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  1. #1
    ou812's Avatar
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    Fuel base pressure gone crazy!

    I've always run my base pressure at 52 psi for the past few yrs to get an 11.9 AFR on a turbosmart FPR800. Lately i've been trying to figure out an RPM issue. I lost 1000 RPM somehow, A slightly rougher idle than usual & at 1/2 throttle I get 7300 rpm and anything beyond that did nothing. The motor wouldn't stumble or stutter, it just felt like it was being held back. Well, everything checks out ok.. Cyl PSI,no boost leaks or IC leaks, etc.. I found that I had to run my base fuel pressure much lower than usual to get 12.0 AFR and get back 780rpm on a lake that's known for crappy performance @ 1568ft.

    Q:
    What would have to happen to make me have to go from a 52 psi base down to 38 psi base to get the same AFR? Oh, my idle is now at a 13.9. Fresh gas, no metal shavings in the oil filter, strong battery, new fuel filters (internal & external) new plugs & what looks to be clean bosch injectors.

    Any Ideas?
    Thanks


  2. #2
    Hydrotoys's Avatar
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    Have you double checked your gauge and/or regulator? Try swapping them out.

  3. #3
    Mod less, ride more! troyheb's Avatar
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    Quote Originally Posted by Hydrotoys View Post
    Have you double checked your gauge and/or regulator? Try swapping them out.
    +1 What was the afr @ 7300?

  4. #4
    ou812's Avatar
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    Quote Originally Posted by troyheb View Post
    +1 What was the afr @ 7300?
    AFR was 10.1
    I have a rebuild kit coming for my fpr.
    Thanks.

  5. #5
    JFizzleJR's Avatar
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    Are you certain about the cyl. PSI being the same? Some of your symtoms sound like a jump in the timing chain.

    Quote Originally Posted by ou812 View Post
    I've always run my base pressure at 52 psi for the past few yrs to get an 11.9 AFR on a turbosmart FPR800. Lately i've been trying to figure out an RPM issue. I lost 1000 RPM somehow, A slightly rougher idle than usual & at 1/2 throttle I get 7300 rpm and anything beyond that did nothing. The motor wouldn't stumble or stutter, it just felt like it was being held back. Well, everything checks out ok.. Cyl PSI,no boost leaks or IC leaks, etc.. I found that I had to run my base fuel pressure much lower than usual to get 12.0 AFR and get back 780rpm on a lake that's known for crappy performance @ 1568ft.

    Q:
    What would have to happen to make me have to go from a 52 psi base down to 38 psi base to get the same AFR? Oh, my idle is now at a 13.9. Fresh gas, no metal shavings in the oil filter, strong battery, new fuel filters (internal & external) new plugs & what looks to be clean bosch injectors.

    Any Ideas?
    Thanks

  6. #6
    ou812's Avatar
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    Cyls 1 2 3 = 140 135 125,
    they started off at 150 142 140 when rebuilt with fresh hone, new rings, head & block resurfaced. It went through hell in the mark hahn race @ it finished in 1 piece under full power.
    Here's something I forgot to mention. After I leaned it out, when it would get to the 7300 rpm mark it would feel flat for just a second & then accelerate to 7800+ every time. 7300 rpm is a flat spot HUMP it seems. I guess I should check the cam gear to see if it slipped in the grooves?

  7. #7
    speedskixp's Avatar
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    Quote Originally Posted by ou812 View Post
    Cyls 1 2 3 = 140 135 125,
    they started off at 150 142 140 when rebuilt with fresh hone, new rings, head & block resurfaced. It went through hell in the mark hahn race @ it finished in 1 piece under full power.
    Here's something I forgot to mention. After I leaned it out, when it would get to the 7300 rpm mark it would feel flat for just a second & then accelerate to 7800+ every time. 7300 rpm is a flat spot HUMP it seems. I guess I should check the cam gear to see if it slipped in the grooves?
    Is it coming out of cold start mode. Does the A?F start out rich when cold then lean out a bit after a minute or so? May be a bad temp sensor tell the ecu it's still cold.

  8. #8
    Sturm215's Avatar
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    Someone correct me if I'm wrong, but I was thinking alot of people didn't have good success with those Turbo smart regulators?

  9. #9
    ou812's Avatar
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    Quote Originally Posted by speedskixp View Post
    Is it coming out of cold start mode. Does the A?F start out rich when cold then lean out a bit after a minute or so? May be a bad temp sensor tell the ecu it's still cold.
    it will start out at 13.8 then go to 14.0 at idle after I dropped the base down. Before, @ 52 base it was like 10.9 and stay there with a sloppy idle

  10. #10
    ou812's Avatar
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    Quote Originally Posted by Sturm215 View Post
    Someone correct me if I'm wrong, but I was thinking alot of people didn't have good success with those Turbo smart regulators?
    I've heard the same.. I ran this setup for a few yrs now & Muddy Rivers ran it before me.. Think maybe the new diaphragm kit will help out?

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