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Thread: Gas tank must be more than 1/4 full for performance

  1. #1
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    Gas tank must be more than 1/4 full for performance

    F.Y.I. Had my 6800 mile V on the dyno on Friday, and was getting poor readings. It was decided to add 10 gallons of fuel since it had roughly 4 gallons in the tank. The added fuel brought performance back up. Apparently the Cadillac persons that More Performance spoke with when they ran into a similar problem earlier were aware of the need for keeping fuel in the tank above 1/4.
    What I learned from this is to be sure and have enough fuel in the tank if I am planning on really running it up near redline.
    Rob


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  3. #2
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    Re: Gas tank must be more than 1/4 full for performance

    Rob -

    So what were your dyno results?

    Also, do you mean 1/4 as indicated by the fuel gauge (which minutes later might read empty), or actually below about 4.5 gallons (true 1/4) as might be tracked in the DIC?

    Wildwhl
    Last edited by wildwhl; 05-15-04 at 10:44 AM.

  4. #3
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    Question Re: Gas tank must be more than 1/4 full for performance

    Why does a car need a 1/4 tank of gas to perform?

    Is this the same on other performance cars?

  5. #4
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    Re: Gas tank must be more than 1/4 full for performance

    Results were 317 RWHP,319 RWFPT.
    1/4 means in the tank, the gasoline gauges seem to be set up for idiots who need two gallons in tank after it says it is empty. I just zero out the fuel used indicator when I fill up so I know what has been consumed and what remains.
    I do not know about other performance cars. The Cadillac has what it considered only one tank. It has plumbing that goes from one side of the tank to the other, which I assume is there to balance the tank which is configured more like two saddlebags. The technical reasons for all this escape me.

  6. #5
    Cal is offline Cadillac Owners Enthusiast
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    Re: Gas tank must be more than 1/4 full for performance

    What type of dyno does MP use? Reason I ask is I saw much higher numbers at the place near me and their fan was meager at best, so that was probably on the lower end of things with little airflow. That was also at 515 miles, so not terribly broken in. The slips are on another thread (search for 'dyno' in this forum) but my best pull was 332rwhp.

    Just wondering why there is the discrepancy, that seems quite low for a V.

  7. #6
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    Re: Gas tank must be more than 1/4 full for performance

    I had a very very empty tank and ran a 13.5 then had mroe gas in there and ran about the same. I don't think it can make a differents

  8. #7
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    Re: Gas tank must be more than 1/4 full for performance

    We use a DynoJet 248X. It is the newest that DynoJet makes and will read up tp 1800HP.


    Amber Huneycutt
    More Performance Inc.
    704-393-8241

  9. #8
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    Re: Gas tank must be more than 1/4 full for performance

    It sort of depends where the pickup is. If its in the front of the tank, it can be a problem when you are on it hard. (throws the gas to the rear). This has been a problem with other models.
    Static, like on a Dyno, it shouldnt make a difference.

  10. #9
    Cal is offline Cadillac Owners Enthusiast
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    Re: Gas tank must be more than 1/4 full for performance

    Even my lowest pull (rwhp) was in the 320s, so I'm wondering whether the problem is unrelated to your gas levels.

  11. #10
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    Re: Gas tank must be more than 1/4 full for performance

    I'm with Cal and the others. Dyno variance, not fuel level.

    Where is that article about Dinan being able to get X more hp/tq, with just environmental variables (no touching the car).

    -Ben

  12. #11
    Cal is offline Cadillac Owners Enthusiast
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    Re: Gas tank must be more than 1/4 full for performance

    Somewhat unrelated, but after letting the car cool down after the first dyno pull it pulled almost 10rwhp higher (same fan, etc). I think it was left maybe an hour, maybe 45 min or so. You could hear the difference in the sound of the car on the 2nd pull after the cool-off period.

  13. #12
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    Re: Gas tank must be more than 1/4 full for performance

    Its generall known that FI cars have a lot more chops when the block is cold. We always did an intake ice down at the drag strip. It made a big diff.

  14. #13
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    Re: Gas tank must be more than 1/4 full for performance

    Dyno's do vary but this was a problem with fuel and the lack of it. We have a direct link with GM engineers because of the fuel problem we are having with our Procharger kit. He had the same problem we had at the beginning of our installation. We are working directly with them and are not the only company seeing this problem. We will hopefully correct this by the weekend as GM is sending us new parts for the fuel system. Better in there eyes.

    Amber Huneycutt
    More Performance Inc.
    704-393-8241

  15. #14
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    Re: Gas tank must be more than 1/4 full for performance

    I forgot about the blower. I ran a turbo, definetly not enough fuel pressure or volume with an air pump. I wound up using a 255l/hr walbro replacement, no problems after that..


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