440-500 lb kept off the gen-1 with aluminum instead steel

[Yinzer]

The recent "Japanese nostalgic car" article (link) reminded me of something I've sometimes wondered about regarding statements that nearly 500 lb. was kept off the gen-1 thru use of aluminum instead of steel. Generally, that just seems like a really large estimate! Wikipedia says 220 kg (484 lb), the Japanese nostalgic car article says 500 lb, and this one from Honda says 200 kg (440 lb). Does that seem about right to anyone more in the know about these things? If the '91 curb weight is 3010 lb, then a 3450 to 3510 lb "steel NSX" seems kind of funny when compared to other larger & heavier cars of the same era:

1993 Camaro Z28: 3,373 lb and 193.2" x 74.1" x 51.3" (link) (plastic body panels except hood & rear quarter panels
C4 Corvette: 3,239 lb and 176.5" x 71" x 46.7" (link) (plastic rear bumper & panels)
1991 "steel" NSX: 3,494 lb and 173.4" x 71.3" x 46.1"

I know that's a pretty limited and simple comparison above and the Camaro & Vette have many/mostly plastic panels. So let's say the Camaro or Vette saved 150-200 lb going with plastic body pieces instead of steel, which would then approach the "~3500 lb steel NSX" weight...does it seem right that a smaller car like the NSX with a mid-mounted V6, no rear seat, smaller tires & wheels, no power steering, and overall smaller size would weigh about the same as the Camaro or Vette, both of which had steel frames, V8 engines, a back seat (Camaro), power steering, larger wheels/tires, a center driveshaft & rear diff, etc...the Chevy's were physically larger than the NSX and (in my pro-Honda mind) couldn't have been as well-engineered for lightweight as the NSX was at the time. I'm not saying the #'s are wrong but for fun argument's sake, doesn't it seem like there should have been a bigger difference between the NSX & Camaro/Vette weights once all were "equalized" with steel bodies? Does 440-484 lb saved seem like a high estimate (would a steel NSX really weigh nearly 3,500 lb) or doesn't it seem that an all-aluminum NSX that's smaller and "simpler" than the ~3300 lb Camaro & Vette should weigh less than 3010 lb?

I'm sure I'm missing something obvious that would blow these thoughts out of the water, but I shut off my brain over Christmas break after a rough Nov-Dec at work!

 

[Old Guy]

The density of steel is greater than aluminum; but, steel has a higher modulus of elasticity than (edit as noted by nsxtasy) aluminum (stronger for the same cross section). As an interesting exercise, if you calculate the cross section of aluminum versus steel samples that will give you the same total yield strength, the weight of the steel and aluminum samples is not drastically different. As an example of this, I was looking at really high end bicycle frames back around 1990 and there was very little difference in the weight of aluminum versus steel frames.

If you took the marketing wankers approach and said 'lets just estimate the weight of these various aluminum body panels and the chassis if they had been fabricated from the same gauge steel', I am sure that those weight estimates would probably be reasonable. However, it kind of misses the point. Aside from the simple rigidness associated with a higher or lower modulus of elasticity, a great deal (maybe most?) of an objects rigidity comes from its shape. Every engineering student who has taken a 2nd year statics and dynamics course will know that an I beam with the same cross section and weight as a square bar will be much more rigid than the square bar. One of the beauties of aluminum is that with the same weight of material, you can fabricate more elaborate or larger structures that will be more rigid than you can with the same weight of steel.

There are some very high strength steels in existence. One of the problems with a lot of those steels is the ability to form them into rigid shapes. However, auto makers are using high strength low alloy steels to form more complex, stiffer and lighter structures. With better and newer design techniques and better alloys, they have been able to design stiff structures that are light. As an example, Honda did not return to the use of aluminum for the S2000. The Porsche Boxster which has aluminum body panels; but, a steel structure is reportedly a remarkably stiff structure with an advertised weight significantly below that of an NSX.

If Honda were designing the original NSX today with today's materials and methods (two really big ifs), it might have been better to take the Porsche approach of a steel structure with strategic use of aluminum or other materials. This would of course end up with a radically different superstructure design.

I really like my NSX as a modern classic. I am attracted to it primarily because of its shape / style which I think will be timeless. However, for a car reportedly built with lightweight materials, I have never thought of the NSX as being a lightweight car. My son's RSX is a lightweight car that at lower speeds drives more like a lightweight sports car (I have no interest in trading the NSX for his RSX).

