Home Forums Tech Talk Question for the day Reply To: Question for the day

#64856

Pete Muller
Participant

I have come to the conclusion over many years that higher compression makes more power through the entire range (within limits, obviously… there comes a point where things start breaking!).

I believe that the “perception” that raising compression increases low/middle rpm power while hurting (or not helping) top end power (or even limiting peak revs) has to do with typically inadequate fuel metering.

I don’t think there is any question that peak fuel demand *per*cycle* is at peak torque.  Generally, I feel what happens when people test higher compression is that they have to richen the mixture to keep the engine rich enough through peak torque (aka: peak heat).  The fuel demands at high revs (past peak horsepower) fall off quickly, and the amount of additional fuel being provided at peak torque when compression is raised is simply a bit too much fuel at/near top rpm.

Of course the exhaust pipe and ignition timing can enter into the picture as well, however I feel the perception discussed (I’d even call it a “myth”) has come about due to poor mixture control.

PM

Karting's News and Information Leader ekartingnews | an HMG publication