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I just sold my ACR-E last month. I had around 8K mi (mostly track) on it. I’m only in my break in period with the ZR1, but I can extrapolate from the 3.5 years I owned my 2015 ZO6/ZO7:
The ZR1 has much better driving feel/feedback than the ACR. The ACR would definitely go where you placed it—but the steering had a bit of a disconnect feedback wise.
The ZR1 is more responsive to throttle input. This is good and bad. It’s fun on mountain roads, but not so great on the track. The ACR was very linear in its power delivery on track—which was very predictable and confidence inspiring.
The ZR1 rides much better on the street.
Not sure about the track comparison yet (as I have not tracked the ZR1), but if it drives nearly as well as the ACR on track—I will be very happy. The only criticism I had of the ACR on track was the tendency for the rear to dance a bit under heavy braking. I never had that issue with my ZO7. Oh, and I never had one heating issue with the ACR—even on 95 Deg ambient days.
Hope this helps!
Last edited by Leadfoot01; 07-20-2018 at 09:02 PM.
Not an on-track comparison - yet - but I did run into this beast in Chandler AZ this morning. Dealer plates. FWIW, I expect the ZR1 to have its greatest advantage with raw power. I get pulled on the straights in the ACR and it will also pull power at anything above 130 degrees IAT. It is subtle, but you can see it in the mph on the straights. I never experienced the tail wiggle during braking that Leadfoot mentioned, but I have seen it with the non-ACR Vipers. The ACR is very neutral and well planted on corner entry, and is easy to get the power down on exit. No drama. The only time I feel a push off the corner is after the Kumhos start to give up. The fronts only last about 2 track days (6-8 sessions) before they are toast. The ACR needs more power, and that is where I expect the ZR1 to excel. I drive the ACR on the street regularly with all the aero installed, but I soften the shocks and raise it 3/4 inch above track height. It is firm, but not too uncomfortable. Here in the 100+ temps I have never seen above 228 degrees oil temp and 216 degrees water temp, on the street or the track.
The ZR1 is a better track car, but much better street car. Better technology, more space and much, much more comfortable (Even with Comp seats).
I've had 7 Vipers, including ACR, twin turbo's, Nitrous Propane injection, etc... they're awesome cars, but it was a purpose built track car, utilizing a dated platform and tech.
These new Corvette's, out perform in every way, can be used comfortably as a daily driver and pick up the groceries (If while out joy riding the Mrs. calls and asks you to stop at the store.)!
I've only owned the C7 Z06 but I got feedback from someone that drove both of them. This guy can drive, the fastest guy on the track when I was in his session. The good news is that the ZR1 runs much cooler than the Z06 while running better laptimes and the ZR1 certainly has a power advantage vs. the ACR-E. The bad news is that the ZR1 cannot put power down anywhere near as well as the ACR-E. Feedback-wise he said the ACR-E is far better as well, especially the brake pedal feel. If this guy says he is substantially more confident in the Viper and quicker, I'm going with that.
Best lap vs. best lap I was a second slower, but I would get closer and closer to the ZR1 as it would heat up. It still has some sizable loss in performance from lap to lap.
The Viper is more planted than a C7Z by far I dont think the improvements to the ZR1 would cover that spread, especially not with the added HP. The Acr feels glued to the track, even one with heads and cam making 700 whp NA. That being said I know some fast ACR drivers and most all of them switch to R7's or Pirelli scrubs. The drop-off in fastest lap from the stock tire to the race tires is minimal to none. Those kumhos are legit as fast as a race tire for a few laps, then fall off and cycle out after a day or two. I think they had some issues with the tires going bad, can't recall exactly.
While I don't think the Kumhos would make the ZR1 feel planted like the Acr, it will result in a significant amount of grip increase for sure.
Last edited by heavychevy; 07-22-2018 at 10:17 PM.
Yeah the difference in downforce produced between both cars is crazy to say the least. ZR1 makes 950lbs @ 202mph top speed vs 1,700 or so for the ACR at 177mph top speed. You can be damn well sure the ACR will feel more planted when its producing (roughly?) 3 times as much downforce as the ZR1 @ same speed. The ACR is a beast of a car. It needs two things IMO: More power and better gearing because 5th gear is...eeeew!
