Weight savings cost/benefit benchmarks

tom @ eas wrote

badfish covered it pretty well here: http://www.m3post.com/forums/showthread.php?p=2756528&highlight=weight#post2756528

I'll have to dig up our notes as well during the swap.

Thanks for the link. I missed that entirely. Well, it looks like KWs result in a slight increase in weight given the OEM housing is aluminum. That will be hard to beat by a significant margin.

Thanks for the info on the airbags in the seats.
Looks like the KW coilovers are heavier than OEM too based on that link.

from another thread to keep things on topic

lucid wrote

I wish they stopped focusing on trunk lids and came up with low cost CF external door panels as those things weigh a lot; the Ericsonn stuff is way to expensive. Did you ever go for the Braille battery by the way? I read that people have been using them with their Z06s without problems. I am thinking about going for it...

Door panels may have safety requirements... though I am not really sure. Also the condition of doors when you sell your car is extremly important. Many appraisers look very closely at whether the bolts have been removed, so I wouldn't mess with it.

The battery... i did want to get it, but I am just concerned about the fuse box. Look at doba's picture and you can see that the fuse box barely fits... I really don't want to short something...

Just a short while ago, i was determined to loose the weight on my car, but now i think it's just not worth the money... you've got to spend at least $10-$20k to loose perhaps 200/250 lb with lighter wheels, body panels, exhaust, brakes, etc... and again, when you sell your car, aftermarket parts are worthless to dealers, so you'd have to spend all the money/time taking them off and part-out...

hence, i thought i'd save some $$ for a used 07 GT3 that has a power-weight ratio of ~300hp/ton from the factory (vs. ~250hp/ton for M3) cheers.

rldzhao wrote

Door panels may have safety requirements... though I am not really sure. Also the condition of doors when you sell your car is extremly important. Many appraisers look very closely at whether the bolts have been removed, so I wouldn't mess with it.

I wouldn't worry about the safety issue too much as I doubt the external panels are significant structural components. There must be one or more cross bars in the door itself. I didn't know about appraisers examining doors so closely though. Good to know.

rldzhao wrote

The battery... i did want to get it, but I am just concerned about the fuse box. Look at doba's picture and you can see that the fuse box barely fits... I really don't want to short something...

Not sure what you mean by barely fits. Do you mean that it is loose, or that it doesn't seem to attach properly?

rldzhao wrote

Just a short while ago, i was determined to loose the weight on my car, but now i think it's just not worth the money... you've got to spend at least $10-$20k to loose perhaps 200/250 lb with lighter wheels, body panels, exhaust, brakes, etc... and again, when you sell your car, aftermarket parts are worthless to dealers, so you'd have to spend all the money/time taking them off and part-out...

Fair point. But 100lb is reasonable. I am considering installing pole positions just for the summers and if I continue to take out the rear seats at the track as well, that is 250lb for about $6k including the titanium exhaust, TE37s, and braille battery. That is not acceptable to many people, but I was fine with driving without rear seats for a couple of months last year and I put them back in when I needed them (takes 15 minutes).

rldzhao wrote

hence, i thought i'd save some $$ for a used 07 GT3 that has a power-weight ratio of ~300hp/ton from the factory (vs. ~250hp/ton for M3) cheers.

I've come to the exact same conclusion as to what my next car will be. My plan is to sell the M in 3 years and get a 07 GT3.

The weight to cost here is more than most drugs... I dropped 35lbs out of my car with no cost at all... I lost 35lbs off of my fat ass

lucid wrote

Not sure what you mean by barely fits. Do you mean that it is loose, or that it doesn't seem to attach properly?

Fair point. But 100lb is reasonable. I am considering installing pole positions just for the summers and if I continue to take out the rear seats at the track as well, that is 250lb for about $6k including the titanium exhaust, TE37s, and braille battery. That is not acceptable to many people, but I was fine with driving without rear seats for a couple of months last year and I put them back in when I needed them (takes 15 minutes).

1. the fuse box is not properly attached to the battery edges as the OE does. It has to be slightly twisted to fit. Also it appears that the - terminal isn't clamped down all the way.



2. Make sure you get some kind of modification for the seat sensors.

rldzhao wrote

1. the fuse box is not properly attached to the battery edges as the OE does. It has to be slightly twisted to fit. Also it appears that the - terminal isn't clamped down all the way.

