z4mc's weight

[ZStig]

Originally Posted by Shereef_Osman

Here you go!

nice way to mess up the rigid body

[ZStig]

Originally Posted by Finnegan

Good question. Answers, if I recall correctly for the 335is vs. M3: massively heavy exhaust to tame the S65's tendency to drone (I'm replacing mine with a full Akrapovic, saves 50 pounds); different seats (more bolstering, as they're heavier as well); additional sub-frame rigidity; other pieces that add weight (and rigidity); heavier duty "M stuff"; additional sound-deadening; oil and transmission coolers; and I believe larger rotors as well.

I agree Porsche has kept the weight down, but it's still creeping up over there generation to generation, just not at the pace of other cars. I looked at that about a year ago and noted that while moving more slowly, weight had really gone up. So I just looked again tonight: a 911SC circa 1983 weighed ~2,500 lbs; the 993 weighed in at just over 3,000 pounds, and the 997 S weighed in 3,100 pounds. Safety equipment makes up a lot of that weight, and Porsche does tend to focus on performance not comfort. But the reason Porsche hasn't increased at the same rate as other manufacturers is, as Jeremy Clarkson puts it, "Porsche has the laziest design team in the world". They haven't increased the size of the 911 variants (look at a 911 SC vs. a 997), unlike BMW who keeps going bigger and more bloated.

I saw an E34 M5 last weekend at EuroSunday. It was actually smaller than my E92 M3! The E92 is bigger than the E46. At the rate we're going the 3er is going to look like a 7 series soon. You'll need a license to drive a truck for the series of the future. I can hear it now "excuse me sir, you have to put money in two meters for that 7 series since it takes up two parking spaces, so you're getting a parking ticket."

So of course these cars weigh more (safety improvements notwithstanding). It's the size of the vehicle BMW is putting out. IMO this reflects the change in people who are growing larger as well, and it's a side effect of the popularity of the land barge sized SUVs which have accutomed the public to having a living room on wheels.

The next generation of BMWs will, I'm sure, prove to be even bigger and more bloated than this one. They'll produce more power, but a 4,000 - 4,5000 pound car, no matter how much power and suspension tricks it has, is just not going to be as much fun as a 3,200 pound car due to the laws of physics.

And that's what makes the Z4M and Z4 (and Z3s) so special. They're light, nimble, and have just enough "luxury" and comfort to be livable while at the same time delivering great performance. It's why the Z4M is a keeper in my book.

agreed agreed! plus combined with the simple weight reduction (wheels, seats, battery, exhaust) + an ess supercharger, you got yourself a REAL keeper =)

[Shereef_Osman]

Originally Posted by Roffle Waffle

nice way to mess up the rigid body

Nothing rigid about the parts that were removed. We would have removed everything but I didn't want to have to deal with a harness everyday. Thanks for the smart ass comment non the less.

[esqu1re]

Interesting removal. Looks a lot more spacious, although you did get rid of the center console thing between the seats. How thick was the metal spanning the middle that you removed?

[JCz04Bimmer]

Shereef_Osman: Very neat. I do know that the metal there is pretty thin but the sum-total of it all is likely a part of the rigidity of the car. If I ever did something like this, I'd do the same thing and replace the part you removed with roll cage bars.

[r4gs]

shereef_osman, that must've been an extensive interior remodelling and the end result looks, and possibly feels, very neat. i'm presuming it's a full leather refinish of the boot area?

[Finnegan]

Shereef,

Looks good! Really, this is a quality job with a great looking result.
Did you weigh the materials after removal? How much weight did this save?

I have the same questions as others about torsional stiffness however. It's not how rigid the materials are per se, but what the overall structure adds to the design in some cases that matters. So it may be more complex than just how rigid the materials are. I poked around a bit, and this type of structure is usually added to a design to aid in maintaining torsional stiffness. I'm no expert, and I'm not an engineer, simply a person with an interest who tends to research and bit and probably gets in over their head in these type of discussions.

Bottom Line: I really like the look, I just wonder what this does (or does not do) in terms of that. I guess the only way to find out would have been to set up a rig to test before and after....

Is that a total replacement to the stock sound system as well? I think I see a head unit missing and different kind of display...interesting....anything to share on that one (sorry if I missed it in the DIY section).

[Finnegan]

Originally Posted by shift@red

I have to disagree here re: Porsche weight. I agree that they have gone up slightly in the 'regular' cars (GT3/RS/GT2/RS not included) they are very lavish on the inside and are still more akin to GT cars in most cases. They have interior creature comforts like nav, bluetooth, ipod, and have the XX adjustable seats as well as adjustable suspension etc. They also have quality, fit and finsih that really no one else out there can touch. Those types of materials, like wrapping everything in leather adds weight. They are the benchmark when it comes to nearly every facet of sports car engineering.

