Compression Ratio

[nortonracer]

Can some one recomend a fairly safe compression ratio, (uncorrected), or cranking pressure for competition use using 110-114 octane race gas.

Thanks.

Nortonracer.

[Patriot Racing]

15:1 UCCR would be a safe target.

 

Pounds on the gage- that can vary with porting. Not a good way to build engines.

 

-Backcountry

[nortonracer]

My engine is 364cc so I will need a 13cc combustion chamber. Are they available this small for the removable dome type heads?

Thanks,

Nortonracer

[Patriot Racing]

Trapped volume at TDC should be 13cc....the piston crown will displace volume into the dome netting you that trapped volume....

[nortonracer]

I have standard deck hieght cylinders with 65.5mm bores, I don't know the displacement figure for the piston dome which leaves me lost as to which size head dome to buy to achieve a 13cc combustion chamber. Any help on this matter is greatly appreciated as is the information already given.

[RK Tek]

Norton,

 

The safe compression ratio for your engine will be based on its application. For example.. are you racing 300ft? Hill shooting 1000ft? etc.. etc... The application will determine what you can safely get away with and still have reliability.

 

It will also be dependant on the cylinder bore size.

 

If you think you need 13cc TRAPPED volume .. then you need to determine your crown height. Are you using standard Banshee pistons? What is your piston deck height? There is NO standard deck height. They vary greatly.

 

These things all need to be considered when determining chamber size.

 

I compliment you on asking the questions.. Most do not and just buy a dome based on the flat plate volume of the dome. This is not the best way to build a high performance engine.

 

Hope this answers a few of your ?'s. Feel free to ask more.

 

Kelsey

[nortonracer]

Thanks again for the info., the pistons I will be using are Wiseco Prolite 65.5mm which I will set up with a 0.033" squish clearance. I have a Pro Design cool head but no domes as yet as I dont know what size to get. The engine will be used for racing on mostly fast tracks, long straightaways, at low, below 1000' elevations, using mostly C12 race gas or better, and vegetable based premix at 30-1.

Thanks again,

Dave.

[RK Tek]

norton,

 

13cc's trapped volume with your bore will yield a 15:1 untrapped compression ratio.

 

This of course is considering that the dome is on Size, which it surely will not be at 65.5mm.. so there is another varible to throw in the mix.

 

Hope this helps

 

Kelsey

[RK Tek]

Remember also...that the trapped volume can be accomplished in MANY ways. What dome you need will be dependent on deck height.

 

Kelsey