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Thread: Autorotor question

  1. #16
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    a summary... ?

    So, where cost is a concern, its get a 94-95 M90 case/inlet/tb, or turbo it, right?

  2. #17
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    Thanks Dave, that was pretty much what I was looking for. May be better for me to just get bigger injectors and pulleys and call it a day. If I could run consistent 13s I would be happy with that . I failed to mention what all the car already has. S-port blower with stock pulley, MP plenum, raised top, 38lb injectors, double IC with fan, MP CAI, 75mm T-body and MAFS, 3:27 gears, long tube headers and SCP exhaust. It has been chipped and tuned but runs rich still. Not too sure what power level its at but it's never fast enough.

  3. #18
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    I would suggest an S port over a MPX. The S ports are rock solid and can put you in the mid 12's with the right parts. And no fab work.

  4. #19
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    Quote Originally Posted by Micahdogg View Post
    I would suggest an S port over a MPX. The S ports are rock solid and can put you in the mid 12's with the right parts. And no fab work.
    I have not heard of one MPx failure where excessive overdrive (20% or more) was not involved. I'll bet s-port's would fail at the same rate as an MPx at 20% or more, it not higher.

    At 15% OD an MPx is just as reliable as a s-port, and it sounds way better!

  5. #20
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    I think you are right, he did say he wanted 13's.

    Only chose the S port if you want 12's.

  6. #21
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    I liked the MPx with 15% OD on a stock long block, vs. a ported 94/95 blower 20% OD with the MP inlet plenum. The grunt did not fall off and it sounded waaaaaaay better, much louder.
    SCCoA Member#: 2515
    1990 SC AOD 2.1L Kenne Bell
    11.676 @ 121.35 mph
    506hp/478tq
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  7. #22
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    Love reading these old posts, never gets old especially with a good gallon of special eggnog to keep you going through the night!!!! Long live the Super Coupes!!!!
    Tom Downs-member#2752
    MPX'd 90 SC Auto~bought Feb. 2012
    RIP MOM!!! I will always miss and think about you 4Ever! 1940-2018
    RIP Rexy boy!!!! Miss my dog 2006-2018
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  8. #23
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    Quote Originally Posted by 89XR7TD View Post
    Love reading these old posts, never gets old especially with a good gallon of special eggnog to keep you going through the night!!!! Long live the Super Coupes!!!!
    Yes those were the times. Now its Turbo, Tvs, Kenne Bell, Whipples, Coyote.

  9. #24
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    Quote Originally Posted by XR7 Dave View Post
    It's one of those things "if you have to ask, it's not for you". Having been intimately involved in HP modifications for these cars for nearly 10 years now I think it's safe to say I've a few valid thoughts to bring to the table.

    First of all, the SC 3.8 engine doesn't have unlimited potential. There are always those who like to say "I wonder what it could do if...." Well, the "if's" have all pretty much been answered. There will always be instances of people making more power or going faster than the naive public thinks they should, and on the flip side there will always be stories of money spent for no good and disappointing results. It's the nature of the game, or business depending on how you look at it.

    A recipe for performance is only a recipe for mediocrity because you can't put together a performance recipe and expect that everyone will get the same results. A performance recipe by it's very nature is a "shoot down the middle" approach that will with a high degree of probability result in satisfactory results. This in and of itself isn't a bad thing, it's just that human nature wants to focus on the best possible outcome rather than a more reasonable expectation which is what a recipe or "recommendation" is going to do.

    That being said, to be asking "what should I do", you are clearly looking for a recipe (and subsequently mediocrity) whether you are willing to admit it or not, and that being said Damon has a good point. An S-port blower is a worthy component. It's not anything special or fancy but it does work. Similar porting procedures can be applied to any m90 blower with decent results or you can simply buy a new case MPx and not bother with any porting at all. Performance for your dollar - eh - that depends on what you are willing to accept.

    The only thing about the S-port that stands out is that it does not sacrifice low end boost in exchange for high rpm airflow. Sounds like the best of both worlds, but in reality it's more of a case of decent from both worlds. Low end boost is great if you don't want to run a lot of total boost or overdrive. 0-10% boost is fine but any more than that on an S-port results in excessive and damaging low rpm boost. The rpms that the stock 3.8 is most efficient at also corresponds with the highest efficiency rpm of the S-port blower. This means that in the 2500-3500rpm range cylinder pressure is maximized and detonation danger is highest. Trying to run an S-port at 15-20% OD, or in other words upwards to 17-20psi boost and you have a recipe for detonation on pump gas. Keep the OD down and you have a very responsive and torquey SC. Since the adage holds true (you drive torque and you race horsepower), this is a worthy goal of any purely street driven SC. Just don't expect to win any competitions. But you can have fun, and it's not all about winning, right?

