13.9 compression ratio what octane fuel do i need

 

Offhand, I would say 91-93. What kind of engine?

 

More than that! 13.9 of static compression is going to require something MUCH higher.

With a VERY good tune, it is possible to get to around 11.0 CR running on 93 octane fuel, but to go all the way to 13.9 CR, you are looking at 110 octane race fuel.

 

4.3 vortec

 

i did the math and with 10 lbs of boost on my 4.3 it comes out to 13.9

 

Seems quite high to me... You need to figure the volumetric efficiency into things.

THIS CALCULATOR seems to be pretty good, but you still need an idea of what the VE of your engine combination would be. I suggest you read up on VE.

If you just put 92% in for VE, you will get that high and your octane requirement would be around 107 octane.

Just so you do not have to ask another question. The 4.3L v6 has a bore of 4" and a stroke of 3.48". Same as the 5.7L (350) v8.

 

My brain exploded.

 

Just... cannot... resist... temptation... too... great...

no harm done lolol

 

Our 81 camaro drag car has 13.5:1 and we use VP C12 racing fuel 108 octane. It won't run worth a crap with anything much lower than that.