Will have the C8 an engine with crossplane or flat crankshaft - CorvetteForum - Chevrolet Corvette Forum Discussion



C8 General Discussion The place to discuss the next generation of Corvette, be it mid-engine, Zora, or whatever form it may take.
Sponsored by:
Sponsored by:

Will have the C8 an engine with crossplane or flat crankshaft

Reply
 
 
 
Thread Tools Search this Thread
Old 02-25-2018, 03:47 PM   #1  
[email protected]
CF Senior Member
Thread Starter
 
Christi@n's Avatar
 
Member Since: Sep 2014
Location: Trieste Italy
Posts: 1,386
Thanked 38 Times in 34 Posts
Default Will have the C8 an engine with crossplane or flat crankshaft

Have someone Heard some rumor about crankshft type of the new c8 vette?

I hope for crossplane
Christi@n is offline   Reply With Quote
Old 02-25-2018, 03:58 PM   #2  
OnPoint
CF Senior Member
Support Corvetteforum!
 
OnPoint's Avatar
 
Member Since: May 2006
Location: Wichita Kansas - 2015 Z06 & 2010 ZR1
Posts: 17,557
Thanked 1,585 Times in 949 Posts
Default

Nothing definitive is known.

If the displacement is above 5.0 liters it'll be a crossplane.
OnPoint is offline   Reply With Quote
The Following User Says Thank You to OnPoint For This Useful Post:
[email protected] (02-25-2018)
Old 02-26-2018, 10:46 AM   #3  
RJ-92
CF Senior Member
 
RJ-92's Avatar
 
Member Since: May 2005
Location: NY
Posts: 11,293
Thanked 19 Times in 16 Posts
Default

Quote:
Originally Posted by Shaka View Post
There is no point for having a flat crank unless you want to rev it. Direct injection is heavy but can't rev high unless you make it much heavier. 50 lb 4000 psi fuel pumps require much HP to run at 8000 engine rpm. Turbo charging negates high revs anyway. High revs uses more gas. As Onpoint mentions, 5 liters is the limit for a flat crank in a V8. GM won't guarantee such a mill. You also can't modify the engine if you don't have access to and have know how to use very specialized expensive equipment. You increase primary and secondary shakes which requires a heavy and complex vibration damper and special engine mounts. The most closely guarded secret in race engines. Try taking a picture of one in the pits.
It is much lighter and has better throttle response up or down which is good for fast shifts. Ain't going to happen at GM. The LS engine engineers were given permission to do as they please and they explored a flat crank. It can't meet future smog and neither can OHV engines and has no virtues except for the above mentioned. It even sounds UTS. Can't even hear a F488 which is a 3rd of the car's value.
RJ-92 is online now   Reply With Quote
Old 02-26-2018, 03:53 PM   #4  
vetteLT193
CF Senior Member
Support Corvetteforum!
 
Member Since: Jul 2002
Location: Tallahassee fl
Posts: 1,218
Thanked 73 Times in 48 Posts
Default

Quote:
Originally Posted by Shaka View Post
There is no point for having a flat crank unless you want to rev it. Direct injection is heavy but can't rev high unless you make it much heavier. 50 lb 4000 psi fuel pumps require much HP to run at 8000 engine rpm. Turbo charging negates high revs anyway. High revs uses more gas. As Onpoint mentions, 5 liters is the limit for a flat crank in a V8. GM won't guarantee such a mill. You also can't modify the engine if you don't have access to and have know how to use very specialized expensive equipment. You increase primary and secondary shakes which requires a heavy and complex vibration damper and special engine mounts. The most closely guarded secret in race engines. Try taking a picture of one in the pits.
It is much lighter and has better throttle response up or down which is good for fast shifts. Ain't going to happen at GM. The LS engine engineers were given permission to do as they please and they explored a flat crank. It can't meet future smog and neither can OHV engines and has no virtues except for the above mentioned. It even sounds UTS. Can't even hear a F488 which is a 3rd of the car's value.
More RPM means you can use your gears better so why wouldn't you want to rev higher? Lingenfelter has built a flat plane LSx already. If they can do it in their shop I'd think GM could handle it with 100000 times the resources.

And more RPM in a smaller engine doesn't equate to more fuel use. In fact the cruising fuel use typically goes down because the engine is smaller.

