by Tony » Fri Dec 19, 2008 4:12 pm
My understanding of this is that swirl is not a high rpm power producer.
What it does do, is promote better mixture distribution and combustion at lower rpm and smaller throttle openings. So high swirl may be of definite advantage in street engines where economy and lean running without misfire are fairly important.
At flat out power producing rpm, air velocities will always be high enough to give good mixture distribution, and break up with very little deliberate induced swirl.
The now ancient original six cylinder Jaguar engine had two very different cylinder heads available for it. The one fitted to most of their passenger cars had the curved offset inlet port to promote swirl. The E type Jaguar had perfectly straight inlet ports located right on the bore centres, and this cylinder head was always preferred for racing development because of this feature.
I have never seen a purpose built high rpm racing engine with offset swirl producing inlet ports. But mild production engines are very often built this way to produce a much more fuel efficient engine at the rpm and loads normally seen by a street engine.
Also known as the infamous "Warpspeed" on some other Forums.