uschardcor

for a quick note...AWD is a damn good system for cornering, but really only if the car has the ability to shift power to the wheels with the most traction. i mean it will work regardless but for the weight added that is the only way i really like it.

besides fishtailing and powersteering is SO much more fun! and by fun i mean potentially life ending at the same time

phish2112

man you all are seriously bumming me out and giving me some hardcore buyers remorse for going with the AWD. The 350 is a totally different car with all that horsepower. And much nicer.

Well, at least I'll have my rims intact instead of those out there with a 350 that someday slides into the curb in light snow.

NotFatBoy

Um... there are many differences between the GT2 and the Turbo, not just drivetrain.

For starters, the GT2 runs larger turbos than the Turbo (we are talking 996 here as the 997 info on the GT2 isnt finalized). You can opt for the X50 package with the Turbo however the boost is still higher in the GT2.

Also there are significant weight savings in the GT2 vs Turbo.

Larger Turbos, higher boost and weight savings (yes, partly due to changing from awd for rwd) are the reasons why the GT2 is faster than the Turbo.... not just the rwd.

Lastly, have you guys ever seen the S4s race at Le Mans? Those Audis, at the start of the race, literally jump 4-5 spots ahead instantly due to their superior traction and acceleration off the line.

LexAppeal

How is it much nicer? If you mean much nicer by it having so many more horses then yeah. But isn't it basically the same car with bigger brakes and engine. Do you have a need for speed?

Lets Drive

iTrader: (3)

Exactly, the porsche GT2 is lighter than the AWD 911 mainly because it is RWD, saving the majority of its weight in the drivetrain (this is the point). They also ditched traction control (saving more weight), yet 0-60 times made by the GT2 are superior to the AWD cars, despite the 'disadvantage' some people would like to say RWD has compared to AWD (which in the ideal should be more consistent). Couple this with the fact that you won't be putting down your max power from a dig anyway, and most would think AWD would have the advantage- but it doesn't. There is no way you're putting that much rwhp to the ground that early, without slipping tires to get a 0-60 that good, as it will require very good throttle control. The trap speeds are impressive (bigger hp), but that has less to do with traction early on.

If you'd like to take the Carrera S and the Carrera 4S, you'll see they both make about equal 0-60 times, given similar hp. The rear weight distribution bias found in porsches, makes RWD a great setup for launches, especially as weight shifts rearward.

As for Audi, if your car jumps off the line, its because traction was made available by your vehicles contact patch, whether it be 2 or 4 wheels- if you're slipping, then AWD compensates, but what if you're not slipping? A hypothetical 100% traction in a RWD vehicle would accelerate just as fast as 100% traction in an AWD vehicle, with all other things being equal.

pokerface

It also dependson how the AWD was set up, right?

ie., EVO and WRX systems were set up for performance, and I'd say the same for Audi's quattro and maybe BMW's xDrive systems. On the other end, MB's 4Matics are primarily for traction in terms of safety. Where does this put the IS AWD?

tqlla3k

iTrader: (1)

That is not a fair, realistic or good comparison at all. The GT2 has a 100HP, and 400lbs weight advantage over an AWD carreraS. Also, I have no doubt that the GT2 has an awesome set of tires. Probably 335s or something in the back. And then you have to consider the power distribution, a car with closer to 50/50 power dist will have better launch charactoristics and more grip overall, a car with 30/70 will turn harder.

In the dry, Drivetype isnt too important for a 200HP car, but when you get into 300+HP.. it makes a difference on the street. You can accelerate through a turn, you can launch the car, you can hit full throttle uphill in the rain.

On a 200HP car, the advantages of AWD are limited to control during inclimate weather. And greater control during turns. (Although, you can turn harder in RWD)

And finally, if there is 0% Slipage, an RWD car will be faster than the AWD car, due to added DT loss. However, on most RWD cars, there is some traction loss, maybe with the 18s(255s)... traction loss should be minimal.

Turkoman

I would so much like to believe that. However, I think a RWD car is not made to be driven in the snow and are best kept it in the garage when it snows, with or without snow tires. And those who say otherwise are inviting agony to themselves if they keep pushing that concept in the snow.

In terms of getting off the line, I actually tried that with a 250 AWD and a 350 and the 250 AWD gets off the line quicker (only to be smoked by the 350 within an additional second or two).

There is a Road and Track comparo involving the AWD IS that was discussed here before. In that comparo, they also looked at a RWD Infiniti G35 and compared it to AWD Infiniti G35. Since they are identical models, all your considerations about weight distribution, the extra weight etc. would have been accounted for. The bottom line is the AWD outperformed the RWD version for handling and posted better slalom and skidpad times. That I think should be a pretty good example as to how AWD might affect the IS.

