Weight savings cost/benefit benchmarks

[lucid]

I am keen on reducing the weight of my car, and am interested in establishing some cost/benefit benchmarks in that regard. The metrics are clear: lbs saved for benefit, and cost of part for cost, which results in cost/lb. Let's get this started. We can add numbers for different aftermarket components as they become available. The cost figures posted below do not include any installation or paint charges. Also, the focus of this thread is weight reduction only, and rotational inertia reduction or power gain benefits are not documented.

EXHAUST
Stock system: 25 kg (55.06 lbs) (supplied by Gruppe-M and Vorsteiner)
Gruppe-M Titanium catback system: 9.1 kg (20.04 lbs)
Cost: ~$4900
Weight savings: 35.02 lbs
cost/benefit: $140/lb
http://www.gruppem.co.jp/en/home.html

Stock system: 25 kg (55.06 lbs) (supplied by Gruppe-M and Vorsteiner)
Vorsteiner Titanium catback system: 17.33 lbs
Cost: ~$3499
Weight savings: 37.73 lbs
cost/benefit: $92/lb
http://www.jlevistreetwerks.com/p172...duct_info.html
http://www.m3post.com/forums/showthread.php?t=137805

Stock system: 25 kg (55.06 lbs) (supplied by Gruppe-M and Vorsteiner)
Dixis Titanium system including H pipes: 17.18 lbs (supplied by member ArsenalFC)
Cost: ~$5400 (supplied by member ArsenalFC)
Weight savings: 37.73 lbs
cost/benefit: $143/lb

X&CONNECTING PIPES
Stock system: 41 lbs (supplied by encoreinnovation)
Active Autowerke system (just pipes; no cats--don't have weight info on optional race cats): ~25 lbs
Cost: $2000
Weight savings: ~15 lbs
cost/benefit: $133/lb
http://www.m3post.com/forums/showthread.php?t=189185

Stock system: 41 lbs (supplied by encoreinnovation)
Encoreinnovation system (with race cats): 19 lbs
Cost: $4299
Weight savings: 22 lbs
cost/benefit: $195/lb
http://www.encoreinnovation.com/prod...fication/id/14

WHEELS
Stock 19x8.5/19x9.5 Wheels (F/R): 23.4/25.4 lb (GregW's numbers 47/51.5 minus 19" PS2 weights; 23.6/26.1)
19" Volk Racing TE37 Time Attack (F/R): ~21.0/22.0 lb (as stated by Tirerack)
Cost: $3400
Weight savings: 11.6 lbs (over stock 19" wheels)
cost/benefit: $293/lb
http://www.tirerack.com/wheels/Wheel...All&sort=Brand

19x9/19x10 Advan RS (F/R): ~20.4/21.8 lb (Wheels STO)
Cost: ~$2800
Weight savings: 13.2 lbs (over stock 19" wheels)
cost/benefit: $212/lb
http://www.m3post.com/forums/showthread.php?t=265756

18" TRMotorsport MT1 Wheels (F/R): 18.5/19.0 lb (as stated by Tirerack)
Cost: $1236
Weight savings: 22.6 lbs (over stock 19" wheels)
cost/benefit: $55/lb
http://www.tirerack.com/wheels/Wheel...All&sort=Brand

TIRES
Stock 19" Tires; PS2s(F/R): 24/25 lb (Tirerack)
19" PSCs Tires (F/R): 21/24 lb (Tirerack)
Extra Cost: $98 (this is how much more you'd pay over PS2s during tire change; they will wear out faster though)
Weight savings: 8 lbs (over PS2s)
cost/benefit: $12/lb
http://www.tirerack.com/tires/Spec.j...5YR9SPORTCUPXL

EXTERNAL DOOR PANELS
Stock (steel): 18.54 kg (40.84 lbs) /door
http://bmwfans.info/original/E92/Cou...1/ill-41_1700/
Ericsson CF door panels: 3.35 kg (7.38 lbs) / door
Cost: $11466
Weight savings: 66.92 lbs
cost/benefit: $171/lb
http://www.bulletproofautomotive.com...il.php?ID=6547

TRUNK LID
Stock (Steel): 10.625 kg (23.40 lbs) (OC weighed his at 26.0 lbs)
http://bmwfans.info/original/E92/Cou...1/ill-41_1638/
CF Vorsteiner lid: 14.9 lbs (OC Kid weighed it)
Cost: $1362
Weight savings: 11.1 lbs (according to OC's numbers)
cost/benefit: ~$123/lb
http://www.vorsteiner.com/bmw/e92coupe-spoiler.html#
http://www.redline-motorworks.com/product/9306%20BMV

