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Thread: Autorotor question

  1. #1
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    Autorotor question

    Was debating buying an AR for my SC. I read on here that they are great upgrades but it seems there is alot of fabrication involved, ie snout. Is there anything similar to the AR that is more of a true bolt on for the SC? I like the fact that the MPX is a direct bolt on so I can do it myself in my garage but is it worth even upgrading to that one over a S-ported 95 blower?

  2. #2
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    Honestly I think the S port is the best overall blower. You will make more power with the AR but the S port has fun written all over it on the street or even the highway. Get an MP inlet larger TB run about 17psi..Maybe some MEth..And you will be very happy. I traded my low end for top end when switching to the AR...I dont race my car so for someone liek me its a questionable mod. If your looking though for dyno queen numbers or better 1/4 times and think a 3500 or so investment is worth it...Well then..
    They don't call me "SLOWPOKE" for nothin!
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    Quote Originally Posted by ricardoa1 View Post
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  3. #3
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    You should be able to use an S-port 95 blower to get into the 12's with the right parts. I ran 12.5's with a home ported 95, MP inlet, 85MM TB, 20% overdrive, but I also had had SCU ported cylinder heads, cam, and other bolt on parts. The real question you need to ask yourself is, "how fast do I want to go", speed costs $$$.

    I picked up a used 1.7 AR a couple years back and after its all installed I'll have $3500+ in it, and its not just a simple bolt on setup. The snout is the easy part since you can buy it, its the modified intake manifold, fuel rails, custom made inlet plenum, custom return plenum, and custom bypass assy that takes time and the right person to build it.
    SCCoA Member#: 2515
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  4. #4
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    Quote Originally Posted by XxSlowpokexX View Post
    If your looking though for dyno queen numbers
    I didnt think blower cars could be dyno queens, those are turbos.

  5. #5
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    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.
    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.

  6. #6
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    Quote Originally Posted by XxSlowpokexX View Post
    Honestly I think the S port is the best overall blower. You will make more power with the AR but the S port has fun written all over it on the street or even the highway. Get an MP inlet larger TB run about 17psi..Maybe some MEth..And you will be very happy. I traded my low end for top end when switching to the AR...I dont race my car so for someone liek me its a questionable mod. If your looking though for dyno queen numbers or better 1/4 times and think a 3500 or so investment is worth it...Well then..
    Damon,

    I've always considered dyno queens to be cars that make big numbers on the dyno, but can't produce equally impressive numbers on the track or lack the driveability needed to use them on the street. The AR blowers have been proven to back up their impressive dyno numbers, with equally impressive track numbers and in some cases, they perform even better on the track than the dyno numbers indicate they should. Driveability is also a non-issue.

    Even after nearly 4 years, I still think it's the best mod I've ever made to my SC.

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

    My Garage

  7. #7
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    In your face SUCKA. Just kidding. Dave said it best if you have to ask then at least search the subject and read up, this has been beaten to death with a stick. Most of the folks that want or need an AR are the folks that want to get over the 400Whp hump. Most are yearly event racers few of us are street playas that want to dominate whatever pulls up next to you on the highway. Pump gas, eaton blower can give us what we need.

    I had both "eaton and AR" on the same car and now have both again although I have not been able to drive the eaton car hard yet, but the eaton car scoots and moves with authority. But the rush of enless RPM and warp speed feel that the AR gives is still unmatched by any eaton. But you cannot use all of that on the street, how many times can you WOT to get that feeling or satisfaction specially with gas being 3bux a gallon. So build up to it then when you are ready make the jump. Do not put on an AR or Twincrew on a stock car or mild set up it is simply not too smart. If you have a mild car then spend more money on going wild and keeping it eaton. If that does not work then you jump ship and go AR. There is about a 30-50HP difference between the two when you jump ship...is that worth the investment of 3-4k? You make that call.

    With that said, HEADS AND CAM should be on peoples list before even thinking about a super duper blower.
    Last edited by ricardoa1; 04-21-2010 at 11:40 AM.

  8. #8
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    Quote Originally Posted by ricardoa1 View Post
    So build up to it then when you are ready make the jump. Do not put on an AR or Twincrew on a stock car or mild set up it is simply not too smart.
    I don't entirely agree with this comment. I spent somewhere within that price range for an AR, and haven't even driven the car yet. Heck, I won't even have it installed until I get back to the States (late August.)

    However, I knew what I wanted, and that is the exact reason I never spent the money on an MPx. I picked up a nice S-Port and abused that while I waited. The S-Port is fine, but is IMO a bit excessive when matched with 3.73's.

    Now mind you, I'll be putting the AR on a stock long-block. I'll be looking at getting heads and a cam from DD, but I'll be waiting until I finish a few other things. I mean, this is going on a car that I won't even race but maybe two or three times a year for the simple fact that it's too nice to abuse.

    I don't know. My comment kind of jumped around, but maybe that's due to it being nearly 2am. Anyways, in the end it simply depends on what you want. You can't let anyone else answer your questions.


    -Corey

  9. #9
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    Quote Originally Posted by 95_XR7 View Post
    I don't entirely agree with this comment. I spent somewhere within that price range for an AR, and haven't even driven the car yet. Heck, I won't even have it installed until I get back to the States (late August.)

    However, I knew what I wanted, and that is the exact reason I never spent the money on an MPx. I picked up a nice S-Port and abused that while I waited. The S-Port is fine, but is IMO a bit excessive when matched with 3.73's.

    Now mind you, I'll be putting the AR on a stock long-block. I'll be looking at getting heads and a cam from DD, but I'll be waiting until I finish a few other things. I mean, this is going on a car that I won't even race but maybe two or three times a year for the simple fact that it's too nice to abuse.