I'm not advocating for a flat plane but it's really nice to have an engine that can rev to the moon. My M3's V8 redlines at 8,400 and it's awesome.
vetteLT193 is offline   Reply With Quote
Old 02-28-2018, 04:25 AM   #5  
[email protected]
CF Senior Member
Thread Starter
 
Christi@n's Avatar
 
Member Since: Sep 2014
Location: Trieste Italy
Posts: 1,386
Thanked 38 Times in 34 Posts
Default

IMO it's all about sound.

I like the v8 cross sound more than v8 flat sound Also on an American car this should be an iconic character
Christi@n is offline   Reply With Quote
Old 03-01-2018, 04:31 AM   #6  
Trackaholic
CF Senior Member
 
Trackaholic's Avatar
 
Member Since: Mar 2013
Posts: 620
Thanked 37 Times in 19 Posts
Default

Quote:
Originally Posted by vetteLT193 View Post
More RPM means you can use your gears better so why wouldn't you want to rev higher? Lingenfelter has built a flat plane LSx already. If they can do it in their shop I'd think GM could handle it with 100000 times the resources.

And more RPM in a smaller engine doesn't equate to more fuel use. In fact the cruising fuel use typically goes down because the engine is smaller.

I'm not advocating for a flat plane but it's really nice to have an engine that can rev to the moon. My M3's V8 redlines at 8,400 and it's awesome.
Your M3's V8 is a cross-plane configuration. Nothing about a cross-plane design prevents it from revving high. It just requires more crankshaft balance mass, but once the mass is added it is actually much smoother than a flat-plane design. It may not have quite the no-load throttle response of a flat-plane design, but it can certainly rev out if designed that way.

The flat-plane design used in my GT350's engine is pretty nice at times, but also causes lots of vibrations that require lots of engineering to quell. I think it would be nice if the C8/Mid Engine Vette get a 4 valve, cross-plane design that is designed to rev a bit higher than the LT1, but not sacrifice too much for an 8000+ RPM redline.

In the end, if the displacement is ~5.0 liters and they want 100 hp/liter (500 HP total) it will still need to rev to make that power.

Really looking forward to seeing how this next gen Vette turns out.

-T

Last edited by Trackaholic; 03-01-2018 at 04:32 AM.
Trackaholic is offline   Reply With Quote
The Following User Says Thank You to Trackaholic For This Useful Post:
[email protected] (03-19-2018)
Old 03-01-2018, 11:58 PM   #7  
Guard Dad
CF Senior Member
 
Guard Dad's Avatar
 
Member Since: Nov 2013
Location: South Orange County California
Posts: 745
Thanked 24 Times in 22 Posts
Default

The flat plane crank V8 is even firing with the main advantages being reduced rotating mass and superior exhaust scavenging compared to a cross plane V8. The trade off is a big increase in vibration. The vibration becomes especially noticeable when engine displacement gets above about 4 liters that’s why you don’t see many large displacement flat plane V8 engines in road cars. Space permitting, it is sometimes possible (see the original Ford GT “bundle of snakes exhaust”) to use a cross plane crank with a 180 degree exhaust system to achieve more optimal scavenging similar to that achieved with a flat plane crank.

Regarding revs, power is power, 500 HP at 4000 rpm is just as strong as 500 HP at 8000 rpm, however the torque curves would look quite different! All things being equal the 4000 rpm engine would be more fuel efficient because internal friction increases logarithmically so that 8000 rpm engine suffers from significantly more internal drag at a given power output. That friction issue is why Corvette engines are designed to stay under 2000 rpm in most cruise conditions. Revs can be fun but due to fuel economy considerations the trend is to reduced cylinder count (less friction per unit of displacement) and turbo charging (more power per unit of displacement at lower rpm) to keep friction losses low and efficiency high.

Last edited by Guard Dad; 03-02-2018 at 12:02 AM.
Guard Dad is offline   Reply With Quote
The Following 2 Users Say Thank You to Guard Dad For This Useful Post:
[email protected] (03-19-2018), pdiddy972 (03-19-2018)
Old 03-02-2018, 02:17 AM   #8  
Trackaholic
CF Senior Member
 
Trackaholic's Avatar
 
Member Since: Mar 2013
Posts: 620
Thanked 37 Times in 19 Posts
Default

Quote:
Originally Posted by Guard Dad View Post
The flat plane crank V8 is even firing with the main advantages being reduced rotating mass and superior exhaust scavenging compared to a cross plane V8. The trade off is a big increase in vibration. The vibration becomes especially noticeable when engine displacement gets above about 4 liters that’s why you don’t see many large displacement flat plane V8 engines in road cars. Space permitting, it is sometimes possible (see the original Ford GT “bundle of snakes exhaust”) to use a cross plane crank with a 180 degree exhaust system to achieve more optimal scavenging similar to that achieved with a flat plane crank.

