What is the most boost people are getting away with running 91 octain pump gas? Seems like 11 psi is all I can get away with. I would think at my altitude, with the cold IAT(50-60deg) , 17 deg of timing I should be able to get away with 15-16 deg. Normaly we can run about 2-4 more psi up hear(7000')elv. Either my boost gauge is wrong, or Im getting fucked at the pump. The regular unleaded is only 84 octain, mid grade is 87, and premium is 91 octain. Do gas stations lie and sell you the cheep **** when you buy premium? Truck seemed to have no det when I was running 12psi on the california gas.

 

i run 10psi here in california with no problems...

 

It's mostly timing. I think Rick@synergy was running 17psi on pump gas.

 

Thanks for the replies guys. I just tried another boost gauge and it reads withen 1 psi of the other. So either I must have got 84 octain, or the timing isn't what it's showing. Im even a bit rich @10.8AFR. I've even heard of some mustangs running up to 17+ psi hear. What brand gas are you guys running?

 

from what ive noticed, as long as i run a decent brand im ok. chevron, texaco, 76, shell...and my usual...vons

 

I was running shell. Im going to pump it out, ang try some union 76, or add a couple gallons of E 85.

 

Detonation comes from a combination of 4 things:
1) octane
2) compression ratio
3) heat
4) spark advance

These 4 are locked in a dynamic relationship -- as octane falls, spark, heat and/or compression have to fall to compensate (assuming a static boost target). Are you running an intercooler?

I ran 15-16psi on pump before (with an intercooler and meth) on 16* advance -- in Florida and high 90s ambient.

 

reg is 84 octane? damn. we have 87, 91, and 93. i thought that was pretty much standard?!?

 

never heard of 84..here its 87 89 and 91..a few places in the state have 93..there are people that go to gas stations and check the octane rating and it should be posted on the pump (+/-)

 

High elevation requires less octane cuz there's less air pressure, so that's what they sell.