Blahzay

After extensive searching and finding nothing, I'm wondering if anybody can point me toward some info about the AWD system in the 2is.

Specifically, I'm looking for info about how it distributes power on dry pavement, and what it does when it senses wheel slip.

Thanks

lifeisgood

I believe that the normal distribution of power is 70% to the rear and 30% to the front; when wheels slip, then the power distribution goes to 50/50.

lobuxracer

iTrader: (2)

There is nothing in publicly available tech info that says what the available splits are. It only says it is controlled by ATF from the transmission. In theory, it is capable of 0/100 to 100/0, but there is nothing indicating what the control limits are as used by Lexus.

The transfer case is a chain drive unit with a planetary gearset and a wet clutch. The ring gear on the planetary set drives the rear wheels, and the sun gear drives the front wheels via the chain. The transmission output drives the pinion gears.

lifeisgood

Always better to rely on facts rather than theories--a quick Google search yielded several IS AWD reviews that commented on the normal 70/30 rear/front power bias of the IS, with the ability to go to 50/50. Nothing mentioned about 0/100.

Also, a close read of the IS brochure comments about the normal rear bias of the awd system and the ability to shift to a 50/50 power distribution.

Finally, here's a quote from Road and Track's review of all-wheel drive sport sedans "The IS 250's awd system defaults to a 30/70 front/rear torque split, though it will shift to 50/50 depending on wheel slip."

lobuxracer

iTrader: (2)

Many magazines reported the TT Supra to have two different sized turbos (they don't), reported the rear wing to be functional (it isn't), and other complete misrepresentations of fact when it was new and being reviewed by them between '93 and '98.

If the information didn't come directly from Toyota, I would not trust it. Magazines don't always report facts, particularly when it comes to details.

lifeisgood

Once again here it is straight from the Lexus brochure--nothing about 0/100 as you "theorize".

2007 LEXUS IS 250 AWD
The IS 250 features available all-wheel drive (AWD) to assist you with better traction, cornering, handling and power—whatever weather conditions
you may face. In fact, while the IS usually maintains a rear-wheel drive bias, up to 50 percent of the vehicle’s torque can be routed to the front
wheels if needed. Additionally, the front and rear suspension system optimizes wheel alignment and helps provide precise handling and a confident
tire grip. To suit the varying needs of dedicated automotive enthusiasts, the IS 250 has a 204-horsepower1 V6 offered in both rear-wheel drive and
all-wheel drive (AWD). And while all models feature six-speed transmissions, the rear-wheel drive IS 250 also offers a sporty manual transmission.

lobuxracer

iTrader: (2)

Why do you insist on discrediting a slice of what I said?

I said There is nothing in publicly available tech info that says what the available splits are.

Everything after that is speculation based on the design of the unit.

There is also nothing about 70/30 or any other split except up to 50 percent may be used by the front wheels in a marketing brochure. Toyota obviously considers this to be proprietary information.

LexusNut13

http://www.wheels.ca/reviews/jan_06_lexus_is.php

According to wheels.ca, it is 30/70 front to rear, but can adjust up to 50/50.

lifeisgood

For now, we'll just have to agree to disagree. I take issue with some of your statements (theories) as to a potential 100/0, 0/100 torque split because they are potentially misleading and quite frankly don't help the questioner. I also think that your comment as to why Toyota does not release torque split information because "it obviously considers this to be proprietary information" to be a bit of a leap by you. Why would it be proprietary? Do you have a basis to support such a statement? Just curious.

While the IS brochure does not give a specific number for the torque split under normal driving conditions, "maintaining a rear wheel bias" sounds to me like something close to the 70% (at least 60% and less than 90%) quoted in numerous magazine articles, not 100% as you suggest.

Sure, a magazine may not always have 100% of the facts right all of the time (and that may be influencing your opinion here), but based on my experience, this would seem to be a low probability occurrence. Also, I believe it more likely that Lexus would have quickly corrected the error by updating its press kit, since this was a brand new product introduction. Lastly, by comparing the descriptions in a number of articles--including one from Automotive Design, to the IS brochure, and to descriptions of the GS AWD system (the IS is based on the GS chassis), I'm reasonably confident that the information is correct.

But rather than debating this any further, the only way to find out for certain is to ask Lexus, so let's ask.

Blahzay

The reason that I asked this question in the first place was becuase I wasn't able to easily find any information about this - just the vague description in the brochure.

I find it slightly odd that there isn't a detailed explanation of this anywhere...

TimboIS

^^ shouldn't be odd. Lexus is always light on details. Hell, they don't even publish the width of the brake rotors. A very common spec.