-Is there any kind of optimum relationship between the exhaust centerline (ECL) and header primary length?
- Will a shorty header perform better with a certain ECL, will a long tube header perform better with another?
Thanks,
-Chad

 

No, what primary length does is that it changes the RPM range where a exhaust system helps or hurts scavenging.

A mid length header will help in the 2000-4000rpm range better than a long tube, but the long tube will be better from 4000-7000rpm. ECL I haven't found a link to the header primary length and it's tuning.

Bret

 

Are there any factors that may cause a cam designer to move the ECL around? I got to thinking about this knowing how important the ICL point is, is there any importance to an optimum ECL placement (as it may pertain to any one particular application)?
I understand that by just moving the exhaust lobe that LCA/overlap change and vice- versa. I`m trying to look at the ECL as a possible RESULT of vehicle application factors and not as a result of where it just happens to end up because of the other cam timing figures.

Or is ECL not very important???

 

I think the big brains of engine design look at all of the valve events independently. Intake opening, intake closing, exhaust opening, exhaust clsoing. They put each of them where they need to be to match the rest of the combo and let LSA, ICL, ECL and such fall where they may.

 

Exhaust events are both important.... too late of EVC will get you too much overlap and a midrange that is soggy and I've found that it's most dependant on the tuning pressures/lengths/cross sections of the intake tract. The EVO is very finiky for a particular amount of cylinder filling in whatever RPM range you are running, it's a lot like the IVC.

I guess the result of those is the duration and ECL.

Bret