Impact of weight reduction
02-05-2013, 06:20 PM
#16
Race Director
Well at that level of competition aspiration, I would go farther and suggest that small differences in car weight and a sunroof would be relatively inconsequential. Lowering an entire ~3000 lb car has more effect on center of gravity than not having a sunroof. The incremental weight of a sunroof (made of aluminum) over the steel of a non-sunroof roof is likely about the same effect as lowering the windows or hiring a skinnier driver). Over the typical autocross course, any such effect is likely to be dominated by whatever will keep tire contact patches at the greatest widths - like PDCC for example.
So, my priortities would be to lower the car, get dedicated R rated tires and optimize the shocks, springs roll bars and alignment away from the compromises for the street that are there for clearance, comfort, tire wear and straight line stability. That would provide the unfair mechanical advantage that (assuming equal levels of skill and concentration and identical driver weights) could affect times in the range you specify.
So, my priortities would be to lower the car, get dedicated R rated tires and optimize the shocks, springs roll bars and alignment away from the compromises for the street that are there for clearance, comfort, tire wear and straight line stability. That would provide the unfair mechanical advantage that (assuming equal levels of skill and concentration and identical driver weights) could affect times in the range you specify.
This small improvement may not be "worth it" in terms of foregoing a sunroof if you want one, especially for a street car, but I don't think it's imaginary. Look at the difference in times lap to lap as an F1 car burns off 3 or 4 KG of fuel per lap. Sure, our cars are twice as heavy, but we're also talking about 30 or 40 lbs at the top of the chassis, not just 2 or 3 gallons of fuel in the tank. Combine a sunroof delete with sport buckets, a lightweight battery, and going easy on other options and you're talking a savings of perhaps 90-100 lbs. That's meaningful.
02-05-2013, 08:39 PM
#17
Race Car
02-05-2013, 08:44 PM
#18
Race Car
(No croissant before runs?)
02-05-2013, 09:42 PM
#19
Race Director
02-09-2013, 06:34 AM
#20
Rennlist Member
Weight on top of the car is not ideal. Know that's why carbon fibre roofs are installed on some cars like the m3. Would be interesting to drive both and see if you could tell the difference.
02-09-2013, 08:37 AM
#21
Burning Brakes
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At about 3,700 lbs the M3 has other things to worry about. I spoke to the head of their engineering dept. by chance a few years ago and asked why they didn't try to put the M on a diet. He said it was cheaper to put more power in than make it light-at least he was honest. As much as I love BMWs, it's not fair to compare it to a 991.
02-09-2013, 11:37 AM
#23
Rennlist Member
At about 3,700 lbs the M3 has other things to worry about. I spoke to the head of their engineering dept. by chance a few years ago and asked why they didn't try to put the M on a diet. He said it was cheaper to put more power in than make it light-at least he was honest. As much as I love BMWs, it's not fair to compare it to a 991.
I'm still a BMW fan but love my Porsche. While I haven't driven one yet, the 991 seems like a terrific car.
02-09-2013, 03:42 PM
#24
Burning Brakes
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You are right with the location of the weight. I share your love for BMWs, and still am a Porsche fan. I'm working on moving from my 997 to a 991. Again, I love both these cars but am very impressed with the 991. Cheers.
02-10-2013, 04:32 AM
#25
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Take your stock wheels off
I took off my stock wheels and went forged! The weight of my stock GT3 wheels was shocking! I went with GMG forged Monoblocks.....saved almost 30 lbs all around! PM me if you need more ideas....but start with the wheels. I am an authorized GMG reseller and can get you pricing.
