Cylinder deactivation - V6

[SomptingGuy]

Has anyone worked on this? If so, are there any examples out there where the full firing order isn't alternating bank-to-bank? I.e. by deactivating one bank, firing becomes uneven.

 

[wwest]

Personally I have always wondered.. "why not have two engines on board?"

Say both engines active, a 250HP engine driving the rear wheels and a 50HP engine driving the front wheels, for quick acceleration up to "speed" as seemingly DEMANDED by the US automotive buyer.

Then shut down the 250HP engine entirely unless extraordinary acceleration levels were again called for, needed.

I have often thought about putting a small genset on a "tag-along" (single swivel-wheel) trailer behind our Prius to continuously charge the batteries so the relatively HUGE ICE would not need be used at all in hwy cruise mode.

The genset engine could be switched on and off as needed for (re)charging the hybrid battery. The genset engine could ALWAYS run UN-THROTTLED. It could make full use of the Atkinson Cycle "extended BURN power stroke concept". 15:1 mechanical compression ratio, 10:1 effective compression ratio via delayed intake valve closing, and reed valves at the intake to prevent reverse intake flow.

 

[SomptingGuy]

Clarification...

I'm not advocating deactivation, I just have to work with customers who want to analyse the effects. And I cannot believe that uneven firing intervals would work (as in the computer model I've been sent).

 

[dgallup]

I know the new Honda Accord V6 is capable of running in 6, 4 & 3 cylinder modes. I believe in 3 cylinder mode it shuts down one bank and in 4 cylinder mode it shuts down 2 cylinders at diagonal opposite corners. They use electrically activated dampers on the engine mounts to compensate for the differing vibration modes.

 

[NickE]

"I have often thought about putting a small genset on a "tag-along" (single swivel-wheel) trailer behind our Prius to continuously charge the batteries so the relatively HUGE ICE would not need be used at all in hwy cruise mode."

What? I just dont think it works that way......

Really, how could this possibly work?

 

[ivymike]

what was the model looking at? If crankshaft vibes only, then maybe there wouldn't be a problem. What about torque recoil? Transmitted vibration through the engine mounts? What about the exhaust sound?

 

[SomptingGuy]

It was primarily looking at intake & exhaust noise. Uneven firing would sound abysmal - like a Beemer suddenly switching to a Harley. I hadn't thought about torque recoil,(or the effects of instantaneous crank speed).

 

[JOHNDOE333]

I do recall some information with regards to noise cancellation on the Honda's. A certain sound or frequency was emitted through the speakers of the radio during multi-displacement modes to combat engine or exhaust noise that was not normally present during all cylinder driving. As far as the number of modes or order in which the cylinders were dropped... I am uncertain.

Good day,

 

[Tmoose]

A 4 cylinder Volvo with a dead cylinder does not run too bad above maybe 2000 rpm

 

[TStaples]

I previously worked on the GM "displacement-on-demand" system, and also a stillborn prooject to do deactivation on Ford's Triton V-10. In the GM system, oil flow to the lifters was re-routed through modified transmission solenoid valves such that individual lifters could be collapsed by shutting off oil flow. Individual cylinders, or groups, or just one bank, could be shut off, depending on how elaborate a plumbing setup you wanted to add to the motor. It's a quite simple and elegant engineering solution. We saw different engine operating modes being utilized by GM during development.(cylinder skipping, shutting down one bank, etc . . .)

The Ford System was infinitely more complex, as the engine is OHC. Special rocker arms, containing rollers within an inner carrier frame, pivoting on a fulcrum within the main rocker frame, with latching pins, were utilized. Each valve had a solenoid to latch unlatch the pin, via an articulated rotating lever arm. If connected, the cam motion was translated through the roller, through the rocker arm to the valve. If you energized the solenoid, and pulled the pin, then the mechanical connection between the seperately framed roller, and the rocker outer frame was released, and the roller rocker would just ride harmessly over the cam profile, and no motion was translated to the valve.

This system was contained entirely on one bank, and added to a hellishly complex electro-mechanical abomination, hiding under that one cam cover, that would have made Rube Goldberg blush with envy. Needless to say, that project died, as least as far as my company's involvement. The solenoids we developed were really trick, modular, and actually cost effective. However, stuffing 15 of them, along with all the mechanical wackycontraptionthingiemabobsandwhatchamacallits that went along with it was a packaging nightmare. It all worked, as a one-off exercise (in futility, perhaps?) However, there was no way you were going to put it into production, and have it assembled in a typical automotive engine plant.

After all of that, the Ford system would have deactivated only one bank, odd firing order and all.

-Tony Staples

http://www.tscombustion.com

 

[GregLocock]

Well, you'd get a whole bunch of half order harmonics (at a guess) from the uneven firing order, but I'd have thought that was a fairly small consideration. Why not synthesise it in your psychoacoustic software and have a listen? I'm pretty sure the HEAD LMS and B&K systems can all do that now. Admittedly getting the noise of a single cylinder firing might be a bit tricky.

Better, quicker and easier would be to disable the rockers in a few cylinders and go for a drive.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[mishar]

V6 has even firing angles in each bank, so by shutting of one of them firing angles will stay even.

 

[amorrison]

Check out the Cadillac V8-6-4 engine here – for historic knowledge.

http://www.popularhotrodding.com/features/0408phr_worst_automobile_engines/index.html

http://en.wikipedia.org/wiki/Cadillac_V8_engine

http://findarticles.com/p/articles/mi_m3012/is_3_179/ai_54216811

 

[mishar]

 

[GregLocock]

Pretty but useless.

I am 99% sure that no V6 would use that firing order. The crank would break due to torionals.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[mishar]

Like it better now?

 

[GregLocock]

It'll still break the crank. Why don't you look up what the firing order actually is instead of messing us about?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[mishar]

I did. This is exactly what I found. If you know different one please post it.

Point was that each bank has even firing angles, unlike V8, so that firing stays even when one bank is off.

 

[BrianPetersen]

That is indeed the conventional firing order for a V6; it's either that way or its mirror image (which amounts to the same thing in the end). Shutting down one bank results in three cylinders firing at equal intervals.

 

[dicer]

On engines that use 1,6,5,4,3,2 it is close to what mishar
has shown, with #1 being the oddball of course depending on cylinder numbering system.
GM V-6 engine fire order is 1,2,3,4,5,6 just as depicted above. Nissan uses the firing order 1,2,3,4,5,6 in some of the V6 engines they make. I haven't heard of any crankshaft breakage issues.