Fair enough. (Oh, I cut your other comments in light of space--I totally agree with them btw.) Two things: A. Porsche does do a very nice job inside--but I think part of the cost we see is found in the use of materials that reduce weight overall in an effort to keep weight down and "luxury" increase. B. Do you agree that keeping the size of the 911 variant has help keep down weight? I think that's part, but not all of the answer.

You know, the more I think about it, it's probably Porsche's mission to minimize weight. Part of their "core values" if you will. Even the Cayenne is 400 pounds lighter this year (haven't confirmed, but that's what was stated by Porsche during the ALMS race last weekend). If that's true that's astounding! Oh, and they increased power while at the same time improving efficiency 30%. That's damn nice work.

Clearly only a subset of buyers care about weight. Your average buyer (and average American) thinks about how many cup holder the car has, how many vid screens for the kids, and how many gadgets the car has. Never mind it weighs as much as an tank and handles just as well. (BMW is really trying to tap into this market--and I can't say from a business perpective I blame them--very few enthusiasts and lots of sheep.) And Porsche seems to be directly targeting those folks (read "us" on this forum). Aside from the Z4M, BMW has gone bigger, fatter, and less focused generation after generation. My E92 is great as a large family car (even in coupe form) but it's not focused, not light, and certainly not what I would call "nimble". It's simply "practical" for trips and so forth (yes, it's funny that we consider it the "family truckster").

Honestly, if I wouldn't take a bath on depreciation selling it, and if we didn't need a "practical" car, the other car in the garage would be a 08 Cayman S with Sharkwerks plenum and GT3 throttle body and an LSD plus other bits. I love the Z4M for it's uniqueness and handling fun, but I love the Cayman S just as much for other reasons. But when you think about it there's a lot shared between those cars. Both meet my requirements for a true sports car: sufficient power (Cayman S with upgrades); lightweight; good brakes; steering feel; nimbleness; and a MT. Advantage goes to Z4M in the power, looks, uniqueness, and diff; advantage to Cayman S on transmission and balance (mid engine).

[Serious]

Originally Posted by shift@red

I have to disagree here re: Porsche weight. I agree that they have gone up slightly in the 'regular' cars (GT3/RS/GT2/RS not included) they are very lavish on the inside and are still more akin to GT cars in most cases. They have interior creature comforts like nav, bluetooth, ipod, and have the XX adjustable seats as well as adjustable suspension etc. They also have quality, fit and finsih that really no one else out there can touch. Those types of materials, like wrapping everything in leather adds weight. They are the benchmark when it comes to nearly every facet of sports car engineering.
I think anything 3300 lbs and under is pretty light these day. If youre 3000 lbs +/- thats extremely light. The trend of bigger cars is because people want all of it. They want a car that will do anything and everything for them, and the parts/accessories add up quickly.
As far as BMW goes...they know they arent really selling to as many true enthusiasts as other brands such as Porsche/Ferrari/Lambo are. The M cars have become just another Audi S or Merceded AMG badging non M car with M packs and making them look as close to an M without actually doing so.
The Z4M is really the last of its kind. I have owned many BMWs (e46 m3, 335i coupe, 335i sedan, e46 m3 competition, z4m roadster and now the z4m coupe all within a span of 3 years or so and also had an e92 m3 on order but canceleld) and the z4m coupe/roadster are the only cars i have really felt 'did it' for me. Nothing else ive ever driven that was available in the US from BMW every really left me with a feeling that the car was something special the way the z4m has.

To be fair BMW has done the same thing, they just have taken a funny path getting there.

Look at the e46 m3 and new 1M, if you ignore the badging or slap some m3 badges on the 1m (which due to its size/HP are the ones that really should be there), then it gives the appearance BMW has reduced size, increased power, and kept weight inline with previous models.

I will admit it's a very pecuilar way of looking at it, but hey that's how I see it.

[RichardTS]

Originally Posted by JCz04Bimmer

I would sooner look at the ridiculously overbuilt bulkhead behind our seats. Did someone say Sawzall!?

Did someone say stiffness like tin foil?

[Huz-Z]

Originally Posted by RichardTS

Did someone say stiffness like tin foil?

Now now. A thin sheet of metal may be weak in compression, but very strong in tension. For example, take a sheet of paper and hold it between your thumb and forefinger, with your left hand holding the top of the sheet and your right hand holding the bottom of the sheet.

