Hay Duke; How Times Have Changed From 1970(Current ZR1 Track Times)

**Duke W.** · February 12, 2025, 11:46 AM

Back then I could have never imagined that in my lifetime any street legal car could lap any race track nearly as fast as a Can-Am car, which were usually a little faster than F1 cars on the tracks were both types raced.

At the time I was working on a MSME at the U. of Wisconsin Engine Research Center, and we knew that catalytic converters would be required to meet the proposed 1975 tailpipe standards, plus add on devices like EGR to control NOx. Add to that both federal and some state noise laws, and we knew power and fuel economy would take big hits.

Invention of the zirconium dioxide O2 sensor and three way monolithic catalyst were a breath of fresh air and hinted that improved performance and fuel economy could be had while still meeting tailpipe emission and noise regulations.

I was surprised and impressed nearly 20 years ago when you could buy a Corvette with an honest 500 NET horsepower in a small block package in a car with a curb weight of a little over 3100 pounds, about the same as my SWC.

So now we have 1064 net HP in a what... 3700+ pound curb weight (full fluids including fuel) package? I'm not sure what one could do with all that power. About the only place you could use it for more than a few seconds at a time is on a big track, but you better be a skilled and experienced driver and be ready to consume a complete set of tires and brake pads in a one or two day weekend track event.

IIRC the McClaren M8 in it's various iterations weighted about 1800 pounds dry. Add 65 gallons of fuel, three gallons of oil, and four gallons of water plus about 200 pounds for "The Bear", and the all up weight on the starting grid was close to 2500 pounds. The 510 CID "Reynolds" linerless block engines were good for about 720 HP (at current SAE net air density), so the weight to power ratio was about 3.5 pounds per HP.

Say a ZR-1 with full fuel and driver weighs about 3900 pounds that yields a ratio of about 3.7 pounds per HP, which is in the same ballpark.

Current "R-compound" street legal tires likely have a little better grip than a 1970 vintage Can-Am tire mounted on so-called "square" wheels (15" dia., 15" wide), and the ZR-1 may have downforce in the same ballpark as a Can-Am car of that vintage, so the numbers show that the ZR-1 could be close to the lap time of a M8, but I wonder if the tires and brakes would last the typical 200 mile Can-Am race, and for sure it would have to make several fuel stops.

Duke

**Larry E.** · February 12, 2025, 01:59 PM

Duke:Thanks for the comments; brings back so many memories!
Now; Since the ZR-1 will be the Indy Pace Car we wonder what kinda lap it could do there and what top straight away speed it can
get? Penske-Chevrolets where getting 241+ for their pole winning car last year. I'm sure one of their drivers will test it. Hay Duke:Care
To guess?? Thanks again-Larry

**Steven B.** · February 12, 2025, 04:06 PM

Aside from the specs the orange cars at RA and the sound of those big Chevs was incomparable, especially back in Thunder Valley.

I was fortunate with my friend John to be in the paddock as guests of a Gulf engineer who was in charge of designing the velocity stacks for the McLarens. I was fortunate to do some testing of an A/P L-88 there and that sound was shattering but nothing like the cars of Bruce and Denny. We may be reentering the good old days.

**Duke W.** · February 12, 2025, 04:31 PM

I think a really good Indy car and driver can still do the course flat assuming optimum track and weather conditions . The ZR-1 doesn't have anywhere near the downforce of an Indycar, so the driver would certainly have to lift and maybe even brake for the turns, and I question whether the OE tires are up to continuous hot laps at Indy, so I really can't hazard a guess at lap times and speeds in the corners or the straights... well, maybe I can... say 150-160 in the turns and close to 200 on the straights.

Anyone else???

You and others might recall that back in 1994 Penske found a loophole in the "stock block" rules and showed up with a "Mercedes-Benz pushrod"-engined (that I think was actually designed and built by Ilmor) car that reputedly had about 1000 horsepower and was hitting 250 on the straights. Al Unser Jr. won the pole, but Emo led the race until late when he brushed the wall giving the win to Jr.

USAC promptly banned the engine, but The Captain had pulled off another coup d'etat!

It was never clear to me how Penske pulled this off, but, apparently, the words "stock block" somehow disappeared from the rule book allowing for a bespoke 209 CID turbocharged pushrod V-8, and he got Mercedes Benz to fund the engine.

I recall a few years ago that one of the car mags compared a C7 ZR-1 with a contemporaneous ALMS spec C7 at the Utah Motorsports Campus, and the race car had slightly better lap times but the showroom stock ZR-1 recorded higher max straightaway speeds.

It's interesting that some modern sports car now have more power than their race legal versions, but the latter are several hundred pounds lighter and likely still cut lower lap times on most tracks, but we'll see if this holds with the new C8 ZR-1.

Another point of comparison is early versions of the Allison V-1710 (1710 CID SOHC 4-valve/cyl. V-12) aircraft engine made a little over 1000 sea level takeoff HP in the early 1930s. They were centrifugally supercharged. I don't recall the amount of boost, but it was modest. Final versions made over 2000 HP on the same displacement, but with a lot more boost allowed by much higher octane fuel.

Duke

Hay Duke; How Times Have Changed From 1970(Current ZR1 Track Times)

Hay Duke; How Times Have Changed From 1970(Current ZR1 Track Times)

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