GM's new 4.2L DOHC twin turbo V-8 !!

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peejay
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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by peejay » Sat Dec 08, 2018 1:33 pm

mk e wrote:
Sat Dec 08, 2018 11:31 am
Ron E wrote:
Sat Dec 08, 2018 10:24 am
I ask again. What is the functional reason? Can turbo a front engine car. So that's not it.
The main advantage of midengine is mostly braking. A car that is 50/50 weight sitting on the scales is 70/30 on the brake and overloads the front tires. A midengine car that starts arc30/70 is 50/50 when braking giving more braking for more laps. You can also brake a little deeper into the turns which also helps.
Corvette chassis engineers in the C6 era have stated, publicly, that they have reached the limts of front-engine performance because they cannot get enough accleerative grip to deal with the amount of power they are able to get from Powertrain.

Their options are to try to package all wheel drive, or to go with a mid-engine design.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by peejay » Sat Dec 08, 2018 1:35 pm

Truckedup wrote:
Sat Dec 08, 2018 12:18 pm
I have to ask, does anyone here think they can take this years highest performance front engine Vette and utlilize all it's performance on a public road other than in a straight line?

I couldn't take a base model Mazda 2 to utilize all of its performance on a public road, not even in a straight line.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Brian P » Sat Dec 08, 2018 2:33 pm

Ron E wrote:
Sat Dec 08, 2018 10:24 am
Brian P wrote:
Sat Dec 08, 2018 10:03 am
Nobody buys a Vette (of any sort) because it's "necessary"!

Chevrolet reached the limit of what could be done with a front engine platform. Ferrari, McLaren, etc use mid engine for a reason ... and it's the same reason GM is doing this. Will it look "different", sure. They'll have to push the driver's compartment forward.
I ask again. What is the functional reason? Can turbo a front engine car. So that's not it.
Bear in mind that every modern Formula 1, Indycar, etc uses a midship/rear layout. You will not win a Formula 1 race nowadays with a car having a front-engine layout!

General advantages:
Better front/rear balance during braking (already covered above)
Better grip during acceleration because it starts off with more weight on the drive wheels, particularly when accelerating out of corners
Reduced polar moment of inertia (for changing directions) - the heavy stuff is well inside the wheelbase

The tradeoff is reduced understeer budget, i.e. reduced stability. Mid/rear is not quite as bad as a rear-engine layout, but it's heading in that direction. I'm sure the suspension engineers have had their work cut out for them, and aerodynamics matters at higher speeds, too.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by MadBill » Sat Dec 08, 2018 4:11 pm

Truckedup wrote:
Sat Dec 08, 2018 12:18 pm
I have to ask, does anyone here think they can take this years highest performance front engine Vette and utlilize all it's performance on a public road other than in a straight line? I have to ask, can anyone here take the highest performance Camaro, Mustang or Challenger and use all the performance on the street other than in a straight line...?
Super performance cars are bragging rights for the manufacturer and the owners...
And how about the tens of millions of drivers getting half the mileage they could in a car while toting nothing but air in their off road-capable HD 4WD pick 'em ups and tip-toeing over speed bumps at 2 MPH? #-o
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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Newold1 » Sat Dec 08, 2018 5:04 pm

We need to keep remembering that this forum is called SPEEDTALK!

We are not here to discuss and delb into grocery getters or your grandfathers Buick!

We are here discussing horsepower, performance and the engines and vehicles that exemplify those characteristics!

Mid-engine Corvettes are not for the everyday driver nor are they supposed to make sense! For those who feel the "need for speed" and want a car that can provide that thrill, I think they will do a great job of that!

If you as a fellow enthusiast are excited about new performance technology in engine and vehicles, the near future seems to hold ever increasing exciting offerings and possibilities!

If you have a problem here on Speedtalk with engines like this new 4.2L twin turbo V-8 and cars like a new mid-engine Corvette then "there's the door"! Just my personal opinion.
The Older I Get, The Dumber I Get :wink:

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by mk e » Sat Dec 08, 2018 8:19 pm

MadBill wrote:
Sat Dec 08, 2018 4:11 pm

And how about the tens of millions of drivers getting half the mileage they could in a car while toting nothing but air in their off road-capable HD 4WD pick 'em ups and tip-toeing over speed bumps at 2 MPH? #-o
LOL
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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by stokerboats » Sat Dec 08, 2018 8:52 pm