Try to buckle or bend it - no problem at all.

Then try to pull it apart. See the difference in required effort?

While I presume the aforementioned bulkhead is not structural and simply serves to separate the cargo and passenger compartments, one must be careful not to delete something that also has a structural function.

Cheers!

[JCz04Bimmer]

Originally Posted by RichardTS

Did someone say stiffness like tin foil?

Nothing a few 1.75x0.120 DOM tubes couldn't solve!

I'd cut the bulkhead just how the other fella did but I'd proceed to have a horizontal tube welded into place across the car in its place and then have crisscrossing triangulated tubing between that horizontal tube and the floorboard. That sort of tubing is about 2lbs per foot and I'm guestimating I'd need about 4ft across and then about 8ft for the support tubing. So, let's round up... 30lbs? Depending on the weight of the bulkhead, that'd be a neat weight-saving project.

Notice something missing...

[esqu1re]

I've never seen so much scaffolding, but then again, that doesn't appear to be a street car.

[r4gs]

my goodness, some major structural work being done!

[aerobod]

Originally Posted by shift@red

How do you figure they are going to be fat, disconnected pigs like the e9x m3? They said curb weight is going to be 1370 kgs, which is 3014 lbs, and lighter than the current generation.
I happen to get a bit more info on what will be coming from Porsche (my family owns a dealership).
The car will no doubt still be the benchmark, but yes it will again be more luxurious with its interior based largely on the panamera and cayenne. It will be wider, flatter and have slight aesthetic changes, but most of the real work will be what you cant see as always.

The 2012 911 may still be the benchmark in the lower end of it's range, but the top end of the range (GT2 RS) will see a new segment benchmark in the McLaren MP4-12C, which is set to compete in the US$250K range. Indications from what I saw at the Goodwood Festival of Speed, where they had it running the hill climb and had chassis cutaways on view, is that it will be a major step forward in the segment when it goes on sale next spring. Carbon fibre monocoques will likely become the norm in this segment, based on the quality of the production-ready one that McLaren was showing.

[RichardTS]

Originally Posted by Huz-Z

Now now. A thin sheet of metal may be weak in compression, but very strong in tension. For example, take a sheet of paper and hold it between your thumb and forefinger, with your left hand holding the top of the sheet and your right hand holding the bottom of the sheet.

Try to buckle or bend it - no problem at all.

Then try to pull it apart. See the difference in required effort?

While I presume the aforementioned bulkhead is not structural and simply serves to separate the cargo and passenger compartments, one must be careful not to delete something that also has a structural function.

Cheers!

And forces that attempt to twist the body would probably place the bulkhead in tension. Think monocoque though I am not sure if the body is a true monocoque because I don't know enough about its construction. But it does appear to have some monocoque properties.

I'll bet that if the body were modeled in SolidWorks and then FEAed the bulkhead would show stresses.

And after spending the last few years consulting in manufacturing, trust me when I say that it would not be there if it were not necessary for safety or structural integrity. That is a material cost that would be eliminated if possible. If it were a mere separator, it could be made from fiberboard or some other weak composite intended for non-structural use.

Cheers

[RichardTS]

Originally Posted by JCz04Bimmer

Nothing a few 1.75x0.120 DOM tubes couldn't solve!

I'd cut the bulkhead just how the other fella did but I'd proceed to have a horizontal tube welded into place across the car in its place and then have crisscrossing triangulated tubing between that horizontal tube and the floorboard. That sort of tubing is about 2lbs per foot and I'm guestimating I'd need about 4ft across and then about 8ft for the support tubing. So, let's round up... 30lbs? Depending on the weight of the bulkhead, that'd be a neat weight-saving project.

Notice something missing...

LOL. Never force anything - get a bigger hammer...

[Shereef_Osman]

Originally Posted by esqu1re

Interesting removal. Looks a lot more spacious, although you did get rid of the center console thing between the seats. How thick was the metal spanning the middle that you removed?

I don't recall the actual thickness but it was quite flimsy, the thicker parts (which hold the seat belts) are the parts we left. Also there seems to be some sort of "beam" running at the bottom of the bulkhead that was extremely thick and strong. We left that part alone, lol.

[Shereef_Osman]

Originally Posted by JCz04Bimmer

Shereef_Osman: Very neat. I do know that the metal there is pretty thin but the sum-total of it all is likely a part of the rigidity of the car. If I ever did something like this, I'd do the same thing and replace the part you removed with roll cage bars.

