Boost problems

[neomccollum]

I Recently went to the track for drag night, was very pleased with how the car ran (13.128 @103mph, 1.860 60ft) Since then I've noticed my car doesn't hold boost under full throttle through 1st, 2nd, and 3rd. I have a Blitz SBC DC controller, on my GT28R I have been running 1.3 bar. Through the first 3 gears it peaks at 1.3 or so but then slowly tapers back to 1.0 bar slower in 3rd than in 1st but holds pretty good in 4th. Now I haven't paid much attention to the boost before so I'm not 100% sure this is a new problem but it does seem to pull less at higher RPM. I'm wondering if it could be the actuator sticking once it opens at full boost or something like that. I tried messing with the controller settings, peak/warn/gain didn't seem to make any difference so I think it's not a controller problem. Any suggestions would help. :der:

 

[ricey]

1.3 bar is alot of boost! has your car been mapped for that sort of boost ?

i would say at higher rpm the pump(unless uprated) and injectors are maxed and they cant maintain it .
its propley dettin lik mad mate!

 

[rams_pulsar]

i'd be looking at changing the actuator mate...especially if it peaks then tails off as the spring will be worn i'm guessing

 

[neomccollum]

If it was detonating I would know wouldn't I>? The engine doesn't run hot and I don't hear any weird noises from the engine... I don't think it's too high boost.

 

[PobodY]

Does the actuator have a diaphragm in it? Could that have let go?
Seems to me that a little bit of rubber can't last forever, and if it ripped it would just leak and....er... wait it would be the other way around; it wouldn't engage, and you'd over-boost.
Same thing with the BOV then?

If the actuator linkage was bent it would stick as it returned, wouldn't it?

 

[ricey]

If it was detonating I would know wouldn't I>? The engine doesn't run hot and I don't hear any weird noises from the engine... I don't think it's too high boost.

1.3 bar of boost is high for a car if its not mapped to run that.
it's not just the boost you have to think about its the fuelin and if your standard injectors cant supply the engine with the same mix of air then you get det

in my 200sx s14a. that is a sr20det (similar) i could only run 1 bar with basic mods .

filter, exhaust, decat etc

to run 18-20 psi ( 1.2 bar )

i had to fit 550 injectors, and a stage 2 remap so the car would not run lean!

you dont always hear an engine pinking (dettin) and you engine dosent need to run hot mate

hope this helps

 

[neomccollum]

Well actually it doesn't help at all, I didn't ask if I was detonating. I asked what could cause my boost to slowly taper off from the peak setting. If the ECU could control the aftermarket HKS BOV and the aftermarket Blitz SBC then I could see how Detonation might be a cause of my problem (computer reducing boost when it senses Detonation). Who knows I might be wrong but I don't think the ECU has any control over that, other than changing the spark to reduce overall RPM.

 

[neomccollum]

Does the actuator have a diaphragm in it? Could that have let go?
Seems to me that a little bit of rubber can't last forever, and if it ripped it would just leak and....er... wait it would be the other way around; it wouldn't engage, and you'd over-boost.
Same thing with the BOV then?

If the actuator linkage was bent it would stick as it returned, wouldn't it?

It's difficult to check whether the Wastegate actuator is the problem being as it is located on the engin side of the turbo... but I'm thinking it could be the cause, when I had the GT28R installed to replace the stock turbo we had to modify the actuator from the OEM turbo to work the new one cause my new didn't come with an actuator or it was meant for use on a different setup. Are there specially designed actuators for the transverse SR20 setups with turbos other than OEM?