Regarding revs, power is power, 500 HP at 4000 rpm is just as strong as 500 HP at 8000 rpm, however the torque curves would look quite different! All things being equal the 4000 rpm engine would be more fuel efficient because internal friction increases logarithmically so that 8000 rpm engine suffers from significantly more internal drag at a given power output. That friction issue is why Corvette engines are designed to stay under 2000 rpm in most cruise conditions. Revs can be fun but due to fuel economy considerations the trend is to reduced cylinder count (less friction per unit of displacement) and turbo charging (more power per unit of displacement at lower rpm) to keep friction losses low and efficiency high.
I've haven't been following the ME vette except for the last few days, but I thought the engine displacement was rumored to be around 5 liters. Maybe that's not correct?

I agree that power is power, but an engine making 500 HP at 4000 RPM is also making ~650 lb-ft of torque. That's not happening on a NA engine.

So, if it is going to be "small", then in order to make 500 HP it will need the revs. Just for fun I looked up the volumetric efficiency of many top N/A engines (torque/liter). Here is what I found:

Honda S2000:
155 lb-ft, 2.0 L = 77.5 lb-ft/L
163 lb-ft, 2.2 L = 74.1 lb-ft/L

Lambo Huracan:
413 lb-ft, 5.2 L = 79.4 lb-ft/L

Ford GT350:
429 lb-ft, 5.2 L = 82.5 lb-ft/L

Ford Gen3 Coyote V8:
420 lb-ft, 5.0 L = 84.0 lb-ft/L

GM LT1:
460 lb-ft, 6.2 L = 74.2 lb-ft/L

GM LS7:
470 lb-ft, 7.0 L = 67.1 lb-ft/L

BMW M3 V8:
300 lb-ft, 4.0 L = 75.0 lb-ft/L

The main point here is that the advanced 4 valve, high performance engines are able to make around 80 lb-ft per liter. If you optimize a 5 liter engine for power, you will likely give up some of that mid range torque in order to have better breathing up top for more power.

If the engine can make 350 lb-ft at redline, it would need to rev to 7500 to make 500 HP.

I would honestly love an updated version of the LS7 for the ME vette. I think that is one of GM's most exciting engines (reliability concerns duly noted); it makes great power with excellent torque, and with DI updates could be even more potent.

Anyhow, I think I just wasted a bunch of time, but I did have fun looking at various engine specs, so there is that.

-T

Last edited by Trackaholic; 03-02-2018 at 02:18 AM.
Trackaholic is offline   Reply With Quote
The Following 2 Users Say Thank You to Trackaholic For This Useful Post:
GettnBetter (03-08-2018), sunsalem (03-04-2018)
Old 03-02-2018, 02:28 PM   #9  
Bill Dearborn
Tech Contributor
 
Bill Dearborn's Avatar
 
Member Since: Oct 1999
Location: Charlotte (formerly Endicott, NY) NC
Posts: 30,964
Thanked 2,313 Times in 1,597 Posts
Default

They want the engine small and that doesn't necessarily mean small inside. They need a compact, light engine and OHC engines historically haven't provided that. Look at the people replacing Porsche 944 4 cylinder turbo'd OHC engines with a simple LS1 that weighs 40 lbs more and comes in a physically smaller package. Replace a 2.5 L Turbo Four producing 247 HP with a 5.7 L 350 HP NA engine with a much better torque curve. The LS1 weighs about 40 lbs more and can be set back further in the chassis due to its smaller size. What if they decided to throw in an LS6 or LS3 which weigh about the same as the LS1? You are then talking about Sudden Impact.

I have ridden in one of those light weight cars with a 350 Horse LS1 and they go like stink. With the engine set back further, the chassis is well balanced and you are sitting at less than 2900 lbs with a non stripped car. Strip the car down, add a cage and you are less than 2800 lbs.

Why should GM constrain themselves to a physically larger and heavier engine to have a pure DOHC that makes more HP per Liter but less HP per pound and unit of total volume?

Bill
Bill Dearborn is offline   Reply With Quote
The Following 7 Users Say Thank You to Bill Dearborn For This Useful Post:
[email protected] (03-19-2018), elegant (03-19-2018), JerriVette (03-03-2018), JustinStrife (03-03-2018), Lavender (03-05-2018), Shaka (03-02-2018), Tamulinas2 (03-05-2018)
Old 03-03-2018, 01:35 AM   #10  
Chrisrokc
CF Senior Member
 
Chrisrokc's Avatar
 
Member Since: Mar 2003
Location: Oklahoma City OK
Posts: 1,383
Thanked 3 Times in 2 Posts
Default

Three engines.
Normal LS based
New OHVT flat crank 5.x
New forced induced

Information came from a source in the know.

