z4mc's weight

[esqu1re]

I've owned my car for a few months now and even though I enjoy it immensely, sometimes I wonder how much better it would perform if it weighed 200 lbs less. I get "lightweight envy" when I look at cars of the same or similar dimensions and wonder why my car weighs so much. To wit: Both the Corvette and 370z are larger cars and weigh roughly the same as the M Coupe. The corvette has almost twice the displacement! An S2000 is exactly the same dimensions as the M, but weighs ~450 lbs less. I understand it has 2 less cylinders and practically no gadgets, but it doesn't use any more lightweight / exotic components than the M coupe.

I don't expect the M coupe to be 2800 lbs like an s2000, but I would have expected something that small to weigh 3100 at most, not ~3270 lbs, as listed in the literature. Anyway, I looked up the engine weight---it's about 478 lbs; how much more is that than an average 3.0-3.5 liter 6 cylinder engine?

I just don't know where the weight is coming from---the engine?

(updated: did some research--the S54 engine weighs within a few lbs of a LS7 from the corvette...wow)

[Serious]

Iron block 6 cylinder engine vs. all aluminum 4 pot is probably the biggest difference.

The ls6 from the corvette's is all aluminum as well, and due to it's pushrod design it is a very light v8.

The seats are also pretty damn heavy.

[Finnegan]

Iron block, VANOS, etc all add up. But look at the power/liter of the S54 compared to the pushrod V8--interesting comparison. The S54 is a high revving motor as well--and your paying a bit of penalty (if you can call it that) vs. the low revving engine, with simple design, in the 'Vette.

That said, I really think all BMW's need to go on a diet. My E92 weighs about 500 lbs more than the Z4M. Talk about weight envy! And that with the S65 engine which is lighter than the S54. The next gen Z4 weighs more than my E92!

[thekurgan]

The chassis itself is probably heavy, as it's one of the world's stiffest production chassis to date.

[esqu1re]

Originally Posted by Serious

Iron block 6 cylinder engine vs. all aluminum 4 pot is probably the biggest difference.

The ls6 from the corvette's is all aluminum as well, and due to it's pushrod design it is a very light v8.

The seats are also pretty damn heavy.

Yeah, the seats...mine are electric too.

Originally Posted by thekurgan

The chassis itself is probably heavy, as it's one of the world's stiffest production chassis to date.

I didn't know that! I thought the convertible Z4m had quite a lot of body flex---I guess there are some things that even a stiff chassis can't fix.

[doozyj]

Actually I believe he was referring to the Z4M Coupe being one of the stiffest chassis, excluding the Z4M convertible.

[thekurgan]

Originally Posted by doozyj

Actually I believe he was referring to the Z4M Coupe being one of the stiffest chassis, excluding the Z4M convertible.

Yep, he's got a coupe, not that there is alot of weight diff between the coupe and the vert, possibly because of the extra pieces of the vert, make up the diff of the roof plus pillars?

[esqu1re]

Originally Posted by doozyj

Actually I believe he was referring to the Z4M Coupe being one of the stiffest chassis, excluding the Z4M convertible.

I thought they were on the same chassis, just different frame and body panel bits making the M coupe more stiff.

Perhaps the guy is saying that the M coupe, chassis + frame, makes the M coupe one of the stiffest sports car bodies out there. If it's true, I didn't know it.

[r4gs]

the coupe body style with a solid, purpose-built roof is much stiffer (if i'm not mistaken, twice as stiff as the roadster) because it is, in simple terms, two large 'parallel' pieces of metal joined together. this will obviously be a lot stiffer compared with the roadster chassis - one large piece of metal only.

on topic though, i do think bmw's in general are getting heavier.

[thekurgan]

From this thread:

http://forums.nasioc.com/forums/show....php?t=1266524

It is one of the stiffest made

[dekaliber]

I find the doors in BMWs to be incredibly sturdy feeling, but that in no small part is probably due to their heft.

Compared to the E46, the M coupe feels like it's machined out of a solid piece of metal, especially with a front strut brace. It really is a brick shithouse of a sports car. From that list on nasioc it looks like most of the cars that are stiffer are tanks -- Phantom, A8, Phaeton, etc.

[thekurgan]

I agree, the doors sound more solid when closing them, windows up or down. I was surprised to see a large difference from the E46 to the E90, could explain the heft on that transition.

[dekaliber]

Originally Posted by shift@red

I would like to see where the boxster/cayman go as I know they are two of the stiffest cars out there...the boxster S IIRC is more stiff than most coupes are and the cayman S certainly is.

Pretty close to the Z4 M.

Cayman S = 31500 Nm/deg
http://www.goauto.com.au/mellor/mell...25713B000F1184

[Nate2046]

Thats a good question. The one thing I noticed looking up the specs of the cars you mentioned is that the S2000 has almost the exact same overall dimensions as the Z4M but is about 4" shorter in wheelbase. If you consider that the main 'structure' of a car is between the wheels that 4" could account for a lot of weight. The overhangs beyond the wheels at either end are much lighter per inch. Of course the Vette has 10" more wheelbase and weighs less so theres obviously more to it than just that. I would guess that the more 'gadgets' (nav, elaborate stereo, additional airbags) coupled with the more luxury feel (additional sound damping, thicker, heavier, high quality materials) adds up to the difference between the two. Along with the heavier engine the Z4 also has dual exhausts with 4 heavy cats. The Z4M also has 18" wheels and tires vs 17" on the Honda. The rear hatch on the Z4MC also has that big heavy piece of glass. Lots of little things that add up.

