Thread: Reduction Nozzle Results
06-17-2009, 06:42 PM #1
Reduction Nozzle Results
OK, so I popped for a reduction nozzle set up
since I was running on the limiter (rxt).
I bought the 81 mm & 82 mm sizes. I was really on limiter
at 85% throttle. So, I put in 82mm and was better, but
still on limiter at 90-95% throttle.
Went out following day with 81 mm.. NOW i'm under limiter
by about 100-120 rpms...
It was a little warmer out 2nd day with 81mm, so I think
I'll go back to the 82 and see if that's about right now that
it's warming up..
I remember reading that 1 size was worth about 100 rpm,
but im my case it was at least 200 rpm.
Any thoughts or suggestions
06-17-2009, 08:22 PM #2
06-17-2009, 09:19 PM #3
That's what I'm thinking..
The acceleration and general throttle response
was SO much better with the 82 nozzle. The 81 just felt
sluggish. Top end felt about equal , but getting there seemed
to take longer.
I'm gonna go back to 82 , then put it 1 size longer cone
in my AAT nozzle.
I'm kinda afraid to tweak the prop right now.. weather
is still going to get warmer here still!
06-17-2009, 11:23 PM #4
- Join Date
- Jul 2007
- PDX - Oregon
I was on the limiter w/ an 82 mm ring. Went down to an 80.5... still on the limiter but felt more sluggish like mentioned above.
I have read 1mm reduction +/- is worth 50 RPM FWIW....
I agree... pitch up to use a larger ring for better punch!
06-18-2009, 04:16 AM #5
foggy, you need to ring changes in the same day. The temp can feel the same but dewpoint /humidity can severly effect hp / rpms. Switch rings to get desired rpm. 1mm = 80-100 rpms. Half sizes are availible.
06-18-2009, 07:29 AM #6
In my case I found the 82 was best all around. In the colder months I liked the 80 or 81mm only because my rpm were so high. I found that the difference between rings was 20 RPM. When I didnt have enough power to push the 81 or 80 mm ring it was way sluggish. My best speed of 77.2 was with the 80mm ring at 8160 RPM. In the end it seems each person likes a different ring. Go with what feels best for your setup. Like others said pitch the prop to use the 82mm ring.
Check my thread out here (I have the difference results listed) - http://www.greenhulk.net/forums/show...t=82232&page=3
06-18-2009, 12:41 PM #7
Point well taken on dew point, humidity, etc
I am going back to the 82 mm and see what happens.
I keep my boats down at the lake in storage so it's a pita
to make changes and get back on water same day.
It's really getting hot now, so I think I just dont have the
hp to push the 81.. IT will be nice to be able to tune
in spring/fall when is cool to keep of limiter.
I had read that 1 ring size was about 50-100 rpm.. Was just
a lot more in my case so I wanted some input.
I will report what I get after this weekend.
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