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All-wheel drive vs. mid-engine performance

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Old 03-24-2017, 07:46 PM
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Stingray222
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Default All-wheel drive vs. mid-engine performance

I am curious which would make a bigger difference to a Corvette's acceleration and track performance, all-wheel drive or a mid-engine layout. My take is that the Z06 is clearly not low on power at any point in the RPM range as compared to other cars in its peer group but rather low on traction. I notice that on my Z06 where it is a challenge to avoid wheel spin from a standing start.

So my question is would a 650hp front engine all-wheel drive or 650hp mid-engine real-wheel drive Corvette offer the best balance and performance?
Old 03-24-2017, 08:14 PM
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Maxpowers
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Depends on conditions. As as a former Audi S5 V8 owner I loved the AWD with cooler tires / temps as a DD. In perfect conditions which rarely happens a mid rear wd could do well on paper.
Old 03-24-2017, 08:21 PM
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fsvoboda
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Originally Posted by Stingray222
So my question is would a 650hp front engine all-wheel drive or 650hp mid-engine real-wheel drive Corvette offer the best balance and performance?
I would suspect that for road use the AWD traction would be superior in many conditions. I don't know enough of the subtleties of track use to judge very well but suspect that rear engine might be best there.

Old 03-24-2017, 08:27 PM
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HPT
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How often is standing-start traction/acceleration relevant to track performance? AWD does not make a car go around a track faster. If you are racing on gravel or snow, then sure...AWD is preferred.
Old 03-24-2017, 08:32 PM
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Gary '09 C6
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suspect an AWD layout would also have added weight to contend with...might be a disadvantage on track (assuming all else equal)
Old 03-24-2017, 08:57 PM
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\Boost Monkey/
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Depends on better performance for what?

Too many other variables to clearly say one is better than the other.
Old 03-24-2017, 09:02 PM
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Originally Posted by Gary '09 C6
suspect an AWD layout would also have added weight to contend with...might be a disadvantage on track (assuming all else equal)
Not just that, but traditional understeer. Newer systems now cope and shift power but the only real advantage is powering out of a corner, in which a RWD with proper tires and aero/downforce can do just the same.
Old 03-24-2017, 09:06 PM
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MACE_Hardware
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I would like AWD myself.

It's difficult to package the differential components for AWD with the current front engine layout, but it would integrate pretty well with mid engine.

I won't be all hot for a RWD mid engine Corvette. When they fit AWD in 2020, then I'll be buying.
Old 03-24-2017, 09:40 PM
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Lacquer
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AWD cars like the GTR rely heavily on computers to regulate the power transfer between front and back. In most performance applications, the GTR is really a rear wheel drive car carrying added weight. AWD without computers is at a big disadvantage in track performance to a ME rear wheel drive car. With Corvette using computers for rear wheel drive cars, the advantage of front wheel drive being added for traction in a few very rare conditions is not justified by the added weight. My .02
Old 03-25-2017, 09:31 AM
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Stingray222
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Thank you for the replies. Going in I had thought that AWD would have had a distinct advantage in most applications but it looks like there is much more to consider than that. I suppose the ideal would be an AWD mid-engine Corvette but that is likely a few generations down the road.

One last question...All other things remaining the same, how much would adding AWD to a current Z06 affect 0-60 and 1/4 mile times. For example, if the current version is 2.95-3.2sec would we be looking at shaving two or three tenths of a second?
Old 03-25-2017, 09:41 AM
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vbdenny
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After owning all kinds of cars and trucks I will say this. I am a V-8 (or larger) front engine, rear wheel drive lover. Why improve on perfect?
Old 03-25-2017, 09:52 AM
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Our C7's have an almost perfect 50/50 balance between front and rear. With the right person behind the wheel as shown in the race series in which the Corvette competes....we are a car to be reckoned with. On a side note...personal experience....I hooked up with a ZL1 Camaro with over 700hp (yes he wasn't stock) a friend of mine and just for fun we hit it on a roll at 30mph....I think he is still there spinning his tires..(sorry Caesar) while I was Gone!!!
Old 03-25-2017, 09:54 AM
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AWD is good for 0 to 60 and all that plus it works well in weather (not cold conditions with summer tires). The thing about canyon roads you have no rear end steering when sliding around turns. All you have is push (understeer) which is just scary.
Old 03-25-2017, 09:57 AM
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Originally Posted by obxchartercaptain
Our C7's have an almost perfect 50/50 balance between front and rear. With the right person behind the wheel as shown in the race series in which the Corvette competes....we are a car to be reckoned with. On a side note...personal experience....I hooked up with a ZL1 Camaro with over 700hp (yes he wasn't stock) a friend of mine and just for fun we hit it on a roll at 30mph....I think he is still there spinning his tires..(sorry Caesar) while I was Gone!!!
Same issue for hellcats, why they can be beat at the strip by much lower power cars.
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Old 03-26-2017, 12:26 PM
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KemahGT
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You are ALWAYS gonna have a weight transfer to the rear in a hard launch. AWD should be an advantage if you are able to get that power distributed between all four tires in a situation where power tends to exceed traction.

You are nearly doubling the contact patch on acceleration. Not rocket science. The GTR launches hard. The GMC Typhoon and Syclones did as well. I'll take AWD any day of the week if the price is right.
Old 03-26-2017, 02:55 PM
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Bill Dearborn
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Originally Posted by KemahGT
You are ALWAYS gonna have a weight transfer to the rear in a hard launch. AWD should be an advantage if you are able to get that power distributed between all four tires in a situation where power tends to exceed traction.

You are nearly doubling the contact patch on acceleration. Not rocket science. The GTR launches hard. The GMC Typhoon and Syclones did as well. I'll take AWD any day of the week if the price is right.
You hit the nail on the head when you said weight distribution but you cut things a little short when you talked about straight line acceleration. Under hard straight line acceleration the tire contact patch increases in the rear and decreases in the front due to weight transfer. An AWD system must redistribute torque based on the reduction grip due to that transfer.

As we learn in HPDE Classrooms there is something called the friction circle for tires. The friction circle varies in size depending on weight transfer and represents the maximum amount of grip a tire can provide for turning, accelerating or braking or a combination of turning with one of the other two. When driving out of a turn a RWD car applies power to the rear wheels which limits how much grip they can provide for cornering. The front wheels can provide all of their grip for cornering but if the car is driven into the corner too fast they don't have enough grip and the car under steers, but if the driver slows down to the capability of the front tires then more power can be applied to the rears and the car exits the corner faster. Front wheel drive cars do everything with the front wheels and as power is applied to accelerate out of a corner much less grip is available to turn the car. Thus corner exit speeds are limited due to under steer unless something is done to counteract it. A lot of times drivers will apply the rear brakes which reduces the steering ability of the rear tires thus inducing oversteer that compensates for the understeer. Now we get to AWD which has all of the benefits of RWD and FWD and every one of their detriments. It takes a sophisticated controller to vary the torque delivery from front to rear as the car is turning and then from rear to front as the steering wheel straightens out.

It gets more sophisticated when you throw in the added complexities of the outside front wheel having the most grip in a corner with the outside rear wheel having the next highest level of grip and then depending on suspension either the rear or front inside wheels having the least amount of grip. I have seen cars pull inside front wheels off the ground in hard corners and I have seen other cars pull the inside rear wheels off the ground in hard corners. All of this varies as the driver then varies the steering and throttle inputs.

Bill

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