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Thread: PSI question?

  1. #1

    PSI question?

    whats PSI to HP ratio?

    like.. for every extra PSI what is that for additional HP?

  2. #2
    Garrett booster
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    Re: PSI question?

    You're going to have to settle for % increase in HP as it depends on your other mods. And the % increase also depends on the modifications you have.

    To top it off I can't give you the numbers ATM. Because I don't have anything like that prepared, others might.

  3. #3

    Re: PSI question?

    everyone says roughly 7-10hp per psi increase

  4. #4
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: PSI question?

    I seem to recall 7HP/PSI increase on a stock TII motor. That is all but out the window once the big mods come though.

  5. #5
    Admin- "Alexandria" Ken... Comes W/4 Car Garage Turbo Mopar Staff GLHSKEN's Avatar
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    Re: PSI question?

    7-10 per psi depending on mods is a good rule of thumb.
    Ken Adler....
    Cars, A few (9)

  6. #6

    Re: PSI question?

    thanks. i saw it in thedodgegarage.com once i think. and in the past week i think i have read EVERYTHING on there. and i have not fouidn it. thanks guys

  7. #7
    turbo addict Tony Hanna's Avatar
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    Re: PSI question?

    What are we looking at to get to 10 hp per psi?
    Bolt on mods, or are we grinding on ports at that point?

  8. #8
    Admin- "Alexandria" Ken... Comes W/4 Car Garage Turbo Mopar Staff GLHSKEN's Avatar
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    Re: PSI question?

    Well... SOMEONE is grinding ports and fabricating front mount stuff... If I ground anything my car would go slower...
    Ken Adler....
    Cars, A few (9)

  9. #9
    Admin- "Alexandria" Ken... Comes W/4 Car Garage Turbo Mopar Staff GLHSKEN's Avatar
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    Re: PSI question?

    We'll use Butch N's old GLHS as a base. Bone stock Exhaust and all, 12 psi to the wheels he made 140 or so hp...

    Jump to clays. Stock stage 2 computer 2 1/2" exhaust 200whp

    Jump to mine, open downpipe (stock 2 1/4) +20's 18 psi boost 107mph in the 1/4. rough but 250 whp 2600 lb car.

    Same set-up but an open 3" downpipe and Rick d ported 2.5" Swing valve. 109.7mph. About 265hp.
    Ken Adler....
    Cars, A few (9)

  10. #10
    turbo addict Turbo Mopar Contributor Dave's Avatar
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    Re: PSI question?

    I know I went from 14.5psi to 16psi in my T1 Spirit (front mount TII intercooler, Garrett, open cut out, COA, stock computer). It made a hell of a difference. I could then roast the tires in 1st gear at 30mph whereas before at 14.5psi I could only do it at around lower 20mph.

    Never did any hard comparison numbers other than feel. I think with some "good" mods (garrett, good intercooler, no exhaust, and a good fuel/spark curve) 10hp per psi is obtainable.

    We could gain a lot more power per psi if Chrysler was smart and put 2 cams in instead of 1!

  11. #11

    Re: PSI question?

    11.78 hp per additional psi on my 8 valve 2.2. Method of calculation:
    - Ran 18 passes on the same combination, only variables considered was my driving ability and boost.
    - Ran multiple boost levels from 15 to 25 psi.
    - Calculated the HP based on the 1/4 trap speed. (this is likely less affected by my driving ability than ET) This math method also matched a pull on the local dyno to within 5 hp, so it appears to be close.
    - Ran a simple regression model using hp as the dependent and boost as the independant variable.
    Result is for every 1 psi of additional boost pressure between 15 and 25, the car picked up 11.78 hp.

    Also graphed results with a fairly linear pattern.

    Interesting, but also shows I have too much spare time.

    'Also found out the left lane at the local track is .05 better than the right for my combination - although not statistically significant'

  12. #12
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: PSI question?

    Quote Originally Posted by thx138 View Post
    11.78 hp per additional psi on my 8 valve 2.2. Method of calculation:
    - Ran 18 passes on the same combination, only variables considered was my driving ability and boost.
    - Ran multiple boost levels from 15 to 25 psi.
    - Calculated the HP based on the 1/4 trap speed. (this is likely less affected by my driving ability than ET) This math method also matched a pull on the local dyno to within 5 hp, so it appears to be close.
    - Ran a simple regression model using hp as the dependent and boost as the independant variable.
    Result is for every 1 psi of additional boost pressure between 15 and 25, the car picked up 11.78 hp.

    Also graphed results with a fairly linear pattern.

    Interesting, but also shows I have too much spare time.

    'Also found out the left lane at the local track is .05 better than the right for my combination - although not statistically significant'
    This is by far the best post in a dead thread in the history of the internet. Congratulations Sir.

  13. #13

    Re: PSI question?

    Quote Originally Posted by cordes View Post
    This is by far the best post in a dead thread in the history of the internet. Congratulations Sir.
    I had to look real hard to find somewhere to post my findings without starting something new

  14. #14
    Hybrid booster
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    Re: PSI question?

    I love it!

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