i've been running 89 ever since i got my TII over the summer. i've heard a variety of opinions on this. isn't the purpose of the intercooler to cool the air before it enters the engine? if so, high octane gas shouldn't be necessary, leave that for cars with like 11:1 compression ratios. if high quality gas is so necessary for the TII, why isn't there a warning by the fuel gage?

Question.

What do you guys mean my "detonate"?

dude, its in the owners manual. warnings right on the guage are for american cars



mike

i dont have an owners manual, i have haynes and FSM, i saw it nowhere in teh FSM

if the compressed air due to the intercooler is cooled back down to ambient temperature, T_o, before entering the combustion chamber, then the change in pressure within the engine delta P due to compression will increase the temperautre of the AF mixture just like a NA engine. only if the compressed air from the turbo is too high will it auto detinate or knock.



i belive it's the compression ratio of the pistons/rotors that determines the gas type, not necessarily the use of a turbo. i understand on blown cars w/o a intercooler that premium gas would be needed, but i dont see about other cars.



PV=nRT --> if T is the same for both a TII and a NA due to intercooling, and compresion or change in pressure is the same, and we know displacement is the same, then the change in temperature has to be the same, resulting in a final gas temperature that is the same between a TII and a NA, assuming the intercooler is sufficient and the initial temperature entering the engine is the same.

its not though, the turbo heats air up to like 250f and the ic cools it down to like 175f, it not as cool as an na. also the t2 intercooler doesnt work very well



mike

On a turbo the compression ratio is infinitely variable. The more boost you're running the higher the compression ratio. https://www.nopistons.com/forums/pub...1047683561.gif

So with a FMIC, you could run lower octane gasoline?

yup



mike

the compression ratio within the engine is set, its the ratio between the intake volume and max compression volume, and has to do with the diminsions of the cylinder/rotor & chamber, not boost.