Gen V Fodder

[hyperv6]

Here is a link to a web story on what one person expects we will see and speculate on some wild cards.

I thought since we have not really spoken much on this this would help us try to predict what GM will do. Lets try to keep realistic here and keep this to what we think they will do not what we wish they will do. I would like to see who here can come closest to predicting what will really go into production.

http://www.enginelab...-block/?print=1

Things have been a little slow here and we need something to help get us rev'd up for Detroit in a few months.

Edited September 11, 2012 by hyperv6

[dwightlooi]

First of all you may want to revise the title to "Gen V Folder". Fodder is means either livestock feed fillers or "Cannon Fodder"!

Anyway, I largely agree with the article's assessments.

• Aluminum Blocks are 100% confirmed (even for truck engines)
  
• Direct Injection are 100% confirmed
  
• Cylinder Deactivation are 100% confirmed (at least on some Gen V engines)
  
• Variable Valve Timing are 100% confirmed (at least the synchronous variety)
  
• Pushrods are 100% confirmed (GM's next Gen V8 will not be an SOHC or DOHC design)
  

What I'll like to see are:-

• Independent Exhaust / Intake VVT via concentric cams (>50% chance)
  
• Variable Valve Lift via variable fulcrum rockers or switching lifters (~25% chance)
  
• Mixed Otto / Atkinson mode operation (<25% chance)
  
• HCCI (<10% chance)
  

It is important to note however that none of the "like to haves" have much of a direct impact on performance potential. Indepedent VVT makes emissions cleaner and the torque curve more linear, but generally speaking will not raise maximum output. Variable Lifters or Lift ratios are the same way -- allows more aggressive lobes without compromising idle and low rpm drivability. The limits imposed by relatively low rpm ceiling 6000~7000 rpm of mass produced pushrod engines mean that cams more aggressive than you currently see on the Gen IV LS6 are unusable anyway regardless of the mitigating effects of VVL and/or dual VVT because they would make peak power above the rpm limit of the engine. Mixed Cycle and HCCI actually compromise power for efficiency.

Given the "known" attributes of the Gen V engine it is safe to project a ~10% increase in output compared to Gen IV simply from the increase in compression and fueling precision of DI alone. That brings us to 468~480 hp if the displacement stays at 6.2 liters -- which is more than enough to be competitive with any other V6 Bi-Turbo or V8 DOHC designs. Fuel Economy can be expected to be at least 1 mpg better than with the Gen IV engine, or minimum of about 18/27 mpg on a 3000 lbs car (Corvette C7), 17/25 mpg in a 3900 lbs car (Camaro) and somewhere in between for a 3600 lbs ATS-V if it uses the V8. This again, is as good as or better than the numbers turned in by 450~500 hp class turbocharged V6 engines on the market.

I do believe that displacement will stay around 6.2 liters because there is no significant improvement in fuel economy from displacement downsizing while keeping an otherwise identical layout. There is no truth whatsoever to a rumored 5.5 liters displacement, the racing engine beinf 5.5 is solely the result of class rules -- otherwise they would be running 7.0 liters -- and is no indication of production displacement(s).

Edited September 11, 2012 by dwightlooi

[hyperv6]

You have to use all the definitions not just what you choose.

noun

1. coarse food for cattle, horses, sheep, etc., as cornstalks, hay, and straw
   
2. something, esp. information, that is thought of as being in large supply and, often, inferior, raw or coarse, etc.: promotional fodder in mass media
   
3. the basis or basic material for something: fodder for gossip
   

The Vette I am expecting power close to 500 HP. Some where 470-490 HP based on GM stating the next entry level Vette will have near Z06 power.

The engine will be interesting to see if they stay Supercharged for the CTS or if they will go with a Turbo. There seems to be a lot of talk about Turbocharging this engine but we have yet to see anything to back up, I expect Eaton superchargers.

I expect the power to be similar in the present CTSv as they will look to gain MPG and more performance with less weight. Being more efficent at the same power will net more MPG. I see similar things with the trucks.

