i'm thinking about droping my compression for my turbo. will droping from 9.5 to about 8.5 drop mileage much and will it make driving around slugish? its a all stock 5.3l with a trick turbo kit. mileage sucks as it is but i don't want it worse.

 

turbo guys seem to think 8.5 compression is too low and will hurt drivability. you should ask this question in the forced induction section

 

I'm sure it would lower your fuel mileage. Higher compression burns fuel more efficiently, and gets better mileage, but on the other hand, you would be able to run a bit more boost.

 

the highest compression you can run without detonation is the most efficient. Hence the reason you will get better MPG when running increased timing and higher compression with 93 than 87. Anyway it will hurt MPG but when running a turbo it wont be as noticable as the turbo is more than likely going to maintain a better compression while cruising with the extra weight of your tahoe and awd system. I would say 8.5 is also low for our engines. I think my TT 3000GT ran 8.5 but also boosted 17psi+ and was only a 3.0L. Try to run some stock 243 heads or maybe even 317 heads to lower your compression.

 

thanks for the help. i have some 317 heads in the closet which is why i asked.

 

more compression = more efficiency = better gas mileage.