[Idaho2018GTPremium]

I am curious everyone's thoughts on why a stock ZL1 seems to not maintain its acceleration rate at 130+ mph compared to other similar cars.

For example:

2017 Camaro ZL1 A10 per C&D: 60-130 in 9.0 seconds (MT was 8.9 sec, for comparison).
2018 Mustang GT A10 per C&D did 60-130 in 11.0 (MT was slower, for comparison)

ZL1 is 22.2% quicker than the GT (comparing the better GT to the slower ZL1 time).

ZL1, same test, does 100-130 mph in 5.0 sec, while the GT did 100-130 mph in 6.3 sec. For that split the ZL1 is 26% quicker. Better than the 60-130 test because the ZL1's higher power is more effective at resisting the increase in drag at higher speeds.

Nevermind that the GT is closer to the ZL1 than it should be given the lbs/hp ratio (6.0 vs 8.3 = 38% difference), which I think is explained by a slight underrating of the Gen 3 Coyote and the extremely flat high end hp curve, take a look at the 130-150 mph times:

ZL1: 6.0 sec
GT: 6.9 sec

Now, this is only a 15% difference, much closer than one would expect and the GT is closing the gap; generally more powerful cars just continue to separate at a quicker and quicker rate as speeds climb, i.e., normally, I would expect a 30% improvement for the ZL1 over the GT, not a drop to only 15% quicker.

I have seen this with other cars as well, where they seem to start to close the acceleration gap at speeds above 130 mph with the ZL1.

One more example: GT500 (base), again, per C&D:

ZL1: 60-130 = 9.0
GT500 60-130 = 7.6
GT500 = 18% quicker

ZL1: 100-130 = 5.0
GT500 = 4.1
GT500 = 22% quicker

ZL1: 130-150 = 6.0
GT500: 130-150 = 4.1
GT500 = 46% quicker - a much larger gap compared to what you would expect given the 100-130 splits.

The ZL1 is falling on its face at 130+ mph. Why?

I have a couple of theories but figured I'd ask the wider audience.

Theory #1: LT4 IC HEXs are undersized and it heat soaks after a certain amount of continuous full throttle and pulls timing as MAT rise. In this case, after about 12-13 seconds of WOT. Dodge and Ford may have more effective intercooler HEXs, reducing that effect, and the GT doesn't have the issue.

#2: Car shifts into 7th (1:1) and with 2.85 rear end, kills acceleration.

#3: While the magazines adjust for DA, maybe the ZL1 was tested in hotter air, and the GT500 and GT were tested in cooler weather. They can correct for DA for the times, but that doesn't account for the lost timing at high MATs due to high ambient air temps. The LT4 pulls a lot of timing as MATs climb.

#4: Some combination of the three above (or all of them)

I've ruled out drag because I would think the GT500 has similar drag to a ZL1.

Thoughts?

[avalonandl]

Your splitting hairs, ZL1 w A 10 is still faster.

[TRZ06]

What are the headwind & tailwind components for each test you listed.

Air resistance increases expeditionary as speeds increase and having a good headwind or tailwind can either help or hurt those numbers.

What is the CO of drag on all the cars listed as well?

You really have to dig beyond car data as speeds increase, aerodynamics play a huge role as well.

[Idaho2018GTPremium]

Originally Posted by TRZ06

What are the headwind & tailwind components for each test you listed.

Air resistance increases expeditionary as speeds increase and having a good headwind or tailwind can either help or hurt those numbers.

What is the CO of drag on all the cars listed as well?

You really have to dig beyond car data as speeds increase, aerodynamics play a huge role as well.

Car and driver conducts the tests in both directions and then averages the results. That negates the head wind/tail wind issue.

Obviously aero plays a role, but the GT500 likely has similar drag to the ZL1, close enough not to show such a drastic difference between 100-130 and 130-150. Aero doesn’t explain it, there’s more to it than aero differences.

