The Eurosport Twin Screw Supercharger's Competition Debut -- First Impressions


I know a lot of people have been waiting a long time (as have I) so I thought I would write up my thoughts on my first competition with the Eurosport Twin Screw.

For those of you that don't know me... I run a 1995 M3 in the Street Modified class in the SCCA ProSolo Series. The car is well sorted and has a fully developed suspension utilizing Moton triple-adjustable shocks, H&R race springs and sway bars, and 285/30/18 tires on 18x10.5 CCW wheels. Prior to this recent power upgrade I was running a 3.2 motor (S52) with Shrick cams on OBD-I electronics tuned by Jim Conforti. On the intake side I also used a Euro HFM and Conforti CAI, and the exhaust consisted of tuned headers and a 3" exhaust of my own design.

The Street Mod rules allow for any powerplant to be used provided the block is made by the same manufacturer as the chassis of the car so any BMW motor was available to me. Forced induction motors are limited to 3.0 litres. There are a few other restrictions (e.g. no modifications to the subframe or steering column are allowed), but basically anything you can squeeze in is allowed.

To get more power I considered a Euro S52, an S54 from an E46 M3, and even an S64 (E39 M5 V8), but settled on supercharging a 3.0 LTW motor. At my shop we've installed superchargers from Dinan, RMS, ESS, Active Autowerke, and others and all have their benefits. But after working with Jim Conforti and Josh MacMurray since the mid 90's I knew I wanted to wait for the Eurosport Twin Screw.

Yeah... there's that word... WAIT. I've been waiting a long, long time just like everyone else.

But Josh and I stayed in touch constantly and when he finally said he thought he could install one in time for me to run at the last 2 ProSolos of the year I jumped at the chance. I'd be beta-testing the OBD-I software, but knowing JC I wasn't too worried about software bugs.

I picked up my car from Josh in SLC in the wee hours of Tuesday June 21. The first thing you notice when you look at the Eurosport TS is how "factory" it looks. The unit is extremely compact with the supercharger, intercooler, manifold, and throttle body all fitting between the head and strut tower. Each piece received a subtle black powdercoat finish for a stealthy, understated look. The intercooler/manifold that Josh manufactures in-house (which is the cornerstone of this kit) is truly a functional work of art.

Josh's attention to detail is evident throughout as the fit and finish is clean, precise, and sanitary. Clearances between components are down to the thousandth of an inch in places.

I'm glad I had the chance to look under the hood before we started it up, because whether at idle or WOT, the TS is so quiet that it's virtually imperceptible. Frankly I was just a little bit disappointed... I mean I paid for a supercharger, I wanted to hear a supercharger. <g> Josh reassured me that on a car with OE exhaust the TS can be heard, although the whine is barely noticeable.

I only had time to drive it down the block and back before loading it in the trailer for the trip to the ProSolo in Oscoda, Michigan that weekend. My first impressions were that the car had incredible power, but at 3:00 a.m. on a back street in SLC on street tires I wasn't about to really wring its neck.

My first opportunity to test the car on race rubber was during practice starts in Oscoda. (At a ProSolo competitors are given a few chances to check the launch characteristics of the surface prior to competition.) It became apparent immediately that I would have to adjust my launch technique or burn the rear tires off the rim. With my previous setup (approx. 300hp) I was used to launching at sea level at 3500-4000 rpm depending on the surface. In Oscoda (concrete) anything over 3k and the rear tires went up in smoke. I ended up launching at 2800 and slipping the clutch slightly for the first 30 feet or so. The 1st-2nd shift had to be done smoothly or the tires would haze through 2nd gear as well. My 60-foot times were 2.0-2.1 and 200-foot times were in the low 4.7's on 285/30/18 Hoosier A3S05's.

During the first heat Saturday morning I noticed immediately that the increase in power was everything I'd hoped for (420+hp). I was still giving up .3 or so per side to the 550-600hp AWD Evos heading to the first corner, but that's .2 less than before!

I borrowed some 285/30/18 Kumho 710's for the 2nd and 3rd heats and my 60-foot times dropped by .1 and overall times by about .5-.6. The ability of the 710 to put power down better than the S05 is undeniable and made quite a difference in the technical "infield" section of both courses.

I ended up winning the event by a little over .8 seconds (see full results here), but the real story is how the new powerplant performed. The three most noticeable things about it were:
- the powerband feels completely linear -- no waiting for it to come up on the cams... big power came on at the moment I went to the pedal.
- throttle response is very progressive -- no on/off switch characteristics... it's as driveable and easy to modulate as OE.
- I needed to dramatically adjust my braking points -- I was arriving at corners sooner and at a higher speed than expected... a pleasant problem to deal with. <g>

Most autocrosses, including ProSolos, are contested almost entirely in 2nd gear. The key to a good autox powerplant is the ability to seamlessly pull from low RPM's (around 2k) to redline. Most courses consist of brief periods of WOT acceleration followed by rapid decel often to low RPM's, and then immediate WOT again. This places a significant premium on responsiveness and torque, and requires that fuel and ignition management be flawless.

Josh and JC got it right with nothing more than a little dyno time to go from.

In order to win a ProSolo Championship you must run two regular season events to qualify for the Finale... and you'd better win both of them. I took a big risk waiting for the Eurosport TS to be done in time for the last two events of the year, but with one win in the bag and one more event to go I'm feeling pretty confident it was worth the wait.

It is truly an amazing package.

For more information contact me directly at bobt@bimmerhaus.com.