What up guys? I was wonder if anyone knew what the best effective compression ratio you can run on 93 octane... i.e. I want to run 9.5:1 with 10psi of boost which gives me an effective of 16.6:1... Is this too much, too little? Thanks

Mike

 

Effective compression ratio calulators are worthless IMHO.

There are ALOT of variables that determine how much boost/power you can make on pump gas.

You need to analyze -everything- when deciding how much power your going to try and make with a certain fuel.

 

Ok... Then I have several questions if you all don't mind...

1.Less restrictive or more restrictive exhaust system with good back pressure?

2.How many degrees of Retard per pound of boost?

3.What Air/Fuel Ratio on 93oct

4.If I wanted to add a 50 shot of NOS on top of the boost, does it have to be a wet shot or dry shot on an LT4 with a MAP sensor? no MAF

Thanks

Mike

 

To answer your questions

1- less exhaust restriction is always better

2- boost vs timing is not a linear relationship. If you pull "X" amount of timing per psi boost, your timing curve will be less than ideal. You want the least amount of timing at peak torque, which can be accomplished through tuning the ecu.

3- Depends

4- You can use either. Are you running SD on a stock PCM, or aftermarket?

A few (of many) things to consider when building a combination, after your goals have been established-


compression ratio

cubic inches, and how they are attained

target HP level vs target boost level (helps when choosing a compressor)

combustion chamber shape (cyl head and piston)

camshaft

quench distance

cooling system

exhaust backpressure

compressor/intercooler efficiency (intake air temp)

engine load (vehicle weight, gearing, transmission, intended use and duration of WOT)


Only "combinations", that are put together and designed as a "combination" as a whole, rather than looking at each part of the car as a separate entity will truly be efficient.

-Everything- has to be considered, attention to detail is what separates average from outstanding.


Rather than asking how much effective compression you can run on 93 octane, I would suggest starting with a horsepower goal, and design the combination to meet your goal, also considering fuel type, driveability, etc.

 

Thanks IN TMD8

 

Mine is 9.8 I have seen as high as 16 psi and I am running on BP 93 OCT. No Knock Retard. and 17 Degrees of Timing.