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Gen VI engine based on XV8 dual-cam in block concept?

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Gen VI engine based on XV8 dual-cam in block concept?

 
Old 04-30-2019, 07:57 PM
  #41  
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Originally Posted by Tool Hoarder View Post
Yeah wouldn't make much sense to chain drive those. DI fuel pump works off cam lobe just fine (primary being electric) and, if anything, the water pump may go electric.
Vaccum pump? The one on the tahoe is belt driven but is kind of bulky. Maybe they integrated into the block. Otherwise idk. The photo makes it hard to tell but the angle the chain appears to go off at isn't necessarily up from what I can see.
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Old 04-30-2019, 10:13 PM
  #42  
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Great thread OP. Quite a refresher if I may say so.
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Old 04-30-2019, 10:24 PM
  #43  
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Originally Posted by Tool Hoarder View Post
Also, note the damper has provisions for 2 belts. Why would you need that if the car is going to be NA or turbo?
48v motor/generator mild hybrid
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Old 04-30-2019, 10:33 PM
  #44  
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Great catch Jeff,

edit, i read the article and answered my own question. This is really cool, thanks for posting.

It will be cool to see how much they can make the engine lope like it has a racing cam... but probably cant do this as the cam lobe would have to grow in "duration open".. so unless they have cam lobes that grow somehow, that's probably off the table.

also, it will be interesting to see if the cams timing can easily be changed via tuning software or how it will work.

This is pretty awesome.

Last edited by Mikec7z; 04-30-2019 at 11:05 PM.
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Old 05-01-2019, 12:43 AM
  #45  
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This would be a really exciting engine if it gets variable lift or at least independent intake/exhaust valve phasing via this new cam design.

Originally Posted by Warp Factor View Post
Yes, it can rev that high, but it makes peak power between 6500 and 6800 rpm (easily attainable with pushrods), so the high-revving advantages of overhead cams aren't really coming into play.
The Ford Coyote 5.0 V8 can rev to 7500, but makes peak power at a measly 6500, about where a pushrod LT4 does.

So the overhead cams in these engines are little more than placebo effect, carrying the disadvantages of increased weight and dimensions.
There are benefits to high revs even if the peak is not at redline. The S2000 made peak hp at just over 8,000rpm but was always faster when revved to 9,000 rpm. As long as the head flow is there and torque doesn't fall too quick average power in gear will be higher. It appears that even the LT4 or LT5 would propel the car forward faster if it could rev higher. The redline is there to reduce wear on valvetrain and supercharger not because the car wouldn't accelerate any faster with a higher redline.

Originally Posted by Jeff V. View Post
Front lift pump would be electric rather than belt driven. Especially if it's an optional system.

But that mystery pulley is too big to be an idler. It almost looks like it's got a magnetic clutch too. Maybe some kind of auxiliary cooling pump?
Another option is to raise or lower the ride height (at both ends) similar to the Ford GT. That system is hydraulic and you would need a belt that big for it. This would allow for far superior aerodynamics on flat smooth racetracks.
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Old 05-01-2019, 12:48 AM
  #46  
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i did hear the c8 has 7 or 8 heat exchangers onboard, so the cooling pump is not out of the question either, but i like where your mind is too SBC

I also dont think a supercharger is out of the question, i know they are going to turbos, but you never know.
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Old 05-01-2019, 01:03 AM
  #47  
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Originally Posted by Mikec7z View Post
i did hear the c8 has 7 or 8 heat exchangers onboard, so the cooling pump is not out of the question either, but i like where your mind is too SBC

