WARNING: This will be a train of thought, rambling commentary born of my complete boredom late at night. So....if you're gonna read it, just realize that I'm all over the place here, and I'm really just trying to spark some discussion of a topic I have interest in 
Ok, so usually I just toss the SCCA rag in the recycling bin after a quick flip-through reveals no substantive rally-x content, but the latest one actually had an article with some analysis (by Jonathan Olschewski, who has an impressive MF Sentra as detailed here: http://www.sccabb.com/forum_posts.asp?TID=11810&title=buildmod-fnt-1991-nissan-sentra-jon-olschewski), so decided to read it.
The main gist of the article is that lightening a rallycross car doesn't help it win/go faster/etc. He states that there "aren't any facts to back the theory." He makes an exception for lighter cars in muddy conditions (which seems kind of an odd exception, seeing as rallycross frequently has muddy/slick conditions, at least in our region).
"In muddy or extremely slick conditions, lighter cars tend to be faster....in all other conditions those cars do not seem to have any advantage"
First problem here: ok....so they may not have any advantage in dry conditions, but do in muddy conditions. So I guess if you rallycross where it's always dry, that is a notable point. But every rallycross venue I've been to sometimes has muddy/slick conditions. So right from the start this would tend to argue that "lighter IS better", if it's good in some conditions and "equal" in other conditions, right?
His second piece of evidence was that after he lightened his car, it was losing to a heavier car, and by that logic reduced weight was not the key. He notes, to his credit, that it's just one anecdote and is subject to other variables.
But then goes on to state "the facts:" - at nationals, light cars only win in Mod FWD. And then not always. - a 3000lb car beat a 1700lb car at nationals, even though the 1700lb car had previously won MF at nationals. - all the cars that won MR and M4 were "stock weight."
Now, I'm a technical analyst for the government. I do analysis of facts for a living. And those data points do not constitute an objective analysis in my book. They're really just a series of anecdotes centered on one specific event: Nationals. Having never been to nationals, most of my knowledge is secondhand admittedly. But my perception is that nationals is usually on dry courses, for one. Does it rain much in Nebraska? IDK. Also this perception that "all the best drivers" are at nationals, which I don't necessarily agree with. I'd say many of the best drivers are. I'd also say there are a lot of great drivers in regions on the east coast, west coast, gulf coast, northeast, etc who don't go to nationals because of the distance, expense-per-seat time, etc etc. And nationals is on a specific surface. So I don't think that constitutes an substantive analytic method there. What if nationals were on a muddy course in Tennessee every year (like SE divisionals last year). What if it was on gravel (like NE divisionals will be this year)? Does that change the analysis? Probably.
"there is simply no proof that lighter cars are the ticket..."
But he doesn't seem to take into consideration that the heavier cars may have substantially more power as well as more weight. a BRZ is a hell of a lot heavier than a 1st gen RX7. And drivers and modifications being equal, the BRZ will almost certainly beat the RX7 in most cases. Is that because it's heavier? I disagree. It's mostly because it has more power, better chassis dynamics and suspension, better brakes, better steering, and the use of electronic nannies in muddy conditions. All of these are of course subjective.
It also doesn't take into account "where" weight is shed. SInce I know e30s, let's go with them first. If you have a 325i, your car is already nose-heavy. If you ditch the back seats, rear glass, spare tire well, etc....well yeah, that's not gonna help. It just exacerbated your problem. If you have a 318i though, your car is already well balanced. If you do all those things above, and then move your battery to the trunk, you've then lost weight while maintaining the good balance. So the weight reduction in the first case is bad for the car (especially since it has good power to start with so weight isn't as much an issue), while in the second case, it allows an under-powered car to gain p/w ratio relative to the 325 without sacrificing balance. The lighter weight allows a car to brake faster, and to accelerate faster (especially a low-powered car) to a certain point.
Are the heavier cars winning because they're heavier, or simply because they are better cars overall? WIthout a lengthly analysis of ALL the cars in all historical rallycross events, I don't believe that it can be determined. And with drivers being the biggest variable, the scientific way to prove this would be to have one good driver drive several cars of different weights and power and see which is fastest.
