Will We Ever Get Another DOHC Corvette?

"S65" (granthp)
08/29/2016 at 12:08 • Filed to: Questions, Corvette, DOHC, ZR-1

Will a DOHC V8 even fit in a C7?

DISCUSSION (35)

For Sweden > S65
08/29/2016 at 12:11

Hopefully not.

BorkBorkBjork > S65
08/29/2016 at 12:16

No real point in it. GM pushrod V8s have similar or better power-to-weight ratios compared to their Overhead Cam competitors, and are much smaller and therefore easier to package. Heres a DOHC 4.6L compared to a pushrod 5.0L:

Kinja'd!!!

lone_liberal > S65
08/29/2016 at 12:16

I’ll answer that with another question, do we need another DOHC Corvette?

Party-vi > S65
08/29/2016 at 12:17

The Vette doesn’t need a DOHC engine. Pushvalves and forced induction are still serving it just fine for the whole 25hp it would get going with DOHCs.

dogisbadob > S65
08/29/2016 at 12:18

They should! I’d love to see an American 100 hp/L NA engine! 620 hp from 6.2L

Too bad the Viper is gone, because an 840-hp 8.4L V10 would’ve been awesome

random001 > dogisbadob
08/29/2016 at 12:20

Pretty sure the aftermarket provides for this, without FI.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Party-vi
08/29/2016 at 12:21

and 50tq it might lose.

My bird IS the word > S65
08/29/2016 at 12:21

I’m still waiting to see how koenigsegg’s camless freevalve works out on production engines. camless all the things!

Bman76 (no it doesn't need a WS6 hood) M. Arch > dogisbadob
08/29/2016 at 12:21

Oops wrong reply

Bman76 (no it doesn't need a WS6 hood) M. Arch > S65
08/29/2016 at 12:22

Man I love the ZR-1

NJAnon > S65
08/29/2016 at 12:22

Maybe some crate engine thing could be made for that engine. But yeah I think the one they have is fine.

Chevrolet isn’t Dodge. The Viper also isn’t gone.

Logansteno: Bought a VW? > S65
08/29/2016 at 12:25

Fun thing I heard from my GM ASEP instructor just today.

The pushrod GM V8 is apparently dying by 2020. From then on they’ll all be DOHC for efficiency gains.

He also mentioned something about a mid engined vehicle being its first application. Not sure how much I believe that but hey, go GM if that's the case.

unclevanos (Ovaltine Jenkins) > BorkBorkBjork
08/29/2016 at 12:25

Ew modular engine.

random001 > dogisbadob
08/29/2016 at 12:26

Also, think of it like a real ‘Murican, and that 378 ci mill is pumping out 460hp, or 1.22 HP PER cubic inch! RAAAAHGHHGHGHGGHGMURICA!!!!

bhtooefr > S65
08/29/2016 at 12:27

It’d be possible with a displacement shrink, and there is a DOHC 4.2 twin turbo V8 being designed for Cadillac.

Also, we know that the C6 (really the same car as the C7, IIRC) could fit a DOHC V8 in a similar sized hole - the XLR was a C6 with a Northstar. A lot smaller displacement, though, obviously - 4.6 NA or 4.4 SC.

However, to get the same kind of power that is expected of a Corvette, you’re talking about either forced induction, or a very high-strung engine. The former could work, but the latter would likely not be a real improvement - a lot of the reason to go DOHC is to reduce valvetrain friction, and stiff valve springs will add that friction right back in. In addition, either of those ways will move the center of gravity up, affecting handling.

That said, there is always the possibility that economics could dictate the move to DOHC - emissions compliance is easier with DOHC 4v/cyl (easier to manage swirl in the cylinder, easier to vary valve timing independently, better flow), and valvetrain friction on low-revving engines can be lower (although it’s worth noting that the current (pushrod, direct injection) 4.3 V6 is around 35% efficiency, not far behind the Toyota 2GR-FKS at 36.5% in the Tacoma application, with similar power output, and much better low-end torque delivery.) This matters for the trucks, where there’s plenty of space in the engine bay for more valvetrain, and the regulations are putting an increasing amount of pressure there.

Conversely, the trucks don’t need the high end breathing benefits that a DOHC engine can give for power, because they’re run at lower RPM...

TL;DR, it could happen, but the Corvette benefits from pushrods I’d argue. If it happens, it’ll be because the trucks that fund the Corvette’s engines switched to chase fuel efficiency.

crowmolly > random001
08/29/2016 at 12:28

131 hp/L

Kinja'd!!!

dogisbadob > NJAnon
08/29/2016 at 12:28

Speaking of the Viper, what they could do to keep it alive is this:

A base V8 Viper, perhaps the SRT Hemi used in the Charger/Challenger 6.4L, 485 hp

Then the current model in the middle. 8.4L, 640 hp

And the Viper SRT-10 would have a DOHC V10 making 840 hp from 8.4L

The Viper would be manual-only, while they can rebadge it as a Chrysler or Maserati with an automatic.

jimz > dogisbadob
08/29/2016 at 12:28

the higher you push the specific output, the more you lose on the low end. would Corvette buyers want a revvy engine?

jimz > unclevanos (Ovaltine Jenkins)
08/29/2016 at 12:29

the Coyote (which is a Modular engine, mind you) is just as large.

