Repair-It

This is an interesting write up. (Car and Driver Link when available)

Drive 3 race cars on public roads, ding them for being harsh (I understand that these cars will be driven on roads for 95% of the time at a minimum).
But they also docked the Corvette for not having a back seat.

They claim that the Porsche is the best car but not worth 2 Corvettes, but with that logic, the Vette is the best car in the world because: Is the Veyron 10 times better? Are Ferraris 4 times better?

Then you get into specs:
The Corvette has the best Skidpad - 1.15 vs. Porsche 1.07 and GT-R 1.02
The lowest weight: 3530 vs. Porsche 3590 and GT-R 3894
Most HP:650 vs. Porsche 560 and GT-R 600
And Slowest Everything
0-60: 3.3 vs. Porsche 2.5!!! and GT-R 2.9
Quarter: 11.5 sec @ 125 vs. Porsche 10.6 @ 130!!! and GT-R 11 @ 128


More to come.

The Z06 completely messes with my mind. Ready? Here it is.

The engine is the least impressive thing about the car.

There. I said it.

The old ZR1 trapped almost 130. So GM already had that in 2009. This one would likely get walked by the ZR1 on the street but lose on the track.

Now that I got that off my chest, we can understand that what this car lacks in sheer HP/weight ratio (I mean RWHP not rated HP) it makes up for in a world-spanking chassis. Look at the braking performance. Hell look at the slalom performance.

If they could just sort out the cooling situation, I think it would take even a Nismo GT-R on most tracks.

I have to respectfully disagree with the cooling comment. Yes, getting the cooling straightened out would be very good. That isn't why it isn't putting the power to the ground though.

This car is losing to the Porsche which weighs 60 lbs. more (sure not a big difference) but 90 HP less, that is a big difference when combined with the weight difference.

This car is losing from 2.5 to 3.3 seconds to 60. If you do the percentages out, the difference is an extra 33%, that is a lot. Sure it is less than a second, but it takes a professional driver to attain a 0-60 time that is 10% longer than GM advertises (10% of 3 seconds is .3, 3 + .3 = 3.3, which is what they got, on a roll because they couldn't beat that from a stop) I bet real world, the Porsche gets pretty close to 2.5 with any average person, because it is automated, and the Corvette would burn tire and get like 5 seconds by that same person, so I guess the Porsche is twice as good. (I may have started an all out war here)

Back on point, the car isn't losing these drag races due to overheating, it is loosing because it can't get all 650 to the wheels. I bet Traction Control is robbing a lot of HP to launch this thing.

Now for the next thing that will piss everyone off. This car doesn't need to be mid engine, it "just" needs AWD to get off the line. I think that is the real reason it is losing. So they need to engineer the car to be AWD and handle well. Maybe they do a setup that is AWD to get off the line, and then it is mostly RWD for handling purposes after launch.

I get that it sucks to carry the AWD drivetrain if you aren't really using it, but maybe they use it to detect what front wheel needs to pull into turns also, and dynamically send power to that wheel like the NSX is supposed to do with electric engines. Maybe GM can engineer a mechanical solution.

billgiacheri wrote:This car is losing to the Porsche which weighs 60 lbs. more (sure not a big difference) but 90 HP less, that is a big difference when combined with the weight difference.

First, the 911 does trap an additional 5mph despite the HP deficit and weight disadvantage. That has nothing at all to do with traction. It's a combination of the aero package and the way German OEMs rate HP. The Porsche is probably making WELL over 600hp SAE.

So there are many things at play here.

Horsepower and weight generally manifests as trap speed. This car should be trapping a bit higher than 125. Traction has nothing to do with it.

What traction DOES have to do with is the 1/4 mile ET, 0-60 and so on. I don't personally care that this car can't dip into the 2's 0-60.

The max aero package is also effecting 1/4 mile times.

If this car was as fast as the ZR1, but with the chassis upgrades, it would do just fine with RWD, despite the lag in 0-60 performance.

