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2ndGenTeg · 04-30-2002, 03:16 AM

Well, SOHC engines will never be as good in an all motor setup, because of the overlap issue. They simply are not capable of ingesting as much air/fuel as a DOHC is.

However...

In an FI setup, overlap is a bad thing. When the air/fuel is under pressure and both sides are open, you get blow by, which is exactly what it sounds like- the air/fuel passes right through the combustion chamber and out the exhaust, with out ever being ignited. Now you know why most turbo cams have a shorter duration than all motor cams- it's much easier to tune that way.

So if you're planning on doing a "moderate" FI setup, a SOHC engine can be just as good as a DOHC. However, you still lose the flexibility in specs and timing.

04-30-2002, 03:16 AM	#10
2ndGenTeg 4th Gear Join Date: Aug 2001 Location: Boulder, CO Age: 43 Posts: 830	Well, SOHC engines will never be as good in an all motor setup, because of the overlap issue. They simply are not capable of ingesting as much air/fuel as a DOHC is. However... In an FI setup, overlap is a bad thing. When the air/fuel is under pressure and both sides are open, you get blow by, which is exactly what it sounds like- the air/fuel passes right through the combustion chamber and out the exhaust, with out ever being ignited. Now you know why most turbo cams have a shorter duration than all motor cams- it's much easier to tune that way. So if you're planning on doing a "moderate" FI setup, a SOHC engine can be just as good as a DOHC. However, you still lose the flexibility in specs and timing.