Last edited by Chrisrokc; 03-05-2018 at 03:03 PM.
Chrisrokc is offline   Reply With Quote
Old 03-03-2018, 02:49 AM   #11  
Trackaholic
CF Senior Member
 
Trackaholic's Avatar
 
Member Since: Mar 2013
Posts: 620
Thanked 37 Times in 19 Posts
Default

Quote:
Originally Posted by Bill Dearborn View Post
They want the engine small and that doesn't necessarily mean small inside. They need a compact, light engine and OHC engines historically haven't provided that. Look at the people replacing Porsche 944 4 cylinder turbo'd OHC engines with a simple LS1 that weighs 40 lbs more and comes in a physically smaller package. Replace a 2.5 L Turbo Four producing 247 HP with a 5.7 L 350 HP NA engine with a much better torque curve. The LS1 weighs about 40 lbs more and can be set back further in the chassis due to its smaller size. What if they decided to throw in an LS6 or LS3 which weigh about the same as the LS1? You are then talking about Sudden Impact.

I have ridden in one of those light weight cars with a 350 Horse LS1 and they go like stink. With the engine set back further, the chassis is well balanced and you are sitting at less than 2900 lbs with a non stripped car. Strip the car down, add a cage and you are less than 2800 lbs.

Why should GM constrain themselves to a physically larger and heavier engine to have a pure DOHC that makes more HP per Liter but less HP per pound and unit of total volume?

Bill
I think it will come down to how much power they want to make in a naturally aspirated engine. Can they make that power and still meet all their emissions requirements. I thought they had mentioned that the C7Z went to the supercharger because they weren't able to hit their power targets with a naturally aspirated engine while remaining compliant.

The cam-in-block architecture is excellent from a weight and packaging perspective, but you are limited with what you can do with valve timing. In reading about the Viper engine, they had to move to a cam-in-cam design that allowed them to vary the exhaust timing. This allowed them to hit emissions requirements and still achieve their power goals.

Maybe that tech is an option if GM wants to stay with the pushrod design.

I do wonder a bit if there will be a general feeling that pushrod is too old fashioned for a mid-engine, modern sports car. That might be another reason to go with a DOHC architecture.

Here is the article on the viper engine:
http://www.hotrod.com/articles/how-t...ts-horsepower/

-T

Last edited by Trackaholic; 03-03-2018 at 02:50 AM.
Trackaholic is offline   Reply With Quote
Old 03-03-2018, 03:37 AM   #12  
JerriVette
CF Senior Member
 
JerriVette's Avatar
 
Member Since: Nov 2003
Location: Bergen county NJ
Posts: 9,684
Thanked 538 Times in 415 Posts
Default

Possible 4 liter Dohc twin turbo in valley v8 is a GM design.

Flat plan crank version is entirely possible for corvette Zora (like 488) while the Cadillac version if produced could have a more traditional build for smoothness. If creating both versions with the same block is possible?

I'm not a fan of Dohc extra weight and exterior sizing but for eurosnobs that seems to be considered something to have...so if Cadillac gets a version of the c8 chassis it will surely have the Cadillac twin turbo v8 that was set for its large TT v8 sedan lineup that has been put on the shelf...

How far that twin turbo 4.0 v8 production went...nobody knows....but it was scheduled...very close to a reality. I doubt it's a flat pan crank for Cadillac since smoothness would be a high priority..

I'd rather have a LT1 , LT4 and LT5 than a twin turbo 4 liter v8 ...flat plane crank or otherwise...

Complication and cost are concerns....
JerriVette is offline   Reply With Quote
Old 03-03-2018, 01:00 PM   #13  
Jinx
CF Senior Member
 
Jinx's Avatar
 
Member Since: Feb 2000
Location: Oakland, CA
Posts: 7,596
Thanked 3 Times in 3 Posts
Default

At this point a flat plane crank would seem like a me-too. While GM is not above following Ford with a me-too, they really don't want it to look like Corvette is following Mustang. They would rather do ANYTHING else.

Even if that wasn't a concern, I think after seeing lawsuits spring up over LS7, LT4, and GT350, GM would rather play it safe with future high-performance powertrains.