Lets Drive

iTrader: (3)

Sure it is. Porsche needs a flagship car that accels in as many areas as possible. They are partial to rear engine layouts and weight biases that see as much as 60% in the rear. So, they accomdate this with a drivetrain layout that best takes advantage of this setup, and that happens to be RWD. Its realistic because its real world.

The GT2 makes about 360rwhp, while I currently make about 350rwhp at a little less than 2,700lbs. I can gaurentee that when you launch a GT2, you're not utilizing the max hp for the first 0-60- you'll see the benefit of more power from the trap speeds after the car has made enough grip to put its full power to the ground. If AWD had any advantage at all, it would be from a dig, but in this case it doesn't. Extra weight is one of the downsides of AWD, therefore using a RWD layout offers a natural advantage of being lighter. Even if you wanted to have power on par with the GT2 in a AWD vehicle, it would still be heavier.

A car with 50/50 power distribution won't have better launch characteristics by default, as it depends on various other factors. Grip strictly depends on tires- applying torque to four wheels is only helpful if you've lost traction with the rear, but that doesn't mean you lose traction by default. Splitting torque between four wheels equals more parasitic loss through the drivetrain, and in the case of the 4S, it loses more hp in this fashion, along with its tranny, than does the GT2. So even if the power was equal on both cars, the AWD would be heavier, and have more parasitic loss through the drivetrain and tranny.

You can accelerate through turns in a RWD car, thats what LSD, throttle and steering control are for. You just have to pay closer attention to what you're doing, as you can encounter oversteer. You will notice though, that AWD cars which are able to handle well through corners, depend more on their torque split being rear biased...leading to a characteristic of RWD. Otherwise, they see a nice bit of understeer themselves. As for flooring it full throttle uphill in the rain...I don't see that as a benefit, but if your tires are up for it, why not?

Traction loss is not because of RWD, its because of the type of tires. AWD only 'gains' traction because its trying to operate with a bigger contact patch (combination of 4 wheels), that can be made useable by the limit in power to the ground. Take funny cars for example, making quad hp numbers, and you'll see that they are all RWD. I digress a bit, but the case of the GT2 speaks for itself.

tqlla3k

iTrader: (1)

That is not a valid comparison for this thread.
1) The weight of the motor is over the rear wheels.
2) The contact patch is probably 50% greater than the contact patch of the IS250
3) The tires are probably a lot more expensive than the ones included on a 250 or 350.
4) The Weight diff between an AWD carrera and an RWD Carrera is only 150 or so lbs. So the 400lbs weight loss of the GT2 is from more than just being AWD.

Yeah, good tires can make up a lot for RWD Drivetrain... but in this case, its just not realistic. We are talking about a car with 225s or 255s in the rear

As far as accelerating through a turn, yes it can be done in RWD on the street, however,
1) Feathering the Gas is not the same as hitting full throttle
2) LSD and traction control limit your acceleration
3) You had better be good or you will end up in a ditch, IE you are much safer in an AWD car.

yon

Balderdash. The wife's RWD SportCross is just dandy in the snow, thank you very much. Between the Blizzaks for grip, Snow Mode to keep the torque down, and Traction Control to keep the tail under control, it works out just fine.

And as I've soapboxed before, the big problem with slippery conditions is usually steering and stopping, where AWD gives no advantage. In my opinion, the often-hyped-up advantage of AWD in the snow is pretty marginal. If AWD was the only reason the car was able to get moving, then you're going to have a nasty surprise when you go to steer and stop!

al503

I've been on the G35 and Z forums for the past 4 years. The consensus on those boards is that a good set of winter tires will perform well enough for most purposes. I'd take a RWD having traction control, etc., with snow tires over an AWD car with all season. In a perfect world, the AWD with snow tires would be the way to go. But a RWD car with snows should be more than adequate.

If you're willing to do a high rpm launch or brake torque, then I might agree that there might be a slight chance that the 250 would launch a little quicker. Otherwise, from a standing start, my $ would be on the 350 in good conditions.

1. Apples and Oranges: IS250: 204 bhp and 175 lb/ft of torque. The AWD G has 280 bhp and 270 lb/ft of torque. With the G's additional power, it can overwhelm the rear tires to a much greater degree than the 250 can. As I mentioned above, the benefits of AWD become more apparent on higher HP cars that have the ability to overpower their rear wheels.
2. On a tighter, more technical track/autocross setting, the AWD car can and often does have the advantage where the front tires can pull them through the corner, which is exactly why it helps in the tight slalom and skidpad. The Subie STI and Mit. EVO come quickly to mind.

