I was wondering on NA set up what everyone is seeing for max compression on 93 pump gas. Iron Block& Aluminum heads.

Let me know what you think the max is. I now the cam plays a role too.

 

I'm at about 11.5:1 and use 93 octane and i dont have even a little reading coming from the knock sensors. I have an EPS 236/242 cam. From what i understand dynamic compression cannot be effectively calculated but a larger cam will allow you to run more compression.

 

You should do a search for dynamic compression ratio (DCR) depending on the cams valve events will determine what your DCR will be with a given static compression ratio. For 93 octane I have always been told you should shoot for a DCR around 8.50

 

Basically: [static compression ratio + cam events = dynamic CR]. So, there are a few variables to consider...

 

I wouldnt trust any DCR calculators. The racing engineers spent years trying to solve for dynamic compression and it was impossible. They could get cranking pressure, but not dynamic compression ratio.

 

Mines at 12 :1cr on 93 I have no problems no detonation iron motor alum heads I wouldn't go anymore then that

 

DCR is easily calculated, its just the ratio of volume when the intake valve closes versus volume at TDC. You need to know the IVC and rod length in addition to the normal variables for SCR, but its not that difficult.

 

you are only slightly misinformed....
they cant get it as exact as they want to.....but they can get it down to single decimals pretty easily....


and....its a common calculation in several engine builder software programs.

 

11.5 to 1 ratio on aluminum block and heads. Never any problems. Need a good quench to make high compression work with crap gas.

 

8.5:1 DCR on 93... and 8.7 ideally. You can run 9:1 DCR if you've got a good cooling system and an awesome tuner...