Just as a reference for anybody else who wants to chime in these are the stats I got from edmunds.com. These were all from 2007 models except the 370z which was 2009.

Z4MC
3230 lbs 162" long 70" wide 98.3" wheelbase

S2000
2855 lbs 162" long 69" wide 94.5" wheelbase

Corvette
3179 lbs 174" long 72" wide 105" wheelbase

370Z
3278 lbs 167" long 72" wide 100" wheelbase

[ZM4000]

Originally Posted by r4gs

the coupe body style with a solid, purpose-built roof is much stiffer (if i'm not mistaken, twice as stiff as the roadster) because it is, in simple terms, two large 'parallel' pieces of metal joined together. this will obviously be a lot stiffer compared with the roadster chassis - one large piece of metal only.

on topic though, i do think bmw's in general are getting heavier.

Sorry to say but you're wrong the coupe isnt twice stiffer as the roadster. talked to my bmw dealer about that point when i was looking for a z4m. He told me that BMW engineers (and all big carbrands) put extra calculated weights in the car(roadster) to loose that wooliness because of not having a roof so that the car gets a lot stiffer.

[k2pilot]

Originally Posted by ZM4000

Sorry to say but you're wrong the coupe isnt twice stiffer as the roadster. talked to my bmw dealer about that point when i was looking for a z4m. He told me that BMW engineers (and all big carbrands) put extra calculated weights in the car(roadster) to loose that wooliness because of not having a roof so that the car gets a lot stiffer.

do you believe everything your dealer says? 90% of those people are fools.

wait you're referring to a salesman... 95% of them are.

roadster/convertible models are indeed reinforced and made stiffer than their typical coupe counterparts, but it's seldom ever enough to actually compensate for the lack of roof. so what happened in the case of the z4mc is that you got the already very stiff for a 'vert z4m, with a torsional rigidity of 14000nm/°, and then added a roof bringing its torsional rigidty to a whopping 32000nm/°. these are simply facts, the z4mc is over twice as stiff as the roadster.

that said the z4mr is atleast stiffer than an e46 coupe/sedan which come in at around 125000nm/°

[GP20]

Originally Posted by ZM4000

Sorry to say but you're wrong the coupe isnt twice stiffer as the roadster. talked to my bmw dealer about that point when i was looking for a z4m. He told me that BMW engineers (and all big carbrands) put extra calculated weights in the car(roadster) to loose that wooliness because of not having a roof so that the car gets a lot stiffer.

FAIL.

[doozyj]

Goes to show you never believe what the dealership tells you 100%, do some due diligence before calling out someone without having your facts straight.

[hansaysso]

Another thing a lot of you are forgetting is built in safety systems.

Also to note, a lot of japanese car manufacturers to shed extra weight use ultra thin metal to make most of the body panels. This is especially true on the s2000 (you can find articles about this), the thing attracts dings like no other (this is with personal experience btw...) don't get me wrong, a boot kick will dent in BMW body panels, but i rarely catch as many rock dings in the M Couper as i did in my old s2000 or RX7.

[ZM4000]

Well next week i'm in the Nuerburgring for Bmw M power training. few BMw engineers will be there and i will bring news and answers.

[Erhan]

There are couple areas that BMW could do a lot better with Z4 M. Lighter exhaust, lighter battery, lighter seats would easly cut 100-150lb of fat. 1000$ RPI exhaust is significantly lighter than stock system. 900$ Recaro seats are ~40lbs/each lighter than stocks.. The Coupe could have used a carbon-fiber roof.. But unfortunatelly BMW didn't want to spend too much time developing this car nor they spend too much time on details.

It is not all that fair to compare Z4M to S2000. Bigger engine weighs more, but not only that, it also requires more oil, bigger radiator etc.. Also more power means you can have bigger wheels & tires. And again, you need more breaking power due to more power. All this add up. Also a metal roof and huge glass on the hatch adds up significant weight too.. I don't know how S2000 and Z4 have similar dimensions though. S2000's cabin is a lot smaller than Z4's.

Although, comparing Cayman or 911 to Z4 M is fair. Porsche is doing a magnificent job. With every new generation they find a way to keep the weight same as the older gen. BMW on the other hand adds up several hundred pounds with every new generation. Good for BMW, bad for people like us, but the BMW we knew is gone. They're now making big, luxury cars and trucks. They're expanding their model range with bigger and heavier "GT" cars and uber-fast SUVs. But there is no true sports car coming from them... So long BMW.

My next car, if I ever decide to move on from my Z4 MC, would be a porsche.. Sad, but BMW does not have a single car in their current line up that I'd consider buying.

[doozyj]

Originally Posted by ZM4000

Well next week i'm in the Nuerburgring for Bmw M power training. few BMw engineers will be there and i will bring news and answers.

New and answers to what??? What are you going to ask them?