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Thread: Real Street Performance

  1. #1
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    Real Street Performance

    It has been repeatedly brought up that certain blower applications are better than others for street performance, so I thought it might be of interest to compare two different blowers in similar applications and how they help the 3.8L SC motor make useable street power.

    I specifically cut off both of these charts above 5200rpm for 2 reasons. 1) street performance is below 5200rpm 99% of the time, and 2) both applications were having issues with either belt slip or insufficient injector above that rpm.

    Both charts are available in full if someone so desires but that is not the topic of discussion here in this thread.

    The cars used for this comparison are both excellent runners and easy 12 second cars. Both engines exhibit decent street manners and could be considered daily drivers. Both motors have some "trick" parts with neither one having a significant advantage in terms of cylinder head flow or camshaft profile.

    In the first case an MPII at 15% OD was used for one run and an MPIII with 20% OD used on the second pull. Some adjustment was made to compensate for an overly rich condition as you can see from the AF chart. Further adjustment of AFR and timing did not result in any more power so the final number could be considered an optimized tune for comparison purposes.

    As the chart shows this netted a gain of 7.9rwhp (2.3%) and 18.5rwtq (4.7%).

    In the second case an off the shelf Magnusen S-Port was used with 5% OD on the first pull and a total of 10% OD on the second one. No adjustments were made between pulls.

    Net result was a gain of 5.7rwhp (1.7%) and 15.8rwtq (4.1%).

    This means that with the MPIII conversion the motor had lost about 51% of the gain in torque it had netted earlier in the rpm range, and the S-Port had lost about 58.5% of it's torque increase by 5200rpm.

    Discuss.
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    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
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  2. #2
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    Nevermind i'm retarded. They seem to be relatively close together. Is almost 10rwhp worth it to switch MPIII, well I just dont know.

    What motor combo is that on?
    Last edited by CMac89; 11-25-2005 at 02:31 PM.
    1994 SC
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  3. #3
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    CMac89 thats a very good question. Hmm

  4. #4
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    So, does this mean that switching to an MPIII from and MPII gains only 10 to 15 rwhp at 5200 rpm? And that is spinning it at 20%??
    Anthony Arnold
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  5. #5
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    but isnt this on motors that already have all the horsepower squeezed out of them? But lets say on a lil bit above stock motor? I am pretty sure you can see a big gain from an MPII to an MPIII? Right?

  6. #6
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    WoW! thats alot closer than expected.

    I was surprised to see the s-port actualy beating the MPIII up to around 4,500. It looks like there is not a significant advantage for the MPII or MPII over the s-port till you get around 5000 rpm, after that it looks like the s-port is starting to really run out of steam. Above 5,000 it apears the MPII and III have a much shallower fall off and more potential if you have the motor and the injector to handle it.

    Unfortunatly these are on different motors so its not a perfect comparison but still a very interesting comparison. How much boost was produce for each example given?

  7. #7
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    Dave, this may be a little off topic, but how's the Supra coming along?

  8. #8
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    When someone has the time/money to do so it would be nice to see the MPI MP II DaveAR and S port on a non slipping belt setup. On both a stock and heavily modified motor. Dan Slys blower should be thrown in tehmix as well to see what one can do with a modified stock blower.

    I dont see this however happening as a lot of money and time would be involved in getting it all done legit. But who knows
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  9. #9
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    Being that this was done on two different cars we cannot come to the conclusion that these facts are 100% correct. We must remember that each car responds different to modification. I will be conducting a similar test this summer swapping my MPIII for a stock 94-95 Blower and dyno the difference. With that being said I can believe what I am seeing. I'm sure there is reason for this too.

    What I would really like to see is the ultimate M90 blower shoot out. ESM, S-Port, MP, MP II, MP III. But it wont happen.

  10. #10
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    I posted this to hopefully initiate some discussion on the effects of blower changes and OD ratio on the performance of the motor in the rpm ranges likely to be seen most often on the street. The S-Port blower and MPIII represent the opposite ends of the spectrum when it comes to porting an M90 which is why I chose to use them. The difference in the power curve from an MPII and MPIII might be hard to see, but it should be much easier to see the difference in how an S-port performs vs. latest MPIII.

    With all the enthusiasm and resulting controversy over the MPIII, I thought perhaps it would be good to look at the real world results of overdriving your blower and what it means to you on the street.

    All too often people focus on peak HP numbers without paying close attention to the area under the curve. As Charles pointed out in another thread, useable HP and peak HP are two different things. I thought there were some interesting things about those graphs other than peak numbers that people might want to talk about.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  11. #11
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    Ok so now I get to sound real dumb again. Wouldnt the better option for the street be a blower that made power without having to overdrive it to much or am I missing something. Move the most amount of air to a point I guess. Is there a diminishing return after a certain amount of overdrive.Say at 15% you get 15 pounds at 20% what would you get? Is the extra boost worth the parasitic loss? It would seem there has to be a point of diminishing returns. Or am I missing something?

  12. #12
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    Has anyone put a MPIII on a STOCK motor and tested for power increases? I know that modded cars have done it, but I am curious about a stock motor with stock cam, heads, IC and all that jazz.

  13. #13
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    We need a bench test comparison

    ....this may be unrealistic but I would really like to see a comparrison of all our sc options on a bench. I dont know how a manufacturer goes about testing their models, but it would be interesting to know.

    There are too many hidden variables that we just cant see on a dyno. For example, seeing comparisons of drive power loses for a given rpm and pressure ratio, outlet temps., and loses to belt tension would be ideal. In the real world though, testing all the blowers on the same car with as much data logging info as possible (inlet/outlet temps, boost pressures ect.) would get us closer.

    Those graphs are a reminder to me about the compromise we have to make with supercharging. Regardless of which blower/pulley combination we chose there will be a certain range that it is most effective. I think there may be potential to extend that range but that is a topic of another thread.

    QUOTE=XR7 Dave] The S-Port blower and MPIII represent the opposite ends of the spectrum when it comes to porting an M90 which is why I chose to use them. QUOTE]

    When you say opposite ends of the spectrom do you mean how exteme they are ported, or the aproach they took with the porting?

  14. #14
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    We need a bench test comparison

    sorry double post.
    Last edited by Swade; 11-26-2005 at 02:40 AM. Reason: double post

  15. #15
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    I agree that all of these blowers need to be dynoed on ONE car. SC's vary too much in order to determine the differences in the outcomes of the blowers accurately.

    Swade, the S-Port is a mildly ported m90 as opposed to the MPIII being the highest end of porting as far as m90's go.
    1994 SC
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