How the heck... (weight reduction)

B

boxedfox

New member
So this past weekend, I scaled my 4th gen Prelude Si at ~2700lbs in race trim with a 160lb driver and fumes in the gas tank. It's a fair bit lighter than it was earlier this season, but it's still almost 150 over the ITS min weight of 2555 lbs in the GCR.

Now I'm looking through the chassis and I cannot for the life of me figure out where I could get another 145 lbs to take out of the car. I have a relatively simple cage, NASCAR bars into the doors, a relatively light seat, and the usual amenities like AC, sunroof, cruise control, and emissions are all long gone. The header and exhaust are relatively light stainless pieces, and I've replaced pretty much all of the obvious stuff that I've been allowed to in the GCR.

Am I missing something really obvious, or is this chassis really hard to get down to min weight?

It's really starting to bother me now, because we just finished prepping a CRX the same way, and it came in at almost 225 lbs under its ITA min weight. What the heck am I doing wrong?
 
Remember that the minimum weight isn't set considering what the car CAN weigh. It's set based on engine power. If you had two cars with the exact same chassis but different stock power figures, they would be spec'd at different minimums. Some cars simply can't get to theirs - particularly the ones with the lowest HP ratings in their class.

K
 
Knestis said:
Remember that the minimum weight isn't set considering what the car CAN weigh. It's set based on engine power. If you had two cars with the exact same chassis but different stock power figures, they would be spec'd at different minimums. Some cars simply can't get to theirs - particularly the ones with the lowest HP ratings in their class.
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Aren't such cars suppose to be bumped down a class and given a sentence of morbid obesity?
 
Roger, 150lbs overweight in S isn't too bad. And, by your own admission you have "reasonably" light components. You might need to get out and search for that last 150 lbs and it might be hard. I'd be trying to get 110 lbs or so and keep the car 30-40 lbs over to account for variances in scales at tracks.

There is/was a well built ITS Prelude like yours on another race forum that is at weigh if I recall. Extremely well built car. It also makes in excess of 177hp at the wheel too, and is quite competitive in ITS. Based on that info I doubt it'll be moved it ITA.

I race an ITS Mustang. I'm hoping to get within 250 lbs of my weight minimum AFTER this season's round of weight improvement and $$$ spending.
 
Ron Earp said:
Roger, 150lbs overweight in S isn't too bad.
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If the vast majority of the cars in a class cannot reasonably make their minimum without without extraordinary measures, then the class weight formula is bustificated.

The basic tenet of setting weights in ITx is a formula based on stock horsepower, with the assumption that the car can make the weight given to it. If it cannot, and you're not willing to wholesale move those cars to the next class down, then the formula needs to be changed to increase the weights across the board. This is what we did last year in STL, so that cars with lower displacement had a chance to get there. Didn't make me happy - I could get to my weight - but it was better for the class overall.

GA
 
Thanks for all the advice (and quick responses). It's true that there are a few parts I have on there which aren't as light as they could be.

After reading your responses and thinking about it for a bit, I realized I still have stock power mirrors, which are probably 4 lbs on each side that I could easily save. My exhaust is full length and has a muffler, so it's probably not that light. The DC Sports header that I have on there is definitely a couple pounds more than the Hytech that I want for the car. And the main hoop and the rear legs of the cage are 1.75" x 0.95" rather than the lighter 1.5" tube. I'm not sure I want to go with the narrower diameter cage tubing, but the other stuff I could probably address with a bit of time and money.

You guys are making me feel a lot better though. I was thinking I missed something really big while I was piecing the car together. If the differences are just in the details, I can deal with that.

My car is at my friend's shop in PA, but I'll take pictures the next time I'm out there.


Ron Earp said:
There is/was a well built ITS Prelude like yours on another race forum that is at weigh if I recall. Extremely well built car. It also makes in excess of 177hp at the wheel too, and is quite competitive in ITS. Based on that info I doubt it'll be moved it ITA.
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Ron, I did a bit of looking and I think I found it (or a similar car). In fact, I think I found it for sale in the classifieds section here. I would love to get a close look at that car to see just what he did differently.
 
Greg Amy said:
If the vast majority of the cars in a class cannot reasonably make their minimum without without extraordinary measures, then the class weight formula is bustificated.
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That isn't the case for S. All the types of cars we regularly race with in S can make weight and I'm pretty sure the Prelude can too.
 
Ron Earp said:
That isn't the case for S. All the types of cars we regularly race with in S can make weight and I'm pretty sure the Prelude can too.
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Roger, Roger. I mis-interpreted "Roger, 150lbs overweight in S isn't too bad." as it was status quo that cars are only within 150# of their target weight.

GA
 
Greg Amy said:
Roger, Roger. I mis-interpreted "Roger, 150lbs overweight in S isn't too bad." as it was status quo that cars are only within 150# of their target weight.

GA
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99% of S is fine. Now, coming from the Mustang viewpoint, yeah, 150 lbs overweight isn't just "not bad", it'd be awesome. But the Mustang is an odd duck. Large displacement pushrod motors with low specific output from the factory generally fail when stuck into the process, i.e. TR8, Mustang, and there are probably one or two others.

Maybe a Monza in ITA, although nobody has attempted one of those I suspect the hp numbers will be spectacular. Fiero might also be one in A that would do well now with the open ECU and a full on prep, but it'd take come cubic money and thus far I've never seen a 99% Fiero effort.

While not 3.8L, the 2.3L SOHC Mustang engine in B is probably larger than average for ITB, I know the full on ITB Mustangs can make some class-leading hp but not too many guys go that route.

Roger, step back and take a fresh look. You'll find areas to drop weight. I still see areas now to lose weight and the car was built with weight savings in mind. You've already hit on some biggies - exhaust, seat, tubing, etc. but the small ones DO add up. We're chasing one, two, three, and four lbs at a time but we're losing weight all along.
 
Also take a look at your wheels. I'm amazed how many people run heavy wheels. it's not just the weight but the rotating mass...........
 
A stainless exhaust is going to be heavy.

Light-weight battery?

Did you remove all undercoating?

Eliminate needless wiring?

Heavy mirrors?

Wheels?

Bottom line: You probably won't get there on account of the cage material, but if you pay attention to details (and further diet shrink yourself) you can get close.
 
Sure. Find the lightest weight battery in the Group designated for the car or of "similar" size or whatever the ITCS states.

Weigh the options. They do differ and it can be a few pounds.
 
Just to be clear, battery "Group" has nothing to do with it. The rule states the battery may be replaced with one "...of similar amp-hour capacity and weight". Doesn't say a damned thing about the size of the replacement piece.
 
...at which point the amount of weight one might save hinges on a definition of the word "similar." If we succeed in actually saving a "significant" amount of weight, swapping batteries is de facto illegal.

K
 
Knestis said:
...at which point the amount of weight one might save hinges on a definition of the word "similar." If we succeed in actually saving a "significant" amount of weight, swapping batteries is de facto illegal.

K
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And then that illegality hinges on the definition of the word "significant". Where does significant start? 5%? 9%? 15%? 25%? 50%?

I'd weigh a sample population of batteries of similar amp/hr capacity. In my sample I would include any battery that met the amp/hr value. I'd then construct a 95% CI around my mean for my sample size. I'd pick the lightest battery that I could not statistically show was different from the mean of my sample.

Having played this game it isn't worth but a few pounds, but it is weight and it adds up.
 
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