KMR RSR 001

Mobonic and CarreraX thanks for the input. We looked at all the wheel options available. The decision to go with Motegi was made for a combination of reasons > quality, engineering, weight, strength, service, cost, lead time, etc. Motegi clearly came out on top. There might be other wheels out there for more or less money that may or may not be comparable but this is where we landed on this project. The Motegi wheels are a little less than the BBS Motorsport one piece wheels.

MSR Racer

Amazing car. I find it hard to believe though that it can be competitive with the fastest driven 997 Cups without turbocharging the car. After all, Porsche moved on from air cooled to water cooled engined cars way back. Perhaps the weight advantage (at least 300 lbs lighter than the GTC4/5 cups) and the carbon breaks will make the difference.

KMR RSR 001

You might be surprised…

My car will mostly be raced with PCA in GT3R and this is what it has been engineered to. The class formula modifies displacement by 110 for an air-cooled 6 cylinder engine and determines a minimum weight. This year the car was running with the following set up:

> original 3.8l Porsche Motorsports 993 RSR engine developing an estimated 360-370hp (we haven’t bothered putting it on the dyno because a new engine is being built by Rothsport Racing) against the formula of 380hp
> with me suited up in the car, the CoolShirt box and the fuel cell ¼ full the car weighed 2495lbs against the formula of 2303lbs
> Michelin slicks, 27/65 front and 31/71 rear

So the car was under optimized based on the class formula, not developing enough power and/or too heavy. In spite of this I was able to set a GT3R lap record of 2.20.1 at Road America, only my second time in the car. Whilst I’m not racing against the Cup cars that are in a different class they do run in the same group as GT3R and it is fun mixing it up with them. Pretty much the fastest lap times at Road America were set in the enduro. If I were to compare my times with the Cup cars 2.20.1 would have been the second fastest time in GTC4 and the fifth fastest time in GTC5. The fastest GTC5 time of the weekend was 2.17.6, GTC4 2.17.8.

Looking to next year I wanted to further develop the car within the formula. Rothsport Racing is building a 4.0l that per the rules will develop 440hp (there are naturally aspirated air-cooled 4.0 engines out there developing over 500hp). Kelly Moss is updating the brakes and aero whilst removing some weight so that the car comes in below the minimum of 2474lbs (per the new rule change 50lbs higher in 2014 because the car runs on slicks so I’ll need to add ballast). With approx. 20% more power, a better chassis and slightly less weight my goals are class wins and lap records.

You’ll see from the Road America video that I can out brake and corner the GTC cars but they just pull away from me on the straights. With the new set up we expect to gain 2-4 seconds per lap (depending on the track) and I should be mixing it up with the front running GTC5 cars next season. There are modified Cup cars out there that are quicker than the GTC cars that also run in our group but I expect to be following them around. Something that I also wanted to avoid was the mid pack GTC carnage that occurred at Watkins Glen and Road America. Being at the front of the group helps to keep you out of trouble…

When the flag drops the bull**** stops. So we’ll see what happens when the car gets on track next year. I will be at Road America again in 2014 so will be able to do back to back comparisons.

MSR Racer

Sounds great. I saw your car run at RA. You certainly have the math down with regard to the formula for PCA GT3 class. Four liter air- cooled engine sounds fantastic. My only question is why Porsche never tried it their racing program. Reliability issues with air- cooling a high revving 4.0 liter motor? Or perhaps development costs. I don't know but I am sure you have got all this covered. I am interested because I have an air cooled PCA race car. Thinking of cup car next!!

Juha G

Very interesting data... and I like the phrase: "when the flag drops the bull**** stops..." I want to use that (if you don't mind) as my motto when I get into Porsche club racing. Thus far I've been racing a BMW in Finnish the endurance saloon serie but next summer I will enter my "GT2" into the PRCF serie.

For a point of comparison, I have data on my 993 with GT2 EVO aero and 390hp engine vs. a stock 996 GT3 on comparable tires.
On slower track I am 2 seconds a lap faster and on a high speed lap that much slower. It all comes down to the aero. My car literally "stops" accelerating after 90mph when compared to the GT3.
That's why I'm ditching the current drive train and putting in a twinplug EVO engine. Don't what it will put out but propably in excess of 700hp.

I don't know how much different the aero is on the KMR RSR but the EVO aero needs at least 600hp on high speed tracks.

KMR RSR 001

I'm no engineer but in the 15+ years since Porsche produced the 993 RSR there has been a lot of engine development. Most of the power increase comes from the heads which are made by Elite. Other trick components help to create the high revving (8,200 redline) high horsepower motor. To help with longevity and reliability the engine is built about 1.5" wider than stock. All this comes at a cost because a lot of the components are basically one off and custom. From my perspective the "weakness" with an air cooled motor is the heat soak which reduces hp over the duration of a race. But they sound great and are a lot of fun to drive At a point in the development process of any model/race car there is a law or diminishing returns and Porsche moves into the next one. That was the 996 GT3R. More power, water cooled so no heat soak, better chassis dynamics, etc, etc.

I have really enjoyed racing my 996 Cup (which are great cars) but driving the KMR-RSR is way more fun

KMR RSR 001

Juha you're right. After driving my car the first time I got out and said it needed 150+ more horsepower! The chassis dynamics of the car are so good it could handle this. But in the class I'm racing the cap is pretty much 440hp. So we have focused mostly on developing aero, brakes and other little things. But aero is the key. There is only so much we can do and still retain the look and feel of the original car (which I wanted to do). The biggest gains are the front end with the ducting thru the bumper, into the trunk and out the hood and rear wing which increase downforce and reduces drag.

And to your point what I gain on short tracks I lose on long tracks. But hopefully the modifications we are making will reduce or eliminate the loses on longer tracks.

mklaskin

Just as a point of reference, Chris Cervelli used to hassle Cups in his factory 993 RSR.

KaiB

Hassling Cups is FUN with an air cooled car!

How often (hours) does Gammer expect before he'll want to open the engine for maintenance?

MSR Racer

Mark,
Your point about newer engine components and Porsche reaching the point of diminishing returns is well taken. Yours is a great car. I have a 993TT that I just started racing and is still very much being "dialed-in.' That's what piqued my curiosity.

Good luck and keep those updates rolling on that air-cooled dream machine. See u next year at RA.

KMR RSR 001

Somewhere between 50 and 80 hours. The brief to Jeff G was that the motor needed to last a season before being freshened up over the winter. I was told it might last longer before maintenance but time will tell. There aren't many of these "wide" motors around so we'll see once we start putting some hours on it...

KaiB

Good fun. I know the shop is excited - and Fred is back to work half days. You're getting the best of the best out there!!!

lopro

what did you say the mirrors were from? Jeez this thing is a beauty.

Kein_Ersatz

@KMR & @Juha I tip my hat to you 2 pioneers and say "well played sir, well played indeed!"
Those of us "hobbyists" running these "vintage" air cooled 993 DE cars just are gobsmacked to see what you guys are getting out of these chassis and air-cooled motors. God speed gentlemen, god speed.

Timeless!

@KMR ran the A-DE at RA @ CR this year, saw your car in the pits and on track, it was wonderful to see.

KMR RSR 001

The mirrors are made by Crawford. They use a donor for the base and their carbon housing with motorised in car adjustment. They are a thing of beauty.

Thanks Kein Wait until you see it next year...