Roush call me crazy, but could there be a mathematical equation? boost : whp

Discussion in 'Special Production' started by 200SICK, Jul 13, 2010.


  1. 200SICK

    200SICK New Member

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    boost : whp, ratio

    you guys are gonna think im off my rocker haha but could it be true?

    i have thrown some numbers together from some dyno comparisons i found.

    What if you could say how much boost you have could get you a relatively close dyno estimate?

    my math...

    my first run 12.5# / 456whp = 2.74%
    my latest run 14# / 495whp = 2.82%
    07 GT/saleen blower 9# / 429whp = 2.1%
    mikebna first run 12.5# / 464whp = 2.7%

    notice the differences....
    429 = 2.1
    456 = 2.74
    464 = 2.7
    495 = 2.82

    They seem to crawl up with power even though every car is different. This would tell me that the higher the power, the less power boost creates, which would make complete sense. For example, a jump from 5 to 6 lbs might give you 60 hp. 12 to 13 lbs might give you 15 hp. That being said...you could estimate that:

    525whp should = appx. 2.9% (conservative) which would = 15.22#
    550whp should = appx. 3.15% (conservative) which would = 17.33#

    Therefore, you could predict mikebna to be approximately around 545-550 on the dyno if his boost is up in the 16 range. We will see if that's true when he posts up his numbers.

    The question is...what kind of boost is a tuned 302 E that dyno's in at 589 whp making? must be somewhere below 16 if thats all the gauge allows for right?

    Anyway, clearly im bored haha. ill do it for you...

    :worthlesa
     
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  2. mikebna

    mikebna Member

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    From what I saw today boost might equal torque:shrug:not HP.
     
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  3. mikebna

    mikebna Member

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    Theres no way a stock S302E should dyno at 589rwhp, unless there were some major mods or the dyno was massaged a little on the numbers?
     
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  4. 200SICK

    200SICK New Member

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    no no, not a stock 302E; this was an E with all the same mods you have, but for the 302E. check it out...:nice: http://http://www.youtube.com/watch?v=7cT9FIhuNb0
     
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  5. mikebna

    mikebna Member

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    I have a friend who will dynoing his 07 Extreme on the same one I used. He has never put it on one, and has less mods than me and is at 12-12.5 psi boost.....so we will have some new numbers to play with in a week or two.

    He has LT headers, exhaust, and the Saleen Ultimate air intake is all added to his car.
     
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  6. 200SICK

    200SICK New Member

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    Cool, looking forward to seeing them.

    i was looking at my blower last night and it looks like the snout is already machined down where the pulley sits. I wonder if ALL VI series blowers are like that or only the E to fit the 2.87"? worth finding out.
     
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  7. 89saleen372

    89saleen372 New Member

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    For a turbo (very efficient) you can approximate HP by comparing the boost to atmospheric pressure. Instead of using 14.7 atmospheric I use 14 psi since there is a pressure drop across the air filter and it makes the math easier. If you run 7 lbs of boost, you would increase your NA horsepower by 7/14 or 50%. If you run 14 lbs of boost, you would increase your NA hp by 100% (i.e. double your NA horsepower). A 300hp NA engine, boosted with 10lbs of boost will result in close to 300 + (300*10/14) = 514 hp (but I would round down to 500whp). Superchargers are not quite as efficient, so the HP numbers would be a little lower.

    I am not familiar with the specific engine you are talking about, but if I new of a stock 4.6L that was making 400hp boosted, I would look at it this way:
    Stock whp is around 270whp. In order to estimate how much boost, I know that the NA hp is increased by 130hp, or 130/270 = 48%. This means that x/14=.48 (x being the amount of boost) and x=6.72. In this case I would round up due to inefficiencies so I would estimate 7 lbs of boost to reach the 400whp.
     
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  8. sema88

    sema88 Member

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    I always thought it was 7% increase in power for every pound of boost. What makes it hard to figure out is efficiencies. So many factors go into a dyno run, air temp, engine temp, humidity, mods, drivetrain etc. As a good rule of thumb 6-7% per pound works. In our Saleen pre blower we put down 218 hp with the blower we made 300 hp with 5.5 lbs of boost.
    5.5 x 7 = 38.5% increase
    1.385 x 218= close to 300
     
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  9. 89saleen372

    89saleen372 New Member

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    That is correct - 1psi/14psi is 0.07 or 7%.
    So 7psi (/14) is 50% additional whp.
    10psi (/14) is 70% additional whp.
    14psi (/14) is 100% - doubled whp.
     
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