hey guys.
this is the situation:
vitara d16
garrett t3/4 57trim
good flowing ramhorn, good flowing 3" exhaust + 2.5" muffler
tial mvs 38 (tried a 9 psi spring and a 14psi spring)
2.5 chargepipes, good known tial 50mm with -10.00 -16in/hg to -19in/hg
anytime i go up over 20 psi i get crazy wg flutter
going crazy

any ideas thanks

 

I had the same issue recently, also with a d16 vitara setup but a cast manifold and t3/to4b turbo. I aswell had a 7psi spring installed and tried to run 16+psi with a manual boost controller, the car didnt want to do that. I added a 14psi spring and it then held the 16-18psi I wanted perfectly.

Now just 2 weeks ago I decided I wanted to try 24-26psi (on 14psi spring) and I also had crazy unsteady boost, the needle on my boost gauge was almost unreadable it fluttered so fast at full boost. I added about 1/2" of washers to the top of the spring and the boost leveled off slightly, would still flutter but not near as rapdily.

So i orderred a 22psi spring and sure enough, it held 25psi this weekend at the races no problem, needle very steady

So what Im trying to say is.... upgrade the spring pressure, run a spring rated very close to the pressure you intend to run. I bought mine for about $15

 

What are you using to control boost levels? it's generally accepted knowledge that you can run double the spring rate in terms of boost, near or after that you run into coil bind and the limited travel of the valve (due to the thicker coil diameter on high pressure springs) and it can cause the boost controller to cycle the valve rapidly.

Random question, do you still work for tig-art?

 

hey everyone, thanks for the reply,

i'm using neptune with a mac solenoid to control boost,

but i also tested the car with a manual boost controller and a 1 bar spring and it still flutter


i dont work ad tigart anymore, tigart got closed

 

if the spring is near it's limit then it's natural tendency will be to bounce which will cause the valve to cycle open and closed. try a stiffer spring?

and dammit, that was the 2nd company that made a manifold I need :/

 

Try relocating your boost reference to the wastegate.

 

if you have the reference off of the compressor housing that could be your problem.

the compressor outlet is very turbulent and won't always provide the most consistent pressure signal. pressure waves leaving the housing can cause boost levels to pulsate.

 

Actually the boost source for the wastegate is on the hot side chargepipe about 1 feet away from the turbo, loose compressor wheel?

which manifold do you need wantboost?

thanks again

 

Try moving it to the intake manifold just to see if anything changes

 

I'll pm you about the manifold

 

I don't like running the wastegate source close to the turbo. The high velocity of the air near the turbo can often cause a fluttering response, because you have the effect of both pressure due to compression of the air and pressure variation due to the velocity.

Post intercooler is almost always better, much of the pressure fluctuations have stabilized and the pressure readings are much more consistent.

 

Yea that's what a lot of people have found. It gets even worse if you're near the limit of the spring. Where I used to work building race bike suspension systems we had our own shock dyno. We would test shocks all the way to coil bind for a given spring rate to find the limit for said spring rate. it turned the output graph into a giant sine wave, spring lost all ability to cope with the travel and would start to bounce violently.