Boost Drop, Stock intercooler or stock Turbo?

[Guest Robo's]

Seems a few of use are under the debate and testing, that we are experiencing boost drop at full throttle. My example was on my recent dyno tune, that i peeked in mid range in the high 11's and low 12's but as revs increased my boost dropped to a point of 10psi at max revs.

So the question is, the guys with FMIC , EBC, or different turbos are you experiensing the same?

Is it the stock intercooler having inadequate flow?

Or the stock turbo ineffeciencies?

Or maybe the Boost controller?

[Steve]

with FMIC and stock turbo I had no probs to 7200 redline at 0.85 bar boost (EBC) which I had at about 2800-2900 rpm. I also had management. Made 203rwkw.

[rob77]

My stock turbo would give me 12.5psi till about 4500rpm where it dropped suddenly off to 9.5psi. I have the blitz sbc boost controller and we put it down to that or the wastegate actuator. With the TD06 on now boost holds nice and flat with maybe a 0.5psi drop in the high end so it was the wastegate actuator spring. HKS make a wastegate actuator with a stronger spring, but even still at around 12-13psi the stock turbo is really reaching the end of its efficiency range so its gonna start dropping a bit of boost at the top end. I've seen a car with a bleed valve and a powerfc make around 270ish HP @ treads with the stock intercooler, though I didnt see his boost graph.

[jayR33]

I have a front mount with a turbosmart bleed valve and standard turbo. My boost drops from about 12psi to 10 psi between 6500rpm - 7000rpm.

Im pretty sure in my case its either the wastegate or bleed valve because everything is relatively efficient ie, new dump pipe/exhaust, HKS filter, PFC.

Hope that helps,

[jayR33]

Sorry, i should have said either the turbo, wastegate or bleed valve.

[wrxhoon]

its normal ,

the turbo is not big enough to hold boost at high revs .

the higher the rpm the more air it has to pump thats way u get a drop in boost , if u can hold max boost at 6000 u r doing well .

[4 Doorz]

Any tried the 1 bar HKS wastegate actuator to fix this problem? Has it helped?

Standard turbo dropping from 16 psi back to 13 psi.

Have FMIC and PFC so I don't think it's the I/C

Also trying to work out if it's leaky BOV, Boost controller (manual now) or wastegate actuator.

[Steve]

Originally posted by wrxhoon

its normal ,

the turbo is not big enough to hold boost at high revs .  

the higher the rpm the more air it has to pump thats way u get a drop in boost , if u can hold max boost at 6000 u r doing well .

Can you explain why then, that my car held 0.85 bar (12.5lbs) all the way to 7200rpm, in fourth gear?

[rev210]

the wastegate acutator is the issue. It isn't the best quality unit in the world.

The HKS actuator will help, isn't really worth it on the stock turbo though. Dropping boost probably saves the factory one from going bang sometimes.

[SeriesIIGTST]

I know when i last ran mine with EBC with stock turbo and intercooler it shot straight to 10psi at about 2600rpm and held flat tapering off maybe 0.5psi all the way til 7 grand.

Now i got front mount....damn i love that thing. boost is super flat.

[4 Doorz]

Do you have standard BOV series II GTST??

[4 Doorz]

lol......guess mine will go bang soon running 16 psi.

Steve if your max is 12, then you wouldn't see drop, mine peaks at 16 and then drops back to 13...in that case, the theory makes sense

[Steve]

4 Doorz, I think yours will go bang - a case of when, not if at 16psi:D as long as you have fun doing it, its all that matters;)

[Nexus_SiX]

Originally posted by rob77

. I've seen a car with a bleed valve and a powerfc make around 270ish HP @ treads with the stock intercooler, though I didnt see his boost graph.

That may of been mine. Even if not i still qualify as stock turbo cooler bleed valve and Power FC

here is a graph before the PFC was fine tuned

[SeriesIIGTST]

4 Doorz: Yep. Standard BOV

[rob77]

Yeah it was you gus, I thought you got more power than 255 *shrug* Nice curve though Holds boost damn well for a bleeder

[Nexus_SiX]

I did that was the one at PSI a few days b4.

SST Dyno day