RB... being very slow

[stevespeed]

Okay so...
I really REALLY hate to admit this, but I just got into a race with a buddy of mine... and barely lost.
But here is the catch... it was an 05 Pontiac GTP.... I am confused as hell.

Here is the sit rep on the car.
S1 RB25
FMIC (s*** piping)
HKS SSQV BoV non recirc
Freddy Intake
3 inch down
3 Inch Cat back
Cat delete (of course)
koyo rad
dual electrics
no boost controller
5-6 ish PSI? basically it goes up to 6 falls back to 5... and thats with the gauge reading like 1-2lbs off already.

I have horrifically s*** piping, and the car breaks up at hte top end. It also feels like the car does not want to rev as high (still no functional tac)

It seems like that htis year the car's wastegate is is opening up alot earlier than before.


Timing was set at 650 RPMS at Stock spec (if I recall correctly) with a Mac Digital Timing Light.

Suggestions cause this was absurd.

[WDRacing]

You could start by fixing all the things you know about already. Bad intake plumbing I assume means it's restrictive. That's an easy fix with some J-bends and couplers. Breaking up is usually ignition related, swap your plugs and check the gap. I used to pull apart my coils and make sure nothing was corroded etc. Install a reliable boost gauge and have the turbo and gauge use a vacuum source from the intake mani, like the FPR line.

Get it running like a top and then add a single stage methanol injection system and crank the boost up to about 14 psi

WD

[Darius]

You must still be running the stock boost solenoid, right? 5-6 psi is close but it should still hit 7 psi and hold. Even a stock-boosted RB25 should take a GTP without a problem.

[stevespeed]

I know this,

I have the Boost gauge (old mechanical auto meter), I have no boost seloniod, i am running the wastegate plumbed straight to the IC piping.

[Darius]

Now that's even more strange. You don't have a boost controller OR a solenoid valve and it still only hits 5-6psi? Is that why you are swapping out gauges because you don't trust the mechanical gauge's accuracy?

I can't remember who it was, but they were running their RB25 without a solenoid or boost controller and I think the OEM wastegate spring opened around 10 psi.

It sounds to me like it either has a ginormous boost leak somewhere or the wastegate spring is losing its tension and just opens early.

[stevespeed]

i think the second is more likely i have seen it open just free revving in the garage numerous times

[Joe]

Now that's even more strange. You don't have a boost controller OR a solenoid valve and it still only hits 5-6psi? Is that why you are swapping out gauges because you don't trust the mechanical gauge's accuracy?

I can't remember who it was, but they were running their RB25 without a solenoid or boost controller and I think the OEM wastegate spring opened around 10 psi.

It sounds to me like it either has a ginormous boost leak somewhere or the wastegate spring is losing its tension and just opens early.

nope the spring is 5.5 psi. its not possible to go UNDER spring pressure so if it was 10psi even with a boost solenoid or controller you would only be able to run 10 psi.

you are 3psi low on your pressure from the factory (that will account for a good 20hp). get a good boost controller and FMIC and crank that baby up to 12. i wouldnt go above 12 tho because they turbo has a tendency to explode randomly above 13 psi.

but dont expect the world, a GTP makes 260hp/280tq stock even tho its heavier and FWD its still a challenge for a stock RB25.

p.s. go to the damn track. street racing makes us all look bad.

[Darius]

OMG duh! I'm sucha dumba$$. I'm thinking that guy's (not you stevespeed) wastegate must not have been hooked up at all in order to get to >5.5 psi without the solenoid or boost controller.

[stevespeed]

we were just tooling around on this big 8 lane divided highway that you can get to in 3 seconds from my house, but I will do that, I have an FMIC, and it did spike back to 10psi for a moment today.

I had PCV hooked up to the turbo like factory and the car was running like crap, I capped it back off and now it runs AMAZING. I also found that one sensor under the intake manifold (its a freddy) with the black connector is mysteriously not hooked up, I am pretty sure its related.

Idk thoughts?

[Darius]

Are the PCV system lines air tight on the turbo intake tube, valve covers, PCV valve, and Freddy? Keep us posted on your developments.

It is a dark blue plug if I remember correctly and it controls the air regulator under idle conditions. Doesn't hurt to have it plugged in

[stevespeed]

thats the problem... its somewhere... I have no idea where

and its more of a black plug isnt it? is it dark blue

Damnit.

Well as soon as I figure out my oil issue I am straight hooking up a boost controller and dailing it up big




With the PCV I have a filter on the intake side its currently capped off on the exhaust side.

i used to have it plumped to the turbo but the engine did not seem to like that.

[Darius]

Did you have the filter on the intake side and plumb the exhaust side to the turbo or did you remove the filter when you did this? If you had the filter on and then plumbed it back into the intake, I could see the vacuum ahead of the turbo pulling in unmetered air through the filter and causing the engine to stumble.

[stevespeed]

Bingo Darius, I think thats exactly what happened.

She still with just the filter and the turbo end capped off stutters a little bit between gears, and at lower revs. I think I need a new set of plugs and some better fuel though.

[Darius]

Ok cool. I'm right there with ya now. Just make sure that filter element stays clean. If it plugs, it will cause the crankcase to pressurize. Not good. Very smoky.

As for the stumbling between gears, I'd attribute that to the non-recirculated BOV.

[stevespeed]

I figured that was possibly the problem, I have an HKS SSQV that is mounted really close to the throttle body, and as much as I do not want to replumb it back to the intake It looks like I am going to be doing so

Also this BOV seems to surge the day lights out of the turbo, I dont know if its not opening fast enough or if its just screwed up.

I tried running a Greddy RS BOV, but from what I could tell the bov just stays open at idle and "closes" when it sees boost, I readjusted that one to stay closed ALL the time, except under vacuum so I am going to throw that one back and see if it helps.

[stevespeed]

Also Darius/Carl/Other Nico experts,

I am currently running an AC Delco Equiv of a BCPRE11 NGK, copper, you think I should keep that plug and what gap do you recommend for a low humidity enviroment.