valve events will dictate cylinder pressure more than static compression ratio.

10:1 will feel a lot better than 9:1 when out of boost.

why not use more compression and drop the boost if your gonna limit yourself to 93

what boost pressure is that turbo most efficient?

 

Because that makes less power.

 

I am leaning towards the 9.6ish ratio for better off boost drivability. Its a good compromise. The 9.1 may be a bit more lazy. Better drivability wins over max hp as far as I am concerned. Thanks for the insight fellas.

 

Is it just me or is 15-18 psi on straight gasoline crazy?

 

All depends on the tune and selection of parts used

Along with understanding plug reading

 

And all that goes out the window with a bad tank of gas.

I understand why people want to use gasoline only, but it just makes no sense to me when the consequences are considered.

 

I've run that boost on a few different setups. A stock 4.8 took 215kpa on 91 octane before knocking. 5.3 with 317s took more than that and didn't knock. I had my last engine set up for 9:1 because it still put 800hp to the ground on gasoline... Wasn't as sluggish as lots of people seem to think, either. Magical things can be done in the tune. Just model your fueling and spark based on what the engine needs and it will perform.

 

not true, dont tune it ragged and youll be fine....make the tune ragged and yes you can have issues

ive tuned a setup that made 1000 rwhp on pure 93, big sloppy heads, very cold range plug, 400 cubes


there are enough safetys in the pcm that will allow you to make **** last, many dont use these and why you see so many failures

 

I cant really tell a difference in the 9.6 engine and 9.0 engine I have had. Same displacement, same cam, same heads, just different head gasket to change compression.

 

Intersting. So in the end it really doesnt matter other than the lower compression is a bit more forgiving from what I understand. Obviously the tune is everything. Someone mentioned a bad tank of gas. Yup been there If I had to do meth injection, I will, I just would rather not. We added 12 degrees of timing with the meth inection on a Turbo 6.0 I built. It would only take about 2 degrees of timing otherwise @ 15psi. Heavy Tahoe, the 6.0 had Mahle Flat tops and stock heads. The transmission grenaded 2 pulls later LOL.