With a higher revving engine you get to eploit the extra rpms with a lower gear. The lower gear will effectively multiply engine torque, creating a greater torque load at the engine. The e46 m3 engine makes a maximum of 269 lb-ft of torque, and its first gear in it's six speed manual is a 4.23:1 gear reduction. Peak torque seen by the transmission in first gear : 1,137 lb-ft of torque. The 05 LS2 GTO has a 395 lb-ft of torque and its first gear in its M12 T56 six speed trans is a 2.97:1 gear reduction. Peak torque seen by the transmission in first gear : 1,173 lb-ft of torque. Suddenly, its looks like the engine with the higher rpm capabilities, despite having less crankshaft torque, is putting its gearbox through just as much stress.
I believe this is the reason as to why the automatic Rx8s only rev to something like 7600 rpm, because the particular automatic they use in them cannot take the torque load. Correct me if I am wrong, but the way Ford has rated some of their trannies, such as the 4r70w, has been torque capacity at the tranny itself, not what the engine is producing torque wise. I think alot of other transmission manufacturers rate their transmissions the same way. Which makes me wonder again, why is the GTO that much heavier than an e46 m3? Especially the old 350 hp LS1 GTO.

 

You have it wrong. The torque you are describing is what the differential will see, but not what the transmission sees. The engine out torque is what the transmission and clutch have to be designed to. The problem with the automatic RX8 is the transmission is limited in how many revs it can take. With 140 lb ft of torque (or whatever it is), torque is not a problem. But at high enough revs, things like lubrication would be. You've got a lot of fluid spinning inside a torque converter. Spin it too fast and you have a problem. You could design a torque converter for 9000 RPM (probably -- I'm not an auto transmission expert), but how many would you sell?

The GTO is heavier than the M3 because it has a bigger platform and a bigger engine. That's why the 550i is heavier than the M3. The 530i is minimally heavier because it has a bigger platform. The CLK55 is heavier than the M3 because it has a bigger engine. The CLK320 is the same weight as the M3 (give or take 50 pounds) because it doesn't have a bigger (torquier) engine. The M3 is the same weight as the 330i because the engines are similar sizes (the M3 is a few pounds heavier -- less than 100).

 

Oh come on now. You're starting to sound like one of these sport import fans, trying to convince themselves it's some kind of 'advantage' that they must wind up their Honda's engine to 4000-5000 RPM to get a snappy launch. You "get to exploit"... or is it you "HAVE to exploit"

Torque multiplier, torque shmultiplier. There is ONLY SO MUCH torque in that engine. (it's clearly plotted on the hp/tq/RPM plot and is the SAME every time you "exploit the RPMs"). It's true that a semi trailer truck transmission is heavier than an automotive manual transmission due to having so many extra gears (that's as close as your torque multiplying argument comes to making any sense here)... but isn't that a bit of an extreme here, since we are comparing cars to cars?

It amazes me, to see some here continue to try and ignore these simple truths. This is a big, main reason for the GTO's weight. I agree this is also a factor:
The skid plate on my GTO is pretty heavy, thick stamped steel. (it is removable BTW, although it kind of leaves the oil filter exposed to do so). The car is definitely built more rugged than other cars I've had. However, I was intrigued by this when I first read about the skid plate and so on, last year... I realize this is not a big draw for the typical muscle car fan but I find such ruggedness an advantage. I drive a lot of miles, on lousy Detroit streets (I recall reading somewhere that there is only one US state (PA?) with worse roads than MI). We've got mucho deep, wide potholes. We've got urban road debris (once a muffler bracket laying on a local freeway hit the floorpan of my 04 GP CompG and tore a fist-sized hole). We've got decades-old, under-maintained, salt-eaten washboard concrete. We've even got a huge number of suburban streets that are STILL dirt/gravel, in 2005! So I appreciate my rugged Goat and don't mind if it costed some pounds to make it so. Besides, those who are weight conscious, can of course remove some parts, the skid plate for example comes of with four hex bolts.
100% agree. This again is not dawning on some here - the key attraction of the new GTO is its performance VALUE. If GM had spent $$$$$$ making the GTO out of exotic graphite and other materials, re-engineered it and optimized it to the nth degree, no way would I have been able to afford it. To me - the LS2 GTO is like a Marine's Ka-Bar combat knife. Hefty, ergonomic, well-balanced, strong, and deadly against its opponent

 

If you want to compare a narrower shorter version of the GTO chassis look at the Catera, a GM2800 car. It was narrower, shorter, and had an all aluminum V6. It weighed in at 3770 lbs. The GTO at 3,774 lbs from this article http://www.highperformancepontiac.co...07pon_gtotest/ Seems like it does a great job of keeping weight down. The Holden V car is a larger stiffer car than the GM2800 and it weighs about the same including the more powerful drivetrain.

