The Pirelli P Zero Trofeo Rs are essentially street-legal racing tires so tacky that, during development testing, they occasionally stuck to the pavement better than to the wheels they were mounted on. To keep the Pirellis from slipping around the rim, the wheels on production Z/28s are media-blasted to increase friction at the mating surface, a common practice in racing.
That's so cool.
There are, of course, stiffer springs and bushings, and the downsized wheels allowed engineers to drop the center of gravity by 1.3 inches and use smaller and lighter anti-roll bars. The cornerstones of the suspension are four spool-valve dampers, a technology used by Red Bull Racing as it claimed four Formula 1 championships between 2010 and 2013. Until now, the closest these shocks have come to a production car is Aston Martin’s $1.8-million One-77.
Spool-valve dampers don’t use electronic components or magnetic fluid, and they are neither driver-adjustable nor adaptable to road conditions. Instead, the spool valve’s merit lies in tailor-shaped internal ports that improve the precision and effective range available to engineers as they tune the shocks. They work magnificently. The Z/28 transitions from left to right to braking and acceleration with nearly imperceptible load transfer. It is stoic and stable as it bounds over the curbing and hunkers into hard braking through the tight corkscrew of Barber’s eighth and ninth turns. On the road, firm doesn’t mean harsh, either. As we bomb over a bridge deck that is set two inches above the road that abuts it, I tense in anticipation of a jarring impact—it never materializes.
Smaller anti-roll bars than....ZL1? Anyway, there's some good shock info here.
I was thinking about this when reading the Calloway article. I wonder if the media blasting is adequate for the Calloway upgrade with all that extra hp. It would suck to pay 20K to spin rims within tires.
Speaking of tires, I can't help but feel that tires were a major factor in the Z/28's quickest lap time. The article alluded to this as well. This is not unlike how the Lotus Elise turned in a quicker lap than a Cayman S and a base C6 while running Yokohama A048s in Car and Driver's original Lightning Lap test at VIR. VIR should definitely favor the high HP cars, but the tires were enough to give the Elise the edge despite being 17 MPH slower down the front straight than the C6 and 10 MPH slower than the Cayman.
In short, I think the car is successful because it combines top end parts with top end calibration of said parts. It's a great package and is apparently quite fun to drive. I imagine it is actually light years better than, say, a 2005 Z06, even though that Z06 is quite a bit faster in terms of raw hp/weight.
I do like cars that combine top end parts with obsessive engineering to get the most out of those parts (of my current/former cars: Elise, Type R), rather than just a big engine, fat tires and stiff shocks (of my former cars: Camaro, Z06).
My Z4M Coupe had a relatively small 3.2 liter engine, but got rotten mileage. It usually averaged about the same as my Jeep Wrangler. Which should tell you something. Of course that engine did put out over 100HP/Liter. Considering that engine was designed 12 years ago, I don't think I'm out of line grumbling about the C7's very meh, specific output.
Your Z4M is a perfect example of a car which would be faster, cheaper and more fuel efficient with an LSx small block chevy under the hood.
Not necessarily. The car would be be much heavier, be nose heavy, have far too much torque for the vehicle's weight/tire size (You'd have to start off in 2-3 gear to prevent wheel spin), and the V8 wouldn't fit anyway do it its much larger size.
And while I see your point. I do have to disagree with your statement that specific output is irrelevant. It is a benchmark from a engineering perspective. Which would you consider the superior engine? The engine making 250hp, or the one with identical displacement and weight that makes 400? That's an easy answer
Wait for it...
Not true. The LS2 6.2L only weighs 418 lbs so in fact it would have been probably 50 lbs lighter than the iron block 6 in your BMW. Also the V8 would move the center of gravity for the powerplant back closer to the firewall since it is not as long.
As for specific output, it's not just irrelevent for a street engine, it's utterly irrelevent. Internal friction goes up with the square of rpm and high specific output engines are generally DOHC with the attendent high valve train losses, so they tend not to make any better fuel economy than the bigger displacement engines which have higher pumping losses (except those with cylinder shutdown). Think about the absolutely atrocious mileage rating of the recent M3 BMW 4.0 v8 (now gone). It was 14/20 mpg vs the Camaro (200 lb's heavier and no cylinder de-activation to boot) 16/24 mpg.
In that sense the M3 4.0 was an utter engineering failure compared to the LS2 6.2. It had 100 ft lbs less peak torque, it had significantly poorer fuel economy, it was heavier by 30 lbs, it was wider and much more expensive to manufacture. Yet by your twisted logic it would be the "better" engine since it had higher specific output. That makes zero sense.