[Lemming]

In my quest to make the 924S3 as light as possible, I'm contemplating deleting the alternator (plus it robs a little power). Is anyone out there running without one? How long is your battery good for, one race weekend before recharging or do you charge it with your tow vehicle between runs?



By the way, I got the 968 engine talking with the DME and the 924S internals, so yesterday I was able to start the beast. It should be track worthy in two weeks <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[Jim Child]

I know people who have tried to run without the alternator on the track, one in a 968 and the other in a 944 S2. Neither of these people managed more than 30 minutes before the battery died. I'd forget this idea unless you enjoy being towed back to the pits <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[Lemming]

Guess I'll look to save weight some other way, thanks for the heads up.

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[Etnier]

Yeah- I had that experience when my belt broke on the highway. Shut everything I could find off and still lost the battery very quickly.



What do you think the drain is? Fans? DME?

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[josephsc]

Wouldn't a lightweight battery be a better way to go, then? I've run Odyssey 680 for street application in moderate weather w/o problems (about 15lbs -- saves about 25lbs).

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[Lemming]

[quote name='josephsc' date='Sep 14 2005, 01:03 AM']Wouldn't a lightweight battery be a better way to go, then?  I've run Odyssey 680 for street application in moderate weather w/o problems (about 15lbs -- saves about 25lbs).

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It's another option, but there's a cost involved $. There are a number of racers that I know that don't bother with an alternator but none of them drive 968's. Deleting it not only saves weight but also drag on the engine.



I have know idea why the battery would die so quickly as some are saying. Unless it's really hot out, I doubt the fans would be running when at speed.

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[Eric_K]

Sounds like too big of a PITA to be worth it. Running a smaller alternator may be more practical.



You should do the light battery anyways. The Odyssey is pretty cheap. I got mine for around $80 via ebay.



Eric

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[flash]

we used to run with no alternator in the mgb - that car was carburetted, had points ignition, a low pressure fuel pump, and a mechanical fan



this car has electronic ignition, electronic fuel injection, electric fans, high pressure electric fuel pump, yada yada



the demands on the electrical system are much higher - the reserve capacity of the battery would have to be much higher to make it



you lose about 1.5-2 hp from an alternator - it weighs about 10 lbs



the larger battery required would probably add about 15lbs - you would possibly come out ahead by a horsepower or so, after calculating wieght loss to effective horsepower, but if you hit a yellow, or there was a starting delay, you could be screwed



a long way to go to get there and a pretty big bummer if it goes the wrong way

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[Greimann]

Under drive pulley?

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[Lemming]

I'll likely pick up a lightweight battery that's the easiest thing to do. I might think about relocating it to the rear passenger floor area as well.



I've thought about the underdrive pulley as well but I'll hold off on that until after the initial testing of the car. When I puchased the Spec Stage 3 clutch I did go with the light weight version (+$75) but did not spend the bucks for a lightweight flywheel. I can't wait for the first test drive, possible this weekend <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[Charles Geer]

Buy a 968 clubsport alternator and you'll save yourself a few pounds. I've got a cessna aiplane battery weighs 6 lbs as compared to 27 lb normal battery. It's still in the box...a may even sell it to you. I believeit cost about 200.oo

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