I would love a screaming flat plane crank mid-engine Corvette, but I don't think it's in the cards.
Jinx is offline   Reply With Quote
The Following User Says Thank You to Jinx For This Useful Post:
JerriVette (03-03-2018)
Old 03-08-2018, 08:46 AM   #14  
King Dranzer
Junior Member
 
Member Since: Nov 2017
Posts: 11
Thanks: 0
Thanked 0 Times in 0 Posts
Default

There is a good possibility of them producing flat-plane engine as a competitive response to Ford.

But probably they gonna continue with cross-plane for now.
King Dranzer is offline   Reply With Quote
Old 03-10-2018, 03:14 AM   #15  
Trackaholic
CF Senior Member
 
Trackaholic's Avatar
 
Member Since: Mar 2013
Posts: 620
Thanked 37 Times in 19 Posts
Default

Quote:
Originally Posted by King Dranzer View Post
There is a good possibility of them producing flat-plane engine as a competitive response to Ford.

But probably they gonna continue with cross-plane for now.
I don't know. GM and Ford often seem to go in opposite directions when competing against each other.

GM has been using pushrod engines forever.
Ford moved to DOHC a while ago, but GM hasn't bothered responding.

Ford did a one-off FPC (which is amazing, but not without drawbacks), and I don't see GM bothering to reciprocate when they haven't even done a Cross-plane V8 with DOHC yet.

Ford did an aluminum truck bed, GM used carbon-filled plastic.

Ford does turbo-V6 as their top tier light-duty truck engine, GM has a version of the Vette engine.

If anything, the fact that Ford did it already means it is less likely for GM to do it, IMO.

-T
Trackaholic is offline   Reply With Quote
The Following User Says Thank You to Trackaholic For This Useful Post:
Shaka (03-10-2018)
Old 03-12-2018, 12:50 AM   #16  
Guard Dad
CF Senior Member
 
Guard Dad's Avatar
 
Member Since: Nov 2013
Location: South Orange County California
Posts: 745
Thanked 24 Times in 22 Posts
Default

I’ve owned Fords and I’ve owned GM and enjoyed them both but since the LS1 came out my performance dollars have all (with the exception of a 370Z) gone to GM vehicles. The instant torque and great drivability of the LS1 and LS3 were too good to pass up. Throw in the low center of gravity and the low profile of these modern small blocks and you’ve got real winners.

I used to wish for all the quad cam goodies but I’ve moved on. Now it’s all about the results and not so much about the goodies.
Guard Dad is offline   Reply With Quote
The Following User Says Thank You to Guard Dad For This Useful Post:
Shaka (03-13-2018)
Old 03-19-2018, 10:16 AM   #17  
pdiddy972
CF Senior Member
 
pdiddy972's Avatar
 
Member Since: Jan 2014
Location: Dallas, TX
Posts: 7,342
Thanked 240 Times in 145 Posts
Default

Quote:
Originally Posted by [email protected] View Post
Have someone Heard some rumor about crankshft type of the new c8 vette?

I hope for crossplane
Me too - flat-plane crankshafts are such a fad and add massive vibration. Look at the GT350 Mustang - shakes itself apart from all the vibrations.
pdiddy972 is offline   Reply With Quote
The Following User Says Thank You to pdiddy972 For This Useful Post:
[email protected] (03-19-2018)
Old 03-20-2018, 10:42 AM   #18  
pdiddy972
CF Senior Member
 
pdiddy972's Avatar
 
Member Since: Jan 2014
Location: Dallas, TX
Posts: 7,342
Thanked 240 Times in 145 Posts
Default

Quote:
Originally Posted by vetteLT193 View Post
More RPM means you can use your gears better so why wouldn't you want to rev higher?
Why does it mean that? Having a wider RPM range, but only producing good power at the top of that range means you HAVE to use it. IOW you have to run at the top of the RPM range to get useful power out of it.
pdiddy972 is offline   Reply With Quote
Go Back   CorvetteForum - Chevrolet Corvette Forum Discussion >
Reload this Page
  • Will have the C8 an engine with crossplane or flat crankshaft
  •  
     
    Reply


    Thread Tools Search this Thread
    Search this Thread:

    Click for Advanced Search

    Posting Rules
    You may not post new threads
    You may not post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are Off
    Pingbacks are Off
    Refbacks are Off

    Forum Jump

    Sponsored Ads
    Vendor Directory

    All times are GMT -4. The time now is 03:22 AM.


    We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
     
    • Ask a Question
      Get answers from community experts
    Question Title:
    Description:
    Your question will be posted in: