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Tracy,
Yes, I was joking, to a point. BUT, since you brought it up. I'd bet that with the longer stroke the best BSFC on the new engine will be at a higher rpm. Mazda probably went to the longer stroke to lengthened the time for the fuel to burn more completely. I'm betting there is a lower exhaust temp there as well. Can't wait to get my hands on one;-).
Bob
On Nov 19, 2007, at 10:32 AM, Tracy Crook wrote:
I know you're kidding, (you know how much time it takes to come up with a new design & put it into production) but here's the other reasons for not doing a 3.5 : 1 gear drive.
I would agree with the estimate but I don't think it makes sense in aircraft use. Not that I'm against the HP, it's the BSFC that bothers me. The rotary gets the best BSFC around 5000 - 5500 rpm. Go higher and it gets worse which is OK for short periods (climb, racing, etc) but if you are going to really spend serious hours in the air, you want the engine running near the sweet spot of BSFC. With a fixed pitch prop, this limits us to around 7250 for top end and still cruise around 5400 - 5600 rpm. A CS prop really helps here but that sort of thing is out of economic reach for most of us. Even if you had the 3.5 : 1 gear drive, the design of the prop gets really funky. If you ask MT or anyone else for a prop that works best at 1500 rpm (cruise setting with engine near 5000) they won't have it.
The 16B plays right into our hands. If we are limited on rpm (7250 is not TOO limiting : ), there is no substitute for cubic inches and lower weight. Even with the 7250 limit, that comes out to ~ 280 HP. Not bad for a 150lb (bare block) engine!
Tracy
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