103 years later, the Chevy V8 still improves.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by peejay » Sat Dec 08, 2018 11:55 pm

mk e wrote:
Sat Dec 08, 2018 8:19 pm
MadBill wrote:
Sat Dec 08, 2018 4:11 pm

And how about the tens of millions of drivers getting half the mileage they could in a car while toting nothing but air in their off road-capable HD 4WD pick 'em ups and tip-toeing over speed bumps at 2 MPH? #-o
LOL
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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Olds455 » Sun Dec 09, 2018 1:20 am

Man you guys love to TRY to show each other up, don't you? You all can barely have a conversation without somebody trying to prove how much smarter they are than everyone else. Don't you guys get tired of this? C'mon.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Newold1 » Sun Dec 09, 2018 10:49 am

If you're talking about my smarts, please reread my qoute- "The Older I Get, the Dumber I Get!"
I hav'nt learned yet one tenth of what I need to or should know!
The Older I Get, The Dumber I Get :wink:

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Ron E » Sun Dec 09, 2018 1:26 pm

Mark and Brian. Thanks. Those were the kind of answers I was looking for. The change kind of makes sense in those terms. I'm anything but a chassis guy. Although I'm still curious how the ZR1 reset the lap record at VIR by a full second from the previous record held by a Ford GT. Ford had a professional driver, the 'vette had an obviously talented driver. But, he's a GM engineer.

Carnut, you suggest "cool" doesn't matter. But, you also say its what the current and future 'vette buyers want. That tells me the "cool factor" remains at the top of the list. As mentioned before, maybe 1 tenth of 1% of the buying public has a prayer of taking the ZR1 near its limits and surviving to tell the story.

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by peejay » Sun Dec 09, 2018 1:30 pm

Engineers can be talented drivers too, they just have different "day jobs".

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Bazman » Sun Dec 09, 2018 5:03 pm

Truckedup wrote:
Sat Dec 08, 2018 12:18 pm
I have to ask, does anyone here think they can take this years highest performance front engine Vette and utlilize all it's performance on a public road other than in a straight line? I have to ask, can anyone here take the highest performance Camaro, Mustang or Challenger and use all the performance on the street other than in a straight line...?
Super performance cars are bragging rights for the manufacturer and the owners...
Well, if you'd like to come on down to lil ol New Zealand and put one into our Targa events, you can have both lanes closed off on public roads and go for broke - speed limits apply on the straights, but trust me, the Camaro, Mustang and Challenger will be out paced no matter what model. Horses for courses.... the ZR1 would be great to see, I'd love to ring its neck on our roads. Biggest problem would be getting adequate clearance, might have to raise it 50mm (2") to compete. On twisty roads that have the odd bump and changes in surface, a worked Evo is almost impossible to beat, though I prefer more challenging cars - like my twin turbo LS3 haha.... not as quick overall - but a lot more fun... so yeah, not everyone just likes to go 1/4 mile at a time

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by Truckedup » Mon Dec 10, 2018 9:04 am

Uh, public roads closed off to traffic are race tracks... :D .. In this country are many remote areas where a car could be driven at or near it's limit for a short period of time.And there are track days on road courses..But I believe many owners do not have the ability or want to risk the chance of a wrecks.... Spend an hour on You Tube and you can see 100's of Corvettes spinning out and crashing on the street at relatively low speeds...When the traction and stability control is turned off, catching a high HP car when it' breaks traction is not so easy...
I don't believe that for one second that HP or performance limits should be controlled by the gov't,but there's a lot of drivers out there that are not as good as think they are..
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire

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Re: GM's new 4.2L DOHC twin turbo V-8 !!

Post by mk e » Mon Dec 10, 2018 9:39 am

Driver assistance like traction and stability control are probably the only reason high hp rear drive production cars exist. I remember back when front drive cars were charging into the market in the 80s...I read most manufacturers believed 15:1 weight/hp was about it for a stable car. Chrysler thought 13:1 is the number I recall and offered a couple "hot"small fed cars. Then came computers and even minivans moved into the once unstable space. I have a bad wheel sensor somewhere on my bmw driver do all the assist system including awd are off-line so rwd, .....it drives terrible......I'd forgotten about things like the inside wheel just spins and you barely move as you pull out while turning...yuck.

Midengine cars are mostly insensitive to hp....things happen faster with more power and you get more throttle induced understeer but a 600+hp midengine car drives just fine on the street or track with no computer helping. When I first started talking about engine work on my 308 the immediate responses were "you're going to throw off the chassis balance, it won't drive right, blah, blah, blah". Going from 240hp to 400 to about 650 the only thing that changed was the acceleration rate and what rpm I normally shifted at around town....and winning autocrosses got easier not harder. The new 900ish hp engine (if I ever get it working right) did make me think it was a good idea to add sensors traction control....but I don't think it will actually be necessary.....this is just a very stable layout.
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