    What the S-port or any similarly ported OE blower lacks, is the ability to intoxicate one with horsepower. Horsepower is not necessarily all that useful on the street, but it sure is thrilling to experience. Having driven an S-port pretty much to its limits (as well as plenty of other ported OE blowers) I can attest that all are somewhat lackluster once rpms exceed 4000rpm. No matter what you do to an OE M90 or how you overdrive it, the problem is always going to be that your power (torque really) band begins at 3000rpm or below and never gets any better after that. It can hang on pretty well for awhile if you have the right engine mods to support it, but it will never thrill you or put butterflies in your stomach after 4500rpm. The reason for this is not that it doesn't work above 4500rpm, but rather because you've already given it "your best shot" before 4500rpm. No matter how you pulley it, you can't make more power (torque) after 4500rpm than you made before 4500. It's just all downhill after that.

    The MPX alters that curve somewhat. By matching low rpm performance of the OE blowers but having a bias in the higher rpm ranges where it clearly exceeds the VE of a normal M90, you can actually experience a significant rush of power beyond the normal "surge and die" phenomenon of the OE M90. The MPX is fun to drive. It can put a thrill into higher rpm use. It can also flirt the threshold of maximum cylinder pressure over a much wider rpm range than the S-port or any other OE M90 version and this is more important than most people realize. It's probably as much fun as pump gas can safely allow.

    When people ask about the AR they usually don't even know what they are asking, and all too often even when people get them on their cars they find ways to talk about what they gave up compared to their M90. This is just such a contradiction I can't find the words. I guess it's kind of like putting drag radials on your car and then complaining that you can't lay as much rubber as before. It just makes me scratch my head. Over time I've come to realize that if the benefit of the twin screw blower isn't readily apparent such that one has to ask, then it's just not for you. An AR wasn't the first thing I tried, nor should it be anyone else's. You'll know when/if you are ready for that when the time comes (if it does).

    It certainly doesn't take an AR to have a fast SC or to have fun in one. But I also noticed a hint of "I want to make xx boost or xxx hp" in the original question, and I just need to point out that regardless of how you make boost or how you make HP, stepping beyond a certain level requires a willingness and ability to go beyond the simple "recipe" grade and take on a higher level of responsibility for the outcome of your efforts.
    So there! LOL

  10. #25
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    Quote Originally Posted by 89XR7TD View Post
    Love reading these old posts, never gets old especially with a good gallon of special eggnog to keep you going through the night!!!! Long live the Super Coupes!!!!
    Okay, so now, almost 10 years later, have opinions changed? What have we learned since then?

  11. #26
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    Quote Originally Posted by Ira R. View Post
    Okay, so now, almost 10 years later, have opinions changed? What have we learned since then?
    Nope, I still think the twin screw supercharger (or a comparable TVS roots) is the best mod you can do for the SC.

    I have learned that deleting the AC was a mistake, should have redone the FMIC and radiator to make it work.

    David
    1991 SC AOD 4.2..2.3 Whipple..........10.910 @ 125.61
    2016 SRT Challenger Hellcat.............10.597 @ 135.78

    My Garage

  12. #27
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    I wonder who wrote all that stuff above? I'd like to shake his hand.
    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.

  13. #28
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    So overall to include comparable size, performance, efficiency and cost, which is the best choice? AR, Kenne Bell, Whipple or TVS?
    SCCOA Member #2406
    '94 SC AUTO - 2.3 Whipple
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  14. #29
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    Quote Originally Posted by nickleman60 View Post
    So overall to include comparable size, performance, efficiency and cost, which is the best choice? AR, Kenne Bell, Whipple or TVS?
    You don't actually have that choice. Your choice is what's available. All are capable of turning a 3.8L SC engine to mush.
    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.

  15. #30
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    Quote Originally Posted by nickleman60 View Post
    So overall to include comparable size, performance, efficiency and cost, which is the best choice? AR, Kenne Bell, Whipple or TVS?
    They all perform well, but as some of us have found out the 3.8l can only digest so much blower. TVS is the outlier. Do you want 20+ psi? and can you put that to good use ie race fuel. The bigger blowers are more at home on the 4.2l cranked cars on 93. But at this point is what you can find or what SCU or Ken W. is willing to build. They all can make 450whp all day everyday on the right engine.

    To get to 600 with PD we need heads.

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