Page 1 of 4 1234 LastLast
Results 1 to 20 of 69

Thread: Jet Boat Tune, again.

  1. #1
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58

    Jet Boat Tune, again.

    I have O2's on the motor now and it still runs bad. It will rev to about 4,000 rpm for the first minute or so, then as it warms it falls flat. During that first minute I can get about 2/3 throttle response. Any more than that power drops off. After the first minute or so when power decreases it falls rapidly to where it will barely run about idle. I do run lake water for cooling so the engine temp usually never gets above 104 degrees.

    I'm running a 5.3 with stock injectors, ported heads that are milled for 10:1 compression with a 226/229 .575/.578 on 112 cam and on a DBW throttle that seems to be working correctly. With the motor not running the throttle blade has full movement.

    It's gonna go back on the water Wednesday night for the next lake test. I'm open to suggestions to get it to run. Maybe go across the board and jack up the ECT tables? I've tried messing with the torque management setting but they had no effect. There has to be something simple that being missed here which is not letting this motor cut loose. This thing should be able to turn 5,100 or so rpm with the impeller that in the pump if I can get the last 1/3 throttle to work and for longer than a minute.

    Here's all the files that go with the motor.
    Attached Files Attached Files

  2. #2
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    I don't know where to look in HPT, but over on LS1 Tech I'm reading about problems with DBW pedal position and throttle position not being within spec of each other and causing limp mode. I know with the CAI off I can see the throttle blade fully opened just past 1/2 throttle on the gas pedal travel. The motor and ECU are from a 2002 Tahoe, the TAC and pedal are from a 2001 Yukon. It shouldn't matter, but you never know.

  3. #3
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Here's the table for the gas pedal. Is this correct? I would think it should go from 16 on the bottom to 100 on the top and be smoothed in between. But the throttle blade is open 100% at 60% pedal travel.

  4. #4
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Looked at a couple of other 5.3 with DBW tunes. A 2003 Tahoe tune I downloaded is way different and a 2000 Silverado tune is exact. I'm only talking about the table in the engine/airflow/electronic throttle max rotation vs. pedal rotation table.

    I now don't think it's a DBW problem. It's doing exactly what the PCM is telling it to do. Something is causing this to go into limp mode very quickly.

  5. #5
    Tuner in Training
    Join Date
    Jul 2011
    Posts
    35
    It looks like you have a huge vacuum leak your MAP should be around 35 at idle

  6. #6
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Interesting. Worthy of checking out. I though I had everything plugged but may have missed something. I only run vacuum to the fuel pressure regulator and the TB. One goes to the PCV also. Another one connects from the valve cover to the intake with nothing in between but open hose. Should something be on it? Maybe cap both of those two off and see what happens since there is a PCV on the other side. The brake vacuum is capped off too.

    Put a fuel pressure gauge on it today just to check. 52psi at idle, a little over 60 with the throttle open, just over 40 with the engine spinning down and the throttle closed.

  7. #7
    Tuner
    Join Date
    Dec 2009
    Location
    Slave Ship
    Posts
    199
    Definitely check for vacuum leaks. Look at your STFTs, they're giving you a clue as to why it's not running well.

  8. #8
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Took it down to the lake and dropped it in the water with a can of carb cleaner. Sprayed that crap everywhere and couldn't find a leak. Pulled the PCV and connected it directly to the TB to eliminate that and the MAP stayed at 70. Even with the PCV and TB vacuum's both uncorked the MAP still stayed at 70. It's just over 100 with the engine not running. I would almost maybe think the cam is off, BUT it runs really good for the first minute.

    Let me look at the STFT and see what's going on there.

    EDIT: WOW, STFT is pegged. Maybe I'll try some new intake gaskets tomorrow. It's got to be leaking somewhere.
    Last edited by blazeracer; 05-07-2012 at 08:12 PM.

  9. #9
    Tuner in Training
    Join Date
    Apr 2012
    Posts
    15
    looks like its super lean at about :35 then it starts adding fuel

  10. #10
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Quote Originally Posted by MikeyZ View Post
    looks like its super lean at about :35 then it starts adding fuel
    It runs really good for the first minute or so. Once it starts adding fuel it's screwed. I'm gonna pull the intake tomorrow and see what gives then lake test it on Wednesday with the STFT's off. We're supposed to have rain here in Texas tomorrow.

    Step 1 should be to get the idle MAP kPa down to about 30, right?
    Last edited by blazeracer; 05-07-2012 at 11:31 PM.

