Autorotor question

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.
 
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!!!!
 
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.
 
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! :D LOL
 
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?
 
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
 
So overall to include comparable size, performance, efficiency and cost, which is the best choice? AR, Kenne Bell, Whipple or TVS?
 
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.
 
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.
 
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.


What is PD...Positive Displacement ? It's not just better heads, you also need a matching intake manifold, which is probably more difficult to build if you want to continue mounting the supercharger on top of it. Then all the supporting stuff would likely require changes too. Before doing that, most people would opt for an aftermarket v8 or more modern motor like Ecoboost 3.5 or Coyote 5.0.

David
 
If i had the money, i would like to find the ecoboost v6 my self. Not sure what i could do but i think it would be a good fit for the coupe.
 
What is PD...Positive Displacement ? It's not just better heads, you also need a matching intake manifold, which is probably more difficult to build if you want to continue mounting the supercharger on top of it. Then all the supporting stuff would likely require changes too. Before doing that, most people would opt for an aftermarket v8 or more modern motor like Ecoboost 3.5 or Coyote 5.0.

David

I think some of us don't want to swap anything really. And yes a set of heads even with a marginal improved intake manifold would be beneficial, I don't feel the intake is as much of a handicap as we make it out to be. Yes longer runners are good for top end HP but the blower is shoving air so less of a variable. Looking at my coyote set up with the PD blower the manifold is nothing to brag about and has the built in IC. But I'm not engine specialist in this group so its all speculation. My point was that the current blower offerings is plenty. Don't forget a street sc engine is not the same as a Race set up, and a 4.3 vs 3.8 also behave differently.
 
Considering the current sc's in the Group, what's the difference between a race and street motor?

I don't know of anyone that's done a "race" style van motor yet. But maybe I'm missing someone?



Don't forget a street sc engine is not the same as a Race set up, and a 4.3 vs 3.8 also behave differently.
 
What is PD...Positive Displacement ? It's not just better heads, you also need a matching intake manifold, which is probably more difficult to build if you want to continue mounting the supercharger on top of it. Then all the supporting stuff would likely require changes too. Before doing that, most people would opt for an aftermarket v8 or more modern motor like Ecoboost 3.5 or Coyote 5.0.

David

Let me first confess for those of you who don't know me or my car, that I am an Autorotor guy and it is the reason I overlooked all of the problems the car had when I bought it. It is the sole reason I bought the car. Now to what David wrote.

What you say is all very true, but what I think Ricardo and you forget, and I am surprised because you have always been a proponent of experimenting with what it takes to make the SC bigger and better, is that we're building these cars because it is what we do. We accept the challenge of making the engines bigger and better. Sure, we can go out and buy something with 500rwhp but what fun is that? Call it a hobby if you like, but this isn't about seeing what an aftermarket engine can do. It's about seeing what our engines can do. Now some of us have done a lot more experimenting than others, so I don't know that making comparisons between cars and blowers and what we did to make our engines run better is fair. But I think what it comes down to is whether or not you are of a mind to see what you can learn from what someone else did and build something bigger and better.

Now if that is not what you have in mind that's fine too. There is absolutely nothing wrong with keeping a clean stock SC running as it should. In fact, I would argue that doing that may very well be more difficult than trying to build something more. But that is not what this thread is about. Sorry.

For myself, I still don't think we have reached the limit of what the engine can do.
 
Considering the current sc's in the Group, what's the difference between a race and street motor?

I don't know of anyone that's done a "race" style van motor yet. But maybe I'm missing someone?

The difference is a car with a outrageous camshaft and valvetrain to take it to 8000 rpms vs one that Doesn’t need he throttle from keeping it from stalling. I guess my definition of race is different than yours. But anything that you do to an engine with a complete disregard about driveability to me is a race mod.
 
Let me first confess for those of you who don't know me or my car, that I am an Autorotor guy and it is the reason I overlooked all of the problems the car had when I bought it. It is the sole reason I bought the car. Now to what David wrote.

What you say is all very true, but what I think Ricardo and you forget, and I am surprised because you have always been a proponent of experimenting with what it takes to make the SC bigger and better, is that we're building these cars because it is what we do. We accept the challenge of making the engines bigger and better. Sure, we can go out and buy something with 500rwhp but what fun is that? Call it a hobby if you like, but this isn't about seeing what an aftermarket engine can do. It's about seeing what our engines can do. Now some of us have done a lot more experimenting than others, so I don't know that making comparisons between cars and blowers and what we did to make our engines run better is fair. But I think what it comes down to is whether or not you are of a mind to see what you can learn from what someone else did and build something bigger and better.

Now if that is not what you have in mind that's fine too. There is absolutely nothing wrong with keeping a clean stock SC running as it should. In fact, I would argue that doing that may very well be more difficult than trying to build something more. But that is not what this thread is about. Sorry.

For myself, I still don't think we have reached the limit of what the engine can do.


Ira I think we are on the same camp. There are for the most part three types of ppl more or less in any type of performance oriented trim model. The purist that leave it stock, the bolt on ppl that want to keep the same heart of the car but make it better, and the ones that does not care how you get there as long as it makes power. The latter doesn’t benefit the community as a whole but does make you unique. And I guess that’s a hard one to pull off being unique and still keeping the heart of the car.
 
If this were a group of even back yard engine builders discussing how to get more out of one of these motors, the opinions would have more impact. But since all of you guys bought your motors, it's not really what "you" can do with the motor, it's what is available to buy. Big difference.

I've built many of these motors in various configurations for many people. Corey was the most willing and able to fix whatever might go wrong when living on the edge, but even then, when it broke it came back to me to fix. Of course, it's what I do, so why not? Well, I can't fix everyone's problems. All the time.

I currently have 5 or 6 SC's sitting here waiting for engine repairs because the owner can't fix, or can't deal with the problems that came about due to running "on the edge" with their van motor. This is a really big problem. If you you can't fix something that goes wrong then why have something running at 9/10's of what it could possibly/theoretically be capable of? To me it doesn't make sense.

Sure a lot more could be done, but why? All it seems to do is create more problems. Since melted pistons, broken ring lands, and blown headgaskets seem to be the biggest problem, how come no one is running active knock detection/prevention? Has no one heard of it before? Has no one figured out how to install one? We can't move forward if we keep going backward.
 
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Good point DD. Guess the fact that the car is rare bites once more cause nobody including yourself hasn’t put a kit out saying. Step one, unplug the stock sensor. Two, plug adapter harness. Three, load tune. Four throw whatever boost you want at it and enjoy living on the ragged edge. :cool:
 
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