I also dont think a supercharger is out of the question, i know they are going to turbos, but you never know.
Wait till you see the cooling on the hybrid bits! If they have to circulate water around batteries to keep them from overheating it could require a much higher water pump load and potentially separate pumps since the ICE needs might vary from those of the electric motor.
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Old 05-01-2019, 02:43 AM
  #48  
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Originally Posted by SBC_and_a_stick View Post
Another option is to raise or lower the ride height (at both ends) similar to the Ford GT. That system is hydraulic and you would need a belt that big for it. This would allow for far superior aerodynamics on flat smooth racetracks.
That's very interesting. I had just assumed the GT had electrically assisted steering like everything else these days. I didn't know that it had normal power steering and that the same pump was used for the suspension. I've often wondered how they get the car to raise and lower so much faster than most other cars. Very cool.
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Old 05-01-2019, 10:10 AM
  #49  
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Originally Posted by Jeff V. View Post
One belt drives the left side accessories, the other drives the right side accessories. A few other current GM engines are set up that way.
I realized that after I posted... my C5 was obviously that way with an "AC belt" and then the main belt. The C7 NA cars have all accessories on one belt and use the other path for the supercharged cars.
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Old 05-01-2019, 10:12 AM
  #50  
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Originally Posted by Warp Factor View Post
So the overhead cams in these engines are little more than placebo effect, carrying the disadvantages of increased weight and dimensions.
I disagree for a couple reasons:

1. You have to look at power area under the curve vs. peak. If the car makes more area under the curve then the added RPM is beneficial.

2. RPM range on track. There are plenty of scenarios where extended RPM us useful for eliminating shifts. VIR is a perfect example where we bumped C5s to 7K to avoid 5th gear on each straight.
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Old 05-01-2019, 10:12 AM
  #51  
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Originally Posted by NY09C6 View Post
48v motor/generator mild hybrid
Nope, it has an alternator on the lower left.
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Old 05-01-2019, 02:27 PM
  #52  
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Originally Posted by vndkshn View Post
^Not sure it is just "placebo". Up to this point, the only real way to do variable valve timing (especially for both intake and exhaust separately) has been DOHC. So DOHC is about more than just RPM.
Don't forget about the concentric cam setup Mechadyne patented that was used in the viper for independent intake and exhaust vvt on a Pushrod.

Last edited by CPhelps; 05-02-2019 at 09:13 PM. Reason: Corrected Multimatic to Mechadyne
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Old 05-01-2019, 03:23 PM
  #53  
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Originally Posted by CPhelps View Post
Don't forget about the concentric cam setup Multimatic patented that was used in the viper for independent intake and exhaust vvt on a Pushrod.
Not finding any information googling "multimatic concentric camshaft".

I do find a hit on Mechadyne. Their video (or any other that I found) doesn't really show the intake timing changing, as well as exhaust timing changing. All the videos I saw were of just one lobe advancing/retarding.
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Old 05-01-2019, 04:01 PM
  #54  
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Originally Posted by CPhelps View Post
Don't forget about the concentric cam setup Multimatic patented that was used in the viper for independent intake and exhaust vvt on a Pushrod.
Cool! A more elegant solution than two separate in-block cams if the only goal is VVT. It's not even all that new: a concentric VVT camshaft was rumored for the gen V small block.

Maybe GM found the concentric cam doesn't hold up to their reliability standards?

Or maybe the extra cam is to enable different cam profiles at different loads/rpms by using DFM's solenoid-actuated rod lifters. Everything optimized: timing, lift, and duration. The intake cam would have 16 lobes but only half the pushrod lifters would be active at once.

They lifters are already there for DFM, all it would take is extra lobes (which we see) and some funky intake rockers that can be controlled by either one of two pushrods.

I guess I can share this: an insider told me that the C8 base will use an LT2. He wouldn't tell me anything about the LT2 except to say it will have a big surprise. "It has a feature that will blow you away," he told me. I should run my crazy theory by him to see if he laughs or goes quiet.

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Old 05-01-2019, 04:05 PM
  #55  
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Twin cam in block seems to be the most logical thing based on the image from the teaser. It would be a "crazy feature" to most of us.
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Old 05-01-2019, 05:04 PM
  #56  
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The LT2 will most likely just be an upgrade in power from the LT1 engine. Much like the LS2 to LS3 since it is being listed as a Gen V engine still.



