MT Article ZR vs Porsche GT2 RS w Interesting ACR Comments

[Pappy]

https://www.motortrend.com/cars/pors...on-power-down/

Interesting Motor Trend article. Pobst didn't like the ZR1, but loved the Porsche. There are a couple of very interesting comments by Pobst regarding the Viper, and in particular his observation regarding the ACR's ability to put power down. Credit where credit is due.

Edit: Here is the quote about the ACR, just in case you're not interested in reading the whole article to find it:

"The Z06 was always a wrestling match to drive at the limit on track, and the additional 100 horsepower makes it even more so, except that the ZR1 is much improved at high speeds. The situation reminds me a lot of the Viper: It's always been a real handful, and its engineers seemed to just accept it as part of the car's masculine personality—until they miraculously, completely cured it with the ACR model in the last year of production."

Pappy

[Arizona Vipers]

Pretty cool an american car is coming very close to Porsche's best still these days, even with that Porsche costing $200K MORE than the ZR1!
Chevy should have done the intercooler spray setup like Porsche

[512BB]

GM develops everything on the cheap so forget about fine tuning with water sprays, etc. The basic design of the C7 is little different than the C6 (same leaf spring, etc.) but it's 2 inches longer wheelbase. Hence, the C7 got better in some corners, but suffers in others. It was specifically tuned for VIR for the lightening lap, so I fully expect it to be slower in most if not all other tracks than the Viper and/or the GT2 RS. I expect the ZR1's Nurburgring lap times to be in the low 7's. The Z06 was 7:10 (though not officially released by GM).

[Pappy]

Don't miss the point that Pobst is trying to make. The big problem with the ZR1 is not a lack of power (although the nannies dial it back in several scenarios and it is too heavy), it is that the suspension won't let it put the power to the ground. The Viper used to be like that - my 2000 GTS with only 405 hp would get out from under me at the drop of a hat. The ACR just doesn't do that, and it is not overburdened with excessive nannies like the e-diff. Pobst implies there is a problem with the rear suspension geometry, and he is probably right. GM probably gave away too much performance in favor of street manners for the weak and mild - spring rates come to mind. Out of curiosity, I have suspension plots of my C6 Z06 (which doesn't put the power down very well either) and I will plot the ACR's geometry to see if there are significant differences (roll center, anti-squat, spring and sway bar forces, etc.). I am more than casually curious as I am finishing the build on a high horsepower, light weight track car with an IRS. The multi-link IRS is, at this point, very adjustable, so after accounting for weight and CG differences I will run a suspension program using ACR geometry to see what it yields.

Pappy

[Nine Ball]

The entire C7 development was a shoestring, budget restricted exercise. They were developing it during the government bailout, at half of their normal budget. The C6 program was such a great jump over the C5 platform, the C7 platform actually had less development than the C6. They just threw more fancy amenities at it, in attempt to dress things up more.

I have two friends that were engineers on the C6 and C7 platform. They even said the C6 was just a better overall car, for the value it delivers. C7 interior and electronics got upgraded, but not much else.

[512BB]

Don't miss the point that Pobst is trying to make. The big problem with the ZR1 is not a lack of power (although the nannies dial it back in several scenarios and it is too heavy), it is that the suspension won't let it put the power to the ground. The Viper used to be like that - my 2000 GTS with only 405 hp would get out from under me at the drop of a hat. The ACR just doesn't do that, and it is not overburdened with excessive nannies like the e-diff. Pobst implies there is a problem with the rear suspension geometry, and he is probably right. GM probably gave away too much performance in favor of street manners for the weak and mild - spring rates come to mind. Out of curiosity, I have suspension plots of my C6 Z06 (which doesn't put the power down very well either) and I will plot the ACR's geometry to see if there are significant differences (roll center, anti-squat, spring and sway bar forces, etc.). I am more than casually curious as I am finishing the build on a high horsepower, light weight track car with an IRS. The multi-link IRS is, at this point, very adjustable, so after accounting for weight and CG differences I will run a suspension program using ACR geometry to see what it yields.

Pappy

Corvettes use leaf springs front and rear, at times and especially when both wheels hit an expansion joint or a bump together, the rear suspension acts like a solid axle and throws the car off (watch Mark Reuss' crash as an example). This suspension design is super cheap and had some benefits about 30 years ago, but it's a detriment at this point. However, their resident race driver, tester, engineer Jim Mero loved the way that felt and given the lack of development dollars they have kept the same general set-up for decades! Essentially the leaf spring causes the suspension to NOT be independent.

[512BB]

The entire C7 development was a shoestring, budget restricted exercise. They were developing it during the government bailout, at half of their normal budget. The C6 program was such a great jump over the C5 platform, the C7 platform actually had less development than the C6. They just threw more fancy amenities at it, in attempt to dress things up more.

I have two friends that were engineers on the C6 and C7 platform. They even said the C6 was just a better overall car, for the value it delivers. C7 interior and electronics got upgraded, but not much else.

Yup, have heard the same things. Sad but true and to be honest there are no "real" engineers left at GM and in particular Corvette. They are basically Program, Project Managers with most of the development and engineering outsourced.

[serpent]

I'm curious, if Dodge was able to work out the power of the Gen V v10 (645/600) and the car was able to grip, why didnt GM make their car (c7z) have grip as well? Was it the extra torque in the LT4 (650tq)?
Does it have to do with engine being further back in the Viper and basically the driver is sitting near the rear wheels?

I wonder at what power does the viper need to bring it to z06/zr1 level of losing grip at the rear wheels when road course driving.

[Snakebit10]

Looks like Dodge did more with their shoestring budget than Chevy did. Could be too that they were really concentrating on the mid-engined C8 so the C7 was basically the red headed stepchild once that got green-lighted..

[512BB]

Looks like Dodge did more with their shoestring budget than Chevy did. Could be too that they were really concentrating on the mid-engined C8 so the C7 was basically the red headed stepchild once that got green-lighted..

The Viper was engineered to a target cost with the engineers free to do what they wanted within those costs and one item within the mission was to make it a halo car. At GM and even for the Corvette the accountants dictate what engineers do as the Corvette is not viewed as a halo car but a purely P&L center. As such accounting dictates the components that engineers they are allowed to use, etc. (I read my statement and it sounds funky, but hopefully the meaning gets through).

Hypothetically speaking, let's say the chief engineer at Corvette has to meet a target of $8K under the hood components, he/she decides to stay within that budget but make the engine bay look really nice to compete with Viper or the Europeans. Let's assume the cost for this is $300 for parts and labor. Accounting in this case allegedly over rules the chief engineer and the engine compartment looks like crap! There are many "hypothetical" examples like this.

[BlueAdder]

If you haven't noticed, in the specs they have the lap times...
Z1 1:32.x
GT2: 1:28.30 (which beat the ACR a some 30ms)

I was expecting the Chevy to do a bit better than that to be honest.

[Snakebit10]

512BB appreciate the info. i'm definitely not versed on the ins and out of that side of the business.

BlueAdder that lap time is terrible in comparison to the competition and what the ZR1 supposed to represent. Barely faster than a TA, Z06 and .1 GT3 RS at Laguna. I wont be surprised if the .2 GT3 RS wipes the floor with it too. From what I've been reading the .2 seems to be ACR fast.

Another "ouch" in the article in regards the ZR1 is what Randy said about the ZR1's overall performance. Quote: "What I see in the Corvette ZR1 is potential; what I feel is frustration. The car is outrageously good at so much and comes tantalizingly close to providing supercar performance." That is insane conclusion to come to about a car packing aero and 750hp. Sad to see the last of the front-engined ZR1s go out like this.