Dynamic Skip Fire for 2019 Sierra V8 Engines

[SubLGT]

GM has announced that the Dynamic Skip Fire cylinder deactivation system developed by Delphi (hardware) and Tula (software) will be implemented on the 2019 Sierra.

Quote:

...DSF is applied to each individual cylinder, and it continuously varies which cylinders must be firing, as it works in sync with the engine’s throttle system. In normal engines, the flap in the throttle body is almost always in a closed position but, with DSF, the flap is nearly always open to control the engine’s power by varying the number of cylinders needed. The cylinders are shut off by stopping the flow of oil with special valve lifters on each cylinder. “The more power you need out of your engine, the more torque, the harder you press down on the accelerator pedal, the greater percentage of your cylinders will fire. This is software-enabled variable displacement,” Tula CEO, Scott Bailey, told Automotive News. Tula says a V8-powered SUV typically only requires 30 hp to cruise on a highway to hold its speed and, with DSF, six cylinders shut down to provide a monumental 21-percent increase in fuel economy, as tested in the real world on a GMC Yukon Denali. Read more: http://gmauthority.com/blog/2015/09/gene.../#ixzz54H15HQ61 ….

http://articles.sae.org/15485/

Quote:

...DSF is claimed to be the industry’s first fully-variable engine cylinder deactivation technology…. ...Delphi and partner Tula Technology have revealed test data showing NVH reduction benefits with use of their jointly-developed Dynamic Skip Fire (DSF) cylinder deactivation system that was designed to reduce engine fuel consumption and emissions ....During DSF operation, the decision to fire or skip a cylinder is made immediately prior to each ignition event, with each event considered independently and in sequence. DSF also allows all-cylinder cutoff during deceleration. Many factors are considered when deciding which cylinders to fire; these include torque demand, NVH characteristics of the engine and the frequencies and amplitudes that must be avoided in order to eliminate any impact on occupant comfort….

https://www.youtube.com/watch?v=ei1NyfgY5Ds

 

[ARCOgraphite]

Isnt this Like what Fiat is doing with Multiair on their 4 cylinder engines? Throttling the engine with valve events timing and lift - of course minus the "skip fire" ( With the unfortunate name "skip fire" I see a tragedy for this tech and GM on the horizon )

 

[SuzukiGoat]

You want a GM designed system doing this.... Really?

 

[DoubleWasp]

GM owes at least one awful ignition system to each decade.

 

[mrsilv04]

Let's see what people think of it sometime around 2022.

 

[supton]

I'm sure those guys know what they are doing. But in my mind... I don't get it. Is it one common throttle valve or one per cylinder? Seems like a "dead" cylinder would be best to be pulling air through a wide-open throttle plate. No drag. With DI just don't inject fuel. I don't know if they snap throttle plates fast enough to make it feel seamless but maybe it's fast enough to have one per cylinder. But the downside would be getting cool air into the exhaust stream; but perhaps by alternating cylinders the exhaust stays warm enough to be diluted by the firing cylinders. Like everything else, the proof is in the pudding. Not sure I want to be first but I'll certainly watch from the sidelines.

 

[PimTac]

All the automakers are working with new technologies for internal combustion engines. The days of getting a simple straightforward engine seem to be going away. I agree. Wait two or three years for any durability effects.

 

[nthach]

Originally Posted By: SuzukiGoat

You want a GM designed system doing this.... Really?

Mopar, Nissan and Mercedes have been using multi-spark ignitions. Looks like this one is using code and algorithms instead of an secondary ignition system to fire the plugs more than once or even skip them. Looks like it might be better than just killing the valves for DoD.

 

[PeterPolyol]

Should be smooth as silk

Originally Posted By: nthach

Originally Posted By: SuzukiGoat

You want a GM designed system doing this.... Really?

Mopar, Nissan and Mercedes have been using multi-spark ignitions. Looks like this one is using code and algorithms instead of an secondary ignition system to fire the plugs more than once.

Don't think it's like wasted spark system at all, probably more like variable cylinder disablement where (eg) anywhere from 2 to 6 cylinders are shut down depending on demand. So really the only diff. between regular cylinder deactivation is that the amount of cylinders disabled can vary instead of just one whole bank.

 

[emmett442]

Originally Posted By: SuzukiGoat

You want a GM designed system doing this.... Really?

Originally Posted By: DoubleWasp

GM owes at least one awful ignition system to each decade.

This was developed by a private third party - Tula Technology. Been around for a decade.

Originally Posted By: supton

I'm sure those guys know what they are doing. But in my mind... I don't get it. Is it one common throttle valve or one per cylinder?

