Superjet Top End Help

[SJET11]

Hey everyone,
I am hoping for some insight on why I am running out of top end. Not sure if this is normal with superjets or not. After about 5/8 throttle the rpm rises but there is no change in speed. Seems like the entire span of the power band should work. Guessing maybe the impeller is the problem but I am not sure.

2012 Superjet
Specs:
mild built 760 ported and polished
dual 44 mikunis
factory b pipe
msd enhancer
Jet maniac water box
tbm lightened flywheel
rrp trim

I also know it has aftermarket ride plate and intake grate. Not sure what the impeller is is though.

 

[kevbo]

A pair of 44s will make very close to full rpm at 5/8 open throttle. A pair of 38 need to be open a little more but will do mostly the same thing. Large carbs will make the pipe hit harder at low speeds but thats about all.

 

[bored&stroked]

Do you have a tach to confirm the rise in rpm's?
My first guess is its blowing the impellor away, maybe from damage, maybe from power, but I'd look there first.

 

[SJET11]

Do you have a tach to confirm the rise in rpm's?
My first guess is its blowing the impellor away, maybe from damage, maybe from power, but I'd look there first.

What do you mean by blowing it away? Like slipping on the mid shaft or something?

 

[WFO Speedracer]

He means either the impeller is damaged causing cavitation or it's way too low in pitch

 

[john zigler]

What impeller do you have? What is the exit nozzle ID?

I too am guessing you are running out of impeller. (too low of pitch)

 

[SJET11]

What impeller do you have? What is the exit nozzle ID?

I too am guessing you are running out of impeller. (too low of pitch)

I am not sure of the impeller. Could i tell if i put the ski on it’s side or would i have to tear it apart?

 

[WFO Speedracer]

You would have to remove the pump housing and get the numbers off the impeller, if it's a stock impeller there may no be any numbers on it

 

[SJET11]

You would have to remove the pump housing and get the numbers off the impeller, if it's a stock impeller there may no be any numbers on it

Alright I’ll look into it and see what i can find.