C7 Z06 vs. Nismo GT-R

[dbk]

Cliffs -

Z06 has more power, less weight, better brakes, but gets clocked on the track and in a straight line, has a tendency to get too hot after one lap and pull power. Appears that wasn't just internet conjecture.

http://www.motortrend.com/roadtests...015_nissan_gt_r_nismo_comparison/viewall.html

[video=youtube_share;F5F18o8xayA]http://youtu.be/F5F18o8xayA[/video]

 

[Specracer]

Ouch.

 

[djs]

Maybe the Z06 was rushed to market? How could they miss the overheating issue, especially if it's cooking the driver!

 

[BelgianGT]

The GT-R has years of perfecting and the Z06 is all new. Surprised it's not that stable and such a handfull.

 

[Cobrar]

No real surprises there. The comparison is more about the differences in vehicle content, than hot soak from a supercharger. Reminds me of 80's Trans Am races where AWD Audi's competed very favorably against the 302V8 Ford Mustangs/Capri's of the era.

AWD is a significant advantage, as was evidenced by the corner-out acceleration of the Nissan. The track performance data really does help to highlight some of the performance differentials advantaged by the Nissan's selection of AWD, turbo vs, supercharger, and auto shift content deltas.

 

[dbk]

Come on Rex - up 50 hp, up 169 (!) lb ft of tq, down 354 lbs and took it on the chin. AWD is an advantage, but it's not magic!

 

[Cobrar]

We agree to disagree on this. But you'll have to wait just a bit so I can convince you.

 

[Indy GT]

I will come to your defense Rex.....

Hold just a minute. I watched the whole video and I never saw or heard a comment as to overheating of the vette. If I
missed this fact please correct me with the video time stamp where they talk about heat soak pulling power so I can go back and hear what they said. What I did hear them discuss is the increased drag caused by the wickerbill on the rear deck of the vette. For this high speed track the increased drag of the vette's aero package hurt its performance pretty badly. Not surprised by this when you look at the huge wickerbill on the back relative to the inverted wing on the GTR. Much less drag with the wing to produce down force. Although do not know which produced more force. Obviously enough to beat the vette by over a second.

And the AWD certainly helped out of the turns....

 

[dbk]

Heat soak is in the print edition. Said it got hot and pulled power after a lap.

 

[598]

Any chance the GT R was a ringer, or Nissan is under rating the car?

 

[Cobrar]

Thanks, Bill. I'm certain GM has a handle on comprehending any step backs in the ECM, whether it advertises it or not. In fairness to GM, what doesn't get any press in these 'tests' is any real download of the actual data from the car. Example, if you get a hack that drives rpm (repeatedly) through excessive limits, the ECM may retard advance or cut altogether. Then there are the known physics of turbos vs supecharging, where heat sink is a design issue when you run more than a couple of hot laps - with any installation.

Sadly I'm old enough to remember the short lived duration of AWD in TransAm. If you don't believe AWD (esp the newer electronically governed) versions isn't a huge advantage, it will be a learning experience when you get one on a track. The Nissan is heavy, ponderous, et.al., but the drivetrain more than overcomes other weaknesses. The turbo is a clear advantage over supercharging on a race track,particularly when you run more than a lap, just physics. My point is it's an interesting comparison, just using two entirely different solutions to do so.

 

[Xcentric]

Then there are the known physics of turbos vs supecharging, where heat sink is a design issue when you run more than a couple of hot laps - with any installation.

I wonder how McGowan drove a GT with his foot to the floor for a few hundred miles without any symptoms of "heat sink."

As I recall (pls correct me), Vmax of 211.89 was achieved near the end of the run.

I can't believe the Z06 didn't go through extended Vmax testing.

 

[Indy GT]

Heat soak is in the print edition. Said it got hot and pulled power after a lap.

Thanks Dave. I did not read the report, just watched the video you posted.

Actually if you look at the logged graph under your video post-

The performance level displayed by the two cars (acceleration/deceleration which is what is represented) is nearly identical until turn 6.

At this point the GT-R shows a slight edge. And after this point on the track until the start/finish, the track is pretty high speed relative to the track between turns 1 and 6, so the higher drag aero of the vette would somewhat handicap it in this track region.

For regular steel rotors on the GT-R, the vette certainly does not show any braking advantage with those huge carbon/ceramic brakes and lighter weight it has. Decel rates are nearly identical. Pretty impressive for the heavier GT-R with inferior brakes as the video intro discusses. Only exception to this is the approach to turn 9 where the vette breaks early with a faster track out speed but above 120 mph the GT-R out accelerated the vette. (aero drag again as the drag increases with the speed squared) and both cars are at nearly 150 mph before breaking into turn 1. As Rocketmam would say, “Slow in, Fast out….and keep it smooth!”.

