. Its my first GTR and im still getting to know all the biz about them. It's hitting 17psi and running the standard turbos. Surely this can't be good! Basic run down of mods are power fc, air filters, full exhaust (standard dump pipes) and from what I believe, the 'free boost upgrade'. I had a look on the boost solenoid and the is no yellow line on the black hose which leads me to believe the hose has been changed? What would be the easiest way to bring the boost down? I was thinking of putting in a bleed valve to get me by or even put in a ebc (which i prefer). I plan on changing the turbos down the track but have other priorities right now and will have to wait a bit hence why I want it to last a bit.

Your help is greatly appreciated.

Thanks,

George

[Jayden.K]

clearly there is already a bleed valve or ebc to get it to 17psi and tune to suit. im guessing you have just bought a car without knowing what aftermarket parts controls its boost??? maybe the power fc ebc kit. remove the vac line from the controller and plumb them straight to the wastegate, if you lower your boost a lot you will run quite rich when the tune expects 17psi and gets 10psi

Edited May 6, 2013 by Jayden.K

[georgeonboost]

Thanks for the info. Yes, i have just bought the car a few weeks ago. It definitely looks as if there is no boost controller of any kind. Still retains all the factory lines from the actuators etc to the factory boost solenoid. When you say remove the line from the controller and plumb it to the actuators, are you referring to the 2 boost solenoid hoses? ie. join them together?

Thanks

George

[georgeonboost]

ok. decided to go out in this cold melbourne weather and have a look around. there is no aftermarket boost control kit or pfc ebc kit. what i did find was interesting though. i pulled off one of the lines found a bolt in one and thought...oh no...and on closer inspection, there was some holes in the actuator line. i pulled the other one off aswell and that was blocked off too. i pulled the bolts out and have connected them to the solenoid so it works as it should. It now runs 12psi @ WOT which im much happier with. it boosts much better, comes on boost quicker and drives better. its a tad slower as the boost has dropped, but i think this is better. attached are some pics. if you have any other ideas on what i could do, please tell me! haha.

[Ben C34]

Wow, good thing you spotted that!

[niZmO_Man]

Lol that is a dodgy way of getting more boost. 12psi is what you want on standard turbos.

[georgeonboost]

Yeah i am glad i spotted this dodgy way of getting more boost lol

The only thing is, it feels like it struggles after 5k to get to 8k. Before it used to scream all the way up no worries. has me confused!

Any ideas?

Thanks,

George

[Jayden.K]

that is some crazy dodgy work lol. now that the boost is lower it wont feel very quick puling from 5 to 8 grand. plus it maybe running rich now which will bog it down, so when it use to see over 12psi it will add fuel to compensate (aka thats it tuned) now the airflow isnt there, its just waking fuel in for 17psi of boost when there is only 12. fact is if you have a pfc, you must get it tuned when you change things like this

Edited May 7, 2013 by Jayden.K

[Jayden.K]

also sense you have a hole in your vac line. it will pay to get your boost leaks check. it will run so much better if you fix any. do this before you tune again. otherwise it will run lean if tuned with leaks, then you decide to fix them

[georgeonboost]

Jayden.K - Thanks heaps for your input. I wasn't too sure if the air/maps are locked in the PFC which sounds like it is. I've just been cruising it and not taking it past 5k as it doesn't really have much pull from there onwards. It sort of flat spots. It definitely runs better they way it is set up now and i have replaced that hose with the holes in it and have gone over the vac lines and have not found any vacuum leaks. Looks like im going to book it in for a tune really soon then

[Jayden.K]

to easy mate, btw vac leaks and boost leaks are 2 different things but if you have a leak at vac you will with pressure. you will need a pressure tester to put into your intake, force air in and when you close the valve you will hear air coming out in all sorts of places, i had no leaks at 5 psi but then leaks at 20psi. things like hose clamps/ split hoses, gaskets etc. then after there fix, it will pay to check it every 6 months or whatever. ask your tuner if they can perform this, if they dont no what your on about get another tuner.

maps are locked, unless at hot idle or cruising then it switches to closed loop and reads the o2 to calculate a/f ratio.

its really shit because if the car knocks, it doesn't retard timing. it just follows the map!!! something that comes in handy on steep inclines, burnouts and hot days which shoot knock readings up from engine load. not sure if other ecus do it like vipec/haltec, motec, wolf v2, nistune piggy back blah blah

Edited May 7, 2013 by Jayden.K

[georgeonboost]

Again, Awesome info bud Yep, i will definitely get them to check for boost leaks when i take the car in.

thanks again,

George

[Ben C34]

that is some crazy dodgy work lol. now that the boost is lower it wont feel very quick puling from 5 to 8 grand. plus it maybe running rich now which will bog it down, so when it use to see over 12psi it will add fuel to compensate (aka thats it tuned) now the airflow isnt there, its just waking fuel in for 17psi of boost when there is only 12. fact is if you have a pfc, you must get it tuned when you change things like this

What?

