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Thread: Boost Fooler

  1. #21
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    Feb 2007
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    Turn it somewhere until there is no defueling. I blocked the sensor hole, easier, but get a 78 code after 50 starts.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  2. #22
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    Jul 2012
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    WA
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    So I put the pot in using your schematic. At first I had the knob turned all the way right and it made the engine defuel. I turned it half way and it was still defueling but not as much. Turned the rest of the way all the way left and it acted normal. Where it's set I may as well not have cut the B wire at all. Not sure if it is correct. Is the A wire supposed to be in the middle instead or was it supposed to be cut going to the computer or sensor?

  3. #23
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    That would be a good idea, you don't want overboost.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  4. #24
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    Jul 2012
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    WA
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    What would be a good idea? I basically want to know of its normal for it to defuel when the knob is turned one way. If I turn it right it's like I'm just turning down the fuel directly and the truck will only make about 5 pounds of boost max with the pedal to the floor. I should be able to control max boost with the mechanical wastegate right.
    Last edited by Tombrewster421; 03-27-2013 at 06:30 PM.

  5. #25
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    I checked the wiring diagram on another site, it is correct. This modification is for use with a mechanical waste gate, you have no details of your truck in your signature, so I don't know what we are dealing with. My last post was a reply in error to a page 1 question.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  6. #26
    Join Date
    Mar 2012
    Location
    Northern BC Canada
    Posts
    7

    Default Mpg.....

    Quote Originally Posted by grancito View Post
    I checked the wiring diagram on another site, it is correct. This modification is for use with a mechanical waste gate, you have no details of your truck in your signature, so I don't know what we are dealing with. My last post was a reply in error to a page 1 question.
    So the way I understand it, you are adding resistance to fool the ECM into thinking the engine hasn't maxed the boost and fuel and it therefore adds fuel increasing boost. If the 10k pot is wired wrong, you can decrease boost as stated before, getting max 5psi. The way the schematic shows, you shouldn't be able to decrease boost by adding resistance......

    Interesting, I wonder what the mpg would do with the minimum boost setting, and careful driving, with economy in mind? One may be able to wire that potentiometer with a 3 way switch to do boost, normal, Economy without spending bucks on a home built chip. Anyone try this?
    Last edited by 94turbo-; 04-17-2013 at 01:30 AM. Reason: Spelling

  7. #27
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    The ECM does not use sensors other than the accelerator to determine the amount of fuel to inject, except in the case of defueling and rev limiting. Boost is controlled by the waste gate. The boost fooler is designed to be used with a mechanical waste gate to allow more boost without defueling. Reducing boost below standard would likely give worse mpg. High boost at low throttle gives bad mpg. GM would have designed the amount of boost to be right for average driving conditions.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  8. #28
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    Mar 2012
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    Northern BC Canada
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    Thought I'd ask, thanks

  9. #29
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    Mar 2012
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    Northern BC Canada
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    Default Codes?

    Do you get SES when de fueling occurred? I felt the engine loose power when the SES light came on. I was reving 3k and the boost was 12 psi (as accurate as my gauge may be ) My SES went away when I restarted the engine, I haven't checked the codes as yet.

  10. #30
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    Yes it gives code 78.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

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