I do not expect the V8 in the ATSv just based on marketing needs alone. Cadillac is working to make each car different and not just in size only. Who needs a mini CTSv when you can have a car that can reach new buyers. Enlarge you market and not limit yourself to one type of buyer.

The real question is would they go three valve or even 4 valve pushrods for the LTS later on. I do expect V series power with some kind of charging. I really think for Cadillac to show case the car they have to move to do something different and not available in any other GM car like the ZR1 engine.

The greatest gains in this engine will be torque. The curve will be much flatter and over a wider range. It will hit hard low and hold it most of the way up. This will pay off with better MPG. GM discouved with the DI VVT engines like my HHR SS that if you add more torque low down it will give you more off gas pedal time. The DI engines pretty much shut the fuel off when you coast and increase MPG. The increase in Torque in my GM Turbo upgrade netted an increase 1-2 MPG even when adding 45 HP.

The engineer told me it was not an expected gain and they were pleased with the results. I suspect that they will use what they learned there in future engines.

[dwightlooi]

The real question is would they go three valve or even 4 valve pushrods for the LTS later on. I do expect V series power with some kind of charging. I really think for Cadillac to show case the car they have to move to do something different and not available in any other GM car like the ZR1 engine.

I do not expect 3 or 4 valve setups for two reasons:-

• It runs counter to and dilutes the key Pushrod V8 advantage -- valvetrain simplicity and minimum valvetrain frictional drag
  
• At up to the mid-6000 rpm range, 2-valve heads can follow enough as much air as the engine can ingest. Therefore, additional flow capacity has very little if any power or economy benefits. This is evident from the fact that an engine like the LS6 has a power peak at 6300 rpm, if the layout is incapable of sufficient volumetric efficiency at 6300 rpm the power peak would have been lower. You really only need 4-valves when you are aiming for power peaks above the mid-6000s.
  

[smk4565]

I'd be surprised if they go 6.2 liters again. If they do, I can't see them sustaining it for very long with CAFE. Unless they keep the 6.2 liter V8 and don't offer it in many vehicles. GM still needs to find another 4-5 mpg for CAFE.

[hyperv6]

Lets keep this to what GM will do as their bacon is in the fire not ours. I think too what ever they choose they have a better handle on it or reason than any internet engineers.

The reasons for the 3 and 4 valve could be many and without more info you can not discount it. There is a lot more to changing the valves than you list. Often they do run into issues with placment of injectors and plugs in a chamber to get the best results. Splitting an large intake valve make it more flexible to this. Also the larger the valve the greater the issues. Larger valves can mushroom and create a lot of bouncing mass too. The mass is about as much of an issue as drag. So I really don't see either in play.

If they chose to go the multi valve route I would think it has more to do with placment and chamber or piston head design than anything and that is something we would need more info on to understand. With this engine you can not fully apply LS logic as the playing ground could be very different in some areas.

All I can say is if they do go the multi valve route they had a good reason as they would not do it for just the cool factor.

The one thing when we look at this from the GM point of veiw and not the Internet Engineer view is that this engine could be around a long time and they may be planning for needs far down the road. I expect with the decrease in V8 demand that this engine will be with us for a long time and will have to evolve for may uses, many standard and regulations and many needs.

Lets face it GM is not going to invest multi billion in a new V8 10 years from with 53 MPG CAFE looming down the road for 4 -5 models some limited. This engine will need to be flexible.

Edited September 12, 2012 by hyperv6

[dwightlooi]

I'd be surprised if they go 6.2 liters again. If they do, I can't see them sustaining it for very long with CAFE. Unless they keep the 6.2 liter V8 and don't offer it in many vehicles. GM still needs to find another 4-5 mpg for CAFE.

As I have discussed exhaustively in the past, the point is that reducing displacement is not an effective means of reducing fuel consumption. So, regardless of CAFE or the lack thereof, the point is that going from 6.2 liters to, lets say 5.0 liters -- a good 20% reduction -- may yield no fuel economy gains or not enough to make a 1 mpg difference. If the point is to reduce fuel consumption, simply closing the intake valves on a 6.2 liter engine 20% past BDC will product greater fuel savings that reducing the displacement by 20%.

[Drew Dowdell]

Moving this to Powertrain.