 

[Yinzer]

Good stuff! Ironically, I design structural frames & supports for work so I'm familiar with those trade-offs. I tried to stay high level and not get into any talk of size & shape differences when designing for frame/strength-design, fatigue resistance, damping, and/or torsional rigidity with different materials but for similar performance, etc. because I'm assuming Honda took those things into account when they published the "200-220 kg of weight savings with aluminum vs. if they had designed for and with steel." (I.e., I assume they they didn't just think about density differences for the same shape parts). Staying kind of high level, it just "feels" like the stock '91 NSX should have weighed less than it did since it's generally smaller and simpler in the ways like I mentioned above. Unless there were certain features not easily pointed at, such as possible improvements in torsional rigidity & localized stiffness a la Senna, for then-acceptable feel & performance that were leaps & bounds better than the Vette & Camaro and which could have added a couple hundred pounds here and there.

I really like my NSX as a modern classic. I am attracted to it primarily because of its shape / style which I think will be timeless. However, for a car reportedly built with lightweight materials, I have never thought of the NSX as being a lightweight car. My son's RSX is a lightweight car that at lower speeds drives more like a lightweight sports car (I have no interest in trading the NSX for his RSX).

I agree. I've never let marketers convince me that $9.99 is so much less expensive than something advertised for $10, but any non-compact sports car weighing less than 3000 lb has always caught my attention as being a rather lightweight car, just like any "sports car" weighing 3500+ has always felt as being too portly to me, no matter how fast it may be 0-60. I'd probably never have considered this post if the NSX came out the gate at 2990 lb, just 20 lb less, ha ha.

 

[nsxtasy]

Does that seem about right to anyone more in the know about these things?

If this were posted by anyone else, I'd be asking, "Have you ever picked up an NSX body panel and felt how much it weighs?" But in your case, Andy, I already know that you have.

The density of steel is greater than aluminum; but, steel has a higher modulus of elasticity than steel

We know what you mean, but you may want to edit the last word of this part of your post...

 

[Yinzer]

If this were posted by anyone else, I'd be asking, "Have you ever picked up an NSX body panel and felt how much it weighs?" But in your case, Andy, I already know that you have.

I was pretty sure the NSX hood would float away if I didn't keep my hands on it and stuff it safely in the back seat of my Accord. But that's just it - I remember the hood being so featherlight that it makes me feel the rest of the panels and frame should be awfully light. One of the stock avatar images available at Prime is the frame on, I think, a rolling platform. I think sduffcomposites (sp?) uses that avatar. Anyone know the weight of that chassis weldment/assembly? A 3010 lb curb weight still seems heavier than it "should" be. Wonder how much the car weighed before Senna's input.

PS-I encourage anybody at a cars and coffee to look at the NSX hood and then a Viper hood. The NSX hood is truly pocket-sized. I still smile at being able to fit it in the backseat of my car a few years ago, LOL.

 

[Old Guy]

We know what you mean, but you may want to edit the last word of this part of your post...

Oh my - the hazards of doing posts first thing in the morning after I have had a few shots of espresso!

 

[Bram]

The chassis with doors is 452 lbs...

 

[Old Guy]

Weight has an interesting way of creeping into a design. I remember reading a review of the early NSX in which the journalist reported that the Honda technical representative explained that they were using the cast iron brake calipers was that Honda believed that aluminum calipers would be too flexible. The journalist seemed to embrace that as a viable answer. It was almost like the design team was burnt out after doing the chassis and engine design and just sort of started to let the final details slip.

 

[MaxGeek]

Kind of like how the LFA has all this carbon fiber goodness, but still weight 3562lbs.
http://www.motortrend.com/news/2012-lexus-lfa-2010-nissan-gtr-comparison/

 

[Patricio]

I've estimated in the past that a 452lbs NSX chassis likely has the equivalent stiffness of around a 1200lbs steel chassis

Very simplified explanation: Although standard per inch ratings are simplified, when you thicken the material there are additional strengths to consider:
Therefore although aluminum is 34% lighter and around 45% weaker per flat 1" thick plate of steel, aluminum that is 50% thicker than steel (1.5" thick) will be 29% stronger and still 50% lighter than the 1" plate of steel

Weight:
Aluminum is 168 lbs per cubic foot
Steel is 490 lbs per cubic foot
Titanium is 280lbs per cubic foot

