SE Pro Kompressor Heads info

[alakso]

Mike, what is the combustion chamber cc's for the SE Pro Kompressor heads?

What are the valve sizes for the SE Pro Kompressor heads?

What is the CFM flow for the stock SE Pro Kompressor Heads?

What would be the corrected compression for a set of SE Pro Kompressor heads on a '08 96" Dyna w/stock flat top pistons with a cams intake closing of 40 or 42 degrees with an .030 head gasket?

Will I need ACR's installed in these heads if my corrected compression is 9:1 or a little less and my mechanical compression ratio is around 10:1 give or take a little?

Mike's response:
The Kompressors are advertized at 76cc. They use stock valve sizes. Do not have CFM values. Based on a 10.5 compression (.030 gasket), corrected would be 9.7 at 40 deg.

Compression releases are recommeded for corrected pressures above 9.5.

[alakso]

Thanks Mike. I can see that with using these heads I would run into some serious detonation issues.

So with the 76cc combustion chamber am I right to assume these heads are for the TC 88" motor?

Or are these heads designed for a late closing intake?

Mike, while we're talking about compression I have a few questions for you.

1) Is there a direct correlation between CCR and Cylinder PSI?
As an example if a motor is running 10:1 compression and the Cylinder PSI is 200. Then no matter what the volume is with a 10:1 CCR the Cylinder PSI will always be 200?

2) In another thread you mentioned a max CCR of 9.4:1 to run without detonation on 92 octane gas. Do you think my target CCR of 9:1 for use with 91 octane gas is right or could I run a little more CCR?

You also said no need for ACR's unless running a CCR of 9.5:1. But with 9.5:1 I run into detonation issues. So this makes me wonder why a person would use ACR"s and why the SE 110" kit comes with ACR's when the CCR is well below your 9.5:1 threashold?

[Mike]

Their use on an 88, 95 or other would depend on cam choice. When used on a smaller motor the cam choice can be more conservative.

Yes, CCR and cylinder PSI are related. Some of these terms are used somewhat loosely and may have different meanings to different people. "Corrected Compression Ratio" (CCR) is the mechanical compression (in your terms, "PSI") "corrected" for intake valve closing. "PSI" is often used to describe dynamic pressures in a runnig motor. Others will use the two as relatively the same.

In your example, volumes (cylinder and head) determine PSI (mechanical) compression. With the same intake closing a 10.0 motor will have the same corrected and so the MEASURED CCP (cranking compression pressure) would be the same. This does not take into account the ability to overfill the cylinders (VE above 100%) but are used strictly for comparison.

The 9.4 CCR number recommendation comes from our real world experiance. It has just been our observation that motors trying to run CCR's above 9.5+ have had detonation and other issues. This can be for a variaty of reasons over which we cannot always have control. We have been successful ruuning some motors as high as 9.8 but since we cannot control all conditions (cross country touring, for example), 9.4 is recommened as a somewhat conservative number to insure owners do not run into those issues. Knowing we may be giving up some performance the higher CCR's give, most owners are willing to do so to insure an enjoyable experiance with their bike. We can, and do, build "monsters" but as a rule we try not to do so for (or experiment with) the majority of our customers.

You will not neccessarily have detonatin issues with 9.5, just tuning latitude is narrower and therefore, the tune must be more precise. The need for MCR/ACR's is also a function of motor size. Big motors just generate more friction and can need more starter energy just to turn over. ACR's can also be useful if the battery gets low. When asked if "needed" or "must have", we may say no if the CCR's are below 9.5 yet still recommend them as good insurance for the above reasons.