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  1. #1

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    Overboost/Underboost/Wastegate Actuator Problem

    I have been trying to figure this ski out for 2 years. Put in water this weekend. All parts I have been chasing around are new. Still has rev. limit at 5,800 RPM @ WOT.

    So I decided run it with seat off and stick my hand on wastegate arm. It is fully extended/maxed out. At WOT, I force the waste gate arm back closed, maybe 1/8". BAM, 7200 RPM. Runs that way until my hand is numb. Let it go, it extends back to max. and back to 5,800 RPM. When I return to idle ski is hunting. Turn it off, wait awhille and it will start up and idle.

    So what is my issue? Wastegate too far open. Do I adjust, do I change wastegate actuator? Any help would be awesome. I feel I am close to getting this thing to rock. Saw 72 mph on dream-o-meter as my hand held wastegate in correct place. Spot on at 7200-7300. Has Desperado's ECU and a new pump unit with updated new impeller.


  2. #2
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    Last edited by FichtEMMRepair.com; 01-12-2015 at 10:49 PM.

  3. #3

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    I hear ya. I did look at it when I 1st bought the ski and it appeared it had been worked on, but I left it alone. Maybe the WG actuator is getting out of adjustment or maybe who ever worked on it last time goofed it up.

    Anyway, I will adjust and report back. Thank you.

  4. #4
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    Last edited by FichtEMMRepair.com; 01-12-2015 at 10:48 PM.

  5. #5
    ripcuda's Avatar
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    I'm curious how much boost you're actually making. You'd have to hook up a real boost gauge to know for sure.

    It's possible the PO messed with the wastegate actuator rod length in an attempt to adjust the boost levels. Harris is right... shorten rod to increase tension on wastegate and increase boost... lengthen rod to decrease tension on wastegate and decrease boost.

    The curious thing is though... the ECU controls boost via the wastegate solenoid (aka boost valve) and it only takes 5psi to open the wastegate and stop boost rise... but if the ECU want to raise boost... it only need to cycle the solenoid... remove boost from wastegate actuator... which then the actuator spring will pull shut the wastegate and the boost will rise. Seems odd your ECU can't raise the boost more (but you can via your hand... slightly closing the wastegate)... unless your ECU thinks your already at the correct boost level... or there's some internal programing for cycling the solenoid that the ECU can't change or overcome.

    I suspect the reason the idle hunts after you manually raise the boost is because the ECU has been trying to control it while you were manually altering the boost. Then once you give ECU back control... it's still trying it's overcorrected parameters to control the boost and they're no longer needed so it's overcorrecting. I've seen this happen with my turbo cars and ECU controlled boost.

    So yeah... tweak your actuator rod length... a little at a time and see what happens. Hopefully you'll find the sweet spot the ECU can easily control and keep things where it wants them.

    Side note... are you running a steeper impeller? If so, you probably can't hit normal max RPM without extra boost... which you should be getting from the reflashed ECU.

    Cheers!

  6. #6

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    Well if the ECU has all that control and can do all that stuff then why did they have an adjustable arm? Anyway, I do have a different impeller with the Stage II ECU that is suppose to spin it 7200. The problems with the ski were all over the place. Last year, it was determined the pump unit was kinda of shot. After getting with Desperado and getting correct impeller, rebuild, and codes cleared it ran spot on for 20 minutes at 7200. Then into limp mode for rest of year.

    Pretty much before this 20 min run last year, it has never run right. Either in limp mode or on rev limiter at 7700. W/O a dealer to help with a DW, it is a long process to clear all areas and get it figured out. Doesn't help I disconnected wrong line when I added the catch can and over heated the exhaust and melted it.

    If it ever stops raining, I hope to get it up and taking nourishment.

  7. #7

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    Well I shortened the arm 1/8", still 5,800 RPM. Shortened 1/4" and 5800 RPM, then after 30 seconds it would pick up the boost and go to 7300 RPM. Seemed to right on the edge of correct boost level. Still hunting at idle. Then did last adjust and I pretty much was out of adjustment and to connect arm, the actuator lever was fully extended. Went out, it started to make boost, heard a bang like turbo blades hitting something. Turbo was shuttering, and check engine light came on. It was maybe 4,000 RPM and I shut it down right there. Waited and re-fired. No check engine light and idled it back to shore. Ran fine, but still hunting at idle. Hope I did not hatch the turbo. Looking like I need a new actuator, check for vacuum leaks, and re-adjust arm back to stock.

  8. #8
    Kosh's Avatar
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    I'll give the idle problem a shot, unplug the 02 sensor it should settle to a predetermined ECU idle. It will tend to be slow to return to idle as well but should stop hunting if it is a defective 02 sensor.

  9. #9

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    It is slow to return to idle right now. Also, when I start it up cold it takes off like a raped ape for about 30-45 seconds at maybe 2500 rpm. Then settles down.

  10. #10
    ripcuda's Avatar
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    Koodat... here's an old post from Desperado... about adjusting the wastegate actuator rod length.

    http://www.greenhulk.net/forums/showthread.php?t=106344

    Might help...

    Cheers!

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