Al strength/weight =171,000 in
Steel strength/weight =375,000 in
Ti strength/weight =812500 in

I design & build apartment building structures but have messed around with, researched and invested in boat structures, go karts and bicycle structures.
here is a great old read that is really very simply explained in steel vs aluminum boat building http://www.kastenmarine.com/alumVSsteel.htm

Although the chassis is aluminum there is substantially more of it, more strength was achieved than other car manufactures would have attempted to achieve through steel. The NSX chassis is substantially stiffer than most cars of that era, thus why it does not flex when jacked up nor do we have all the interior squeaking sounds like early cars, and why our cars still have superb handling even after 25years of age.

as far as overall weight of the car there is also more sound deadening and high quality made interior parts than most sports car builders used at that time, even spares and tool kits where not included in many sports cars. Our interior roof/and door dash materials don't sag and de-laminate, our interior panels don't disintegrate like my 10 year old BMW's....

This and also explains why its easy to get an NSX to 2600-2800lbs with just a few weight reduction mods without losing any typical sports car amenities....

 

[BBVNSX]

When the weight goes up, you will need bigger brakes... bigger wheels... bigger engine... just to achieve a similar result... so this could also help explaining the 500 lbs...

 

[Yinzer]

as far as overall weight of the car there is also more sound deadening and high quality made interior parts than most sports car builders used at that time, even spares and tool kits where not included in many sports cars. Our interior roof/and door dash materials don't sag and de-laminate, our interior panels don't disintegrate like my 10 year old BMW's....

This and also explains why its easy to get an NSX to 2600-2800lbs with just a few weight reduction mods without losing any typical sports car amenities....

That's the type of answer I was looking for. The more I thought about things while this thread evolved, the more I started to think the NSX's hidden weight for its size had to have come from things it offered that aren't flashy and don't stand out in an obvious way but were pretty big differentiators to other sports cars of the time. Torsional rigidity & stiffness where it counts came to mind (especially after the famous Senna input) but not so much all the comfort and durability/robustness of the trim throughout. Makes a lot of sense now.

This does bring up another enigma that I've thought about at times and mentioned at least once in another thread months ago: the 1991 NSX really makes no sense. Cutting edge technology and reasonably high performance in a super lightweight aluminum body but with a heavy BOSE stereo and super comfy interior treatment throughout that added more weight. Would love to know what inner turmoils and justifications, if any, that the engineering team and planners may have acknowledged and argued over....or if the team overtly realized that they had to add both performance and comfort, and then the owner could then later increase the performance by decreasing the comfort if he wanted. I think I recall Senna kind of touch upon this in that video where he goes for a lap with the engineers all around, and then comment about the NSX being a good trade off between comfort and the "sportive" side of things.

Thanks [MENTION=15790]Patricio[/MENTION] !

 

[Bram]

In addition to all the points highlighted above.
Here are some others to consider:
- sounding reduction material
- corrison material on the underside
- steel bolts and brackets used throughout the car
- large glass area (based on design)
- all the luxury items - leather seat,, thick carpet & Mats, AC, radio, CD etc
- spare tire and tools
- engine cover

I'm sure there are other items that can be added to this list

Bram

 

[JMChristopher]

Wonder how much the car weighed before Senna's input.

I have the NSX ultimate portfolio and there was an article about estimated curb weight on a preproduction test model. It was 2860lbs. Seems like a reasonable weight before additional strength was added.

 

[Yinzer]

I have the NSX ultimate portfolio and there was an article about estimated curb weight on a preproduction test model. It was 2860lbs. Seems like a reasonable weight before additional strength was added.

Thanks! Things are making so much more sense now.

 

[FF Drifter]

If Honda were designing the original NSX today with today's materials and methods (two really big ifs), it might have been better to take the Porsche approach of a steel structure with strategic use of aluminum or other materials. This would of course end up with a radically different superstructure design.
.

Isn't this exactly what happened with the second-gen NSX? There are indeed aluminum bits, but it seems the majority of the frame is high strength steel and of course there is always the option of the CF roof. At first glance this doesn't seem nearly as impressive as the all-aluminum first-gen but I trust Honda know what they're doing.

 

[BATMANs]

I never did understand why the NSX weighed more than a 3rd gen RX7 which had a steel chassis....

 

[dablackgoku1234]

I don't think a rotary engine + tranny is 650 pounds.