[Stephen12ZL1]

my previous '17 and current '21 are about the same... after 130mph they are pretty dead feeling. 7th gear in the 10 speed is a large drop off. I feel 7th should be steeper and 8th should be 1:1. A stock GT500 leaves me on the straight a bit and it is definitely worse above 130mph...no worries as I catch up in the braking zones.

[Flowtie1]

I will put an M6 against the A10 in anything except a drag race.

[Z OH 6]

HP matters when accelerating at high speeds. The Hellcat makes 717-797hp depending on which variant you get, and the GT500 makes 760hp, those HP ratings matter as the car is trying to overcome drag. I'd like to see a modified 700whp ZL1 compared to a Hellcat Redeye and GT500 in some high speed tests.

[FoundNemo]

Originally Posted by Flowtie1

I will put an M6 against the A10 in anything except a drag race.

All cars equal and traction/weight out of the equation for drivers/passengers, M6 will lose every time unless A10 driver is manually shifting and or delayed. But, M6 is better driver car I agree. A10 stays in powerband more efficiently.

[TheRealJA105]

Just wait for Mr. Whole's brilliant incoming answer. He races 180mph+ all the time so he will tell you everything.

[jdsgn]

Its most likely a combination of extra down force compared to the 5.0, the extra RPM the 5.0 has extending those gears before hitting 7th, extra rolling resistance of the wider tires and wheels on a ZL1 etc.... A friend with a stock Zl1 did 60-130 in 8.4 on a 90* day so magazine test, while accurate for that particular car on that particular day are not always a true representation of their capability.

[Jaxcam02]

Originally Posted by Stephen12ZL1

my previous '17 and current '21 are about the same... after 130mph they are pretty dead feeling. 7th gear in the 10 speed is a large drop off. I feel 7th should be steeper and 8th should be 1:1. A stock GT500 leaves me on the straight a bit and it is definitely worse above 130mph...no worries as I catch up in the braking zones.

Dead after 130 is not my experience with both my 18 1ss 1le and the 17 ZL1. I still felt plenty of pull left until about 160. I could be hazy on memory but I remember getting to 160 pretty damn quickly.

[Camaro1973]

Add some power and you’ll be easily into
The 6’s and 5’s 60-130

[infinitereality]

For what it's worth I took a 60-165 video from Mexico and edited down to 60-130. It came out to 8.8s including the gear drop in there.

https://youtu.be/gSb_SttJfhU

[Idaho2018GTPremium]

Here's more examples, info. from the test published today by C&D on the M3 Comp vs Alfa Giulia:

'21 M3 Comp:
60-130 mph: 9.3 sec (3% slower than ZL1)
100-130 mph: 5.2 sec (4% slower than ZL1)
130-150 mph: 5.5 sec (9% quicker than ZL1)

'21 Alfa Giulia Quadrifoglio:
60-130 mph: 10.3 sec (14.4% slower than ZL1)
100-130 mph: 5.7 sec (14% slower than ZL1)
130-150 mph: 6.5 sec (8% slower than ZL1)

The ZL1 should be getting quicker and quicker compared to these lower powered cars as speeds climb, not as in this case noticeably slower than an M3 Comp 130-150 mph. And the Giulia should not be closing the gap vs the ZL1. Obviously, with the M3 Comp running 1/4 mile in 11.6 @ 124 mph it is a lot more than 503 crank hp, but the ZL1 is quicker below 130 mph, yet slower above 130 mph.

I might chalk this up to the one test by C&D having a ZL1 that was a bit slow, but MT ran the exact same time and trap speed (11.5 @ 125 mph as C&D, however w/ 91 octane), and I noticed the same large drop off above 130 mph in the ZLE A10 test by C&D (vs. the GT500 and Redeye in 2019). Again, aero can't explain it because the GT500 CFTP has a large wing and aero bits as well, and was MUCH quicker above 130 mph than the ZLE. More so than the 110 hp Delta suggests.

Anyway, I'm still sticking to my theories #1 and #3 above. I think it's a combination of undersized HEXs that can't keep up for long WOT applications + hotter ambient air testing conditions (can't make up loss of timing with DA corrections) + subsequent timing loss = slower at the end of a long WOT pull.