How the heck... (weight reduction)

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

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Originally Posted by Knestis

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.

Are you at the minimum roll-cage tubing size?

Here are a couple of threads on the topic:

https://improvedtouring.com...ight+reduction

https://improvedtouring.com...ight+reduction

You've got to use the rules to the max. Post pictures and I bet we can find ways to drop you some weight.

If only you could remove that dang 150lb washer bottle... ;)

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Originally Posted by Ron Earp

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.

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Originally Posted by Ron Earp

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.

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Originally Posted by Greg Amy

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.

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Originally Posted by Ron Earp

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

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Originally Posted by Greg Amy

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...........

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Originally Posted by JLawton

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 and unsprung mass...........

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Fixed.

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.

battery?

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

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Originally Posted by Knestis

...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.

Haven't gotten a chance to get to the car yet, but according to the bathroom scale I'm 3 lbs closer to min weight. If only it were possible to take 145 lbs out of the driver...

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Originally Posted by boxedfox

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.

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Roger,
He wouldn't be able to answer much for you, since I built it. When it left me in January of 2011, it weighed about 2400lbs, with ~15lbs of fuel in it and no driver. When the 4th gen Prelude Si got its weight dropped back in about 2007 or so, we put our car on a serious diet.

- Entire sunroof assembly was removed and replaced with a .060" thick piece of sheet metal.
- The passenger side door was completely gutted (re-did the passenger side door bars to go inside the door, to be legal per the rules). Drivers side already was gutted.
- Completely removed the side mirrors and replaced with small convex mirror attached to the roll-cage A-pillar bars
- Replaced the entire exhaust system with a 2ft Thrush, ~4ft of "damn near aluminum can thickness" pipe, and a turndown all before the gas tank (but still behind the driver, per rules).
- Pulled out the entire dashboard and removed everything underneath or attached to it that didn't absolutely have to be there per the rules.
- Removed any and all wiring that didn't absolutely have to be there.
- Removed the entire ABS system (wiring, pumps, lines, everything) and ran completely custom lines from the master cylinder to the four corners. Prior it had only been disabled, per the minimum rule on ABS.
- Removed any last bit of trim, seal, bracket, weather stripping, sound deadening, etc. that was anywhere on the car.
- The Kosei K1's helped.

I'm sure I'm still forgetting some other things we did. I was actually amazed at how much we were able to cut from that car, once I really started looking at it with a fine tooth comb. The best part is, most of that stuff cost next to nothing but time (if one did it themselves). The car still had an 8-point, fully-welded, safe rollcage too.

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Originally Posted by R2 Racing

Roger,
He wouldn't be able to answer much for you, since I built it. When it left me in January of 2011, it weighed about 2400lbs, with ~15lbs of fuel in it and no driver. When the 4th gen Prelude Si got its weight dropped back in about 2007 or so, we put our car on a serious diet.

- Entire sunroof assembly was removed and replaced with a .060" thick piece of sheet metal.
- The passenger side door was completely gutted (re-did the passenger side door bars to go inside the door, to be legal per the rules). Drivers side already was gutted.
- Completely removed the side mirrors and replaced with small convex mirror attached to the roll-cage A-pillar bars
- Replaced the entire exhaust system with a 2ft Thrush, ~4ft of "damn near aluminum can thickness" pipe, and a turndown all before the gas tank (but still behind the driver, per rules).
- Pulled out the entire dashboard and removed everything underneath or attached to it that didn't absolutely have to be there per the rules.
- Removed any and all wiring that didn't absolutely have to be there.
- Removed the entire ABS system (wiring, pumps, lines, everything) and ran completely custom lines from the master cylinder to the four corners. Prior it had only been disabled, per the minimum rule on ABS.
- Removed any last bit of trim, seal, bracket, weather stripping, sound deadening, etc. that was anywhere on the car.
- The Kosei K1's helped.

I'm sure I'm still forgetting some other things we did. I was actually amazed at how much we were able to cut from that car, once I really started looking at it with a fine tooth comb. The best part is, most of that stuff cost next to nothing but time (if one did it themselves). The car still had an 8-point, fully-welded, safe rollcage too.

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Wow. Thank you. That's actually extremely helpful.