2. Make sure you get some kind of modification for the seat sensors.

Yes, it does seems slightly twisted, but I can't see enough to say that it does or does not clamp on properly. Doba_s can comment maybe?

There will be a small mod available to address the sensor issue, but I read somewhere that the sensor might not be a binary switch, and might be feeding back load info, which might be factored into the deployment rate of the airbag. Honestly, that seems over the top as I don't think that it is possible to control the deployment rate of the airbag to begin with (the nozzle diameter would have to be adjustable or something like that and I just can't see that being the case). Anyway, I'd like to find out for sure though before buying anything.

lucid wrote

Yes, it does seems slightly twisted, but I can't see enough to say that it does or does not clamp on properly. Doba_s can comment maybe?

There will be a small mod available to address the sensor issue, but I read somewhere that the sensor might not be a binary switch, and might be feeding back load info, which might be factored into the deployment rate of the airbag. Honestly, that seems over the top as I don't think that it is possible to control the deployment rate of the airbag to begin with (the nozzle diameter would have to be adjustable or something like that and I just can't see that being the case). Anyway, I'd like to find out for sure though before buying anything.

The black pieces on the fuse box are the clamps that holds on to the edge of the OE battery. The Braille battery is narrower than OE, so the clamps won't work.

Also I think Doba already got rid of the Braille battery? See his recent DIY thread: http://www.m3post.com/forums/showthread.php?t=242963

IMO the easiest/safest way to reduce the weight of the battery is to get a lesser capacity OE battery that have the same width/height (but may be slightly shorter). A 70 amp hr OE battery is about 15lb lighter than most people's stock 90 amp hr battery.

rldzhao wrote

Also I think Doba already got rid of the Braille battery? See his recent DIY thread: http://www.m3post.com/forums/showthread.php?t=242963

Yes, I know he was thinking about selling it. I had a few PM exchanges with him, but I don't think it had anything to do with the battery being problematic. I can't recall the exact reason though. I'll PM and ask him. I'll also look at the fuse box more carefuly today.

i still have my battery ... i didn't sell it to anybody ... the reason i was thinking to sell is to go with the 15lb one ... i had it for 3 days with 0 problems ... my car is making some weird noise and i am constantly taking it to the dealer ... to avoid any issues with my SA i put my stock one back temporary ...

The fuse box is a bit bigger and only one side can be properly attached. Since it is connected to the main positive terminal it seats pretty firm on the battery and the upper rubber mount doesn't let it to move at all ... Terminals fit OK , no issues there

doba_s wrote

i still have my battery ... i didn't sell it to anybody ... the reason i was thinking to sell is to go with the 15lb one ... i had it for 3 days with 0 problems ... my car is making some weird noise and i am constantly taking it to the dealer ... to avoid any issues with my SA i put my stock one back temporary ...

The fuse box is a bit bigger and only one side can be properly attached. Since it is connected to the main positive terminal it seats pretty firm on the battery and the upper rubber mount doesn't let it to move at all ... Terminals fit OK , no issues there

Thanks for the clarification.

lucid wrote

Stoptech F caliper assemb: 13.11 lbs with pads & bracket (Badfish weighed this)
Stoptech F disc assemb: 20.01 lbs (Badfish weighed this)
Stoptech R caliper assemb: 19.33 lbs (Badfish weighed this)
Stoptech R disc assemb: 11.15 lbs with pads & bracket (Badfish weighed this)
Cost: $6050
Weight savings: 4.6 lbs
cost/benefit: $1315/lbs

Lucid, as always thanks for this thread.

It was pointed out to me that one of the numbers is off on the original post. The overall weight savings of 4.6 pounds is correct still, however the 20.01 number for the front rotor should be 22.01. You can reference this thread.

Thanks!

I think you should Sticky this thread for quick reference. Good info in here.

jm1234 wrote

So, your trying to measure every lb in a luxury sport racer? Pull the AC, pull the rear seat, pull the dash (replace with an aluminum shell to hold the tach and spedo). But, is that really the car you paid $70K for? If you do that, why have a muffler? Pull the cats too, carpet. Strip the trunk and headliner...

If you're willing to pull the nice comfy seats and replace them with lightweight ones where are you drawing the line between removing comfort and reducing weight? The things you are doing might add up to 100 lbs. Will that really make a handling difference and wouldn't it be cheaper from an acceleration and cost/benefit perspective to add horsepower?

lol 100lbs, are you joking?