We just so happen to do this all the time in WDCR. I'll use my own example here: My car is the lightest in MR, and possibly the best set-up locally. I am NOT the fastest driver locally though. But I finish top-2 almost every event, mostly because of my car (IMO).
To test this, I've had the other top drivers (who I regularly beat) drive my car. They both drive heavier cars than I do, by a good margin (and also far more powerful). We all use fairly equal tires and have fairly equal experience.
Chris Nonack drove my car last season against me at an event. He has never beaten me (I don't think) in either his MR2 or his Mustang or his Celica. I don't think he ever won a WDCR event. Until he drove my low-power, very light car. He beat me handily in it, as well as the other 10 cars in the class.
Nick Drymalski has driven my car several times. He usually drives an e28 and puts up times very close to mine in that heavy tank. In my car he is equal to or faster than me pretty consistently.
Both of these guys are slower than me in heavier cars. Both of these are faster than me in my own light car. So they are faster in a lighter car. As I lost weight from my car, I won events by larger margins as well.
Again, these are anecdotal and at the "local" level not the nationals (though again I submit that many top local drivers are just as good as many national drivers - it's not like bad drivers aren't allowed at nationals.....anyone can enter). But it is evidence no less. And the amount of experience and car prep at our (and other) local events is no less than at any divisional or national events, in many cases.
So, sorry for the diarrhea of the keyboard here, but that article just seemed kind of silly to me. While I respect peoples' opinions regarding their own car prep and that of what they've seen personally, I think it's pretty ridiculous to claim that this limited evidence is proof of a "fact," just because it is a general trend at a small number of events.
In our local events, the lighter GC subies generally beat up on heavier STis and WRXs with drivers of similar experience and prep. Adam Kimmet's gutted 2.5 locally beats pretty much the entire (large) M4 class, other than Matt Berk's H6-swapped impreza - which is slightly heavier and WAY more powerful. They both generally beat up on any STis in the class (which are heavier and more powerful). So there's another anecdote that means nothing by itself.
One of these days, I'd love to do a full analysis of this using local and national results for the last decade and see how hit pans out (I'll never have the time to, but whatever).
Actually, would be interesting to see GRM put this to a test. Make a random rallycross car. Run it with a few drivers. Take some weight out (or add weight, if that's easier) and run the course again. Do it semi-scientifically if possible. WOuld be a real analytic comparison, rather than a comparison of a bunch of different cars with different prep and different drivers - which proves essentially nothing.
In any case, if the author is by any chance on here - don't get me wrong....I enjoyed the article. I just found that it was a bit weak on analytic method and thin on "facts."
There are a few facts about cars: 1. lighter weight results in increased acceleration (traction-dependent, of course). 2. lighter weight results in decreased braking distance (traction-dependent also) 3. lighter weight results in less lateral inertia during turns (which is a good or bad thing depending on where the car's balance is and what the driver's style is, of course).
None of these facts says that a car HAS to be faster if it's lighter. But I can't find any "facts" that support the case that a heavier car is just as fast, or faster. Worse acceleration. worse braking, more lateral inertia. Weight over the wheels helps to a certain point, and too light may not get enough "dig" for traction. Too heavy may dig in too much. Too much power can't be used in some conditions. Too little power and you're simply gonna be slow on any straight areas. All of these things are factors. The key is to find a balance. Taking weight off in the right areas is helpful, and hurts if in the wrong areas. Taking off "enough" weight is the key, but I can't see in any way how leaving a Mod-class car stock weight is an advantage vs. that exact same car with 200lbs removed from the appropriate area, that's all I'm saying.
and so on and so forth.
Thoughts from the peanut gallery? I know some of you guys rallycross light cars, and other heavy cars. I know we all have opinions on how much power is too much power (as we say in NONACKs mustang build thread), but haven't heard much opinions regarding how much lightness is too much lightness (or is any lightness good)?
GO!
