Looking for the ideal blower setup for new build.

I'm in the process of finally finishing the new motor on my car and was looking for some input on the ideal supercharger setup. First I'll say the car is a street car first and foremost, and will be a nice weather daily driver, that I can take to the strip when I'm in the mood. The new motor is a 4.3 stroker, 8.8:1, forged pistons and rods with ported big valve heads and custom DD cam, plus bolt-ons. I also plan on running water/meth injection. From what I remember, the stroker motors aren't very rev happy and tend to make a lot of low end power. The MPX tends to make more high end power. I currently have an MPII to top it off when it goes back together, OD is undecided.
What would you consider the ideal M90 setup for this motor configuration? Right now I have the following options, but I'm willing to change them.

1. Run the MPII as is.
2. Put MP rotors in the MPII for an MPII-S. As an aside, has anyone done this?
3. Pick up a pre-owned MPX case/inlet and run that with bare rotors, and maybe some time down the line put the coated rotors in.

If you think OD is relevant to the discussion, I'm not interested in spinning the blower like crazy, I was thinking 15%OD MPII, 20%OD MPIIS, 20-25% MPX.

Thanks.

..Bueller?

I don't know what makes you think the stroker doesn't like to rev. David's makes peak power at 6500, and in fact makes more torque at higher rpm than his 3.8L did. It's all in the heads/cam, not the shortblock.

The ideal blower for that isn't an M90 so I guess just pick your poison. You will want as much airflow as possible.

None of your options are what I would consider ideal for the the motor you are building. I would be tempted to live with what you have. That will make plenty of torque and give you decent power for driving on the street. Track it in the 13's depending on gearing and such.


Then save up for getting a TVS or a AutoRotor or Whipple, or whatever down the road. I also wouldn't discount the stroker to make power up high. You should be able to get a cam and heads and valve train to make power into the upper rpm range to support a better blower down the road.

XR7 Dave said:

I don't know what makes you think the stroker doesn't like to rev. David's makes peak power at 6500, and in fact makes more torque at higher rpm than his 3.8L did. It's all in the heads/cam, not the shortblock.

The ideal blower for that isn't an M90 so I guess just pick your poison. You will want as much airflow as possible.

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Went with a .520 212/218 per your recommendation when I was figuring out what to do. I didn't plan for the big valve heads when that decision was made. It's a little more encouraging to hear David makes peak power up high but then again he has a lot more $$ and Dalke wizardry in his motor than I do.

I know a tvs/twin screw/insert blower here will always be better on a built motor but the budget for that on this car just isn't there. I want to get it back together and enjoy it for a bit before I move on to something else.

Mike, if the car runs in the 13s I would consider the entire build an extreme disappointment.

As with anything, having a package that works together is the key to success. I don't see anything wrong with what you have, but "big valve ported heads" can mean just about anything including "worse than stock" depending on how the work was accomplished. Most likely your combo is not going to outrun the MPII so I guess you might as well stay with that. Do keep in mind that not all MPII's perform the same, but you should run at least 15% OD on it no matter what and 20% isn't out of the question. The camshaft is going to give up by 6000rpm and will make peak power at about 5000-5300 depending on how it all works together so you need to target your power goals for the 2000-5000rpm range.

I've run combinations like that well into the mid 12's but you have to make sure everything is working right. I've seen other people struggle running 14's using similar parts. It's all in the combination.

OP, my engine combo sounds fairly similar to yours, though I have more cam. I have an MPX on mine, and while the car's a lot of fun, there's no question that the engine can handle more, and the current blower is holding it back. However, I think the only thing better is going to be a non-M90 based blower, and since you say that's not in the budget, I guess I'd go with the MPX.

bigpoppa822 said:

Mike, if the car runs in the 13s I would consider the entire build an extreme disappointment.

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It really depends on the combination. High to mid 12's are by no means a given when using a M90 based blower in an SC chassis. These are heavy cars. If Mid 12's are your goal, then you have other things besides building a motor to work on.