However, on a longer, less technical track, the RWD cars usually have the advantage.
3. Weight: Weight is the enemy. The effort and expense that racing teams go through to reduce the weight of the car and it's components is probably in the top 2 considerations. The AWD hardware adds weight period. This tranlates into additional wear and tear on almost EVERY suspension, braking, and driveline component in the car. Accelerating and decelerating 1 lb is easier than accelerating and decelerating 1.1 lbs. I can't argue against the laws of physics. Can you?
4. Weight distribution: The AWD components increase the weight where you don't want it for handling purposes. How many cars do you see in any racing circuit that has more weight over the front tires than the rears? All other things being equal, a car with a 50/50 weight distribution will probably handle, brake, and accelerate better than a car with even 51/49 (F to R) distribution.

Finally, there's a reason why you see the AWD Audi's (in the german racing series) passing several cars at the start.
1. they have the power overcome the inherent additional inefficiencies inherent to AWD, at the same time,
2. you have to ask yourself why they're not in the front row to begin with.

al503

Thank you, Sir.

Lets Drive

iTrader: (3)

Thats because I wasn't comparing it to the thread. My post regarding the GT2 were in response to al503, and there was mutual agreement with regard to what we were talking about.

Hence why I said the main difference is in the drivetrain. Between the AWD and RWD IS250, the difference is some 200+ lbs, yet according to lexus, the RWD version makes it to 60 quicker (can a novice driver make it to 60 quicker in the AWD, sure...but that doesn't mean its faster). Between the the Carrera S and the Carrera 4S, they have different weights, yet the same power, while the 0-60 and other performance specs are still very much similar...meaning in a sprint to 60, AWD is not the dominant force its made out to be. You're not going to see dramatic decreases in times until the amount of weight difference is more significant than 150lbs...which in a good bit of cases, could be something as simple as the weight of a driver.

Not realistic? You can't dismiss tires in any way when talking about cars, especially in 0-60 performance...its the only portion of the vehicle touching the road. Tires don't 'make up' for RWD, they work in unison with it, just as they do with the rest of the car. You choose tires carefully, just as you do inflation PSI, just as you pay attention to temperature rating, speed rating, wear, etc. By the logic you're using, running similar tires on an AWD vehicle would make things 'fair', but it does not automatically mean an AWD car would then perform better from 0-60. Keep in mind that tires also add weight, which is why some cars run skinnier ones in the front. Weight shifts rearward when you accelerate, while the front gets lighter, meaning AWD is not making the most out of the front wheels if it is running a 50/50 torque distribution as you described above. This is why cars like the Nissan Skyline (save for the R33) don't run a 50/50 (or otherwise), torque split 100% of the time, instead sending torque to the front wheels as necessary when or if the rear wheels have broken traction (its a form of traction control really). RWD is not a disadvantage when launching a car, its a great thing, but as with the rest of the car, relies on the tires to get the most out of the performance- the same goes for AWD.

Accelerating though turns can be done on the track too...I've seen it dozens of times myself, you just have to watch your entry and exit speeds as you do with any other technique. Also, you don't go full throttle into most turns, just as you don't apply max brake pressure simply because you have ABS or some other brake distribution aid. Throttle control is important to driving technique, sometimes you jab the throttle more to rotate the car, other times you don't, but simply because you don't go full throttle, does not mean its a 'disadvantage'. Full throttle is not the fastest way through a corner. BTW, AWD cars going full throttle through a turn can just as easily see an understeer situation depending on the torque split and suspension, in combination with the tires ability to grip the turn. The 'ideal' AWD setup still runs a rear wheel torque bias for a reason.

This is not true. Mainly because AWD vehicles also have LSDs, and an LSD aids in lateral acceleration, as has been proven for years now. Traction control depends on the amount of slip allowed, and how advanced the technology is. For most road going vehicles, its very restrictive because its built for safety and not max performance. However, take a read below on the uses of traction control regarding formula one cars.

http://www.formula1.com/insight/tech...fo/11/462.html

I see what you're saying, but if anything this is a stretch. You can end up in a ditch in ANY car... Like everything though, you have to be a capable driver, or else you shouldn't be driving beyond your limits. AWD may be more stable, but by that logic, I could also say that FWD is most predictable. If you want to say AWD is 'safer' for the novice driver, then so are traction control and stability management systems, as found on the IS 350. Safer is not faster however, and RWD is the dominant layout for most dry performance racing.

Lets Drive

iTrader: (3)

Short and simple, but very true.