The C8 Z06
07-12-2019, 01:14 PM
#42
Melting Slicks
It was actually one of the complaints from the competition that it wasn't fair they were using pushrod motors.
ette-racings-competition-complains-about-its-pushrod-engine-design/#ixzz5tU5KIz5c
The Corvette C7.R made its racing debut at the 24 Hours of Daytona in January. Despite the advantages that the new and improved C7.R brings, Corvette Racing’s two cars finished fifth and tenth in the GTLM class at Daytona and will be hoping for a better result in the second race of the 2014 TUDOR United Sports Car Championship, the 12 Hours of Sebring.
One of the main advantages that the C7.R has over the rest of the pack is the pushrod design of its 5.5 liter V8 engine. As Corvette Racing program manager Doug Fehan told Car and Driver, pushrods allow for a smaller, simpler engine package, which in turn reduces weight and keeps the center of gravity of the engine low.
“I rue the day we would ever have to go to overhead cams. Bigger, heavier, giant heads. Cams in head, higher center of gravity, bigger package, in most cases more weight. All the additional parts like chains, pulleys, and gears—you just increase the opportunity for things to go wrong. Fuel-efficiency and emissions standards may at some point cause us to have to go that way, but when you look at the size and weight of our C7.R package, plus its power and reliability, there’s nothing that beats a two-valve engine,” Fehan said.
Surprisingly, the overhead valve design provides such an advantage, that Corvette Racing’s competitors have tried to get it penalized in the past.
“I sit on several FIA engine councils and it always comes up from our competitors. Whether it’s Porsche, Ferrari, or Aston Martin, they’re always complaining about what they perceive of as the advantages the two-valve engine has [over] their [designs], and want the two-valve engine penalized, said Fehan. “To that I say, ‘go back to the road car—if the two-valve engine is that much better for racing you ought to put it in your car.’ To which they have no answer.”
Corvette Racing might have some more complaints to deal with if it gets the finish it’s hoping for at the 12 Hours of Sebring on March 15.
One of the main advantages that the C7.R has over the rest of the pack is the pushrod design of its 5.5 liter V8 engine. As Corvette Racing program manager Doug Fehan told Car and Driver, pushrods allow for a smaller, simpler engine package, which in turn reduces weight and keeps the center of gravity of the engine low.
“I rue the day we would ever have to go to overhead cams. Bigger, heavier, giant heads. Cams in head, higher center of gravity, bigger package, in most cases more weight. All the additional parts like chains, pulleys, and gears—you just increase the opportunity for things to go wrong. Fuel-efficiency and emissions standards may at some point cause us to have to go that way, but when you look at the size and weight of our C7.R package, plus its power and reliability, there’s nothing that beats a two-valve engine,” Fehan said.
Surprisingly, the overhead valve design provides such an advantage, that Corvette Racing’s competitors have tried to get it penalized in the past.
“I sit on several FIA engine councils and it always comes up from our competitors. Whether it’s Porsche, Ferrari, or Aston Martin, they’re always complaining about what they perceive of as the advantages the two-valve engine has [over] their [designs], and want the two-valve engine penalized, said Fehan. “To that I say, ‘go back to the road car—if the two-valve engine is that much better for racing you ought to put it in your car.’ To which they have no answer.”
Corvette Racing might have some more complaints to deal with if it gets the finish it’s hoping for at the 12 Hours of Sebring on March 15.
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07-12-2019, 01:19 PM
#43
By "efficiency" you mean specific output, which technically isn't engine efficiency. It's: specific output. :-) And you're correct in that outside of our country, specific output is far more interesting. Places such as a lot of European countries (or all of them?) where folks get taxed on engine displacement. In places like that, having a higher specific output is more useful to keep costs in check. We don't have to worry about that here in the US and are free to have engines of any size we like. What we do have to keep in mind is FE and emissions; which can be tied into displacement in some cases.
It doesn't make an OHV engine any less capable or interesting or powerful or... anything like that. I think the Corvette has, thus far, done a fantastic job of proving just that. :-)
It doesn't make an OHV engine any less capable or interesting or powerful or... anything like that. I think the Corvette has, thus far, done a fantastic job of proving just that. :-)
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07-12-2019, 02:20 PM
#44
Exactly. No way I want the first model year of a completely new car. Too great a risk of quality problems. I also don't want the first model year of a C8 Z06. Same risk. The 2015 Z06 had issues. My 2019 Z06 has the benefit of all the problems resolved and also all the improvements built into it.
