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Just as we regain our
position as the world’s largest oil producer we want to go electric so we can import lots of rare earth minerals (for batts) from the flippin Chinese. Our govt and its crazy CAFE standards are nuts, but I realize this ship has sailed....
Very good way to state this reality. We have gone from so called oil shortages, gas crisis, impending ice age, global warming, tree hugger radical riots, and a bunch of other environmentally driven nonsense. Now we are totally energy independent with abundant fossil fuels and we have decided to go full speed ahead on electric. This really does not make good sense on more levels than one can count.
Comical statement given how old the OHC engine design is. Thus far, no technical, engineering, or performance advantages have been provided that would indicate GM should go DOHC. Mind you: I'm not saying they will or won't; just that the discussion has thus far been basically between facts about the OHV advantages vs the supposed "sophistication" (whatever that means) of the OHC. As I said earlier, what matters is:
Can the engine produce the torque it needs to, in a drive-able RPM range?
Can the engine do this while meeting various FE/emissions regs?
Can the engine do this while packaged appropriately (packaging includes mass)?
Can the engine keep costs under control (It does this by being shared)?
At this point, today, the OHV engine does those 4, and it does so far more superbly than any DOHC V8 in existence. That's been proven over and over again.
So, again I ask: why, exactly, should GM move the Corvette to a OHC engine?
It is an achievement. But not a huge one. After all, they are supercharged engines with big displacement.
What reasonable person cares, as long as they produce big power, aren't too heavy, are long-lived, and meet emissions standards?
Originally Posted by PerKr
Don't get me wrong, I love the traditional V8. The sound, the power... But it's also rather stone-age.
It is not by any means "stone-age", for anyone who cares more about performance than contemplating their navel.
See post number 121 for real-world comparisons. That supposedly "stone-age" Corvette competes quite well with the megabuck McLaren.
Last edited by Warp Factor; 08-14-2019 at 11:08 AM.
Engines are in essence, air pumps. The more air you can move through an engine, the more power you can create. The simplest way to pump air is a piston, so piston displacement provides the cheapest way to increase output. Forced induction adds a pre-stage of induction and compression. Forced induction therefore increases the air pumping capability of any engine. A forced induction OHV engine has the highest power-to-weight ratio of any IC engine, and it was proven with the magnificent Pratt and Whitney 28 cylinder air-cooled WASP Major engines that powered the B-29's. These engines were supercharged to provided more power at altitude, making up to 4300 HP out of 71L of displacement. HP/Wt. in 1945 was over 1.2:1.
The 2003 BMW P83 V10 engine used in Formula 1 made over 900HP and weighed less than 200 lbs. When it comes to power to weight, the old turbocharged OHV aircraft engine doesn't even come close to the DOHC F1 engine at 4.5:1. Assuming the 2005 engine wasn't heavier, that went up to 4.75:1. And note, it was not forced induction.
I had to look at the dates when I saw this thread. It reads almost identically to a pissing contest about OHV vs, DOHC about a year ago when folks were speculating about what engine would debut in the C8. Here we go again.
Street cars are not displacement limited in the same way as a racing series, which is the common use of the term. Yes you are technically right, a 100 liter OHV motor is not in the cards. But is that an honest way of looking at it. I've owned many more DOHC motors than pushrod motors....911's, a 2018 TTRS, my current S4, various Hondas, GTI's, my 308GT4, etc. so I'm not an advocate for one or the other. I think for the street an LS/LT is nearly optimal given the superior power density of the package. Would I trade my Ferrari just because it is a DOHC motor? No, I love the motor and noise it makes. Would I consider LS swapping a 996 4S...hell yea.
No the FIA does not mandate DOHC but that is a default when the many constraints of the formula are applied...small displacement, have to make lots of power, therefore it has to rev or boost or both.
Street cars are completely displacement limited. Space is at a premium, fuel economy a requirement, the list goes on and on. So it is an honest way of looking at it.
Originally Posted by Jaye Bass
Boosting a 6 liter motor can make way more than 1500hp. I think what is going on here, is analogous to the "conventional wisdom" of 20 or so years ago that Macs were less vulnerable than PC's to cyber threats...originally this was mostly because Macs were a tiny fragment of the PC population.
That just proves my point. The replacement for displacement is more money (ie, throwing boost at a 6 liter to make it more powerful).
Originally Posted by dmaxx3500
real q is
how big is the engine bay
can the car be assembled on a production-line,by fitting the engine from the bottom?
Looking at the structures, that is exactly how they are getting the engine in there. It looks like a real bitch to get it out from the top.
What extra weight? What is the weight of a complete 3.9 Liter, twin Turbo Ferrari 488 engine?