There does appear a slight acceleration change in the vette after turn 6 relative to the other graphed acceleration rates, but it is not very much. It is not like it went into limp-mode or anything major like that. Certainly realistic the ECU could have pulled a bit of spark advance due to engine temperature. Same can be said for out of turn 9 as accel rate is a bit shallow, but after 100 mph it again picks back up to the same earlier accel rate.

Interesting.

Thanks, Bill. I'm certain GM has a handle on comprehending any step backs in the ECM, whether it advertises it or not. In fairness to GM, what doesn't get any press in these 'tests' is any real download of the actual data from the car. Example, if you get a hack that drives rpm (repeatedly) through excessive limits, the ECM may retard advance or cut altogether. Then there are the known physics of turbos vs supecharging, where heat sink is a design issue when you run more than a couple of hot laps - with any installation.

Absolutely correct.

The turbo is a clear advantage over supercharging on a race track, particularly when you run more than a lap, just physics. My point is it's an interesting comparison, just using two entirely different solutions to do so.

Agreed. Although I would throw in normally aspirated in the advantaged track configuration as well.:thumbsup

 

[Indy GT]

I wonder how McGowan drove a GT with his foot to the floor for a few hundred miles without any symptoms of "heat sink."

As I recall (pls correct me), Vmax of 211.89 was achieved near the end of the run.

I can't believe the Z06 didn't go through extended Vmax testing.

Gary,

Your Vmax speed quote is correct, and Mark was at continuous WOT all around the track.

Cooling is the issue. At wind speeds of 200+ mph across the radiator the heat dissipation rate is fine for the output power on a Vmax run.

On the track at low speeds delivering the same power levels, in many cases there is not enough heat transfer across the radiator to remove engine heat and the coolant temperature goes up. At some temperature limit, the ECU begins to pull spark (or go into limp mode) to lower power output (and thus heat generation).

Air flow across the radiator is key.

 

[Xcentric]

Bill, Thank you. That makes sense. Was the GT put through test hot laps similar to this Z06/GTR test?

I had the privilege to ride with specracer for several hot laps at Spring Mountain. He had already been flogging his GT for a good part of the day. Temp gauge was in the high normal range.

I guess I'm questioning the part about supercharging heat soak being a design problem with any installation. Theoretical vs. practical. Of course, I know some GT owners have wrestled with overheating when tracking. But others have not.

 

[dbk]

GT chronically overheats but certainly not after one lap. Willow is fairly high speed which mitigates the issue somewhat.

 

[nota4re]

GT chronically overheats but certainly not after one lap. Willow is fairly high speed which mitigates the issue somewhat.

Absolutely correct. The GT has pretty severe heat soak in track applications with a driver capable of pushing the car. This will be even worse with larger blower with more boost and more (hot) mass.

 

[FENZO]

By reading the post I expected to see the Vette get trounced. I guess "Ford" IS in the title of this website. :biggrin One test does not a conclusion make.


I don't believe you.

So the Chevy is less than 2% slower on one track with one driver, but 30% less $$$ for everyone? Not bad. GTR sounds like a blender and looks like someone tried to draw an Aston from memory.

I'd be most concerned about getting hot in city traffic, not 1.4 s with a guy driving who clearly didn't feel comfortable around the bends.

Maybe he kept the revs too high. I noticed my GT would stay cooler on the track when I utilized the torque vs keeping the revs high, was more settled when exiting corners too. Plus manual vs paddles, AWD. Not a huge fan of either, but the Vette still wins IMO.

 

[dbk]

FWIW, Randy Pobst is a professional race car driver that's won the 24 hours at Daytona twice, so it's fair to say he's pretty comfortable behind the wheel going fast. :lol

 

[Indy GT]

Was the GT put through test hot laps similar to this Z06/GTR test?

During the GT development program the GT was tested at a number of different tracks. Certainly longer tracks with high speed portions are more favorable to get high velocity air across the radiator of a SC engined car. In discussions with many of those around during the development program, I have not heard of any overheating or limp-mode complaints. But defer completely to Messrs McGowan, Brooks and Breitenback who were ever-present during car testing.

I guess I'm questioning the part about supercharging heat soak being a design problem with any installation. Theoretical vs. practical. Of course, I know some GT owners have wrestled with overheating when tracking. But others have not.

I am not sure I would classify engine supercharging and attending heat soak as a design “problem”. It is certainly an issue which needs to be addressed in the design of the vehicle. And along with this is how and where the car will be driven. The engine and heat transfer guys can certainly design a system which will work, but much depends on the target driver and his car-use style which varies widely for the general population. The same can be said for how the designers size various air conditioning components. The system should cool the car in summer Arizona heat as well as summer in North Dakota but the sizing requirements are considerably different. You try to balance the needs of all but the outliers may not get a design optimized for the small percentage of use in this category.