07-12-2019, 02:29 PM
#45
Exactly. No way I want the first model year of a completely new car. Too great a risk of quality problems. I also don't want the first model year of a C8 Z06. Same risk. The 2015 Z06 had issues. My 2019 Z06 has the benefit of all the problems resolved and also all the improvements built into it.
07-12-2019, 02:31 PM
#46
Corvettes and Ferraris are apples and oranges...other than performance numbers, there is no comparison.
07-12-2019, 02:52 PM
#47
Instructor
Yes, yes, I knew these arguments would come out, it is the wicked FIA holding back the Corvette team because they only want the European or Asian teams to win! The regulator sets rules to attract as many manufacturers as possible to enter and to try to provide exciting racing. When your primary markets have $15 per gallon gas, you can't sell a 7.0L V8 pushrod that gives back 5 mpg.
By efficiency, I was referring generically to emissions and fuel economy along with power, etc. But when you can kid yourself that global warming is not really happening and gas costs $3 per gallon, of course using higher capacity engines is the way to go.
As I said, just take a look at ALL of the race series globally and see what the engine is and who makes it. Who wants to pick up the phone to call Mercedes, Ferrari, Honda, Renault, Cosworth, etc. to point our their mistake?
Like leaf springs, solid rear axles, drum brakes, ladder frame chassis', etc. time and technology move on, typically for good reason. I am certainly no engineer, but as I've said, I doubt that the collective wisdom of many that are would be so misguided. Maybe I'm wrong.
By efficiency, I was referring generically to emissions and fuel economy along with power, etc. But when you can kid yourself that global warming is not really happening and gas costs $3 per gallon, of course using higher capacity engines is the way to go.
As I said, just take a look at ALL of the race series globally and see what the engine is and who makes it. Who wants to pick up the phone to call Mercedes, Ferrari, Honda, Renault, Cosworth, etc. to point our their mistake?
Like leaf springs, solid rear axles, drum brakes, ladder frame chassis', etc. time and technology move on, typically for good reason. I am certainly no engineer, but as I've said, I doubt that the collective wisdom of many that are would be so misguided. Maybe I'm wrong.
07-12-2019, 02:58 PM
#48
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07-12-2019, 02:58 PM
#49
Instructor
By the way, I own a 2016 C7 Z06 and love it, and frankly could not care less whether the engine is OHV or DOHC. Would I like to see the C8 Z06 (or whatever they call it) move to a DOHC design, maybe, but I'd be more concerned that it was light and nimble and quick!
07-12-2019, 03:00 PM
#50
Instructor
07-12-2019, 03:03 PM
#51
Look up fuel economy figures for the LS and LT motors... they don't get "5 mpg". Even the 755 horse supercharged LT-5 gets over 20 highway. Most Corvettes get near 30 if not slightly more in real world use.
07-12-2019, 03:25 PM
#52
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Well then don't throw easy chum out into the water like that.
Um... huh?
Well, sort of. If you believe there aren't politics at play in most of these racing bodies, I have a bridge for sale in a one of the big cities in New York State. But that's another topic.
You just sort of fell over here. Obviously, GM's ability to hit epic FE numbers for a given displacement with the OHV engines is legendary. Even if the countries in question would rather just blindly and ignorantly tax on displacement versus actually testing the vehicles.
You went off the rails again here. Stay on target?
No one's saying their engine choices are or aren't a mistake. YOU'RE implying that GM's choice is a mistake, however, and GM has thus far flipped you the bird. So far, the SBC has hit its FE and emissions numbers while providing prodigious amounts of torque through a pretty broad RPM range. All in a neat, tidy little package. There's a reason it's called Mighty Mouse.
That's clear.
They're working within their restrictions, we're working within ours. Fortunately, our restrictions are less... restrictive... than theirs are.
it is the wicked FIA holding back the Corvette team because they only want the European or Asian teams to win!
The regulator sets rules to attract as many manufacturers as possible to enter and to try to provide exciting racing.
When your primary markets have $15 per gallon gas, you can't sell a 7.0L V8 pushrod that gives back 5 mpg.
By efficiency, I was referring generically to emissions and fuel economy along with power, etc. But when you can kid yourself that global warming is not really happening and gas costs $3 per gallon, of course using higher capacity engines is the way to go.
As I said, just take a look at ALL of the race series globally and see what the engine is and who makes it. Who wants to pick up the phone to call Mercedes, Ferrari, Honda, Renault, Cosworth, etc. to point our their mistake?