Car weights, both from Car& Driver:
Ferrari 488 = 3241 lbs
C8 est. = 3600 lbs
Can't get engine weights but the cars are about the same overall size. That 3.9 Liter Ferrari engine is no doubt significantly lighter than a 6.2 small block!
One issue not mentioned here is the maintenance of a DOHC. In a rear engine car that means dropping the engine. This has to be done every 30K miles on all those high end Italian cars, but they just say if you can afford a car like this you can afford the maintenance. People who own Corvettes have a hard time accepting that cars with low profile tires bend wheels when you hit things.....How do you think they would feel about having to spend $10k after 30k miles to drop the engine and change the timing chains. Dohc would be great if there were better ways to drive those cams. Koniseg has been working on electrically actuated valves because of the problems with driving those overhead cams. In a front engine car changing the timing chain or belt does not require pulling the engine but in a rear engine, you have to pull the motor.
Sorry, they don't play in the same sandbox. The buyers are vastly different and the C8 isn't a supercar. It's a great car that appeals to a different set of buyers.
Do you think if they added a DOHC engine they would be in the same sandbox or would they still be excluded? You say they can't compete until they go DOHC, but yet they do. When it is pointed out they do you say they are not in the same league. You may have a point, but if they changed to DOHC you still would exclude them based on some other metric. Push rod engines do have some advantages as do DOHC engines. The lack of pushrods will not change your view or anyone else's view on a Corvette. I am sure there will be plenty of plastic parts to complain about as the C8 laps your favorite car.
One issue not mentioned here is the maintenance of a DOHC. In a rear engine car that means dropping the engine. This has to be done every 30K miles on all those high end Italian cars, but they just say if you can afford a car like this you can afford the maintenance. People who own Corvettes have a hard time accepting that cars with low profile tires bend wheels when you hit things.....How do you think they would feel about having to spend $10k after 30k miles to drop the engine and change the timing chains. Dohc would be great if there were better ways to drive those cams. Koniseg has been working on electrically actuated valves because of the problems with driving those overhead cams. In a front engine car changing the timing chain or belt does not require pulling the engine but in a rear engine, you have to pull the motor.
That hasn't been true for a long time.... they have timing chains which do not require maintenance like the old timing belts.
Car weights, both from Car& Driver:
Ferrari 488 = 3241 lbs
C8 ext 3600 lbs
Can't get engine weights but the cars are about the same overall size. That 3.9 Liter Ferrari engine is no doubt significantly lighter than a 6.2 small block!
The LT1 weighs 465 pounds so by your logic / math the Ferrari engine weighs 106 pounds. Cool
The 2003 BMW P83 V10 engine used in Formula 1 made over 900HP and weighed less than 200 lbs. When it comes to power to weight, the old turbocharged OHV aircraft engine doesn't even come close to the DOHC F1 engine at 4.5:1. Assuming the 2005 engine wasn't heavier, that went up to 4.75:1. And note, it was not forced induction.
It also lasted an hour and thirty minutes and then went boom. That wouldn't work out so good on a three hour flight.
Car weights, both from Car& Driver:
Ferrari 488 = 3241 lbs
C8 ext 3600 lbs
Can't get engine weights but the cars are about the same overall size. That 3.9 Liter Ferrari engine is no doubt significantly lighter than a 6.2 small block!
No..not really. Especially with the turbochargers intercoolers and all the piping.
Nissan GTRs 3.8l TT V6 weighed at over 630lbs for like 530hp.... C6 ZR1 LS9 weighed at 529lbs for 638hp...
Yep Im sure the 3.9l TT V8 is significantly lighter. Yeah... Wake up please!
What extra weight? What is the weight of a complete 3.9 Liter, twin Turbo Ferrari 488 engine?
The similar MacLaren motor weights about 430lbs.
The weight differences between the mid engine exotics and the ZR-1 are down to chassis materials...carbon fiber to be exact. The CF tubs of these cars are very light but very expensive.
I had to look at the dates when I saw this thread. It reads almost identically to a pissing contest about OHV vs, DOHC about a year ago when folks were speculating about what engine would debut in the C8. Here we go again.
Yep! There are diehards that insist a pushrod V8 is more efficient! They'd have the 502 cid BB in my Street Rod operating with one cylinder before admitting there is a benefit to smaller turbo charged engines! (It probably could with a very big flywheel and I'd improve my 10 mpg!)
Even showing what was done in WWII with turbo compounding, i.e. a Turbo for engine boost and several more directly powering the propeller, quoting," Turbo-Compoundsystem was developed to deliver better fuel efficiency. In these versions, three power-recovery turbines (PRT) were inserted into the exhaust piping of each group of six cylinders, and geared to the engine crankshaft by fluid couplings to deliver more power. They recovered about 20% of the exhaust energy (around 450 horsepower) that would have otherwise been wasted!" Latest EPA numbers, about ~33% of th energy in gasoline is wasted going out the exhaust!