As I understand it, there is no throttle valve: like a diesel. That way, since there is no air restriction, whichever cylinders are selected to fire are operating at peak efficiency every time they fire = less emissions and better fuel efficiency. If that's correct, I suppose that means either they've done away with all vacuum operated equipment or they're going to use a vacuum pump to retain it. As far as complication, it seems to me they'd be able to eliminate the throttle body and it's associated management. Not sure EXACTLY how this is implemented, but there's a chance that this could actually be a simpler (mechanically) system than what we currently have!

 

[AZjeff]

Some people's heads are exploding as they read this..

 

[mrsilv04]

Originally Posted By: AZjeff

Some people's heads are exploding as they read this..

No, but I am trying to reasonably calculate how many more years that my 2004 Silverado, which I can still work on myself, might last.

 

[supton]

Ah, so one "flap" which is more of an on/off control. Enable/disable valves to limit pumping losses. Interesting. Must be able to "turn on" a cylinder pretty fast.

 

[Tman220]

Originally Posted By: emmett442

Originally Posted By: SuzukiGoat

You want a GM designed system doing this.... Really?

Originally Posted By: DoubleWasp

GM owes at least one awful ignition system to each decade.

This was developed by a third party - Tula Technology. Been around for a decade.

Originally Posted By: supton

I'm sure those guys know what they are doing. But in my mind... I don't get it. Is it one common throttle valve or one per cylinder?

As I understand it, there is no throttle valve: like a diesel. That way, since there is no air restriction, whichever cylinders are selected to fire are operating at peak efficiency every time they fire = less emissions and better fuel efficiency. If that's correct, I suppose that means either they've done away with all vacuum operated equipment or they're going to use a vacuum pump to retain it. As far as complication, it seems to me they'd be able to eliminate the throttle body and it's associated management. Not sure EXACTLY how this is implemented, but there's a chance that this could actually be a simpler (mechanically) system than what we currently have!

The way I understand it is that a throttle valve will still be used, you will need it to idle smoothly because that will most certainly be done on all 8. Under load however the throttle will be adjusted by the PCM to establish a zero vacuum condition, then power will be adjusted by how many cylinders are firing and then will be smoothed out by throttle position. This is nothing new, the pcm’s in the 2014 and newer trucks are already using that strategy. Also to clarify, when cylinders are shut down they are shut down immediately after a power stroke, the lifter is shut off via oil pressure and the exhaust valve doesn’t open, this maintains cylinder pressure (air spring) to seal the rings and to avoid the type of mis-fire that you can feel. To me this sounds like more of an expansion of the current system. Most of the oil plumbing is already there, there will just by 16 special lifter rather than 8. But now the computer will have even more flexibility to make for an absolute seamless system. Right now it’s either 4 or 8. Also this is not ignition based, the spark plugs will keep firing away because they don’t need to be shut down, If valves don’t open and fuel injectors aren’t fired there is nothing to burn.

 

[ARCOgraphite]

yopr Chrylser /Ddoge Multiair 4 banger uses something similar minus the cylinder deactivation.Back in the 80's My plasma chamber vacuum pumps slowed down when pumping air (load) and speed up when at near perfect vacuum, so I don't fully understand pumping losses. If you aren't moving a fluid mass the work performed is less.

 

[PeterPolyol]

Originally Posted By: Tman220

Also to clarify, when cylinders are shut down they are shut down immediately after a power stroke, the lifter is shut off via oil pressure and the exhaust valve doesn’t open, this maintains cylinder pressure (air spring) to seal the rings and to avoid the type of mis-fire that you can feel.

After all these years the faith in the "air spring" is still greater than ever. Like they don't expect the pressure will bleed down to a point where top half of the stroke is positive pressure and the bottom half of the stroke vacuum? Like we havent seen this configuration start loading the cylinders full of oil? Perhaps the ECM logic alternates dead cylinders so that one or more dead cylinders don't start bleeding down and sucking oil? Real world performance again, is yet to be seen in this minor revision of DoD

 

[emmett442]

Originally Posted By: PeterPolyol

After all these years the faith in the "air spring" is still greater than ever. Like they don't expect the pressure will bleed down to a point where top half of the stroke is positive pressure and the bottom half of the stroke vacuum? Like we havent seen this configuration start loading the cylinders full of oil? Perhaps the ECM logic alternates dead cylinders so that one or more dead cylinders don't start bleeding down and sucking oil?

further research indicates that both valves are held closed, but firing cylinders are continually alternated.

 

[Linctex]

Originally Posted By: DoubleWasp

GM owes at least one awful ignition system to each decade.

Truth! ....and with this, I keep thinking back to the late 70's Cadillacs with multi-cylinder control.

 

[emmett442]

The theory behind Cadillacs variant was sound (that theory is pretty much identical to the systems used recently), and they did a good job with the tech they had AT THE TIME <- but that's the problem. It was simply a technology ahead of it's time. It's easy to slam the old Cadillac variant - but then if you can be so critical, then you should be able to tell us what they should have done differently to make it work...

 

[JustinH]

So we will need a VCMuzzler for this engine also?