I am no engineer so I can't say anything for certain, but having tracked the car before and after the removal, it didn't seem that we affected the structural rigidity. We did consult with two race shops here in Toronto (Raven Performance & Engineered Automotive) before doing it and they both said the bulkheads were there solely for the purpose of the roadster and that BMW was lazy and didn't want to redesign it for the coupe so they left it in place.

Initially we were going to replace the whole bulkhead and do as you mentioned, put a roll bar with some members attaching to the rear struts (as per Raven's recommendation) but it was getting too costly and I really didn't want to have to deal with a harness everyday.

[Shereef_Osman]

Originally Posted by r4gs

shereef_osman, that must've been an extensive interior remodelling and the end result looks, and possibly feels, very neat. i'm presuming it's a full leather refinish of the boot area?

Ya it was a big job, I have to say Matt @ Defined Designs is truly a master at molding parts together, he basically recreated the whole trunk, creating more space and making it look much more in line with the rest of the coupe (personal opinion obviously). He did all that while hiding two smaller batteries, a large Zapco amp, a Mac Mini, power supply, etc.

[Shereef_Osman]

Originally Posted by Finnegan

Shereef,

Looks good! Really, this is a quality job with a great looking result.
Did you weigh the materials after removal? How much weight did this save?

I have the same questions as others about torsional stiffness however. It's not how rigid the materials are per se, but what the overall structure adds to the design in some cases that matters. So it may be more complex than just how rigid the materials are. I poked around a bit, and this type of structure is usually added to a design to aid in maintaining torsional stiffness. I'm no expert, and I'm not an engineer, simply a person with an interest who tends to research and bit and probably gets in over their head in these type of discussions.

Bottom Line: I really like the look, I just wonder what this does (or does not do) in terms of that. I guess the only way to find out would have been to set up a rig to test before and after....

Is that a total replacement to the stock sound system as well? I think I see a head unit missing and different kind of display...interesting....anything to share on that one (sorry if I missed it in the DIY section).

Thanks! I was very happy with the end result. Unfortunately we didn't weight the materials as they were removed, but it wasn't just the metal that was removed, there are all kinds of electronics hidden in that wall, I couldn't believe how big the bluetooth module was. I don't know if all coupes have this but mine even had a TV module, lol. All those extra things were removed and all the wiring belonging to it all were also removed, along with all the metal, factory subwoofers, factory rear speakers, I'm sure it would add up to at least 60-70 pounds. That being said, our goal was not to reduce weight, especially since we added two Morel Ultimo subs, a zapco amp, and obviously lots of MDF, fiberglass and leather.

As for the stiffness, I really can't say for certain but it doesn't feel as if anything was weakened. After the V was cut out, it was plated with 1/8 thick steel to try and regain any stiffness lost, if any?

Ya the whole sound system was replaced. Morel Elate 3 ways in the front, Morel Ultimo 8s in the back and a Zapco DC1000 amp powering it all. For the deck we used an AVIC-Z110BT. For entertainment a Mac Mini runs iTunes so I can get my whole library on the go.

[Finnegan]

Originally Posted by Shereef_Osman

Thanks! I was very happy with the end result. Unfortunately we didn't weight the materials as they were removed, but it wasn't just the metal that was removed, there are all kinds of electronics hidden in that wall, I couldn't believe how big the bluetooth module was. I don't know if all coupes have this but mine even had a TV module, lol. All those extra things were removed and all the wiring belonging to it all were also removed, along with all the metal, factory subwoofers, factory rear speakers, I'm sure it would add up to at least 60-70 pounds. That being said, our goal was not to reduce weight, especially since we added two Morel Ultimo subs, a zapco amp, and obviously lots of MDF, fiberglass and leather.

As for the stiffness, I really can't say for certain but it doesn't feel as if anything was weakened. After the V was cut out, it was plated with 1/8 thick steel to try and regain any stiffness lost, if any?

Ya the whole sound system was replaced. Morel Elate 3 ways in the front, Morel Ultimo 8s in the back and a Zapco DC1000 amp powering it all. For the deck we used an AVIC-Z110BT. For entertainment a Mac Mini runs iTunes so I can get my whole library on the go.

That's one hard-core entertainment set-up! It sounds like the main structural component--the bottom of the bulkhead--was left intact. And you did your homework.

I'd have more concerns about the mod if this were the roadie however. The coupe has some inherent structural advantages, so if there is an "issue" it's probably minimal.

Like I said before, I really like the look and enhancements.

It does sound like, if you wanted to cut weight, this type of mod could help. And if you're uber worried about torsional stiffness, some custom "scaffolding" could probably address that and stiff provide net weight savings.