Last edited by radrace19; 05-01-2019 at 05:21 PM.
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Old 05-02-2019, 09:16 AM
  #57  
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Originally Posted by radrace19 View Post
The LT2 will most likely just be an upgrade in power from the LT1 engine. Much like the LS2 to LS3 since it is being listed as a Gen V engine still.

Yeah it looks like placeholder data. Basically the description of the LT2 is identical to the LT1? It won't even have DFM despite being built at Spring Hill which has been updated to build DFM small blocks? I don't think so.
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Old 05-02-2019, 10:13 AM
  #58  
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Originally Posted by Zaro Tundov View Post
Yeah it looks like placeholder data. Basically the description of the LT2 is identical to the LT1? It won't even have DFM despite being built at Spring Hill which has been updated to build DFM small blocks? I don't think so.
When did they say it was moving from Tonawanda to Spring Hill? I must have missed that.
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Old 05-02-2019, 10:47 AM
  #59  
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Originally Posted by Jeff V. View Post
One of the still images that was flashed on screen during the official GM teaser video showed a very weird engine cutaway. It's got two oil pump gerotors, and two timing chains. The positions of some of the other parts are identical to the current 6.6L L8T V8. It's a long shot, but it might be something very old made new again.



Back in 2001, GM had a concept engine they called the XV8. It had two cams in the block, 3 valves per cylinder, direct injection and displacement on demand. It also had two oil pumps. The dual oil pumps were so it could run with deactivated cylinders at idle speeds.

This article has a ton of interesting info. It directly addresses the dual oil pump situation, and the diagrams below explain the 2nd timing chain.

https://www.acarplace.com/brands/gm/xv8-engine.html





I seriously think this is an evolution of the XV8 concept.
Great find! Solves two issues of why I have thought a double overhead cam was needed. Twin intake valves and most important the ability to separately control Intake and cam timing independently for optimum low end torque, high end power and mpg at cruising!

Maybe that is why it's a 6.3 Liter engine, larger bore shorter stroke! We'll soon see.

Not quite like the Rodger Penske pushrod Indy engine but that high cam does shorten the large exhaust valve pushrod length! With two lighter intake valves the large exhaust valve would be harder to control at high rpm.

Last edited by JerryU; 05-02-2019 at 11:05 AM.
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Old 05-02-2019, 12:42 PM
  #60  
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Originally Posted by Jeff V. View Post
When did they say it was moving from Tonawanda to Spring Hill? I must have missed that.
Investment in Spring Hill plant for DFM.

Well now. This isn't such a good source for the LT2 being manufactured at Spring Hill. Herron makes it sound like the LT1 is already built at Spring Hill but GM states only 6.2L V8 destined for trucks are manufactured there.
GM’s engine plant in Spring Hill, Tennessee, will continue to make 6.2-liter engines for the traditional Corvette after the mid-engine car is launched at Bowling Green, said Mike Herron, chairman of UAW Local 1853 at Spring Hill.
Thanks for asking for the link, made me realize it's not definitive at all.

Originally Posted by JerryU View Post
Great find! Solves two issues of why I have thought a double overhead cam was needed. Twin intake valves and most important the ability to separately control Intake and cam timing independently for optimum low end torque, high end power and mpg at cruising!

Maybe that is why it's a 6.3 Liter engine, larger bore shorter stroke! We'll soon see.

Not quite like the Rodger Penske pushrod Indy engine but that high cam does shorten the large exhaust valve pushrod length! With two lighter intake valves the large exhaust valve would be harder to control at high rpm.
Two intake valves for NA engines only move the power band higher up. There's not much point doing it with pushrods since the result is a low revving engine that doesn't wake up until midrange rpms. With DOHCs it's great for track use: more area under the power curve and at high speeds it's easy to keep the engine at optimal rpms. For street use? Who wants an engine that only wakes up at over 4000rpm?

Where is this 6.3L displacement coming from?

Last edited by Zaro Tundov; 05-02-2019 at 12:53 PM.
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