Yeah the difference in downforce produced between both cars is crazy to say the least. ZR1 makes 950lbs @ 202mph top speed vs 1,700 or so for the ACR at 177mph top speed. You can be damn well sure the ACR will feel more planted when its producing (roughly?) 3 times as much downforce as the ZR1 @ same speed. The ACR is a beast of a car. It needs two things IMO: More power and better gearing because 5th gear is...eeeew!
Agree, but even at lower speeds (less than 80 mph) , where grip is mostly mechanical, the Acr is on RAILS! I drove a C7Z on pirelli scrubs and it could still light the tires up on corner exit. The ACR feels like you almost have to try to break it loose. The ZR1 should completely walk away on the straights though. The C7 chassis accels at early corner (turn in - apex) speed. If you use it properly you shouldn't have a lot of issues staying in touch with the Viper.
Why does the aero significantly assist braking from 60mph!?
Originally Posted by heavychevy
Agree, but even at lower speeds (less than 80 mph) , where grip is mostly mechanical, the Acr is on RAILS! I drove a C7Z on pirelli scrubs and it could still light the tires up on corner exit. The ACR feels like you almost have to try to break it loose. The ZR1 should completely walk away on the straights though. The C7 chassis accels at early corner (turn in - apex) speed. If you use it properly you shouldn't have a lot of issues staying in touch with the Viper.
The ACR, and MT confirmed it (The Kumo's have a 200 Tread Wear).
(A child's hand floating outs the window on the freeway.) Indisputable! The ACR just shattered our braking record, stopping from 60 mph in a neck-snapping 87 feet. Why? The big carbon Brembos help, but so do the ultra-sticky Kumhos, as well as all that fancy aero.
I contend separately that less relative Huge DF is being applied to less lateral G-force.
Last edited by johnglenntwo; 07-23-2018 at 01:16 PM.
That's an astonishing feat considering it is rated to have considerably less torque, less power, and considerably more downforce (probably 5 times more!). When you put together the exit speed in turn 11, the low drag on the straight, and how late it can brake I think the ZR1 will likely be tied with the Viper on most straights. Sure, VIR or CA Speedway will give the ZR1 the upper hand in the straight, but on most straights I think it will be a tie.
I'll be astonished if the ZR1 will do 5 mph faster on the main Laguna Seca straight and I'm guessing it will hit the same top speed everywhere else on track before braking.
What I would like to see is how the ZR1 will do on the Kumho ACR tires. Might be enough to tie it on most tracks.
Someone needs to make a proper higher downforce rear wing for the ZR1 with some adjust-ability. There is some performance to unlock here.
The ACR, and MT confirmed it (The Kumo's have a 200 Tread Wear).
(A child's hand floating outs the window on the freeway.) Indisputable! The ACR just shattered our braking record, stopping from 60 mph in a neck-snapping 87 feet. Why? The big carbon Brembos help, but so do the ultra-sticky Kumhos, as well as all that fancy aero.
I contend separately that less relative Huge DF is being applied to less lateral G-force.
Nice try there to throw in the kumhos treadware but most people know by now that manufacturers set their on tread ratings. And we also know the kumhos are Hella faster than 200 treadware. The kumhos are why the Viper stops so fast from 60. Period.... From 160 and you have a case.
I was testing you to see if you came back with something good to debate. Not quite there just yet.
But to answer your question DF adds drag at all speeds. Drag is what slows you down if you let off the gas. More drag slow down faster. It does not have t be DF. It takes a lot of DF to feel it on a 3700-3800 lbs with driver car. There are plenty of articles on this.
As far as tadge, collective roll eyes at the statement "tadge said so". Do the math......
As you can see from this graph, the Acr only makes a couple hundred lbs of DF at 80 Mph. Balanced over the whole car. You won't feel that much if at all in slow corners on a car that heavy.
07-20-2018, 08:48 AM
C7 ZR1 / Viper ACR Extreme
