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OK, the weigh-in is done. Ugh. When I first let the car down on the scales using my lift, it was reading in the 2500’s, but after jumping up and down on the door sills to take the friction out of the suspension, the weight settled down at a supremely depressing 2867 pounds. So, 944and951 wins. That’s without me in it, the sunroof off, and about a quarter tank, or about 30 pounds, of gas. So, after all that work, the car is still a porker. And sadly, I’m pretty much at the end of what I can do while still being able to drive the car on the street, and leave it in a parking lot with at least the outward appearance that it’s secure (even though neither door lock works). About the only thing left would be a lexan hatch window, but based on my measurements and the relative density of glass vs. lexan, that would only save 9 pounds. At a cost of $400+, it hardly seems worth it. Anybody know where I can find a turret to mount on the roof?
So, from what I've gathered after reading this, and other threads on the subject of cutting weight out of these cars, the only way to get down to really low (e.g. sub-2500 lb) weights is to use an additive, as opposed to a subtractive approach. By that I mean stripping the car to the bare chassis, cutting a bunch of holes in the chassis, adding a cage to restore stiffness and safety, and then adding back just the absolute minimum mechanical and electrical components to allow it to run on a track.
You're right - I made a mistake in my calculation somewhere along the way. The window measures about 54" x 40" x 3/8" thick, or 137 x 102 x 0.5 cm. Using 2.7 g/cm^3 for the density of window glass, this works out to 41.5 pounds. The density of lexan is about 1.2 g/cm^3, so the same thickness window in lexan would weigh about 18.5 pounds, for a savings of 23 pounds. Given how high up on the car that weight it, switching from glass to lexan would probably make a noticeable difference, and would bring my car below 2850 lb. I may spring for one if the next bonus is decent. Still seems awful heavy for a car with zero creature comforts.
I got my scales today, and I plan to weigh the car this Saturday. Here's what I've done to lighten it (1992 968):
-Sparco Evo drivers seat, some sort of Corbeau fixed-back fiberglass racing seat on the passenger side that I bought used. Carbeau seat weighs 19 lbs, Sparco about 17 lbs plus mounting hardware, for a total weight savings of about 65 kbs. I bolted the Corbeau directly to the floor, so no mounting hardware on the passenger side.
- Fiberglass hood, with aluminum louvers. Removed struts, but kept hinges and latches. I'm guessing total of 10-15 lb savings
- 4 lb Battery Tender battery
- Fixed headlights (featherweight Hella bi-halogens) ~30 lb savings
- Removed front bumper bar - 15 lb savings
- Removed fog lights, and replaced with fiberglass brake duct scoops
- Removed rear bumper bar - 20 lb savings
- Removed windshield washer reservoir - 12 lb savings
- Removed cruise control
- Removed passenger side air bag and control module
- Removed the surprisingly heavy eyelets that I think were used to strap the car down on the boat ride from Germany
- Converted electric sunroof to manual
- Removed stereo and speakers (almost always drive with the sunroof off, so I can't hear it, anyway) - Saved about 12 lbs
- Removed AC compressor, radiator, drier, and assorted plumbing, Built my own brackets to relocate the alternator to the A/C compressor’s spot – Saved about 25 lb.
- Removed fuel rail cover
- Removed rear seat
- Removed rear quarter interior panels, cargo area carpet and pad
- Removed rear window wiper and motor
- Removed hatch opener motor (converted to manual operation)
- Removed spare tire, jack, and tools
- Replaced stock exhaust with RS Barn cat back
- Single-mass aluminum flywheel – 17 lb, I believe
I added a half cage, Racers Edge heavy duty control arms, a Design1 Racing strut brace and caster block brace, and it has 1989 TurboS calipers and Zimmerman cross-drilled rotors
The car is listed at 3086 lb stock. Anybody want to hazard a guess as to what it weighs now? Whoever comes closest wins - what, I don't know, other than some oohs and aahs...
I don't know if this is already done, but if not, you could change your radiator fan / air scoop from 95110614300 to 94462402103 / 94410614102 (944, 968 Club Sport). So just one fan instead of two. Or take a spalautomotive lightweight fan.http://www.spalautomotive.com/public..._catalogue.pdf
Should save another lb.
Interesting idea about the single fan - I definitely hadn't thought of that. Any idea what the single fan weighs compared to the 2-fan assembly? Do you think it's up to the task of keeping the engine cool in sweltering central Texas? I never drive it in stop-and-go traffic; mostly just to and from (and of course on) the track. And I can't get the link you provided to spalautomotive to work.
Interesting idea about the single fan - I definitely hadn't thought of that. Any idea what the single fan weighs compared to the 2-fan assembly? Do you think it's up to the task of keeping the engine cool in sweltering central Texas? I never drive it in stop-and-go traffic; mostly just to and from (and of course on) the track. And I can't get the link you provided to spalautomotive to work.
Humboldtgrin - Any idea what a horn weighs?
Turbo Cup only had 1 fan like Cloud968 suggests. I have never had any issues on my car other than that the fan is running for a longer time when its on.
Interesting idea about the single fan - I definitely hadn't thought of that. Any idea what the single fan weighs compared to the 2-fan assembly? Do you think it's up to the task of keeping the engine cool in sweltering central Texas? I never drive it in stop-and-go traffic; mostly just to and from (and of course on) the track. And I can't get the link you provided to spalautomotive to work.
Humboldtgrin - Any idea what a horn weighs?
The 968 Club Sport (50kg lightened) got the single fan for the reason of weight saving. The double fan is more or less nessesary only if you still have your AC.
The two stock fans are really pretty heavy. I assume you could save around 5kg, if you change from stock to a modern single fan like the one www.spalautomotive.com offers.
5 kg is a fairly significant savings. I have a belt job coming up soon for which I always remove the fans to improve access; that might be a good time to make the change. Thanks for the suggestion. Do you happen to know which model Spal Automotive fan would be a good fit for a 951/968? And what is it about the air conditioning system that drove the move to dual fans? I wonder if a modern single fan wouldn't draw less current that the dual fans, this not draining the battery as much when they run after turning the engine off.
I'm still not sure which fan would fit best (I'm working on it :-)). You can see the dimensions below. I think a 12" or 13" single fan like the VA10-AP50 or VA13-AP51 (1.52kg) should be feasible to adapt. The single stock fan is around 3.5kg. The modern fans draw less current and are more efficient. The blades have a much more advanced design. With AC on at idle, the compressor puts load on the idle speed, so the IAC valve opens a bit to keep the correct idle speed. So more load on the engine, more heat at idle. And the AC condenser need cooling too. Thus two fans are better than one. Porsche was always on safety side.
Don't have any data at all but it seems to me, that a single fan would have to have +100% in efficiency (less the variable of water temp incoming to the second fan) over the pair of fns.
Water travels horizontally so lets say inlet temp (engine out) is 260F.
The amount of heat removed by the fan cfm/ambient air/radiator efficiency is still measurable in BTU.
When passing the first fan's stream of air, let's assume 20F reduction, to now 240F as measure between the two fans en route to exit (engine in).
Second fan takes another 20F off for a total difference of 40F in/out.
One single fan would have to be twice as efficient in design/space/size to equal the two fans and I don't think the factory fans are bad enough where that will be easy to do.
Seems to me that all a fan can do to contribute to cooling the coolant is blow as much air as possible. In stop-and-go traffic on a hot day, the fan is the only significant source of air flow. But it's a different story on the track, particularly on a car with no AC condenser. So as long as the single fan blows at least as many cfm of air as the stock fans, I would think it should be OK. Anybody know the specs on the stock fans?
09-09-2018, 03:43 PM