SidewaysOnDirt still misses Bowie > BorkBorkBjork
08/29/2016 at 12:30

4.9*

BeaterGT > jimz
08/29/2016 at 12:32

No.

dogisbadob > jimz
08/29/2016 at 12:32

They wouldn’t notice anyway, given how they’re driven (rarely, and even then, only on like a cruise or something).

Besides, with a big V8, it’ll still have plenty of usable torque. They’d still have some 300+ lb ft to play with.

Jayhawk Jake > BorkBorkBjork
08/29/2016 at 12:33

This. K.I.S.S., and if it ain’t broke don’t fix it. If there was a distinct advantage to switching to DOHC the C7 would probably already have it.

jimz > BorkBorkBjork
08/29/2016 at 12:34

plus, for most “street” performance a Corvette owner would be interested in, the LS’s fatter bottom end would make the car feel faster. Back in the muscle-car era, the 440 Six Pack could walk the 426 Hemi on a drag strip. The Hemi’s much freer breathing up high just didn’t come into play much in only a 1/4 mile. Put the 440 and Hemi on a speedway, and the Hemi would run away.

random001 > crowmolly
08/29/2016 at 12:34

Excuse me for a moment....

crowmolly > jimz
08/29/2016 at 12:39

You could add the first gen Z/28 in there too.

MultiplaOrgasms > Smallbear wants a modern Syclone, local Maple Leafs spammer
08/29/2016 at 12:40

Lol no. The ten year old 1.4L in my Nissan has a nearly identical tq/displacement ratio as the the current LT1 without DI and way lower compression (9.8:1 vs 11.5:1) plus it makes peak torque about 1500rpm earlier.

Smallbear wants a modern Syclone, local Maple Leafs spammer > MultiplaOrgasms
08/29/2016 at 12:48

Lol no for the most part yes. Generally speaking, SOHC or DOHC V8's tend to produce a noticeably smaller amount of low-end torque than a pushrod V8, the AMG 6.2 engine being an obvious exception.

BorkBorkBjork > SidewaysOnDirt still misses Bowie
08/29/2016 at 12:51

Pedant

MultiplaOrgasms > Smallbear wants a modern Syclone, local Maple Leafs spammer
08/29/2016 at 12:53

Its called displacement.

Smallbear wants a modern Syclone, local Maple Leafs spammer > MultiplaOrgasms
08/29/2016 at 13:41

Not necessarily. Ford mod 5.4 springs to mind... OHC engines tend to be more revvy, which there isn’t anything wrong with. As a result they tend to go for the approach of using less displacement and making it rev higher to reach the desired power output. The more you make something rev, the more you lose at the bottom end. It’s all about where you design the engine to be comfortable. Pushrod engines tend to be less rev happy (though it can be done, set up properly you can have a fairly large displacement pushrod engine WELL north of 10,000rpm) and therefore lend themselves well to being set up for low-end. It is true that either engine can be set up for either duty, but the facts are that each one lends itself to one easier than the other. But I have an idea that we’re arguing two different things here. You’re saying that OHC doesn’t absolutely mean poor torque, I’m saying that in the Corvette it would.

Really what I’m going for is this. In a Corvette, a DOHC would be heavier, higher and generally bigger. Since they can get great power out of the current engines, one potential advantage would be to give the Corvette an engine which follows the more traditional sports car trait of being happy to rev. But the Corvette is associated with that low-down grunt and it’s highly likely that such an engine would wreak havoc with the Corvette brand, much the way the electric P/S system was a hit to the 911. They could get over it, like the 911, but that leads us on... Another advantage COULD be economy. But the Corvette already gets some pretty phenomenal figures, largely due to the torquey engine with a large displacement and AFM. There’s a reason GM never downsized that engine, and that was so it would have a more powerful 4cyl with AFM active, which meant it could run more of the time. If you’re taking away the torque for the sake of revs, you’ll need to have a MUCH smaller displacement to better the current economy figures. Which in turn means you’ll lose even more torque and need even more revs, to the point where the brand may not be able to weather the storm. To match the economy of the Corvette as it sits, they would have to go for a larger displacement OHC engine, use AFM, and set it up for low-end torque. Thereby losing the revs. You may recognize that as exactly what the Corvette has right now, but in a lighter, more compact package. So economy as a reason for going OHC is out. The only reason that remains is to make a rev-happy sports car. To match the current economy (because they would be able to go backwards) it’ll have to be a smaller engine. Which between that and being set up for revs WILL result in torque loss. Which was my original point.

!!! UNKNOWN CONTENT TYPE !!!

SidewaysOnDirt still misses Bowie > S65
08/29/2016 at 14:59

Northstar swap in the CletusVette? Northstar swap in the CletusVette!

SidewaysOnDirt still misses Bowie > Party-vi
08/29/2016 at 15:01

Think about how many more revs can be had without long pushrods to worry about though! It’s impressive that they got over 7000 with them, but that means they could have reached for over 8 with DOHC.

Party-vi > SidewaysOnDirt still misses Bowie
08/29/2016 at 15:28

OCH engines reach stratospheric RPMs because they can’t make the same power at human RPM levels.

CaptDale - is secretly British > S65
08/30/2016 at 13:21

DOHC is too big a package. They are doing just fine without the high revs.