    I don't know. My comment kind of jumped around, but maybe that's due to it being nearly 2am. Anyways, in the end it simply depends on what you want. You can't let anyone else answer your questions.


    -Corey

    Well Corey, your goals seem to be the same goal the big dogs want. You are already talking big heads and cam. I chuck your order of operation due to an opportunity. But seems your goals are BIG so you are not different then a guy building up to it. You got the carriage before the horse but thats because you had the opportunity to get the hard to find carriage first.

  10. #10
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    Ricardo,

    If doing it over again and if they were even avalible at that time, I would have gone straight to an AR on a stock long block, instead of messing with a mountain of bolt on parts. I've seen a stock motor SC make 300 rwhp with nothing but a 1.7 AR, bigger injectors, fuel pump and a mail order tune.

    Eight years ago it took a CMRE stage II (or comparable) motor and all the bolt ons to break 300 rwhp.

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

    My Garage

  11. #11
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    If I had to do it again, I would be single (for story sake only), so I could afford to build another one. I have run into nothing but problems with everything I touch in the last few years. Learning curve of purchasing things because they work was not that great of an ideal. I wanted to make parts myself and go from there. Sure, I made headway on a few things, but if I had to do it again today, I would pick up an auto SC, throw a stall, exhaust, gears, and pick up the inverted whipple that Casey has for sale. Add supproting mods to that and call it a day. I think you could hit high 12s with the right tire and conditions.

    SWS

  12. #12
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    Quote Originally Posted by David Neibert View Post
    Eight years ago it took a CMRE stage II (or comparable) motor and all the bolt ons to break 300 rwhp.

    David
    308 rwhp, w/ stock TB
    Kurt K (e-mail)
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    '92 SC AOD -- 11.521s @ 116.748mph, 2.0 AR power
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  13. #13
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    Quote Originally Posted by David Neibert View Post
    Ricardo,

    If doing it over again and if they were even avalible at that time, I would have gone straight to an AR on a stock long block, instead of messing with a mountain of bolt on parts. I've seen a stock motor SC make 300 rwhp with nothing but a 1.7 AR, bigger injectors, fuel pump and a mail order tune.

    Eight years ago it took a CMRE stage II (or comparable) motor and all the bolt ons to break 300 rwhp.

    David


    Does not make sense to me. You are bound to blow a head gasket bolting that on a stock car. For god sake I blew mine with a K&N filter. So you are already taking the heads off it makes financial sense to build up your long block first. Parts are readily avail and Dave is willing to port these suckers. So why not get that out of the way first you will be in about $2500 maybe less on a AR you will be 3-4 in the hole to then work backwards and fix the blown head gaskets that AR inflicted. Everyone says "dont listen to dynos" thats when power is down and goals are not met and then take it to the track, but people seem to swear + live by them when it does ring out a good number.

    Dave I did 325HP with an Sport long ~~~ time ago with steig heads $1500 at them time. $4000-$1500= $2500 dollar savings.
    Last edited by ricardoa1; 04-21-2010 at 05:02 PM.

  14. #14
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    If you have the funds and you can find a kit for sale, as they were custom made kits by Supercoupes Unlimited, the AR hands down is the best blower to get if you're looking for the ultimate supercharged SC. Other than 1 MPX powered race SC and at least 1 turbo powered SC, the AR powered cars are the fastest and have the highest hp, at least until we see what a couple of Whipple powered cars have. I have a MPX with a 75 shot of nitrous and a ton of mods and I'm hoping that I can just keep up with the AR and Whipple crowd this year at the Shootout......
    SCCOA Member #2406
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  15. #15
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    A lot of people here including myself really haven't answered the guy's question in the first place. Damon did when he said he thinks the S-Port is the best value. If I had an S-Port on a stockish motor, would I upgrade to an MPX? Well, maybe.

    The S-port can't be beat if you are keeping OD low. I ran my S-port at -0- overdrive at just over 300rwhp. Can't argue with that. It was only making about 12.5-13psi at the time and the car was running low 13's consistently with no heat issues. I then added the MP inlet and went to 5% OD which dropped the car into consistent high 12's. I beat Kurt's CMSII at the first Shootout with that combo. I later increased OD on the S-port and picked up more dyno HP but the car never went faster at the track. I ran 12.48 with my S-port with 5% OD and that's the fastest it ever went with the M90 on it.

    I did not run an MPX on that car, so I can't say how much better or not an MPX would be. What I have observed though, is that when running higher OD's than 10%, the S-port starts to have a disproportionately high low rpm boost without an accompanying increase at high rpm. When you have boost that flatlines at some value throughout the rpm range (at least with an M90) the result is boredom. I have found that slightly underdriving the MPX (10-15% od) makes for a very fun combination. It will make moderate boost at first but will build boost continually as you approach the high rpms. This is more fun than a flatline boost which is the source of the RUSH then lag feeling that is so common in SC's. Allowing boost to creep also serves to prevent excessive cylinder pressure in the lower rpm ranges which allows you to run higher peak boost #'s for more power without sacrificing reliability (detonation) in the mid-low range.

    I also feel that an AR on a stock motor is a bit of a waste of time. The thing will try to make too much boost and if you pulley it back so that it makes moderate boost it won't be much if any faster than a comparably equipped M90 car. On a stock motor I'd never be afraid to run a good S-Port along side anyone else, AR or not. I think I really prefer the MPX though because it has more balls on the top end.

    So I didn't answer the question either, but I did put some thoughts out there to where maybe someone can come up with their own reasonable conclusion.
    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.

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