 

[BATMANs]

I don't think a rotary engine + tranny is 650 pounds.

It's probably not, but in the case of the FD there are the other parts like intercooler, twin turbos, the "rats nest" of wires and tubes to make the twin turbos work, duct, etc.

The FDs that do the LSx conversion kit more or less retain the weight of the car, which is still lighter than the NSX.

 

[Patricio]

to get a better understanding of where the weight is, just compare stripped track cars.
i belive the luxury quality branding/finishing of the NSX is highly responsible for allot of it unecessary standard spec weight when comparing to most other cheaply finished cars that rattle like tin cans inside after only being a few years old like corvettes.

this whole "supercar you can drive everyday" objective is a very porky comprimise.

a stripped track car NSX is 2200-2300 lbs.
what does a stripped FD weigh?

 

[BATMANs]

to get a better an understanding of where the weight is, just compare stripped track cars.
i belive the luxury quality branding/finishing of the NSX is highly responsible for allot of it unecessary standard spec weight when comparing to most other cheaply finished cars that rattle like tin cans inside after only being a few years old like corvettes.

this whole "supercar you can drive everyday" objective is a very porky comprimise.

a stripped track car NSX is 2200-2300 lbs.
what does a stripped FD weigh?

http://www.rx7club.com/3rd-generati...-diet-what-have-you-done-907142/#post10038918

Right in that range.

 

[Patricio]

makes sense. then we're back to my explanation in post #10 .. where the NSX used allot of aluminum, allot more than necessary. primarily to make it stiffer without weight penalty and not just to make it ligther.... we all know the NSX is substantially stiffer than other cars even after 25 years it has virtually zero flex compared to other cars and the reason it handles so well and is still a excellent platform for track cars.

 

[BATMANs]

makes sense. then we're back to my explanation in post #10 .. where the NSX used allot of aluminum, allot more than necessary. primarily to make it stiffer without weight penalty and not just to make it ligther.... we all know the NSX is substantially stiffer than other cars even after 25 years it has virtually zero flex compared to other cars and the reason it handles so well and is still a excellent platform for track cars.

FD is pretty stiff.

Even the RX-8 is stiffer and around the ballpark of the NSX in weight.

 

[Patricio]

Ive traked allot of cars over the years and I seriously doubt those cars to be as really as stiff as the NSX.
the NSX is ungodly stiff for a "sports" car. without a roll cage .. I rember having to cage older stripped 2700lbs 911's with over 400-500 hp becuase the frame would twist.. many cars need cages to avoid twisting under power... never once has there ever been a frame twisting problem with nsx regardless of track abuse or hp... newer cars are substantially heavier for this is reason as well to handle the force of the oem hp with traction.

two cars being the same weight but one made out of aluminum indndicates a substantial amount more of aluminum material. I don't think it's phisically possible to engineer a steel frame car to the same strength as a aluminum car of the same weight. you can use twice as much aluminum. and in sometimes 5x as much aluminum in certian spots... making it substantially stronger.

I really don't think we're even in the same ball park if the conversation is "stiffness"..

 

[Old Guy]

Isn't this exactly what happened with the second-gen NSX? There are indeed aluminum bits, but it seems the majority of the frame is high strength steel and of course there is always the option of the CF roof. At first glance this doesn't seem nearly as impressive as the all-aluminum first-gen but I trust Honda know what they're doing.

Impressive doesn't come from using new materials, it comes from how you adapt the design to use those new materials. The original F1 cars had tubular steel frames. Switching from steel to aluminum and then FRP materials while retaining a tubular space frame structure would have been stupid. The switch to aluminum and FRP materials in F1 came with the switch to more and more elaborate monocoque construction techniques. The original NSX was a creature of 1980s design and perhaps with a view to both engineering requirements and marketing potential, Honda made the decision to use aluminum for the structure. With improved high strength steels and improved design techniques, they may have decided that it is more effective to create a hybrid structure with different materials (sounds like the GM strategic use of aluminum versus the Ford all aluminum truck debate - more marketing wanker speak!).

I also agree with others that a lot of the weight in the original NSX has to do with its civilizing features, although I think that they could have done a better job on some items - brakes being one. I have ridden in a Ferrari 360. If I had to drive anywhere on the highway for more than 1 hour, I will take my NSX hands down. The 360 might be a nifty ride; but, it isn't particularly civilized. I don't know why they bothered to put a radio in that car. Maybe you use it when its parked!