Sunday, July 10, 2011

The pros/cons of doing an LS conversion on a Porsche...

Why we should or shouldn’t throw-out the original
Pros/cons of a Porsche-LS swap...

Stuffing a V8 into a Porsche, whether a 911 or a 914, is definitely not a new concept, but with the invention of the LS motor, certain dynamics of this once common conversion have certainly changed.
When the LS series was first introduced by General Motors in 1997, LS-conversions in pre-LS cars were relatively uncommon. Actually, the closest thing to a late-model engine swap that could be seen in pre-1975 rods and customs was the then-common, LT1 motor from the ‘80s and early ‘90s ‘Vettes, and this was a trend that popped-up at hot rod meets and other kinds of car-buff venues during what seemed to be the late ‘90s, all the way into the early 2000s.
The V8 Porsche experience, on the other hand, is one that goes back 30-some-odd years, back to a time when V8 swaps in Luvs and Vegas were prevalent. Of course, many of these amateur engine swaps were “backyard” projects that were built mostly for street and quarter-mile use, but when V8 swaps in the mid-motor 914s became a reality in the ‘70s, it became clear to a lot of us that having an American V8 in a European road car was the best way to go. The 914 Porsche, in particular, was a hotbed for Euro-American motor retrofitting because of its mid-to-rear layout; Euro automakers had understood, for years prior, that a rear-to-mid motored car maintained the best center of gravity, and therefore handled the best on road courses and oval tracks. The problem that existed within the world of Euro performance was definitely not one of road-handling, since even Porsches had always been keen on this aspect of overall performance. The problem was that most Euro sports cars of the era simply didn’t have the brake horsepower to back-up their superb handling/cornering capabilities.
But there was also a paradox that was created by the Euro-American, small-car V8 trend, as several members of Sportscarforums.com have pointed-out: some water-cooled, V6 and V8 applications are not only more powerful than a lot of factory Euro motors, but they’re more efficient. As one forum member observes, the 3.0 liter flat engine that can be found in the 1980 911 SC only produces around 178 bhp at 5600 RPM, and is actually 66 pounds heavier than GM’s LS1 motor, despite the fact that the LS is a V8 while the Porsche motor is a flat-six.
Probably the most famous V8-powered Porsche 911 on the Web is the “Toy Rocket,” an ’80 911 SC with a supercharged, LS1 motor in place of the archaic flat-6. With the original motor in-place, the 911 SC can top out at around 139 mph; with the supercharged LS1 and stock, Porsche axles, the same 911 can run an 11.94 pass in the quarter-mile, while capable of doing 184 in 4th and over 200-mph in 5th. This kind of performance comes from an American-made, all-aluminum V8 that weighs-in at approximately 434 pounds, a considerable jump from the 911 6-cylinder’s rather heavy, 490 pounds.
Another key point that should be made about the LS block in general is that, no matter what kind of car it’s in, it’s geometrically small, which means that it’s universal in the kind of platforms that it can be used in. Technically-speaking, inline and flat-six motors are heavier and take-up more space than a V8, so bay space is actually being saved by doing an LS conversion on a 911.
The last point in this defense of doing an LS swap on a Porsche is the location of the motor in the car. As one member of Sportscarforums observes, the displacement of an LS1 motor (5.7 liters), because it is considerably larger than that of a Porsche flat-6, demands that the motor be placed slightly in front of the default motor location. What this means for road-handling, especially in the case of the 914, is that handling and cornering characteristics are actually optimized instead of hindered.
All-in-all, an LS conversion on a Porsche seems to make the most sense; not only does GM build an aluminum V8 that is lighter than a Porsche motor, but cubic inch for cubic inch, it produces twice the power within the exact same RPM range, and that’s without a supercharger. In fact, the LS1, in naturally-aspirated form, produces more than 50 bhp over a late ‘70s/early ‘80s 911 turbo; with a supercharger bolted-on, that same LS1 is capable of producing well over 500 bhp.
There’s no question of a doubt in my mind that there is a difference between American and German engineering, but there are pros and cons to both, and what V8 conversions in small, Euro cars has brought to the senses is that handling needs to back-up power. In this context, the LS series from General is a motor that almost seems to fit a 911 or 914 chassis perfectly, because it’s lighter and more compact than any other series of small block, while also being more technologically-advanced than previous generations.
- Sal Alaimo Jr., B. A. (7/10/11)
S. J. A.

2 comments:

  1. Nice article!

    I just want to chime in on this topic of the pros and cons of the LS engine in a Porsche 911 and 914. Just to clarify: My silver 1980 LS Porsche is the "Toy-Jet". My metallic copper colored LS Porsche 914 is the "Toy Rocket". My 11.94-quarter mile run in the Toy-Jet was very conservative because I had stock axles and this run was done back when I was beta testing the integrity of the conversion. I later ran 11.59 with turbo axles and unfortunately missed fourth gear during the run (so the LS has much more potential than I displayed).

    See the 11.59 quarter mile run at:
    http://www.youtube.com/watch?v=wo3Mi0XhwME

    I was not allowed a re-run because the cutoff time at the track for streetcars was 11.99 at the time. I now have a 930 four-speed transaxle installed and I plan to go back to the track within the next two months. I will make sure to post my run via You Tube also.

    Toy-Jet

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  2. Actually, the closest thing to a late-model engine swap that could be ... ls1engine.blogspot.com

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