[ckolsen]

I was reading the Car & Driver review, and I don't think the car had the LSD, judging by the price, and it didn't list it in the options, but they mention it in the review. Since C&D is one of the most accurate 0-60 (they use the 5th wheel method), was wondering if the 7.6 sec time was due to lack of LSD?

 

[kota]

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[This message has been edited by kota (edited October 19, 2000).]

 

[S38]

Typically, LSD will only come into play under cornering. Shouldn't affect 0-60.

 

[dude]

I believe without LSD and if you're accelerating with one rear wheel spinning, what do you think the other rear wheel is doing??? The energy is wasted on the spinning wheel, and therefore not all power is transferred to the rear wheels, hence power loss and will definitely slow down the acceleration time.

 

[ckolsen]

I don't know much about LSDs, but I know Lexus claims it helps acceleration, and I know that losing traction is a big impediment to fast 0-60 times, so that would seem to suggest an LSD would improve it. However, fast 0-60 times require some wheel spin. My question was really whether or not C&D had one on their test car.

 

[dude]

You're correct, it does require some wheel spin, but on both wheels.....not just one!!

LSD's job to prevent one-wheel spinning applies here.

[This message has been edited by dude (edited October 04, 2000).]

 

[kota]

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[This message has been edited by kota (edited October 19, 2000).]

 

[dude]

I definitely do not agree that the wheels CAN have the SAME amount of grip on a flat dry surface....

Simple facts: When the IS accelerates, the engine actually creates a certain amount of torque from the engine, and therefore the chassis is actually torqued to the opposite direction of the crankshaft turning direction, WHICH MEANS that the weight will be shifted to one side of the car.....How can the wheels have the same grip??? Besides, one driver in a car will definitely throw the weight of the car off balance to one side; PLUS the gas in the gas tank will be tossed around.....AND how can you guarantee the road is dead flat and uniform???

On a dry asphalt road, the results may not be as apparent (but are present), but imagine going to the extremes: a dry super glossy smooth concrete surface, what do you think will happen???

I can go on and on, but the main thing is, without LSD, acceleration (with a certain amount of wheel spin applied) will be slower.....

[This message has been edited by dude (edited October 05, 2000).]

 

[Daniel]

Actually, there is also one thing you guys are not taking into consideration, and that is the gear ratio of the limited slip differential. Even when you are not engaging the worm gears in the LSD, it should still reduce the gear ratio somewhat.
I highly doubt that the gear ratio at the LSD and the ratio at the transfer box of non LSD car is going to be the same, and therefore that may result in different amount of torque being transfer to the rear wheel.
Maybe someone can dig into a Lexus spec sheet to find out all the specs on the LSD and the diff used in the non-LSD version. This way you can find out whether or not power transfer to the wheel are the same for both version of the vehicle, which I don't believe it is.

 

[kota]

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[This message has been edited by kota (edited October 19, 2000).]

 

[S38]

Was reading an old review on the 330i in the BMW club magazine and noticed an interesting thing. BMW actually changed the rearend in the 330 to a 2.91 or something vs. 3.47 in the 328i, with the same transmission ratios, and still gained .2 seconds to 60mph. So, changing back to the 328i rearend would likely dip the car towards 6 flat or 6.2. However, this would affect gas mileage and freeway engine noise but it might be tolerable for the gains

I know the auto isn't quite that tall but Lexus has to ask themselves what they aren't doing. If they can't match the 330i with a 3.91 final drive they need to change transmission ratios or engineer a better torque curve. If you put a 3.91 final drive in a 330i, the IS300 would have no chance of keeping up.

 

[Daniel]

It seem like BMW has better efficiency in their drivetrain than Lexus. Maybe that explains the difference in performance data when comparing the IS to 330i. Hopefully Toyota will go back to the drawing board and reduce the amount of loss in their transmission.

 

[dude]

Originally posted by kota:
dude, not to be rude, but can you post cites? I gave you links to 2 authortative sites that tell you the LSD has minimal effect going straight on dry road. Your arguments are based on conjecture. Do you really think C&D would test their cars in anything but a level surface and clear road conditions? I can post a couple of other links that say the same thing. I will concede that it helps during cornering and bad road conditions, but NOT when going straight on a dry surface.

[This message has been edited by kota (edited October 05, 2000).]

Please don't apologize, I certainly don't think you're rude or anything.

Yes, I do know what exactly you're talking about, but law of physics just doesn't really concur with the claim.....Again, if I may ask: How can you guarantee that both wheels have the exact same weight on them??? I don't have any web-sites to back up my claim, but the law of physics just don't seem to concur.....

As I said before, WITH CERTAIN AMOUNT OF WHEEL-SPIN APPLIED during acceleration AND without LSD, one wheel will spin faster than the other, WHICH MEANS THAT not all energy required to accelerate the car has been transferred efficiently.

I'm just thinking about the simple law of physics, that's all.