I feel you can do better then mid to high 12's with a MPX and that setup I got a low low 12's out of a home ported 94/95 blower uncoated rooters in a 3.8l back then I drove the car on the street all the time. You just have to work all the bugs out and get it to run right.

Your cars setup reminds me of this thread:

http://www.sccoa.com/forums/showthread.php?85479-MPX-Test-Car-Details

-Tim

That is close I just have reg ported heads stock seats with a bit larger valves that Dave D. built for me, what I call mild to mid cam don't have #'s right now that Dave helped me pick out, H beams w/ forged 10:1 pistons. My lower intake is stock still run a AOD that is killing me, 3:73 gears,huge front mount knooks mids with home made exhuast still has cat and mufflers, all seats radio ect car has lost about 4-500 lbs but I weigh 280 there is tons more I can do to go faster yet but it takes time and money neither do I have much of. But over all I got my biggest gains came from correcting all the small problems as they come around witch takes most of the time I have in the car. (gives me something to think about while at work) but over the years I have learned with all my cars ect that the dumb things is what causes you the most HP. Air filter, t-stat, o2's, IAT, all + more have cost me a 1/2 second or so in the 1/4 mile but to drive the car daily you would not notice. I guess what I am saying is alot of guys put alot of money into there stuff and if it puts down bad#'s they give up, and it is hard for someone that takes a few hours or what not to put on a dyno fix all the probblems. If I had to pay myself 20.00 an hour to work on my car I would be broke? or rich? not sure.

Also big thanks to DD he has helped me alot over the years.

Tim Groth said:

Your cars setup reminds me of this thread:

http://www.sccoa.com/forums/showthread.php?85479-MPX-Test-Car-Details

-Tim

Click to expand...

Interesting spot to make a post - Phil decided to give up his MPX-S so that he could afford his T56 swap, so he took the MPX-S off his car and put on an S-Port we had here with MP plenum. The difference?

The MPX-S was running @ 20% OD and making a consistent 19-20psi all the way through the rpm range. The S-Port we are running at 10% OD but it starts to lose boost above 4500rpm - the motor simply outruns the blower at that point. It makes a peak boost value of 14psi but then falls off to about 13 by 5500 and HP along with it. Peak HP is down from 403 to 321, so basically 6psi works out to about 80hp, or 13hp/psi. We didn't change the tune any, so everything should be very comparable.

It is interesting to note that to make 6psi from an additional 10% OD reflects a massive increase in VE between the two blowers. The S-port is a lot quieter though! I think an MPII would be much better, especially if it had the new rotor pack in it. I would run an MPII-S at 15% and I bet it would make 17psi and about 370rwhp. With bare rotors probably 340rwhp.

Sounds like MPX for drag cars, and MPII/S is just fine for street cars.

Wow did not think the #'s would be that far apart. The s-port has a stock inlet correct? If so I think that will cost you a good bit. And the coated rooters from what I found have to be run for about 1000 or so miles till they start to work there best. I also run 30% od but was not able to untill I put the miles on the blower to loosen it up. No Idea of the HP in my car or the boost psi it does pegg the stock gauge as soon as I give it gas.

XR7 Dave said:

Interesting spot to make a post - Phil decided to give up his MPX-S so that he could afford his T56 swap, so he took the MPX-S off his car and put on an S-Port we had here with MP plenum. The difference?

The MPX-S was running @ 20% OD and making a consistent 19-20psi all the way through the rpm range. The S-Port we are running at 10% OD but it starts to lose boost above 4500rpm - the motor simply outruns the blower at that point. It makes a peak boost value of 14psi but then falls off to about 13 by 5500 and HP along with it. Peak HP is down from 403 to 321, so basically 6psi works out to about 80hp, or 13hp/psi. We didn't change the tune any, so everything should be very comparable.

It is interesting to note that to make 6psi from an additional 10% OD reflects a massive increase in VE between the two blowers. The S-port is a lot quieter though! I think an MPII would be much better, especially if it had the new rotor pack in it. I would run an MPII-S at 15% and I bet it would make 17psi and about 370rwhp. With bare rotors probably 340rwhp.

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