Boost Question

[bishir]

I've only had the car for a week so I'm not that familar with how the boost levels fluctuate on GNs. I just wanted to describe my boost and see if it sounds okay. When I stand on the gas the boost will quickly spike to 20 pounds then settle to 15 quite fast. Then it will gradually rise to about 17-18 lbs and stay there. Is this normal? The only mods are: adjustable wastegate, stainless exhaust, and a 93 chip. I was running 93 octane at the time. The car idles and runs nicely.

Thanks,

James

 

[nastysix]

Does it do that if you punch it in third gear? Because if it does, you had better turn the boost down or you will be changing head gaskets or worse very soon. 93 octane will not support 18lbs of boost in third gear (or second gear for that matter). First thing to buy is a scan tool to check for knock. Don't run more than 15 lbs of boost without one. Don't blow up your motor before you have had a chance to play. Octane is the key to more boost. The more you have the more boost you can run.
Larry
p.s. It is not normal for the boost to spike and creep up as you describe unless something is built into the chip. Try another chip to see is it does the same thing.

 

[bishir]

This is from First gear...

 

[nastysix]

In that case, it is probably your chip program. I know Thrashers are programed that way. First gear can tolerate higher boost levels. just make sure you have no more than 15 lbs in second or third gear. Get on the freeway, put the shifter in third (not overdrive) nail it and see what boost it holds. If it is more than 15, turn it down until you get a scan tool. Remember, Scanmasters are cheap compared to engine rebuilds.
Good luck,
Larry

 

[bishir]

Thanks, I'll do that. I thought I read somewhere that factory cars had anywhere between 15-17lbs boost stock.

 

[bishir]

The chip I have is a 93 Red Armstrong. The chip literature said 17lbs of boost with 93 octane is expected with that chip.

 

[nastysix]

Red makes excellent chips, so you are probably o.k. That's why I mentioned the chip program in my original reply. My point is, don't guess if it is knocking, know for sure! You won't hear or feel knock until it is severe enough to do damage. Generally speaking, the amount of boost you can run is determined by how much timing is in the chip. The popular chip programers walk a fine line between timing and boost levels. Stock or nearly stock cars usually respond better to more timing as opposed to more boost. My car will actually e.t. quicker on an old Hypertek stage 3 chip which only allows 15 lbs of boost without knock on 93 octane than a thrasher 92 which makes 17-18 lbs of boost but has a more conservative timing curve. Sooo, the answer to your original question is yes the boost is normal for your chip program.
Best regards,
Larry

 

[motorhead]

bishir,
My car does the exact same thing. It is mostly gear/load related. It also has to do with the "age" of the wastegate and its ability to react to the pressure, IMO.

I am running a JC94 and 94 octane in my car, my boost is set at 17-18psi depending on the weather.

HTH,