Stripping back seats- 50 pounds
Removing FULL exhaust after headers- EASILY 75 pounds.
Swap front seats for recaros- easy 100 pounds
Dash, A/C, Navigation/stereo- Like 150 pounds

Just by removing shit from the car that is almost 400 pounds. That makes a SIGNIFICANT difference in braking, handling, toss-ability, and acceleration.

I did not even mention putting lighter wheels and brakes(less rotational mass and unsprung weight, so though you decrese the weight by a little, it ends up accounting for alot...if you know what i mean)

badfish wrote

Lucid, as always thanks for this thread.

It was pointed out to me that one of the numbers is off on the original post. The overall weight savings of 4.6 pounds is correct still, however the 20.01 number for the front rotor should be 22.01. You can reference this thread.

Thanks!

Done. Thanks for the reminder.

I also added the Peformance Friction kit and the Brembo 365/345 kit numbers. Thanks to JamesC and Sparkyg.

OC kid wrote

I could not get a value for the dust shields, they were too light...similar to an empty soda can...we're talking ounces. Caliper weights do include pads, as you mentioned.



lucid: Thanks for waiting...I've been real busy with work.

My trunk weights did not include the lights/carpeting, trunk release or hardware. They were already transfered to the VRS lid. My measurements are as approximate as the tolerances in the $50 digital bathroom scale. (...sorry swamp.)

VRS double-sided cf bootlid w/o hardware, carpeting, etc.---- 14.9 lbs.
OEM trunklid w/o hardware, carpeting, etc. 26.0 lbs.

Brembo 380 x 34 front rotor 24.8 lbs.
OEM front rotor 26.6 lbs.

Brembo 380 x 28 rear rotor 17.0 lbs.
OEM rear rotor 22.8 lbs.

Brembo 6 pot front caliper 13.0 lbs.
OEM front caliper 15.2 lbs.

Brembo 4 pot rear caliper 9.6 lbs.
OEM rear caliper 12.1 lbs.

OC, not sure if you are still hanging out around the forum. I am not including the numbers you provided because your scale seems to be off. Your stock system numbers are significantly different than Badfish's numbers (front system difference of 4.6 lbs), whereas JamesC's numbers are consistent with Badfish's. Therefore, I must assume something was off with your scale?

J08M3 wrote

I think you should Sticky this thread for quick reference. Good info in here.

I can make it a sticky, but I am not sure about where it should be stickied exactly. I'll think about it...

lucid wrote

OC, not sure if you are still hanging out around the forum. I am not including the numbers you provided because your scale seems to be off. Your stock system numbers are significantly different than Badfish's numbers (front system difference of 4.6 lbs), whereas JamesC's numbers are consistent with Badfish's. Therefore, I must assume something was off with your scale?

Thanks for the update lucid!

Good to correct and clarify the thread. I think I may have mentioned last year that the bathroom scale used was potentially suspect. (even posted pics of the crappy thing)

My measurements are as approximate as the tolerances in the $50 digital bathroom scale. (...sorry swamp.)

And yes, due to workload and gf, I don't hang out here as much as I'd like, but it is nice to check back in and see that you still have a handle on things.

Happy to see the progress on the lighweight RAC's too-I'm looking forward to seeing the cost/benefit numbers once production begins...

Take care and keep up the good work.

lucid wrote

Done. Thanks for the reminder.

Hey Lucid, one other error I noticed. The caliper weight needs to be swapped with the rotor weight for the rear for the Stoptech brakes.

Stoptech R caliper assemb: 19.33 lbs (Badfish weighed this)
Stoptech R disc assemb: 11.15 lbs with pads & bracket (Badfish weighed this)

Should read:

Stoptech R caliper assemb: 11.15 lbs (Badfish weighed this)
Stoptech R disc assemb: 19.33 lbs with pads & bracket (Badfish weighed this)

Sorry for not catching it the first time around but just want to make sure all the data is correct...

Good to hear from you OC!

This is a long shot, but if you just happen to have that 380mm brembo kit sitting around collecting dust--the way expensive BBKs do--can you weigh the parts again?

Right!

badfish wrote

Hey Lucid, one other error I noticed. The caliper weight needs to be swapped with the rotor weight for the rear for the Stoptech brakes.

Fixed. You can see why I am not an accountant; I would rapidly put any company out of business with my accounting skills...

lucid wrote

I can make it a sticky, but I am not sure about where it should be stickied exactly. I'll think about it...

Ha, good point. Why not just sticky it here in the General forum?