I briefly looked at weight saving tactics for the S. Seems like you can't really do much besides spare tire and tools without major changes and functionality loss.

Since most of the S body is lightweight material already how do the other manufacturers do it?
*The car that comes to mind first is certainly the Lotus Elise which weighs a whopping 1900 lbs with a hard top.
*Mazda Miata weighs about 2400 lbs and although I'm sure a lot of that is engine/tranny. I kinda doubt that car has all the lightweight stuff that the S does.
*The Mini Cooper has a supercharge and 4 seats and still weighs about 200 lighter than the S.
*Porsche Boster weighs about the same but has 2 extra cylinders.
*Heck my 91 Jeep Cherokee with a 6 cylinder engine designed in the 70's, 4 wheel drive, heavy steel everything, and tons of room only weighs 200 lbs. more.

What are we missing?????

 

The car has an aluminum frame and chassis covered with a fiberglass body. Little to no sound deadening, no carpet, and very minimal interior bits.
Both cars are significantly smaller than the s2k.
Length/Width:
Mini 144"/66.5"
Miata '06=157"/ 68" (and is 2500lb) '99-'03=155"/66"
S2k 162"/69"

More body = more weight
This one is a good question. The Boxster is larger, and appears to have just as many or more aminities. I'm not sure how much aluminum is used in the car (suspension and body panels). Perhaps Poindexter can chime in and give us his thoughts as to how Porsche got the Boxter to the same weight.
Does it have side impact bars? Dual air bags (or even one air bag). Look at the 2001 model year of your Jeep...I think that was the last year of that body style. It weighs in at nearly 3200lbs. And does it have the structural regidity of the s2k?

 

Yeah, the Lotus is a totally different animal so it cannot really be compared.
As stated above it has a lot of aluminum used in the frame, fiberglass exterior, and a very minimal interior.
Not to mention the price is about $10K more so I would hope you get something for 10 grand.

 

s2k body panels are soooo thin i doubt aluminum would make a dif

 

The lotus uses an aluminum monocoque: expensive as hell. And as mentioned is has no sound deadening, no carpet, no front bumpers (it had to get an exemption for this), etc.
Furthermore, I'm not sure if has any impact beams in the doors for side protection.

The Miata is significantly smaller than the S2000, and the motor is a shade smaller. It has no powertop, except in PRHT form, and I'm not sure its drivetrain and suspension components are as strong as the ones in the S2000 since the car was designed around a 170hp motor, and not a 240hp one. However the main thing with the Miata is that is does not have the same structural rigidity as the S2000, making its frame lighter.

The Mini only has a 1.6L motor, and uses FI to boost its power. It too is a much smaller car than the S2000. Importantly however, it does not need a very stiff chassis due to the presence of a roof. Case in point: the convertible version of the Mini Cooper weighs 2850lbs, a shade more than the S2000.

The previous gen Boxster (when the S2000 launched) was approx. 150lbs heavier than the S2000. They have since reduced the weight of the 987 Boxster. However, as in the case of the Miata, it too does not have as much chassis bracing as the S2000 has, including the critical X-bone. As a result, I doubt it has the torsional and especially the bending rigidity of the S2000's chassis (I've never driven the 987, so I'm assuming this - please feel free to correct me if I'm wrong. Some reviews I've read, have stated that they detected a hint of cowl shake through the car). Add to that, the fact that the Boxster is a 5 year newer design.

Your 91 cherokee has no airbags, or side impact protection among other things.

One of the key reasons as to why the S2000 weighs as much as it does - which to be honest is not a whole lot given the design and performance targets for the car - is due to its X bone chassis. This chassis affords the S2000 is superior bending rigidity and comparable torsional rigidity when compared to its competitors. This chassis design was necessary in order for Honda to meet its design goals in an open top vehicle. However, in comparison to the traditional method of reinforcing the side sills and floorpan of a convertible version of a car, it provides a much MUCH stiffer frame (stiffer than even some closed top cars!), and a significantly lower weight. Just look at the weights of the 350Z convertible, the Audi TT convertible, 986 Boxster, Z4, and others which weigh a lot more than the S2000.

 

Forgot to add: the S2000 curiously uses cast iron suspension pieces. I would assume this was done due to cost restraints at the time. Many recent competitors have begun to use forged aluminum bit and pieces in the suspension. A switch to forged aluminum in a "next" gen S2000 would undoubtedly save a few pounds.

 

That does explain quite a bit. I also didn't know that soft top cars actually weighed more.

 

That pretty much sums it up. I try to explain this to a guy at work who drives a miata and doesn't understand why my S2000 weights more

 

Well I guess I HAVE been spoiling it a little much lately and I've noticed it gaining a few pounds...

 

Most soft-top cars weigh more because they add a lot of bracing materials to the body...this is especially noticable in coupes that get a 'vert version (Z, Mini). They lose the roof, so they add a lot of reinforcement to make up for that lost framing.