Thread: Breaking up in high RPM
05-11-2015, 08:09 AM #1
Breaking up in high RPM
I am having an issue with getting my ski dialed in. Over the weekend, I was running around and blew off an intercooler hose. This is the third time it happened this year. (once broke a constant tension clamp, the other 2 were the same t-bolt clamp that will be replaced) Once the clamp was done, the ski would run up to 8300 rpm and felt real solid. This was with the finger throttle at 3/4 down and really, it is running where the ski should be at WOT. If I go past that, it will go from 8300 to 7500 and back and just jump around. The ski was at 12.5 at 3/4 down, then the WOT would go from 14 to 10 (obviously it is breaking up)
What do you guys think this could be? I was going to look for other boost leaks this week, but don't know where to go from there. Any ideas would be great, my mods are in my sig.
05-11-2015, 08:12 AM #2
The ECU pulled your timing due to detonation (Knock Attack) and you're having trouble recovering after the attack (knock decay). Get that 14 WOT crap under control and give it another go.
Make sure your fuel pump is doing its job and that the Walboro is a real walboro. I just had an issue where my brand new walboro sucked up the rotten strainer sock and ruined the impeller. I compensated it with my fuel map and now I need to basically redo my entire IFR map.
05-11-2015, 08:22 AM #3
The walbro is a real walbro pump, we use them at my work all the time. My Rotax ECU does not have a knock sensor program on it, so that should not be the case. My ski should run right around 8300-8400, so I am not too far off, but yes, I do believe the ECU is pulling timing at some point.
05-11-2015, 10:59 AM #4
I missed the fact that you're running this with 48s. You need a minimum of 60s. You might have a injector hanging open from going static.
05-11-2015, 12:10 PM #5
hmm, never thought I was running out of injectors. I thought the 48s were good for the 137 wheel. Do I need the 60s since I am spinning the motor faster now?
05-11-2015, 12:15 PM #6
may as well go for 80s man. That way you have compensation room plus room for 9K
05-11-2015, 12:20 PM #7
Yeah, I was looking in the store and it says the 60s are for the rotax ecu. I guess I suck at doing research lol. I am thinking I am just going to jump to the 80s so I don't need to worry about this again. Thanks for the input, I would have never guessed on injectors. Looks like some 48s will be for sale soon.
Thanks imposter for the input.
05-11-2015, 12:25 PM #8
Check your intercooler for a leak... The symptoms you have are classic symptoms of a leaking intercooler... runs fine at lower RPM, but when you get under boost and higher RPM water gets mixed with the fuel mixture and the engine will start to sputter/cut out
05-11-2015, 12:32 PM #9
Yeah, I can do that as well. I hope that intecooler is fine, I have low hours and only fresh water on it, but I will look anyways.
05-11-2015, 02:16 PM #10
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