I can show you AWD cars that produce great 0-60 times but aren't anything special on the track. By the way, the Corvette gets the 0-60 time the old fashioned way. Either modulating the throttle in the automatic or slipping the clutch and working the throttle. The GT-R and 911 Turbo 0-60 have little at all to do with driving. Not sure why you want that. Would it be even cooler if the cars were 100% automated and both people pushed the "launch" button at the same time (not too far from the truth, aside from steering)? Do you even need to be in the car at that point?

Good point about the Porsche probably having more HP, I didn't realize that they aren't measured the same in this day and age. You would think Car and Driver would Dyno the cars if this is the case for equal stat playing field.

Also:

I can show you AWD cars that produce great 0-60 times but aren't anything special on the track.

I agree, and I think this has to do very marginally with the added weight, but more to do with all wheels pulling around a turn causing understeer (understeer - is that right? I get these mixed up even though it should be obvious, understeer means you turn and the car doesn't turn as much as you would want, and the car doesn't turn in enough. RWD is the opposite, causing the rear to slide out and the car turns in more than desired)

That is why you would need an engineered solution that allowed for all of the wheels to not pull during turn in, but specific wheels to perform the turn without over or understeer. I believe Acura engages the inward wheel in the front to pull the car through the turn, while still powering the rear wheels.

Do they have AWD Dynos?

Yes.

I'm never going to lust over AWD + DCT + turbo, and that's partially because much of the internet thinks that's the only combination worth talking about. Hopefully, the Corvette doesn't turn into that.

Of the three, I'd take the turbo first, hands down (turbo V8? I could live with that). Next, I think I'd take the DCT (turbo V8 mid-engined C8? I could see that). AWD is last for me. I just don't associate it with performance even though most people definitely do. 0-60? Yeah, launched abusively. WRC? Sure. But I guess there's something a little annoying with a car where the driving style is put the throttle to the floor before you've finished turning.

Speaking of the GT-R, that shit is getting old. The way they describe it almost reminds me of a 3rd gen F-body. If you had a smooth track and/or didn't know anything about handling, it probably feels really good (flat cornering, like HP/L, is not the be-all end-all of performance). Chassis compliance (that doesn't induce stability control over a bump), like engine flexibility with an engine in a milder state of tune, is actually very helpful when trying to wring max performance from a vehicle.

I agree that a turbo shouldn't be a big deal if the Z-06-07 has a supercharger already. Both are forced induction, but a turbo is more efficient.


Going back to a mechanical solution to the crappy handling in turns with AWD.

If the front wheels power was based on the position of the front wheels/steering wheel, that might work to make AWD a performance setup.

If the wheels are straight ahead, all 4 wheels get 25% power - best drag/0-60/1/4 mile situation.

as the steering wheel is turned, if the wheel is turning left, gradually, power is transferred to the left front wheel, and the rear wheels, so maybe left front 25%, rear 75%, this percent would vary based on angle of the turn, peaking at maybe 75% of the degrees to the left.

So, power would disengage from the outside front wheel during a turn at a certain degree. Obviously tests would have to be done to determine best performance.

I think variations of your idea have already been done. It's difficult to make everything feel natural. Kinda like the active anti-roll systems that make a car feel like it is cornering flat. It's artificial and doesn't help the driver determine anything about what the chassis is doing, or about to do.

The new fancy feature with the C7 is an electronically controlled limited-slip differential. That doesn't mean fake posi (like so many OEMs are guilty of, both with RWD and FWD), but a real limited slip. The new part is that the computer can control to what degree the limited slip is "engaged."

From a mechanical solution standpoint, I very much like planetary gear differentials.

http://en.wikipedia.org/wiki/Limited-sl ... Geared_LSD

I have one in my Caprice (Detroit Truetrac, now owned by Eaton).

How does this work into it?
https://www.youtube.com/watch?v=F5F18o8xayA