8100 RPMs

[trapperjack1]

for you guys that are turning 8100
and run 78 to 80MPH what pitch prop are you running?
thanks guys

 

[red2blue]

Ah see?....you gotta be more specific.

You gotta ask...Of the rxp's turning 8100 and seeing 78-80 mph and are running as few mods as I'm gonna be, what prop are you spinning to get those numbers?

 

[trapperjack1]

Ah see?....you gotta be more specific.

You gotta ask...Of the rxp's turning 8100 and seeing 78-80 mph and are running as few mods as I'm gonna be, what prop are you spinning to get those numbers?

its hard to belive turning 8100 with a 14-19 and going 69.2 and
then turning 8100 with a 15-20 and going in the high 70s
I under stand the hull tuning it just seems like a lot of gain
with one pitch of prop, also can anything be done with the
ECU on the 04s?

 

[red2blue]

its hard to belive turning 8100 with a 14-19 and going 69.2 and
then turning 8100 with a 15-20 and going in the high 70s
I under stand the hull tuning it just seems like a lot of gain
with one pitch of prop, also can anything be done with the
ECU on the 04s?

Have you tried adding a bit to your 14/19? See...here's where things get into the minutia.

A 1mm bend added to the rear of the prop will net you 1mph...if you got the ponies...2mm will get you 2mph. A 15/20 would get you 2 mph or so more than that...right off the bat...if you got the ponies...add more to the trailing edge and get even more.

Every lil bit helps...you can't just throw a lil money at this and walk away with a world beater. To stay low budget you need to squeek everything you can outa what you already got.

Re your ecu...yes there are upgrades you can do to the ecu to see more r's. Rotax had a comp ecu...woulda got you to 8800 or so...if I remember right. Riva had a better one...don't think they make them anymore...would have to find one in the classifieds. The Riva's ignition curve, if memory serves...heh, was less likely to cause detonation. A very real worry for those with the Rotax. Fuel and air/fuel ratio along with valve train upgrades were also crutial to any sort of longevity....with either of them.

One last thing....re props.

I run a 14/19+2....meaning I've added 2mm to the trailing edge of my prop. I'm only turning though about 8050 on a good day...meaning I've got another 100rpm available....if I had the ponies. I'm running 72.7mph on those good days. Yes...I now have an S3 wheel and a rear air intake...but that's it along the hp creating mods to the motor.

The rest comes from all the work and other extras I've done to the hull, grate ect.

I have a 15/20 sitting on the shelf in my garage. I have tried it on my ski...because I foolishly thought I had enough ponies to twist it....wrong. I will get there...one day...and hope to see 75...consistantly and reliably.

 

[trapperjack1]

thanks red2blue, im running a 4" intake,riva wedge, riva grate,
going to a s-3 wheel with 42s made my own pro opas,
i look at the stickys on here and they are going high 70s
with my combo, im trimming the bucket today, ride holes filled-sanded
is the nozzel 81mm a big key
how many mm diference between 14-19 and 15-20

 

[red2blue]

thanks red2blue, im running a 4" intake,riva wedge, riva grate,
going to a s-3 wheel with 42s made my own pro opas,
i look at the stickys on here and they are going high 70s
with my combo, im trimming the bucket today, ride holes filled-sanded
is the nozzel 81mm a big key
how many mm diference between 14-19 and 15-20

Ah..tough question re the difference between the 14/19 and the 15/20. Wish you'da asked that a coupla days back...I just pulled my pump to grease it before I go out next and had the opportunity to do a side by side. Too late though now.

The pitch will be completely different stacking them side by side. The 15/20 steeper up top as well as on the trailing edge...it's grabbing a lot more water at the beginning and forcing it out faster still. Personally...I'm thinking you'd need 400rpm above stock to twist it.

One mod you might consider..dunno if anyone's talked about yet to you. Adjustable rings in the nozzle.

Riva Pro Series reduction nozzle...new is around $400. You can pick them up in the classified occassionally for around $250. They are a must have when you are looking for your last bit outa your set up....especially when dealing with daily fluctuations in temp ect. Saves tons of time swapping a nozzle out instead of a prop...heh.