I am certainly no engineer
but as I've said, I doubt that the collective wisdom of many that are would be so misguided.
07-12-2019, 04:02 PM
#53
Instructor
You're right, the US is best at everything. Let's just leave it at that. Nothing I say or the rest of the world does will change your mind. You should go into politics.
07-12-2019, 04:09 PM
#54
Instructor
Do you know that from personal experience? I have a C7 Z06 and I'm sure it could give 20mpg on the freeway in 4-cylinger mode in 7th gear with a totally flat and wind free environment, but in real life....no.
07-12-2019, 04:16 PM
#55
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07-12-2019, 04:18 PM
#56
The "US is better" is yet another example where you attack those refuting your claims that has nothing to do with the facts either.
Anyhow, if we focus on only what you are writing with regards to engines, I think you'd find that designing an engine to meet various specifications is a trade-off, or balance, of many different compromises.
A push rod engine allows for lighter and tighter packaging given similar specifications for power deliver at a variable but typical load. For example, constant cruising at 60-80MPH that most Americans drive on highways takes around 13-25kWh just to overcome rolling + air resistance. To meet costs, emission requirements, crash, weight and a whole host of other requirements limits your choices fairly rapidly.
Americans buy mostly automatic transmission cars which favors engines with low-end torque, not the 'super high output' of OHV engines that require high RPMs to generate the same amount of power.
For the Corvette, specifically, up until now, the engine bay has required an engine to have very small packaging, tight cost requirements and high output. Something a DOHC engine would have a hard time delivering with it's much larger form factor for the same low-end torque.
Not saying DOHC engines aren't fantastic for the specs they are great for, but the trade-offs may not be right for the application.
Finally, if the same power output can be done for 50kgs less than a DOHC, but maybe .5% more emissions, which engine, overall, produces more pollution over the lifetime, all other things being equal? It may be that having to pull a lighter load reduces emissions more than a more emission friendly engine that must pull a heavier load throughout its lifetime.
Anyhow, I _am_ an engineer and an engineer's life is the many, many choices and compromises that must be made when building a final product.
Last edited by ToddC7; 07-12-2019 at 04:20 PM.
07-12-2019, 05:02 PM
#57
Instructor
All I was trying to point out, as a layman, was that the global consensus appears to be that the DOHC solution for most race and road cars (and bikes for that matter) is the more appropriate choice. Are they all wrong? I have nothing against the OHV engine or GM or anything else, but the points I made about the majority approach were true and valid. Also, the points I made about global warming and the different opinions and approaches that governments take to address them (technical restrictions and taxation) are directly related to the design goals of the engine manufacturers. The US has an approach that is less stringent than they have in Europe specifically because of the opinions and views of its politicians.
Having others intentionally misinterpret my arguments, and attempt to disregard or not even read them is pretty offensive to me, no matter who the poster is. I did not disrespect or attempt to belittle JVP but for some reason he chose to take that approach with me, when I called him on it, he took the typically bully retort of calling me out for disrespecting him. Really, I genuinely appreciate your sympathy, it really does mean to world to me.
At the end of the day, I stand by my comments on OHV vs DOHC, not because I technically can discuss which is or isn't better, but because most manufacturers take that route. If you can show me that the majority of manufacturers of auto engines favor the OHV over the DOHC, go ahead.
Having others intentionally misinterpret my arguments, and attempt to disregard or not even read them is pretty offensive to me, no matter who the poster is. I did not disrespect or attempt to belittle JVP but for some reason he chose to take that approach with me, when I called him on it, he took the typically bully retort of calling me out for disrespecting him. Really, I genuinely appreciate your sympathy, it really does mean to world to me.
At the end of the day, I stand by my comments on OHV vs DOHC, not because I technically can discuss which is or isn't better, but because most manufacturers take that route. If you can show me that the majority of manufacturers of auto engines favor the OHV over the DOHC, go ahead.
07-12-2019, 05:29 PM
#59
I recently spoke with someone who would know that Chevy is already testing the Z06 version of the C8. I live about ten miles away from the GM Proving Grounds. The individual has a relative who works for GM. He had no other details. I recently purchased a 2019 Z06/Z07 and he asked why I didn't wait for the C8. Told him I have to have a manual trans plus it was my guess the Z06 version would not be available for at least a year after the base model. That is when he told me they were already testing them.
07-12-2019, 05:35 PM
#60
My C5s easily did 29-31 verified. My C7 Z51 got 33 in eco mode. Real world, not perfect 60 mph tail wind flat.
