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Treadmill Dyno
Mary B:
Wonder if a timing chain might be better than that belt(looked like a belt anyway)? Looked a bit sloppy.
taylorp035:
My current engine uses a #25 chain and a 2:1 ratio for the drive to the rotary valve. Version 1 used a Kevlar stranded timing belt and we broke several nylon stranded belts due to the high loads from the aggressive cams that held the valve down.
taylorp035:
Finally hooked the rotary valve engine up to the dyno and was able to do two runs. Both were at full throttle. The first one was just to measure peak horsepower, which yielded 2.4 shaft horsepower at ~3800 rpm. Not bad considering the stock engine is only rated for 1.5 hp. The second run, we did a fuel economy test and it yielded 13.4% efficient at 2.3 hp. That kind of efficiency is comparable to a stock 3.5 hp briggs. Both the peak power and efficiency numbers could of been higher due to a pretty large groove that was forming in seal and was causing it to leak. After those runs, it was misfiring and not holding idle very well... so it looks like it is time build a new seal and possibly a new valve. The current "valve overlap" between the intake and the exhaust is 5 degrees. I plan on making that a bit more aggressive. The question is how much. I also need to question the heat transfer ability between the seal and the head, as it was pushing ~330F after the dyno runs.
SparWeb:
That's excellent Taylor!
The production of 60% more power implies the production of more heat (even considering any improvement in efficiency). Many parts could be running hotter than they did, even the stock components.
taylorp035:
https://www.youtube.com/watch?v=RjvYnzo0Qe0
We designed and machined a new seal, now with 36 degrees(crankshaft) of valve overlap between the intake and exhaust vs the previous 11. Now it sounds more like a performance oriented engine and shoots a few more flames. It definitely seems to have more power, and we can't wait to put it back on the dyno. We also swept the shape of the port for better flow on the intake stroke.
Last night, we replaced the hoses and fittings on the fuel system so it stopped leaking, so we tried to use all the gas in the tank. Managed to get the center of the valve up to ~550 F, at which point it decided it didn't want to idle much more. I think the gooey oil that cakes itself to the valve and seal started to melt and caused more leaks. The intake gases do a good job of cooling the one side of the valve and the part between the chain and the seal was about 350F.
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