Turbo vs Blower fuel flow and boost

Discussion in 'PSI Superchargers Tech Questions' started by Bjs344, May 21, 2020.

  1. Bjs344

    Bjs344 Member

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    For a given hp, how much more boost and GPM does a roots blowerneed vs. a turbo setup. I know there’s a lot of variables, just looking for known existing comparisons. NHRA promod or any other combo just to get a range.
     
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  2. jay70cuda

    jay70cuda Active Member

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    Steve petty told me that roots uses more fuel because of the mfi. It's crude and just does enough to get by. That the barrel valve is the issue. But efi is so efficient because you can control each cylinder and it can run ideal afr from idle to max rpm.
     
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  3. Bjs344

    Bjs344 Member

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    Thanks, but I was looking at it from a bsfc type perspective. The roots takes more fuel/air to turn than the turbos. That will be true whether efi or MFI on the roots.

    The NHRA cars should be a decent comparison but I have seen very little on how much boost a legal roots car can make or how much fuel either combo flows.
     
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  4. bandit496

    bandit496 Member

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    This might not help but having run both blower and turbo, but in a tractor pulling scenario....I am now running twin 85 mm turbos on a 540 BBC (waste gates open at 40 psi). A friend runs a 526 hemi with a 14 (DMPE or Janis-not sure) at 45% over. Both are MFI as EFI is not allowed and alcohol. We were comparing notes a couple of weeks ago and surprisingly the fuel usage on a pass was similar--about 3 gallons on a 320 foot run (hard to really gauge since one might have a little different starting procedure). The parasitic loss turning the blower is an issue. Don't know if it is relevant but feedback nevertheless.
     
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  5. Bjs344

    Bjs344 Member

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    Thanks bandit. I see guys talk about 1.2 bsfc for a turbo and 2.0 for a roots and I just have trouble believing those numbers. That would put a turbo promod at like 8 gpm lower than a roots for the same power????
     
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