Stock (Steel): 10.625 kg (23.40 lbs)
CF Ericsson lid: 7.04 lbs
Cost: $6400
Weight savings: 16.36 lbs
cost/benefit: $391/lb
http://www.bulletproofautomotive.com...il.php?ID=6423

HOOD
Stock (Al): 10.20 kg (22.47 lbs)
http://bmwfans.info/original/E92/Cou...1/ill-41_1611/
Ericsson CF hood: 12.54 lbs
Cost: $6400
Weight savings: 9.93 lbs
cost/benefit: $645/lb
http://www.bulletproofautomotive.com...il.php?ID=6422

AIRBOX
Stock: 4.95 kg (10.90 lbs)
http://bmwfans.info/original/E92/Cou...1/ill-11_4129/
Unknown German Manufacturer CF Airbox: unknown
Cost: $2700
Weight savings: ~8 lbs (see link below for approximate savings figure, which is realistic)
http://www.ca-automotive.co.uk/produ...faWQ9OA==.html
cost/benefit: ~$340/lb
http://store.bimmerworld.com/shared/...t=products.asp

BRAKES
Stock assembly (F/R): 37.2/30.7 lbs
F caliper assemb: 14.5 lbs with pads and rubber line (Badfish weighed this)
F rotor assemb: 22.7 lbs (Badfish weighed this)
R caliper assemb: 11.0 lbs with pads and rubber line (Badfish weighed this)
R rotor assemb: 19.7 lbs (Badfish weighed this)

Brembo 365x34 (F) 345x28 (R) Kit
Brembo F caliper assemb: 14.0 lb (weighed by sparkyg)
Brembo F rotor assemb: 24.5 lb (weighed by sparkyg)
Brembo R caliper assemb: 9.5 lb (weighed by sparkyg)
Brembo R rotor assemb: 15.0 lb (weighed by sparkyg)
Cost: ~$6100
Weight savings: 9.8 lbs
cost/benefit: $622/lbs
http://www.m3post.com/forums/showthr...15#post5194815

Stoptech 380x35 (F) 355x32 (R) Kit
Stoptech F caliper assemb: 13.11 lbs with pads & bracket (Badfish weighed this)
Stoptech F rotor assemb: 21.01 lbs (Badfish weighed this)
Stoptech R caliper assemb: 11.15 lbs with pads & bracket (Badfish weighed this)
Stoptech R rotor assemb: 19.33 lbs (Badfish weighed this)
Cost: $5890
Weight savings: 4.6 lbs
cost/benefit: $1280/lbs
http://www.**********s.com/product.a...BK_E92_M3_RS10
http://www.m3post.com/forums/showthread.php?t=150944

Performance Friction 371x32 (F) 372x30 (R) Kit (prototype, production will use slightly ligther brackets)
Performance Friction F caliper and rotor assemb: 28 lbs with pads & bracket (James C weighed this)
Performance Friction R caliper and rotor assemb: 34 lbs (James C weighed this)
Cost: $8000
Weight savings: 12 lbs
cost/benefit: $666/lbs
http://www.m3post.com/forums/showthr...=232463&page=3
http://www.nexternal.com/bimmerworl/Product1060

BATTERY
Stock: 27.250 kg (60.02 lbs) -- 90 Amp/Hr
http://bmwfans.info/original/E92/Cou...1/ill-61_2091/
Braille B3121: 21 lbs -- 31 Amp/Hr
Cost: $180
Weight savings: 39 lbs
cost/benefit: $5/lbs
http://braillebattery.com/index.php/batteries/b3121/
DIY: http://www.m3post.com/forums/showthread.php?t=233195
Warning: There are issues with the reserve capacticy of the Braille B3121 when used in the E9X M3; read the DIY for more info.

Stock: 27.250 kg (60.02 lbs) -- 90 Amp/Hr
http://bmwfans.info/original/E92/Cou...1/ill-61_2091/
OEM Mini battery: 34.4 lbs -- 55 Amp/Hr
Cost: $128
Weight savings: 25.6 lbs
cost/benefit: $5/lbs
http://www.trademotion.com/partlocat...&siteid=214672 Part#: 61217571896
DIY: http://www.m3post.com/forums/showthr...=233195&page=7
Note: This is the OEM battery for the MINI and the E46 CSL.