Those Ferrari folks just don't know what they are doing!
Wright R3350 Compound Turbo in WWII Airplane Engine!
Yep! There are diehards that insist a pushrod V8 is more efficient! They'd have the 502 cid BB in my Street Rod operating with one cylinder before admitting there is a benefit to smaller turbo charged engines! It probably could with a very big flywheel and I'd improve my 10 mpg!
Even showing what was done in WWII with turbo compounding, i.e. a Turbo for engine boost and several more directly powering the propeller, quoting," Turbo-Compoundsystem was developed to deliver better fuel efficiency. In these versions, three power-recovery turbines (PRT) were inserted into the exhaust piping of each group of six cylinders, and geared to the engine crankshaft by fluid couplings to deliver more power. They recovered about 20% of the exhaust energy (around 450 horsepower) that would have otherwise been wasted!" Latest EPA numbers, about ~33% of th energy in gasoline is wasted going out the exhaust!
Those Ferrari folks just don't know what they are doing!
Wright R3350 Compound Turbo in WWII Airplane Engine!
I didn't say pushrod engines were more efficient. I said your math was wrong. The difference in weight between the c8 and the Ferrari is largely unrelated to the engine weight.
That 3.9 Liter Ferrari engine is no doubt significantly lighter than a 6.2 small block!
Highly doubtful. Ferrari is cagey with the overall engine weight, but both the F154 CB and LT1/2 are all aluminum. I can find a few dimensions in Ferrari's press release on the 488.
F154 CB
Height - 25.51"
Width - 27.56"
LT1
Height - 25.26"
Width - 27.88"
Even if we assume the Ferrari's internals are lighter, there simply isn't going to be a lot of weight savings there. In fact the additional hardware of the DOHC design is likely to negate any of this.
The real weight savings here is in the chassis. GM simply can't produce a carbon fiber tub chassis at the price point they want to hit.
I didn't say pushrod engines were more efficient. I said your math was wrong. The difference in weight between the c8 and the Ferrari is largely unrelated to the engine weight.
That 360 lb car weight difference for essentially the same size car (the even look similar) is no doubt partly due to the weight difference between the higher ho 3.9 Liter turbo and the 6.2 liter LT2. It has leess weight in the rear. Frankly the 60% rear weight on the C8 is high, essentially equally to a rear engine 911! The math shows you need that rear weight to get the low 0 to 60 mph! Just follow Jason's presentation:
For all the diehard pushrod folks, I'm a fan as well! Built my first engine, a '50 Olds I stuffed in my "41 Ford Coupe in 1959! Put that together from parts I bought in peach baskets from a friend. Had it bored 1/8 inches for '55 pistons, 3/4 race cam, 4 barrel. Built a 502/502 from 35 boxes for my street rod 20 years ago (when they were available unassembled.) Still runs great. In between sponsored Richard Petty for 15 years starting when they were in Level Cross until I semi-retired. Recall Dale Inman saying one day, go talk to the new engine builder he sounds like you (he was also a Yankee!) Dale was a fun, great guy to work with! Watched and appreciated how they got extra power!
But like I advanced from a "slip stick," there are more advanced designs. This is my 5th Vette with a small block as was the one in my '56 Chevy! Liked them all. Chevy did a remarkable job getting 495 drivable hp from a 6.2 Liter small block. It does require a "stump puller" low gear DCT to get the 0 to 60 mph number. I've only had DDs with a 3rd pedal but that performance trumps the transmission for me. I have "hold-a-spot money down on a C8 and will enjoy that small block as well!
Highly doubtful. Ferrari is cagey with the overall engine weight, but both the F154 CB and LT1/2 are all aluminum. I can find a few dimensions in Ferrari's press release on the 488.
F154 CB
Height - 25.51"
Width - 27.56"
LT1
Height - 25.26"
Width - 27.88"
Even if we assume the Ferrari's internals are lighter, there simply isn't going to be a lot of weight savings there. In fact the additional hardware of the DOHC design is likely to negate any of this.
The real weight savings here is in the chassis. GM simply can't produce a carbon fiber tub chassis at the price point they want to hit.
Enjoy the dialog with pushrod lovers! I know I'll never convince you but F1 engines weigh ~300 lbs, are 1.6 Liter twin turbo V6's and produce 850 to 900 hp! They do run on gasoline! They also have to run for a number of races, no rebuilding after each! Now I'm a big Drag Racing fan and think Prostock has some of the most sophisticated engines. They get ~1500 hp from 8.2 liters (also on gasoline.) That's 180/hp/Liter. F1 is 560 hp/Liter!
PS Ferrari uses aluminum construction for the 488:
08-14-2019, 10:29 AM