I already have the aluminum sunroof plug, NASCAR bars both sides, and entire ABS system gone except the ABS Module (to be removed soon). I think it reinforces that I need to go through the entire car this weekend with the GCR in hand and get rid of everything that I'm allowed to. And to continue the whole diet and exercise thing.

This is going to be fun.

I believe your sunroof replacement needs to be the same material as surrounding roof....

have you dry-ice-then-smack-with-hammer'd the sound deadening "melt sheets"? You'd be surprised how much it can all weigh. What wheels ?

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Originally Posted by R2 Racing

- Entire sunroof assembly was removed and replaced with a .060" thick piece of sheet metal.

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Originally Posted by adamjabaay

I believe your sunroof replacement needs to be the same material as surrounding roof....

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Yup, you are correct. Per the rules, if you remove your sunroof panel, it has to be replaced with something of the same material. That's why I specifically said "replaced with a .060" thick piece of sheet metal".

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Originally Posted by adamjabaay

I believe your sunroof replacement needs to be the same material as surrounding roof....

have you dry-ice-then-smack-with-hammer'd the sound deadening "melt sheets"? You'd be surprised how much it can all weigh. What wheels ?

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Well, I'm back from a weekend of working on the car. I forgot to take pictures, but I found a chunk of weight in random spots:

• Removed random wiring left over from the SRS, ABS, and audio system that went from nowhere to nowhere
• Removed windshield washer bottle
• Replaced the alum sunroof plate with a steel one
• Removed the passenger side seatbelt reel (I completely forgot about that)
• Removed some leftover soundproofing carpet on the firewall
• Power side mirrors are apparently 5 lbs each. Replacing them with manual replacements would make a surprisingly big difference
• Apparently, I have what appears to be the heaviest battery I could possibly get for my car. Switching to a NAPA or Walmart equivalent with the same amp rating and group size would be a 10 lb diff, an Optima Red Top is a 15 lb diff

All of the soundproofing is out of the car, but the undercoating is still there. Next time I go up, we take out the ABS module and take that crap off the underside of the car. My race wheels are Motegi Racing SP10s, 15x7 and 14.5 lbs each.

I also noticed that my wedge racing seat brackets are tremendously heavy. Are we allowed to mount seats to the floor or weld/cut into the stock seat mounting humps? I've got a good 20 lbs there that could go away real easily.

I think you can make simple mods for seat mounting, IIRC. Read the good book to be sure.
Not sure how comprehensive your "NASCAR" bars are. They only NEED to be any kind of bar that protrudes into the door cavity to qualify for gutting the door and the door interior panel. Don't go overboard here. I've seen insane setups with a gazilion bars and gussets get t-boned....and the driver still got injured because the whole setup was attached to the roll hoop which was attached only at the floor location. Those door bars could have been eliminated nearly completely, and a transfer bar added and the result would have been safer AND lighter.
Concentrate on the front. I imagine thats where the weight savings will make the most difference.
Hollow sway bars? The solid ones weigh a ton. Camber plates aluminum? The steel slabs are heavy, high up, and in the front.
sometimes cars have oversized radiators. Remember, it's not just the radiator, it's the coolant that weighs as well.
Some of those intake tubes weigh a ton, and sink heat INTO the incoming air. Aluminum is a GREAT heat sink...
If you are running an airdam and splitter, look there as well.
And tires. Look at weights of tires. Hoosiers are known for being light. As mentioned above, thats a triple benefit...less unsprung weight less static weight and less rotating mass.
There's even possible weight to be saved in the dampers....
Divers seats can vary greatly.
Headlights: plastic lenses instead of glass.

Just to reiterate: Wheels. It is not an inexpensive change, but Enkei RPF1 wheels at 9.5 pounds each will save 5 pounds per corner. That's 20 pounds total, 13% of your 145 pounds needed and it is all unsprung.

Again not cheap but I got 4 brand new delivered for $700. Used ones can be found but you have to be quick!

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Originally Posted by Greg Amy

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The basic tenet of setting weights in ITx is a formula based on stock horsepower,....
GA

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C'mon Greg, we all know that a formulaic approach to setting weights in IT will never work. ;)

Kirk,

With all due respect, if that is the case, why did the New Beetle end up in ITC?