How much boost?

[BLACK MAGIC RACING]

I ran at around 17 lbs of boost with my setup, 02's were at around 780, and knock was at 2.5 max, but only from the shift. how high can i go with 94 octane before there is a danger of blowing a head gasket or something else? it seems as though I can still go acouple of more pounds... Also-is your boost psi setting noted from where the highest point during the run is? the needle on the boost guage never settled on any one spot during any of my runs. it was as high as 20 and as low as 15.

 

[blackbuick87]

I wouldnt turn it up any more at all. The only way to get more boost is to run less timing, port the heads or get a better intercooler. You are getting a little boost creep, probably due to a poor seal on the wastegate puck. That is probably causing your knock

 

[ALBERTAN]

Your combination is pretty much identical to mine. I never ran any significant boost with the Thrasher 92...I stepped up to the Thrasher 100 and a Xylene mix right away. You could increase the boost in increments of 1 lb until you start to see true knock. That's assuming you are 100% confident that what you are seeing right now is false. A better idea might be to leave the boost lower and run a chip like a Thrasher 100 which has a little more timing. It's been proven fairly conclusively that more or less stock cars respond better to a low boost/higher timing setup than vice versa.

But...

You have got to get your boost control more solid than what you are describing. If your boost starts at 15 and slowly creeps to 20 during a run than I think as blackbuick87 mentioned its time to pull the turbo and get a looksee at the puck. If it "surges" back and forth between 15 and 20 throughout third gear, then it could be the puck also. But you may have to look into a possible header crack or a faulty wastegate solenoid and/or actuator as well. It's fun to turn up the boost but a 5 psi fluctuation is a recipe for disaster left uncorrected...especially on pump gas. Get that fixed before you turn up the boost. Chances are the fluctuating will get worse as you turn the boost up. Mine never even started until I was at 20psi. GOod luck. Keep us posted when you find the solution.

 

[UNGN]

In first gear a thrasher 92 chip will "flash" the boost 2-3 psi higher then settle on the boost actually dialed into the wastegate.

If you are seeing 20 psi at this time that is the reason.

If your boost is spiking to 20 psi in 3rd and its set at 15 psi, you've got some wastegate issues.

As for fluctuating boost, a header crack can cause this and a few other problems. If its still cracked, fix it first.

 

[BLACK MAGIC RACING]

upon further inspection, guess what? drivers side header crack. I guess i jinxed it by bragging that i was one of the lucky ones without a crack......