 

Just out of curiousity, I'd like to see a weight comparison of a fully-dressed LS1/LS2 vs a fully dressed M3/330 I6 powerplant.

Bet they're very close, as the LSx engines are quite lightweight and compact for their displacement.

BTW I love torque....I love it even more when you multiply it by rpm.

Gee...that's HP. Imagine that.

 

Just out of curiosity, Why? They're not in the same league, when you look at output...

 

Actually... the Catera was narrower, but longer. It also had more rear legroom, more height and more luggage space than the GTO. So it's risky to compare the two. Overall it seems to come out in the wash, comparing the various dimensional tradeoffs between the two along with the heavier V8 and driveline/suspension components to handle the ungodly, Ford-stomping POWER of the amazing LS2

 

I'd be interested in seeing that also. And I bet they're very close as well.

I'd also like to see how their external dimensions compare.

 

Because I'm curious - do I need another reason other than "curiousity" in order to ask a question? And I still bet they are very close in weight.

Also, their output is indeed in the same league - 343 isn't that far off of 400....Unless of course, you race from 0-4000 rpm, or just like to "feel fast" from a stoplight (emphasis on "feel"). Speaking of rpm....thats another reason the motors are in the same "league" for a sporty car whose intention is to go fast - though it might be counter-intuitive as to why.

Charlie....one being and I6, the other being a V8, I'd say its pretty safe to say the BMW will be longer and narrower, whilst the LSx will be wider and shorter. Heighth is likely about the same, though I suspect the LSx is somewhat shorter.

 

Bob Doesn't BMW mount their 6s at an angle? Is that something they used to do?

 

I don't *think* so, but I could certainly be wrong on that. The wife's car is a 2002 330i, and it appears to be mounted straight up. Appearances can be deceiving, of course - and I'm not even sort of a BMW guru (not real fond of the cars for that matter).

 

No... of course neither do I....
What exactly are you babbling about here? And where do you get this 343 hp figure? I've always seen the current M3's output listed as 333 hp and a measly 262 ft lb of torque. Sorry. That's NOT in the same league as my GTO's 400 hp and 400 (400!) ft lb torque. And you darn well better believe my Goat feels quicker in traffic - because of stump-pulling torque being on tap at just about any reasonable RPM. Incredibly - the LS2 Goat also gets better MPG than the M3 while doing this

Chalk up another Yankee engineering victory

 

Soon we will see the curb-weight-worriers chime in... "See! The M3 is lighter than a GTO... and has a quicker 0-60 even with less power!" This may be true. But even if I could stand shelling out huge dollars on a lawyermobile BMW, it wouldn't fit my needs due to having significantly less rear legroom than the GTO. It goes back to what teal98 said... about weights and classes of different cars, and what each platform is meant for. The M3 just doesn't have as much... class

 

Oh yeah, I'm sure it's longer and narrower.....but I'd bet it's also taller....maybe even alot taller. Overall, I'd bet an LSx is a much easier engine to package than a BMW I6.

Which would once again bring up the question about what the needs are/aren't of overall vehicle mass, to package a specific powertrain.

In fact, I wouldn't be surprised if an LS2 fit in a 3 series engine bay with no issues. Afterall, M3 is getting DOHC V8 next year....which I am very sure is larger/heavier than an LS2 in every single dimension.

 

I am not trying to convince myself of anything. Perhaps you should try to convince the Formula 1 guys that revs aren't really that important afterall.


Yeah, I am reading it now and it isn't all that correct. Heh, I don't even remember making that post. Last night at 3 in the morning when I made that post of wasn't exactly "of sound mind". I can't see why you couldn't design a torque converter for a 9000 RPM engine, as long as you have a great cooling system for it to pump its fluid to. Honda has hinted that their next s2000 will have an auto option; I wonder if the automatic will be tuned down Rx8 style or not.