FRONT BUMPER
Stock: 9.91 lbs
http://bmwfans.info/original/E92/Cou...1/ill-51_6244/
Ericsson CF front bumper: 5.28 lbs
Cost: $9800
Weight savings: 4.62 lbs
cost/benefit: $2121/lbs
http://www.bulletproofautomotive.com...il.php?ID=6419

INTERIOR DOOR PANEL
Stock: 3.1 kg
Ericsson CF interior panel: 1.25 kg
Cost: $6600
Weight savings: 4.07 lbs
cost/benefit: $1621/lb
http://www.bulletproofautomotive.com...il.php?ID=6425
http://www.e90post.com/forums/showthread.php?t=168900

FRONT SEATS
Stock: 62.6 lbs each (weighted by Sam@AutoTalent)
BMW performance bucket seats with side airbag: 25.3 kg each (55.7 lbs) (weighed by BMW-M-Mexico)
CF aftermarket bucket seats: ?
Cost: $5000
Weight savings: 13.8 lbs
cost/benefit: $362.3/lb
http://www.turnermotorsport.com/html...FORMANCE-SEATS

REAR SEATS (excluding rear headrests and storage cartridge in fold down seatback)
Stock: ~43 lbs (I weighed these)
Remove them
Cost: $0
Weight savings: 43 lbs
cost/benefit: $0/lb
http://www.m3post.com/forums/showthread.php?t=177061

REAR HEADRESTS
Stock: 783 grams each (1.73 lbs) (I weighed these)
Remove them
Cost: $0
Weight savings: 3.45 lbs
cost/benefit: $0/lb

STORAGE CARTRIDGE (in fold-down rear seatback)
Stock: 738 grams (1.62 lbs) (I weighed this)
Remove it
Cost: $0
Weight savings: 1.62 lbs
cost/benefit: $0/lb

MOBILITY KIT & HOLDER
Stock: 1096 + 275 = 1371 grams (3.02 lbs) (I weighed these)
Remove it
Cost: $0
Weight savings: 3.02 lbs
cost/benefit: $0/lb

PLASTIC BATTERY COVER/TOOL HOLDER
Stock: 1276 grams (2.81 lbs) (I weighed these)
Remove it
Cost: $0
Weight savings: 2.81 lbs
cost/benefit: $0/lb

TRUNK FLOOR COVER/MAT
Stock: 3750 grams (8.26 lbs) (I weighed this)
Remove it
Cost: $0
Weight savings: 8.26 lbs
cost/benefit: $0/lb

TRUNK LID LINING
Stock: 939 grams (2.07 lbs) (I weighed this)
Remove it
Cost: $0
Weight savings: 2.07 lbs
cost/benefit: $0/lb

FRONT LICENCE PLATE & HOLDER
Stock: 378 grams (0.83 lbs) (I weighed these)
Remove it
Cost: $0
Weight savings: 0.83 lbs
cost/benefit: $0/lb

WASHER FLUID
Stock: 3.79 kg (8.35 lbs)
Drain it
Cost: $0
Weight savings: 8.35 lbs
cost/benefit: $0/lb

BODY FAT
Stock: ?
Sculpted body: ?
Cost: ?
Weight savings: ?
cost/benefit: ?

What else?

[enigma]

FYI: I have a full set of 18x9.5" rims, front and rear sitting in boxes awaiting the new car. They are ~20lbs each (I need a better scale). Thats about as light as you can get for a quality strong wheel for this car.

[T Bone]

Wheels are best if you are looking to improve performance since it is unsprung weight.

But the easiest and best weight reduction will be seats. You will be able to save 100 pounds by going to carbon seats.... The question is can you live with them?

[Davinhci]

all this stuff is beyond me, but love to learn what you guys post up here.

[lucid]

Originally Posted by enigma

FYI: I have a full set of 18x9.5" rims, front and rear sitting in boxes awaiting the new car. They are ~20lbs each (I need a better scale). Thats about as light as you can get for a quality strong wheel for this car.

Yep. That's pretty much what I figured on wheels. What kind of wheels did you get for the track?

[lucid]

Originally Posted by T Bone

But the easiest and best weight reduction will be seats. You will be able to save 100 pounds by going to carbon seats.... The question is can you live with them?

This will somewhat depend on how difficult it is to remove the front seats. If the swap is relatively quick, I might consider it--given I can always put the stock seats back for whatever reason...

[T Bone]

Originally Posted by lucid

This will somewhat depend on how difficult it is to remove the front seats. If the swap is relatively quick, I might consider it--given I can always put the stock seats back for whatever reason...

It will be a couple of hours. Pick whatever seat you want then you need to find rails that fit the E92..... The question is the impact on the 2 stage airbag, since there is a sensor in the stock seats.

You will notice a big difference here....also run on 1/2 tank of fuel.

[jm1234]

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?

[lucid]

Originally Posted by jm1234

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...

Where did I mention any of that in my OP? I omitted those intentionally. I have no intention of tearing up the car like that. I am talking within reason considering this is a luxury car, which is obvious in what I posted.

Originally Posted by jm1234

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?

