Robert Linton

Some friends and I have been working on a modern version of the classic Porsche 6 cylinder air cooled engine. It should be in excess of 500 HP and quite light due to the extensive use of titanium, carbon fiber and other composites including aluminum metal matrix composites. Do you think that anyone else would be interested in such an engine?

GrantG

Yes, I'd be extremely interested for my 73 911 hotrod but very nervous at what it might cost.

FastLaneTurbo

The basic reason for moving from an air cooled engine to a water cooled engine was for more even heat distribution throughout the engine. More even heat distribution means that internal stresses
due to localized hot spots within the engine are reduced, each cylinder is producing more equalized power and total engine longevity is increased with equal power. Porsche’s overhaul recommendation for its 450 rated HP last air-cooled Turbo-Charged racing engine on the 993 GT2’s was only 30 hours.

Furthermore, the large mechanically driven blowers required on air-cooled automobile engines require more parasitic power than the water cooling circulation pumps. Other than nostalgia and retro-fit applications, is the slight weight-saving of returning to air-cooled engines worth the trade-off of power and longevity?

Al Pettee

Interesting that you conveniently leave out of your post the reality that Porsche recommends rebuilding GT3 Cup Car (water-cooled) engines every 30 hours, as well. Just saying....

FastLaneTurbo

Sorry for the omission. I never owned a Cup Car and my GT2 Engine actually went 50 hours before breaking, but at $75K for OH, plus $25K for Tranny OH it made a very expensive Track Toy. I've been very impressed with the general reliability of the later water-cooled higher HP street Engines being tracked. Despite a relatively small number of failed Engines and a few chronic problem areas, the Porsche Engines, both water and air cooled, IMHO have been far more reliable than competitor's Engines when tracked extensively.

Even if reliability with similar Power is arguably close for both designs, I just don't
know why anyone would invest a small fortune in tooling a new Air cooled Engine design when many used rebuilt air-cooled Engines are available at far less cost.

Z356

That's is because you don't know Robert Linton and Cartridge! I have heard many interesting things about this individual from a friend who used to be the editor of a well-known Porsche magazine. When Linton sets his mind on a project, expect something very special! So yes, Robert, I think there would be many folks in the know interested in YOUR modern version of the classic Porsche 6 cylinder air cooled engine, with HP in excess of 500 and very light weight due to the extensive use of titanium, carbon fiber & other composites! I wish you well on this project and hope your are successful in making it a viable motor for our Porsche hobby! Please keep me & other interested parties informed on your progress.

Saludos,
Eduardo
Carmel

amdevo

judging from the prices of engine rebuilds with good builders, id say this is going to be one expensive unit

Petevb

Interesting and timely. I've been pondering doing something similar at some point, though it's a hell of a project very few can expect to pull off well. Robert would be one of those few.

As mentioned, thermal management is the critical issue for air cooled cars, however realize that the factory left significant room for improvement in this area. When the last air-cooled motors were designed critical technologies like CFD flow simulation were in their infancy, and essentially unavailable to Porsche's engineers. This, plus their relatively tight parts budget, made it very difficult to fundamentally address hot spots that limit engine output. Even so, Porsche was able to do significantly better than it might appear: the GT2 Evos with 30 hour rebuild schedules were in excess of 600 hp through restrictors; the very last 450 hp GT2 street motors had a much longer time between overhauls in their usage.

In the intervening two decades material technology has advanced and design tools have improved greatly. CFD can be used not only on the air side but the oil side: BMW motorcycles proved that 110 hp per liter can be exceeded in street usage using 4 valves per cylinder and air/oil cooling. Applying these and other lessons and technologies should allow significant advances over what has been achieved up to now.
Weight would be the main reason I'd personally look to pursue this path, and I wouldn't underestimate it. Great cars nearly all have great engines at their heart, and the measure of a great engine is power to weight ratio. A high power to weight ratio motor makes the rest of the car better, think CGT to McLaren F1 to E30 M3. In the case of a high HP 911 a reduction of over 150 lbs may be practical with this path, and that weight removed from the tail and nose (radiators) of the car would be enough to transform a 911's handling.

I'm interested to understand the philosophies being used with this new motor: race or street, forced induction or normally aspirated, "cost no object" or built to a power to weight target, building on existing Porsche designs or clean sheet? Depending on the answers to some of these questions I could be quite interested for another project, and would like to follow it either way.

You're thinking World Challenge and RSR motors with 2 ring pistons. The newer 3 ring cup motors are 60 hours, and that's conservative. Older 3 ring cup motors were longer.

911Jetta

This is spectacular news!

You've already almost re-created the "modern version of a classic" with your America GS project. All you needed was an engine that was up to the level of the rest of the car.

I've long imagined how amazing a Singer by Cartridge Limited would be...
Someone please commission this car!!

Magnus Walker 911 on the Auction Block (post #20)
https://rennlist.com/forums/showthread.php?t=768940&referrerid=19642

Petevb

I'm not quite sure how to put this without sounding dismissive, but compared to Robert's car the Singer is a simple styling exercise. The America GS really on an entirely different level, to the point that I'd personally try not to put it in the same sentence with any other efforts I can think of.

From another thread:
Over the top... Perhaps not practical enough for what I'd have in mind, but it sounds epic...

911Jetta

I fully understand what you are taking about, and totally agree.

Over the years many people have asked about acquiring American GS parts that Mr. Linton has graciously displayed in various forum posts. Invariably the cost or production numbers haven't made that feasible for most 964 owners to acquire.

Singer vehicles opens up a whole new market segment for these 964 products... A Singer with carbon fiber suspension and brakes sounds pretty good to me.

The quality of execution is one thing they both have in common (and a thing for 964s also).

...I just see a really interesting synergy here.

Al Pettee

The point I was trying to make was not that water-cooled flat-6's are as unreliable as air-cooled flat-6's, but rather that air-cooled flat-6's aren't necessarily less reliable than modern water-cooled flat-6's. And when properly built and maintained, the air-cooled motors can be fairly reliable if not more so compared to more modern designs.

And nothing sounds like an air-cooled six, NA or turbocharged.

Petevb

At an equal (relatively high) power level they are absolutely less reliable. Today a 400 hp normally aspirated air cooled motor can't last half as long (time between rebuilds, etc) as an equally built water cooled motor. Not even close.

Turbohead

OEM Porsche Air cooled Turbocharged engines have been extremely durable and reliable.
for example an OEM 3.6 turbo engine easily runs 550 hp with modern fueling,ECU and bolt on mods like exhaust , turbos and intercooler .
All of this with stock internals.
I'd say that is a pretty good . for this" antiquated design."
Elliot

Petevb

It is good. However for some perspective that means reliable power is finally approaching levels the factory ran at Le Mans nearly four decades ago. And rebuild frequencies for the air cooled turbo motors are undoubtedly higher than either their normally aspirated or water cooled counterparts in similar states of tune.

For a case in support of the technical (as opposed to historic or anesthetic) merits of air cooled motors I'd look at the power to weight ratio of the engine, including the cooling system, on a 993 GT2 EVO vs more modern 911s...