[93SupraTT]

I've been having an issue with my Supra lately and I'm trying to narrow down what the cause could be. I'm seeing fluttering on high boost with stock twins. I rigged up an adjustable wastegate spring to keep tension on the otherwise piss poor rod. It can hit up to 1.5-1.6 bar (21-23psi) with full tension. I have it backed off to hit a peak of 1.4bar. Lately I've noticed under WOT it hits 1.4 then down to 1.3 and then back up until I take my foot off the throttle.

Could this be something with my spring? My plugs are 3330s gapped down to .30, brand new coil packs and brand new ignitor as well. My only other thought would be the boost controller, Profec B Spec II. Any input is appreciated.

 

[supradupaflyguy]

could be the boost controller, or you could just be experiencing a slight case of boost spike and boost creep.

 

[crossways]

I noticed nonlinear fluctuations with the spring attached. You might want to take it off and see how the boost reacts.

 

[93SupraTT]

If I take it off, I won't see higher than 1.0bar. Do you think the spring is too tight? Not tight enough?

 

[McGregory]

Is it fluttering very fast? Can be the sparks.

 

[crossways]

If I take it off, I won't see higher than 1.0bar. Do you think the spring is too tight? Not tight enough?

Not necessarily either, but I think the spring rate doesn't move linearly especially when coupled with the action of the wastegate tension. So what you have is the wastegate arm pulling in one direction and the spring in another resulting in a slightly erratic response, at least this was the case in my experience. So try removing the spring and see if the problem goes away. If it does, then try playing with the tension or using a different spring.

 

[QSMKIV]

Take off the spring and the stock twin's and go single. That's what I'm doing to fix the problem.

 

[93SupraTT]

Yea, I'm slowly building up to single status. The car is currently on it's third set of twins and I don't plan a 4th. A 67dbb will make me much more happy and I won't be chasing gremlins.

The tranny was pulled out this week to be sent to Boost Logic so I'll have to wait until it returns to do some more concrete testing on the spring. I'm also going to go with Denso Ik27s. I just don't feel comfortable with the 3330s in there. I also dug up the manual for Profec B Spec II:

Troubleshooting
Inconsistent Boost. Boosts up and down.

Possible Cause
GAIN is set too high.

Solution
Lower the GAIN setting.

Really hoping that's it. I have a date with an H/C Firehawk with 90/90 Fast intake and I definatly need my A game. Thanks guys and if you think of anything else to check, post up.

 

[93SupraTT]

And yea, the fluttering is pretty fast.

 

[QSMKIV]

Yeah, I got tired of chasing the bpu "gremlins" too. My stock twin's were starting to go out and I just decided it was time. I went with a 67 also. Have fun beating up on that firehawk.

 

[McGregory]

Check the spark gap. That is done in 15 minutes

 

[93SupraTT]

Gap is either .30 or .28, I can't remember.

 

[Speedmaster747]

Check that your blow off valve is not the problem!

 

[93SupraTT]

Funny you should mention the blow off valve as I was thinking of it as a possiblity too. How do I go about checking it? Are stock BOVs notorious for shitting the bed at higher boost levels?

 

[Speedmaster747]

Funny you should mention the blow off valve as I was thinking of it as a possiblity too. How do I go about checking it? Are stock BOVs notorious for shitting the bed at higher boost levels?

Yes!