Dropping the boost won't make it run rich. if it is tuned for 17, it can obviously run 12, because it would have been with part throttle. The afm will read the airflow and add the correct amount of fuel, less boost, less afm voltage, less fuel.

[Kane_R32]

What?

Dropping the boost won't make it run rich. if it is tuned for 17, it can obviously run 12, because it would have been with part throttle. The afm will read the airflow and add the correct amount of fuel, less boost, less afm voltage, less fuel.

I agree, ECU will adjust fuel depending on load (AFM voltage) Regardless of PSI. Would be different had the boost been raised above 17..

[GTSBoy]

I concur with the concurring. Jayden no correct.

[georgeonboost]

Wow. More info. I knew with the standard ECU they self-adjusted, just wasn't too sure with a Power FC (never owned a car with aftermarket computer before so its all new to me!)

From what i have read, running the way i have it now, a lot of people get 1bar (14psi) boost. Why would i only be getting 12psi? It also doesn't feel like it pulls from 5k-8k the way it use to. Can anyone shed some light on this? Should i disconnect the battery to reset the computer?

Thanks,

George

[Jayden.K]

What?

Dropping the boost won't make it run rich. if it is tuned for 17, it can obviously run 12, because it would have been with part throttle. The afm will read the airflow and add the correct amount of fuel, less boost, less afm voltage, less fuel.

I agree, ECU will adjust fuel depending on load (AFM voltage) Regardless of PSI. Would be different had the boost been raised above 17..

I concur with the concurring. Jayden no correct.

sorry, i thought that was how it worked with power fc.

Edited May 8, 2013 by Jayden.K

[GTSBoy]

Yuh, PowerFC same as Nissan ECU. Measures load with AFM, so it's not tuned "for a boost level" so much as it is tuned quite naturally according to the amount of air going in. Less boost = less air = just running from a lower load part of the fuel and timing maps, exactly as if you were using part throttle.

When I say "not tuned for a boost level".....that's not entirely true, but it's close enough. Obviously if you have more boost you end up needing maybe richer mixtures and more conservative timing. But it's not really possible to separate these effects for a given turbo+ECU+AFM+engine combination....so the tune is effectively not dependent on boost as much as it is on raw measured airflow. For that given combo, less air must mean less boost, whether that airflow/boost is turned down by throttle or by boost controller doesn't make much difference.

If you increase boost above what it was tuned at, you will go off the end of the old tune and out into unexplored territory and you might blow it up (lean mixtures or too much timing the main thing here).

[Jayden.K]

Yuh, PowerFC same as Nissan ECU. Measures load with AFM, so it's not tuned "for a boost level" so much as it is tuned quite naturally according to the amount of air going in. Less boost = less air = just running from a lower load part of the fuel and timing maps, exactly as if you were using part throttle.

When I say "not tuned for a boost level".....that's not entirely true, but it's close enough. Obviously if you have more boost you end up needing maybe richer mixtures and more conservative timing. But it's not really possible to separate these effects for a given turbo+ECU+AFM+engine combination....so the tune is effectively not dependent on boost as much as it is on raw measured airflow. For that given combo, less air must mean less boost, whether that airflow/boost is turned down by throttle or by boost controller doesn't make much difference.

If you increase boost above what it was tuned at, you will go off the end of the old tune and out into unexplored territory and you might blow it up (lean mixtures or too much timing the main thing here).

yep cool, i just thought powerfc were really basic computers and once it set thats it, guess i learn to never assume anything. sorry about the incorrect information

[georgeonboost]

you've all been very helpful with the problems i've experienced.

But can any one shed some light on what i posted earlier?

see below.

thanks

From what i have read, running the way i have it now, a lot of people get 1bar (14psi) boost. Why would i only be getting 12psi? It also doesn't feel like it pulls from 5k-8k the way it use to. Can anyone shed some light on this? Should i disconnect the battery to reset the computer?