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The Porsche 944 Turbo: Technical Tidbits

January 14, 2013 by Matt

Porsche 944 951 Turbo Bronze Silver

As an avowed sufferer from Automotive ADD, this is what I want today. Saw one trundle by yesterday—bronze with black Fuchs—while I was putting up beadboard for my in-laws and I was freshly reminded of how much I like them.

Besides its universally-acclaimed attributes like world-class handling, good looks and a startling turn of speed in Turbo guise (internal model code 951), the Porsche 944 has a few technical quirks that particularly endear it to a fan of unconventional engineering like myself.

Porsche 944 951 Turbo Differences Ad Advert

Click image to enlarge.

Take a look at the Porsche advertisement above. What seems like a fairly conventional layout (front-mounted, water-cooled engine) from an automaker known for beating their own path with the 911, upon closer inspection the 944 Turbo reveals some neat little engineering details:

  • Rear transaxle. Perhaps the most obvious difference between the 944 and a more mundanely-engineered sports car is the location of the transmission. A key element of the car’s perfect 50:50 weight distribution and stellar handling, an unfortunate side effect is the fact that the clutch and trans arrangement is more difficult to service for those of us used to a more conventional layout.
  • Rear suspension torsion bars. Another noteworthy feature of the 944 is the absence of coil springs at the rear of the car. Instead, Porsche equipped the car with torsion bars. Advantages include lower unsprung weight for better suspension geometry response, as well as a more compact installation, but aftermarket upgrades can be hard to come by.
  • Under-engine exhaust manifold. This, to me, is the most interesting 944 Turbo quirk. When I first saw a 944 4-cylinder on an engine stand, I remember thinking, “The turbo’s on the wrong side.” However, given the compactness of Porsche’s installation and the fact that the engine is strongly canted toward the passenger side of the bay, the engineers must’ve run out of room to install a turbo and its required plumbing, so they simply routed the exhaust manifold under the engine to the driver’s side and located the turbo there. It’s a fascinating bit of make-it-work development rivaling Audi and Saab’s occasionally Rube Goldberg-ish turbo solutions. The length of the exhaust manifold isn’t ideal for quick spooling of the turbine, but Porsche compensates for this through careful manifold design, allowing them to incorporate a:
  • Divorced manifold and post-cat wastegate exhaust return. Porsche was an early master of turbocharging technology, and their engineering decisions on the 944 Turbo show it. The wastegate location and intersection with the manifold and exhaust pipe are all crafted to allow the smoothest, highest possible energy flow into the turbo itself. Yes, there’s a bit of extra piping and complexity, but the arrangement pays dividends in performance and shows Porsche really knew what they were doing, in contrast to many of their less-experienced, downmarket contemporaries.

I love cars like this, ones that seem so common and run-of-the-mill externally but hold more than their share of mechanical uniqueness. In the 944 Turbo’s case, the external design was so successful that it spawned a number of imitators like the FC RX-7, and as such the styling blends in to the automotive landscape perhaps more than it should for something so attractive. The prevalence of its shape means one has to dig a bit deeper to find the design quirks, but they reward seekers with how well they reflect on their manufacturer’s performance expertise.

Filed under: Porsche, Technical

10 Comments

  1. John D says:

    This has always been one of my favorite cars.

    I did some tile work for a very wealthy gentleman who had one of these (an ’86 turbo, I believe) with around 40k miles on it. He had bought is as a toy but pretty much never had the time to drive it. It was classic red with black wheels and he let me ogle it for quite a while and even back it out of the garage when we needed to gain access to a tub drain in the garage ceiling.

    I absolutely love the mechanics of the car and the looks…but the interior is hopelessly 80’s. It was a bit of a let down when I get in the car and behind the wheel. Every other aspect of the car has aged so gracefully that I was extremely disappointed with the interior, realizing then and there that I would never want to spend any significant time inside that car. It’s just too…ugly. Dated, and not in a good way. Which sucks. Because the rest of it is so beautiful…especially for the time period.

    Ah well. I’m still glad that there are other who feel differently about the interior, because I do very much enjoy seeing a nice one pass me by on occasion. ;)

    • Matt says:

      I can actually see you driving one of these. With a few mods, they’re actually pretty FD-like in their power-to-weight ratio and handling capabilities. The car’s shape is iconic and influential as well.

      Shame you don’t like the interior. I don’t have a problem with it, but…we all know where my tastes stand. :)

  2. Lovely analysis. And lovely car, obviously. Make mine an S2 :-)

  3. Nick says:

    My brother drove a 951- definitely deserves a spot in my fantasy garage. Little known fact- the 1987 944 Turbo was the first car to have standard dual airbags in the USA.

  4. Chris says:

    Correction: The clutch is on the back of the engine, not in the transaxle’s bellhousing. You can actually see it in that picture pretty clearly. :P You don’t need to touch any suspension components to replace it either. Just the transaxle and exhaust, and you just have to move the torque tube out of the way. It’s still a pain to do, but you don’t need to disassemble the whole car.

    • Matt says:

      Thanks for the correction, Chris. I’ll amend the post. I’d always heard the clutch was integral with the transaxle, hence my description, and truth be told I was a bit confused when I saw the pic and spotted the clutch up near the engine. Question: Am I understanding correctly that the transaxle does need to be removed to service the clutch? If so, why, since it’s on the opposite end of the car? Honestly curious.

      • Chris says:

        The transaxle does need to come out, just so you can move the torque tube toward the rear of the car and out of the way of the clutch housing. The rear suspension needs to be removed if you want to take the torque tube right out though, and that’s probably why you heard that. Maybe it’s part of the procedure in the service manual. Even without that mess though, it’s still not a weekend “doing it out of boredom/for fun” kind of job. It’s things like this that really show you the car was designed to perform, not to be cheap and easy.

        • Matt says:

          No argument here about the car being designed to perform, and thanks for the insight. For the record, I respect Porsche’s mindset in engineering the car the way they did—more performance-focused and more interesting is a win-win in my book, even if it comes at the expense of ease of maintenance. :)

  5. areopagitica says:

    Transaxles never manage to have the directness of linkage that satisfies the tactile sense on a device that is operated almost continuously by the driver. They require a driveshaft to spin at engine rpm which creates a commotion until they have settled down into top gear. However, they allow a narrower tunnel that may or may not permit a better pedal ergonomic package or even a narrower car overall.

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