Originally Posted by scottherbert

Lightweight is great but...

According to the most racing references, 10lbs of weight reduction nets you about 1hp of net effective value - maybe a bit less. I can state that my Cobalt SS, with the GM stage I and other parts I have alredy installed, has so much torque and hp that I can easily spin fresh Hoosier 285/30 x 18 A6 slicks at the start and in turns - so I'm having to use throttle control (less throttle) to get faster, I can't just stab the gas and go - so do I really need more net effective torque and hp?

If I was road racing (which I can't afford), more hp particularly would be great because I'm pushing a lot of air at road racing speeds (100+ mph). I'm autocrossing (speeds of about 60 mph) so torque is a bigger deal -- and I can't use it all right now...

I've done many of the bigger savings discussed, like Cold Air and a custom bent 3" exhaust with the resonater and stock muffler removed (I use a simple 3" ID glasspack - not even a cool tailpipe), I've replaced the stock driver's seat with a light racing seat, I bought the car new without a sunroof to save weight, but beyond this everything else become $$$ in -- weight out. Custom, lighter wheels (track use only, they aren't DOT legal) can easily cost more than $1000 each - what's the value return on that? I plunk down about $1500 for a full set of Hoosiers and go through at least a set (sometimes more) each year - those $$$ are worth more to me than $1000 wheels. And racing tires don't get any lighter BTW - they are already as light as can be made -- my Hoosier 285 A6s weigh about 20 lbs each, so do BFGs, Kumhos, Goodyears, Hankooks, etc., etc.

So how much money do you spend and how much capability to you reduce to get maybe 10 hp value return? I don't know the best answer but I do know that I've already had to make some of those decisions.

At least one guy (it's on this site somewhere) removed everything he could off our Cobalt, gutted the interior, no carpets, no sound deadening, no seats, no head rests, no side panel facias, no spare tire, sub-woofer, etc. -- he saved a total of less than 300lbs from his gutted Cobalt -- about 30 hp worth of lightness. And it isn't legal to run like that anywhere except 'real' road racing or drag racing. If you just want to look cool, go for it, but if you're planning to run the car somewhere, check the rules first. Carbon fiber hoods and trunks which really are lighter than stock, for example, throw you up a class or two in SCCA.

I'll admit that I've already gone a bit the other way, I have installed an autopower competition rollbar which added about 50 lbs to my overall weight - I've probably balanced my current weight saving with the added weight of the rollbar (I really want to try time attack some day).

I'm waiting for someone to suggest lighter brakes, drilled rotors for example, which mean less braking because more mass, not less, equals better thermal efficiency.

An alternative for example, or perhaps a question: might it make better sense to add a big, heavy trailer hitch; a bigger, heavier battery; and a heavier spare to get a better front-rear balance on our FWD car? I don't know the answer to this but it bears thought.

I don't want to throw either water or gas on this thread, I'm not trying to be a schmuck, this isn't intended to be inflammatory, I just want to add some additional thoughts to the process.

Scott

Originally Posted by Mark Aubele

If you guys are interested, I can link to an interesting build thread (Vorshlag's) of an E46 DSP car.

Originally Posted by Spank

I personally would love a link to the build thread.

Thanks for offering.

Slowbalt

Originally Posted by Mark Aubele

No problem, let me dig it up.

Vorshlag BMW E46: DSP Auto-x Project - Corner-Carvers Forums

May have to be a member to view some pics.

Originally Posted by Spank

Great build thread. Reminds me why I sold my previous BMW's. Expensive to get power. So I really don't know where the big power some people say the BMW has in DSP. I think they are below 300, and in reference to weight I hear some are below 2700 but have not seen one or had someone actually say there car was 2700 let alone 2600.

Slowbalt

Originally Posted by Spank

So my thinking is lets say 250 max, lets say 2700, we can be at 300 easy, and be at the same weight. Same size tires. I think we can give them a run for their money. Yes we have FWD, however you know in the wet you have to give us the advantage. Dry??? My thinking is it will be close.
But Mark, you have personal knowledge of BMW's being in the 2600, 2700 legally? Again, I have heard but never seen. It just seems to difficult for a 3200 - 3400 lb car to lose that much weight and still be in SP.

Slowbalt