The GruppeM unit is an Eaton M-90, a modified Roots type.
Features:
1. Wider, stronger drive belt reduces belt failure rate.
2. Design puts more boost on lower =’s more torque sooner
3. Intercooler option coming adds 20+ HP.
4. No background compressor whine while cruising.
5. Different ECU programs available for 92, 98 and 105 octane gas. Custom computer system that allows for full engine management control
6. ECU programming upgrades free for life to original purchaser.
7. Custom polished kit available, custom powdercoat available.
8. 12psi kit available. Lower compression forged pistons required
9. Includes new higher flowing injectors that come from the *factory* and is a direct replacement for the stock injectors.
The Gruppe M Supercharger kit consists of precision engineered parts, made from sand castings and billet aluminum. The blower is specially made by Eaton for Gruppe M. Eaton is an industry standard in supercharger blowers, and is OEM to numerous auto manufacturers. It comes with a one year or 12,000 miles parts only limited warranty, whichever comes first. A “Blueprinted” Kit is available (all tubes and castings Extrude Honed).
[AV – 99/10/7] Those who were at Laguna Seca during NSXPO ’99, have seen my car with the Gruppe M supercharger kit. It was only a week old at that time, but since then I have put on 4000 miles, and three track events, and the performance of the supercharger has been impeccable and glitch-free. It is also the only one of its kind in the US so far.
gruppemsc2.jpg (19464 bytes) gruppemsc3.jpg (33408 bytes) nsxpo99-may07-0032_small.jpg (5902 bytes)
In a nutshell, here are my comments and highlights on this kit:
1. Works right out of the box. Like I said, it was only installed a week before NSXPO, and driven almost immediately to Monterey, driven at the track (with at least 8 sessions on Sunday), and back home with no problems whatsoever. I must admit though, that the software that came with the kit was tuned for 98 octane gas (available right out of the pump in Japan), so I was either running race gas or octane boosters that weekend. This discrepancy was corrected since when they have sent me a new chip with a revised program for our local (more inferior) gasoline. I have been running on regular pump gas since with no problems.
2. Typical Japanese attention to detail and extremely high quality of the parts. Sand casted parts wherever possible. My car wouldn’t win “Best Engine” at the concour event at NSXPO for nothing .
3. Ease of installation (4-6 hours, maybe 7-8 if you clean every part before reinstalling). A purely bolt-on kit that is easy to remove if you decide to do so when you sell the car.
4. The overall design of the kit lends itself to future improvements in power, such as an intercooler kit, which, by the way, is under development.
5. Proven reliability. In Japan, this kit has been driven in excess of 80,000 miles, with no problems. Engine compression has been checked on those NSXs and all are normal.
6. Drivability is just like stock. Idle is smooth, no hesitation or “herky-jerkies,” and an ultra smooth delivery of power with lots of low end torque.
7. Uses the maintenance-free Eaton supercharger, arguably the best in the market and used as OEM by major car manufacturers.
I have yet to do an “official” dyno of the car, but my clutch has started to slip (at 30K miles) (means more $$ to be spent), so it would not do justice to the kit. However, here are some subjective observations and comments from those who have driven or ridden in my car:

• From an NSX owner who has a 100-shot NOS kit: “This feels a lot faster than my car…”
• From a “famous” NSX master technician in SoCal who has extensive experience with the other supercharger kits: “At 7 psi, this kit feels at least as strong, if not stronger than the (other) 9-psi kit.”
• From a famous NSX Speed Racer: “This car is frickin’ fast, faster than my NSX…”

OK, so they are all subjective, with a lot of individual variances. But most chassis dynos don’t tell the absolute truth either, as there are a quite a few variables in that as well.
I have written a more extensive report on the Gruppe M supercharger, and look out for it in the next issue of the NSX Driver. The car will also be at the Silver State NSX Challenge in Las Vegas, and I’ll be most happy to give anybody rides at that time.
[MYK – 99/10/8] I had a chance to ride Gruppe M equipped 91 NSX in Japan with Mr. Mamoru Ogose, the “M” himself on tiny little streets and on super smooth Tokyo freeway. Holly Shit! I used to drag race my 450 HP, Kenny Bell Equipped, and 11 second 1/4 mile running 87 Buick GN (Ran 22 – 24psi turbo boost) but the Gruppe M NSX with 5 psi felt much faster and had more torque than my ex-Modern Detroit Muscle.
His aggressive driving style and the power of the car instantly made me to say, DAMN! I gotta have this kit NOW!!! The car had 370ps (364HP to 366HP, I think) at 7300 RPM and it was running on the stock clutch. He said that the stock clutch is good enough for his ultra power kit. 370ps may not be enough for those of you like to compare NSX with new Porsche Twin Turbo but hey, if you get a chance to ride on this car…
Mr. Ogose claimed 4.4 sec for 0-60 mph and 12.7 sec for 1/4 mile or better. I think Alex has the Japanese Best Motoring Video with the Spec for this car in it. The video showed the top speed of this kit at 300 km/h or so (around 180 mph, I think)
Everything seemed to be find with the kit and as Tino S. depicted it, the kit looks awesome. I met Oscar Jackson of Jackson Racing at the 1999 Tokyo Auto Salon in January in front of the Gruppe M booth and even he said that kit looked good. However, Oscar said that he can make a better looking kit if he had time and BIG demand for the kit. I guess he is still too busy working on his Integra, Miata, and Civic Supercharger kits.
The car was very loud but it was like the F1 Honda Music, which Honda F1 engine made in McLaren MP 4/5 to MP 4/7 to my ears. The kit is big by the way and you have to get rid of your engine cover to install the massive Eaton M90 along with re-located throtle body on top of the engine.
I don’t think those of you with NSX-T will appreciate the size of the kit unless you leave the top in garage when you drive NSX-T. Hey, real man drives NSX coupe, right?
In summary, I think this is the kit that will give you the reliability and the great sound and looks if you are going after the Supercharger kit for your trusty NSX. I am getting one as soon as I finish up projects here in Asia. As I told Doug “Speed Racer” Hayashi, I can’t wait for Honda to produce V10 or V12 NSX forever.

The GruppeM Supercharger is no longer in production .