08-26-2005, 05:39 PM #1
RXP Rotax RPM problem... we're helpless
we have a customer that we did alot of work on his RXP... one disappointment after another...
with these mods:
BOV and Plumbing
Riva air intake
Riva intake grate
OPAS block offs
PPG Solas pitched
ski would only run 72 MAX ... 7900-8000 rpms if we werre lucky... customer not satisifed, and we were not impressed either... purchased RR ECU... did appropriate knock sensor removal, tested the ski.... performed horible! upper 60s... rpms weren't happenin, lsot acceleration... was smokin blue-ish a little.... IT WAS BLOWN UP.... so we got a brand new long block 215 SC IC for the ski.... put it in and 15 minutes later brand new motor SC clutches blew and had to take apart a 15 minute old motor... w/e... put ski back together with some mods like IC, power pipe, BOV, riva air intake, grate, etc.... NO RR ECU at this time...
we personally at the dealership broke in the ski for the customer for 6 hours.... at WOT 7700 rpms 66mph or so... wtf!? .... so we add the RR ECU..... same speed and same RPMS.... but lsot acceleration again... the stock ECU was an animal! RR ECU slower
we tried 3 different props, different nozzles, different ECUs (04 ECU, 05 ECU, RR ECU) ..... no matter what we do, no matter what prop and what ECU... we're at 7700-7750 rpms and only 66-67mph or so...
can anyone lend us some advise and get us going here?
08-26-2005, 05:41 PM #2
The ski from hell.... LOL!
I tried helping Jay with that ski some time back.
How was it running before the engine blew up? RPM's? GPS Speed?
From what i remember that ski never did really run right. Did he get the
problems ironed out before the engine blew?
Okay, now you can't get more than 7700 with the new engine and RR ECU. Did
the new engine come with a wire harness? If so it is probably an 05 wire
harness and a modification has to be done to the knock sensor side of the
If that isnt the problem did the new engine come with a throttle body? If
so then you need to take the throttle position sensor off of the old engine
and put on the new one as it marry's itself to the ECU.
Both of these things can cause low 7700 rpm's with the RR ECU.
08-26-2005, 05:48 PM #3
as usual jerry... the ski ran it's best jsut before it blew.... with stock ECU and all those parts we had in it it would run 8000 rpms but only 72 mph.... customer wanted 75 so we said aright lets try the ECU.... we do that.... rpms were way off, speed was gone, jsut didn't sit well with it... went back to stock ECU and same thing.... remove motor and Rob took motor completely apart and it wasn't completely messed up... jsut worn out, tired.... things kinda maxed out to spec i guess....
new 05 motor.... we removed the integrated knock sensor in the harness...
so as usual... she ran good just before she blew!! well that's when we had best rpms... but still lacking speed.
so no, i would NOT say that EVERYTHING was ironed out before she blew.... it's all new motor and ECUs....
next step we're checking fuel pressure..... and maybe TOPS valve....
i'm almost 100% postive rob kept the throttle body bc we knew it stayed married to the RR ECU... but regardless... the ski won't run right even with an 04 ECU or 05 ECU.
Ski from hell is an understatement! lol...
u can ignore the e-mail i sent you jerry concerning this issue since u answered it here
08-26-2005, 05:58 PM #4
check your email shibster!
08-26-2005, 06:11 PM #5
LMAO.... i just got that last e-mail.... probably not a bad idea at this point, geesh... i think the poor guy should honestly sell everything he put into it and keep it stock bc he's slower than stock right now, haha...
best mod he bought for this thing so far was an extended warranty
we'll putse around with the thing a little more tomorrow and see what we come up with... but the ski has to go back to the customer bc we've had it way too long trying to dial it in and it's gettin absurd now.
thanks for the help jerry... i appreciate it.
08-26-2005, 06:18 PM #6
didn't the 03'sc's come with a different size SC gear? Could it be possibly on the sc by mistake? just an idea...
08-26-2005, 08:11 PM #7
Rotax ecu needs tons of air..AND I MEAN TONS!!.. The more air the better!!.. I still say the riva air intake is to restrictive!!..As well the riva grate scrubs speed...If the solas is re-pitched too tall then it could cause low rpms...Not sure why you have the bov...you don't need it..As well check the ic plumbing to see if it is not leaking..If you are running the GTX SC motor the Pistons are cast and the sc gearing is different..
I know alot of this you might allready know but I am just thinking out loud...Hopefully it helps...
08-26-2005, 08:44 PM #8
I have a ski that just won't accept the RR ECU. 7650 RPM no matter what. 4 different props and always the same thing. Some of these RXP's are just haunted I think
08-26-2005, 11:29 PM #9
Franko.... i swear that's exactly it!! we've gone thru like 10 prop/nozzle combos.... it will not budge from 7700 rpms
twocorrupt.... that was one of our next thoughts.... 4" flex tubing air intake straight to the front hood kinda like what Jerry did...
the engine compartment in this ski is freaken hot as hell... today we had temps in the mid 70s and it's cooling off from the mid 90s we had been having... despite the 20 degree air temp, the engine comaprtment was flamin hot... so we gotta help this thing breathe and the rive air filtert is chillen next to the motor in the middle of that swamp land heat.
08-27-2005, 07:15 AM #10
This is why you should not "multi" mod a ski of any kind.
Do 1 mod at a time, test it and if it performs, do the next mod.
It takes a lot longer but maybe in the long run saves a lot of frustration.
Good luck with it!
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