  11. #11
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Just scanned my 2000 GMC and it's MAP is at about 38 at idle. I'll start by switching the MAP sensors to eliminate that as the problem. Have work for a while so it won't be till later today. The one is the boat is the cheap one from Orielly Auto.

  12. #12
    Advanced Tuner
    Join Date
    Mar 2005
    Location
    DFW
    Posts
    293
    There's no way your idle will be 30 or 35 kpa with an aftermarket cam.

  13. #13
    Tuner
    Join Date
    Dec 2009
    Location
    Slave Ship
    Posts
    199
    This thing has ported heads and a camshaft yet the tune file you posted is damn near stock. There is a reason it doesn't want to run. It's not tuned.

    And FYI, the 4000rpm limit you're hitting is probably when it switches over to using the MAF for airmass calculations. Is there even a MAF on the engine?

  14. #14
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Quote Originally Posted by Nodnarb View Post
    This thing has ported heads and a camshaft yet the tune file you posted is damn near stock. There is a reason it doesn't want to run. It's not tuned.

    And FYI, the 4000rpm limit you're hitting is probably when it switches over to using the MAF for airmass calculations. Is there even a MAF on the engine?
    Yes, running a MAF. I sent the guy that did my harness (Todd McCullough from S&S Performance in Arkansas) my cam specs and he was supposed to give me a base tune to get started. Looks like the tranny and rear O2's got deleted and that's about it.

    I have a cam but it's not huge. Like a stock Camaro cam. What kind of MAP pressure should it be pulling? Not over 70, right? If so than what's setting off the STFT's to peg after a minute, and how do I get it over 4k rpm? It really doesn't seem like the intake is leaking. I hear no whistle or whoosh noises. Carb cleaner didn't raise the RPM's anywhere I sprayed it.

    ALSO, I have to run a MAF cause if I unplug it the DBW goes totally unresponsive.

    Can I add 5 to the VE table for base tune on the cam? Heard some guys do that to get them started. You're 100% right about it being stock. Looked at a 2003 Tahoe and the VE is identical.

    I wonder if the cam needs to be retarded maybe?
    Last edited by blazeracer; 05-08-2012 at 04:57 PM.

  15. #15
    Tuner
    Join Date
    Dec 2009
    Location
    Slave Ship
    Posts
    199
    Plain and simple.......It needs to be tuned.

    Step 1: Get a wideband

    Step 2: Tune it.

    I'm used to seeing tamer camshafts idle in the 50-55 kpa range. For your camshaft, it may end up a bit higher.

  16. #16
    Have you tried running MAF only? Set High RPM disable to 200 or so.
    Do Gen III's need a speed signal to get out of Idle spark tables?
    If I was doing it, I would start by just tuning the MAF with the O2's up to about 4k or so and see if you can get a handle on the fueling...if not then most likely a vacuum leak.

    Sorry havent been tuning in a while or I would try to help more.

  17. #17
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    Do I need 1 wideband or 2? Can I use widebands without the Pro version or do I need to upgrade.

  18. #18
    Tuner
    Join Date
    Dec 2009
    Location
    Slave Ship
    Posts
    199
    1 wideband is fine. Using the pro version is the easiest but others have had luck going through an A/C pressure switch I believe. Try searching around.

    BTW, what's your fuel pressure set to?

  19. #19
    Tuner
    Join Date
    Apr 2012
    Location
    East side of DFW
    Posts
    58
    55-60 range when on the pedal. About 52 at idle. Seeing as how this is in the boat there a ton of empty spots on the PCM to hook onto. Read about using the EGR too, but in both cases the resolution is not at good as just upgrading to pro. Still, could use ideas for a base tune to at least get it to run. Now it won't do squat. Should I bump up the VE table and turn off STFT's and LTFT's? What other stuff needs to be adjusted for a big ole cam?

    Actually, if it comes to shelling out another $500 to get it to be able to tune correctly, I may just take it to a guy and get er dun, then sell what's left of my HP Tuners with the 6 credits on it. Other than this boat I have no use for it. Right now it's frustrating have worked on the conversion all winter and now it won't run. If I could get a good starting point that may raise the bar on the satisfaction of doing it myself rather than paying someone.... Then maybe soup up the wife's 08' Tahoe once the boat is squared away. LOL
    Last edited by blazeracer; 05-08-2012 at 05:45 PM.

  20. #20
    Tuner
    Join Date
    Dec 2009
    Location
    Slave Ship
    Posts
    199
    Check the tune repository. There's a couple 5.3's with camshafts you could steal info from.

    Bump up your Base Running Airflow, MAF transfer and VE table and learn how to use the scanner. You can get it done.