I have been thinking about going to some sort of Forced Induction during the off season.

Right now the car has Schrick cams, pullies, Euro HFM, 24# injectors, exhaust, custom software, (NO M50 intake), and I have a 3.46 LSD.

The car is making decent power, and the 3.46 feels great, and really helps in autoX. Although on some bigger courses I do find myself hitting the rev-limiter.


If I buy an FI setup, I want to buy the correct one right off the bat.

So I have been looking into the Stage 2 C-38, and the Stage 1 TwinScrew both from AA.

A stage 2 C-38 centrifigal blower will put me around 350-370whp, and around 290 ft/lbs of torque, with the bulk of that power in the upper RPM range (4k on). Which with a 3.46 diff I seem to be in 80% of the time.

A stage 1 Twin Screw will give me around 300whp, and 250 ft/lbs of torque, most of which will come on around 2,500 RPM.

I have driven Neil's EuroSport stage 2 or 3? twin screwed Mcoupe, and it felt great, but who knows what is going on with Eurosport, and at 11k it is WAY out of my budget.

Some things that concern me....

1) Not sure if stage 2 C-38 will fit an Mcoupe. Wondering how the intercooler will fit up front. But I have access to the old ERT shop, and would like to think we could fabricate something to get it to fit.

2) Many rumors going around about the availabilty of Twin Screw blowers (if I decide to go that way) some people are waiting up to a year.

3) How the Schrick cams will affect my tunning. Neil is running Schrick cams in his Twin Screw, and several people on the FI forum here have said they should be fine.

4) The 3.46 diff....even now I find myself hitting the limiter time to time, and that is with a 7k redline. Both AA kits have a 6,800 redline. Any chance they could raise it to 7k or will this cause problems.


After looking at several dyno sheets from both setups, it looks to me that the Stage 2 setup has almost as much torque at 2,500 rpm as the Twinscrew, and it keeps climbing all the way to redline. Where as the twin screw has a table top looking torque curve.

I would like to stick with AA.


Any thoughts from the auto/track guys.


Thanks ;)

Jason Becker #125 SM2
Brian Hair #25 SM2

You know what I would do. ;)

Flat/linear power delivery is good IMO. Of course, more power is hard to argue with.

Do you think you have enough tire to actually harness 350WHP?

Hey Jason,
First in regards to your question about coming over to see the car, you're more than welcome to. Just PM me with a weekend you're thinking of and I'll let you know whether I'm free. I have to warn you though that the original tires are still on the car and they're almost bare now. Probably won't be putting new ones on till spring since we don't drive the car much in the winter. I'm not sure what the offsets are on the mcoupe, but if you have a set of wheels you'd want to put on my car to try it out that would be fine too.

So far the stock clutch has been fine, and hasn't slipped at all. However, the first couple times I pushed the car after installing the kit, I smelled a little bit of clutch. It never happened again after the first couple times, so I'm not sure what it was - maybe some kind of a secondary breaking in. The clutch also only has 26k gentle miles on it, so that might be why it can hold the power. Another member (lemansgts) who installed the stage 2 kit on his m3 said his clutch is starting to slip, so I'm guessing the power is right around the limit of the stock clutch, and it might be a toss up as to whether your clutch will handle it. Either way I have a used Active clutch in the garage and just bought a used Euro flywheel (about 5 lbs lighter than stock) that I'll install this winter.

To determine the fit of the IC, it would help to see a picture of the car without the front face on. Then judging by the location of the shock mounts you should be able to get an idea of what the fitment would be.

I don't know enough about camming to say how the cams will affect the SC. And do you really need that last 200 rpms? With the stage 2 c38 the needle climbs so fast once you get over 5k that I'm not sure you'd notice that last 200

The power delivery is great. None of that "no real power until right before the redline" stuff people complain about. In first gear I can't get traction at full throttle and have to shift by about 5k. In other gears you definitely get punch by 3k (if you look at the dynos you'll see its common for the C38's to make over 75% max torque by 3k). At 2500, below the vanos switch, the car still picks up noticeably faster than stock, but after 3k you really feel the power. I have about 300 miles on the kit, and it still takes courage to go full throttle past 6000 rpm. I've actually never gotten to redline, as the needle is climbing so fast by 6k rpm that I'm afraid of hitting the rev limiter.

Even though I don't feel any need for more power, after hanging out on the FI forum for longer than I should have, I can't help fighting the itch to someday build a forged internal custom turbo setup. Don't read this as "I wish I went turbo because the stage 2 c38 isn't fast enough for me." It's just that there's a certain coolness to forged internal custom turbos and I see that as being part of my idea of the ultimate m3. I'd never even consider spending money on that route though until the rest of the car is upgraded though in terms of suspension and brakes. The car right now is pretty much stock other than the SC, hg, and headstuds.

One of the things I love most about the sc is the way it highlights all the aspects of the car. Its like having the extra power now shows you just how good the handling and feel of the car is. The car doesn't feel overpowered, and instead feels more like it now has the right amount of power to match the incredible handling.

Austin

I've raced an M coupe with a supercharger, and short gears. A car that was owned by Jamal Mardini and now Pete Lier and went to Nationals in SM2. You run out of 2nd gear in a hurry.

I'm a big fan of twin screws, and like their power delivery.

The cams shouldn't affect it too much. Superchargers have a tendency to "calm down" cams.