[ZR1North]

I've read this threat several times. Thanks for starting it, Chris, and for everyone for the usual informative contributions. Now, for something a little different....

I'll start with my reason for adding - I have a whole new respect for the economy-performance balance of our ZR-1s having just driven my '16 Z06 from Michigan to Florida to extend its use when I am there on-and-off over the winter (gotta get some miles on it while warranty is still in effect).

My '91 ZR-1 has 4:10s and Marc's 510 pkg (sans the SM flywheel, so it's really 490hp). My first drive with the pkg. was Mountain Run 2015, and I noticed two key things - 1) having the 4:10s made the run through the mountains a whole lot better than what I experienced road racing it previously with the 3:45s (to Paul Workman's point in an earlier post); 2) having a useful 6th gear on the freeway made cruising a great experience from a drivability and economy perspective (I made 24 MPG highway on the trip) running @ 75MPH revving at 2K RPM. I found that I was able to accelerate around traffic in 6th quite easily; previously I was constantly downshifting to 5th to do so.

Fast forward to my trip this weekend in the Z06. After I got 1,000 miles on it, I started to experiment with various modes. I noticed that when I switched it to "Eco" mode and the computer switched the engine to "V4" for fuel economy, I was getting about 34 MPG, but that was only on flat surfaces running @ 75 MPH in 7th gear on cruise (RPM were 1,500). When I encountered a grade, it switched to "V8" mode and the MPG dropped to 22-29 range (instantaneous computer calculations). Overall, I averaged 27 MPG, mostly in 7th gear @ 1,500. When I shifted to 6th for passing, RPM jumped to 2,000, but acceleration in 6th was unlike anything I've experienced in anything else I've driven. For comparison, gear ratios in the Z06's Tremec gearbox are: 1st, 2.97; 2nd, 2.07; 3rd, 1.43; 4th, 1.00; 5th .71; 6th, .57; 7th, .48; final drive is 3:42. This compares to our Zees with: 1st, 2.68; 2nd, 1.80; 3rd, 1.29; 4th, 1.0; 5th, .75; 6th, .5 - my final drive now is 4:10.

All that to say, even with 30 years of technological advancement, our Zees are still pretty respectable in terms of performance and economy when upgraded. As for the 4:10 vs "other ratios", I wouldn't change my decision to switch to the 4:10s, but I am more of a road racer than a drag racer. I ran the NCM track in May, and as with the MR in 2015, I found the combination fantastic on both the slow corners and fast straightaways. I think it's a great combination for highway and road racing and while I haven't drag raced the car, I think what I've read here would not cause me to change from the 4:10 for the odd drag run.

FANTASTIC THREAD!

Bob