Thread: Third Test with repitch
06-15-2006, 04:58 AM #1
Third Test with repitch
Well I put the stock impellers back in yesterday and took it out for a blast. I've been all over the place with pitch. The stock impeller was 10/21 and it ran 7800 rpm. Then I re pitched it to 10/19 and it ran 66.0 @ 8500 on the limiter. Then re pitched it to 10/20.5 and now it's 67.1 @ 8000 RPMís. I'm happy with that (for now).... However my Skat 3 blades are 13/17 and they ran 67.0 at 8500. Soooo if I were to go to 13/19 would it come up to 68 or 69???? Who knows but I did find out on an S200 one degree of pitch is 300 RPMís. Because when I went from 10/19 to 10/20.5 it cam down 500 R's. Next on the list are the 4" intakes and then the RR impellers. 4" inch this summer and impellers over the winter (something to look forward to)
06-15-2006, 08:59 AM #2
rather than changing the prop an ENTIRE degree at a time, change the trailing edge just a millimeter at a time. 1 degrees change is alot of cahnge to do at once to a prop, they are VERY sensitive as you found out.
i would say get a 10/20 in there and leave it at that pitch, and just play with the very back trialing edge at one millimeter increments.
have you tried any SOLAS props yet? ... i'd send ya one to "TRY" but i don't have them in pairs for your two engines, lol
06-15-2006, 09:54 AM #3
Shibb I didn't know you could do that. I think I'm right on now with the stockers re pitched to 10/20.5 the top R's are 8000 so Now I can mess with the intakes and try to get a little more out of her. I'm in the process of going from 3" intake that are about 25" long with two 90 degree bends in them that then go into the stock intake hose off the super charger (that can't flow smooth) to a 4" about 6" long to a sweeping 90 that changes to a 3". I think I should see something for this Mod. So if I'm at 8000 grand now I'd love to see it go to 8100 or 8200. Then I'm done. Or at least until next season..... What do you think about this mod think it will do anything??
06-15-2006, 10:46 AM #4
I agree...somefun, you should try taking out a mm and bring those revs up to 8350-8400 then when the summer heat kicks in you'll still be slinging 82ish. It's really easy to do and it would save you shipping them out to Skat.
Although I made full degree changes on my impeller 10/21 > 12/19... I'm probably going just do 1/2 degree or follow the mm rule now. I'm spinning 7850 and need to get it up to 8100 which should be 1 degree of change max, say...12/20. It seems sportboats are destined to have some cavitation instead of the instant holeshot like a pwc just because of sheer weight, but I am still contemplating playing with my leading edge some more to see if I can get better hole shot performance. My midrange is much better so maybe I'll try bringing the leading edge up to 13....hmmm is 13/18 the ticket?
06-15-2006, 10:52 AM #5
oh...and about the intake. I would go 4" all the way! I used the Kanaflex hose but if I had a choice it would be 4" piping with minimal bends and smoooooth on the inside so there is no induced turbulence. I was going to bring along a short 4" diameter PVC pipe and try running it using warm in hull air as opposed to cold outside air. I wanted to see the rpm and performance difference between "Intake Length" vs "Colder Air Temps". I figure short runs, cool air, smooth bore, and least amount of bends is the forumula for max efficiency.
06-15-2006, 10:54 AM #6
I Haven't tried the Solas yet. I'm about done with pulling them on and off. But I have heard that the Solas are good props. Do they make a 10/20? Also do you change the trailing edge? I know you use a wrench of some sort but are you only doing the last few inches of the blade?
06-15-2006, 10:56 AM #7
Yuji are you installing your voltage box in the intake like stock or just letting it hang out by itself?
06-15-2006, 12:52 PM #8
I installed mine in the side vent which is where my intake draws air from. The rectifier cooling fins need to have air passing over them to avoid overheating. Not sure if there is any performance loss but I think it would be bad for the 12volt/electrical system (ignition) if it were to stay at elevated temps for too long.
Rectifier and CAI
With Side Vent On
06-15-2006, 12:55 PM #9
WOW! thats a good idea Yuji
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