Read my previous post. I would swap the seats only if I thought the swap can be done in reasonable time so that I can put the stock seats back on for whatever reason. Apart from that, if you think about the items I posted, you can see where I'm drawing the line.

Regardless, it would interesting to know how much the rear seats weigh for instance--not that I would remove them.

I would rather spend the money to lose 150lbs than gain 40hp on this car, but that ultimately depends on the cost of each. Have you driven it?

[enigma]

Originally Posted by jm1234

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?

I once went down this path. I ended up with a car that was neither fun on the track or street. So I put the E46 back to stock and bought the elise for the track.

Now I choose comfort or a 1500lbs weight reduction based on which key I grab in the morning.


Now I am doing 2 things for the BMW. I have the wheels which I bought to help fix the understeer by adding more front tire and give me wheels on which ot mount race tires. I will also be doing a sway bar set for the car, the idea there is to control the lean in corners with a minimal impact on comfort.

Keep the car cival on the street but a big increase in weekend fun when I run with the BMW club at their autocrosses.

[OC ///M]

Originally Posted by lucid

I am keen on reducing the weight on my car, and am interested in establishing some cost/benefit benchmarks in that regard. The metrics are clear: lbs saved for benefit, and cost of part for cost, which results in cost/lb. Let's get this started. We can add numbers for different aftermarket components as they become available.

What else?

Great topic, I tried making a similar thread, but this is much better. I will definitely be adding to this, and you can expect a whole lot more info by the end of next week.

My initial thoughts are these:

Exhaust
As you pointed out, a significant amount can be saved here very easily. This is must.

Wheels
Based on GregW's calc's, we know that the stocks are pretty light as is. One-piece forged will be the only way to go here, I think.

Front Seats
Stock:super heavy with all of the motors...Big savings to be made here, I think as much as ~100lbs. but as T-bone mentioned can you live w/o your leather & lumbar support?

Boot lid
With the double-sided CF, it's significant. I expect ~10-15 lbs. I will post real results on this after install next week.

Hood
The stock hood is already very light, not much to gain here.

BBK
This is a big one that you missed. The stock brake assembly is very heavy. The benefits are multiplied in that it reduces the unsprung weight as well. I will be posting the results after install of the Brembo kit w/ differences in weight. Brembo just took measurements last week and I should have them in before Bimmerfest. TBD.

[enigma]

Originally Posted by lucid

Yep. That's pretty much what I figured on wheels. What kind of wheels did you get for the track?

fikse, I had them custom made for the car. Fantastic service and quality, but you pay for it. Same ET will work front and rear so I can rotate the tires if I want to.

[lucid]

Originally Posted by OC kid

BBK
This is a big one that you missed. The stock brake assembly is very heavy. The benefits are multiplied in that it reduces the unsprung weight as well. I will be posting the results after install of the Brembo kit w/ differences in weight. Brembo just took measurements last week and I should have them in before Bimmerfest. TBD.

Good point. Added to the list.

[T Bone]

You can't pull this off in Boston but if you get Lithium Ion battery you can save another 40-50 pounds. But they don't work well at all in the cold.

[ruff]

Lucid,

I like. You sound like Michael Rasmussen.

[lucid]

Originally Posted by T Bone

You can't pull this off in Boston but if you get Lithium Ion battery you can save another 40-50 pounds. But they don't work well at all in the cold.

Yeah, those suck in the cold, but added to the list regardless. Do you have pointers to a specific vendor for weight/price info? Does anyone know the weight of the stock battery?

[T Bone]

Originally Posted by lucid

Yeah, those suck in the cold, but added to the list regardless. Do you have pointers to a specific vendor for weight/price info? Does anyone know the weight of the stock battery?

Voltphreaks http://voltphreaks.com/

[OC ///M]

Originally Posted by lucid

Does anyone know the weight of the stock battery?

Didn't Greg pull his while checking for evidence of regeneration?

[lucid]

Originally Posted by ruff

Lucid,

I like. You sound like Michael Rasmussen.

Yeah, the guy's a goat. He weighs 130 lbs. In top form, I weighed 148 lbs, but he is 2 inches shorter. D:

[WCH]

I think the seats are going to be hard to remove. The airbag sensors are located there and the seats are an important part of the design for the safety of the car.

[Epacy]

Originally Posted by lucid

Yeah, those suck in the cold, but added to the list regardless. Do you have pointers to a specific vendor for weight/price info? Does anyone know the weight of the stock battery?

Odyseey.





Good thread Lucid. I will stay tuned.

I am familiar with the effects of over-moding and the impact on the ride. I hope to steer clear of that with this car.

[lucid]

Originally Posted by OC kid

Didn't Greg pull his while checking for evidence of regeneration?

Don't know. GregW?