Cylinder Deactivation

[StorminMatt]

Originally Posted by rh77

At idle, deactivating the 2-cylinders that worked together yielded in a very unbalanced combustion process, and caused the engine to rock violently forwards and backwards. The only way I could get smooth operation was to run the vehicle at engine speeds upwards of 4000 RPMs. The "LS" engine is a transversely-mounted 4-cylinder that fires at 1-3-2-4 – meaning that cylinder #1 combusts, moves downward, then the same for #3 (probably together). Then the cylinder moves back upward into the compression cycle while 2 and 4 fire. Cylinders 2 and 4 are at Top-Dead Center, when 1 and 3 are at their bottom-most position, etc. Basically there would be a firing of the top 2 cylinders (#2 and #4), then a long pause when 1 and 3 came back up and then down, creating very unbalanced sequence of events and a rocking sensation. This wasn't noticed at higher RPMs because the cylinders were coming back around quick-enough to not create a significant vibration.

I know this is an old thread. But given the fact that a new link was made to it from a new thread about cyliner deactivation, I thought that I should clear something up here. Specifically, this is NOT right about the firing of an inline four cylinder engine. Cylinders 1 and 3 do NOT fire simultaneouly, or even move in the same direction with one another (ie TDC and BDC does NOT occur simultaneously). The same goes for cylinders two and four. Rather, cylinders 2 and 3 move together with each other, and cylinders 1 and 4 also move with one another. BUT, cylinders 2 and 3 are 180 degrees out of phase with cylinders 1 and 2. So while 1 and 4 are at TDC, 2 and 3 are at BDC.

Also, although 1 and 4, and 2 and 3 both move as pairs, they do NOT fire together. Basically, when one cylinder of the pair (1 and 4, or 2 and 3) fires, the other is in intake stroke. In this manner, you get the firing order of 1342 (NOT 1324) for a typical inline four.

Therefore, in order to deactivate two cylinders in the smoothest manner possible, it is necessary to deactivate every other cylinder to fire. This means deactivating either one and four, or two and three. Deactiating one and three, or two and four will result in EXTREMELY rough running.

[rh77]

Originally Posted by StorminMatt

I know this is an old thread. But given the fact that a new link was made to it from a new thread about cyliner deactivation, I thought that I should clear something up here. Specifically, this is NOT right about the firing of an inline four cylinder engine. Cylinders 1 and 3 do NOT fire simultaneouly, or even move in the same direction with one another (ie TDC and BDC does NOT occur simultaneously). The same goes for cylinders two and four. Rather, cylinders 2 and 3 move together with each other, and cylinders 1 and 4 also move with one another. BUT, cylinders 2 and 3 are 180 degrees out of phase with cylinders 1 and 2. So while 1 and 4 are at TDC, 2 and 3 are at BDC.

Also, although 1 and 4, and 2 and 3 both move as pairs, they do NOT fire together. Basically, when one cylinder of the pair (1 and 4, or 2 and 3) fires, the other is in intake stroke. In this manner, you get the firing order of 1342 (NOT 1324) for a typical inline four.

Therefore, in order to deactivate two cylinders in the smoothest manner possible, it is necessary to deactivate every other cylinder to fire. This means deactivating either one and four, or two and three. Deactiating one and three, or two and four will result in EXTREMELY rough running.

It's been forever since I did that test, and background research.

If I remember properly, I tried a variety of cylinder pairs and ended up with the smoothest two.

The main conclusion to draw from the whole experience is that the Oxygen Sensor is expecting more burnt-fuel to pass by, so more fuel enters the equation. If an engine management computer in involved, there might be some potential here...

RH77

[ss54]

Another issue that is sure to eventually rear its ugle head is head warpage due to thermal gradient issues. Aluminum heads aren't going to tolerate one cylinder being cold without gaskets failing prematurely.

My thought (although clearly not a DYI) would be to continuousy rotate which cylinders are being "killed". But that would get seriously complex given the mechanical issues.

Now back to thoughts of retrofiting my Gen 2 Camry (wagon) with a plug-in Hybrid ...

[snedden]

Sorry to jack the thread but... I read some folks opinions on removal of connecting rod and pistons for deactivation and wanted to share an experience. My dad who taught me all of his redneck engineering, once made a 2 cylinder VW that lasted over a year only because it was on its last legs to start with. (Case threads were stripped). At any rate, he pulled two pistons out because of a spun bearing on one journal so it would not shake so badly. He used a hose clamp and a strip of beer can around the journal to keep oil pressure to the other journals. The car took almost a half mile to get up to 55mph, but he drove it for over a year before the case studs gave up for good. It ran smoothly, idled fine and got well over 30mpg. Thanks for everyones efforts here...cheers.

[cfg83]

snedden -

Originally Posted by snedden

Sorry to jack the thread but... I read some folks opinions on removal of connecting rod and pistons for deactivation and wanted to share an experience. My dad who taught me all of his redneck engineering, once made a 2 cylinder VW that lasted over a year only because it was on its last legs to start with. (Case threads were stripped). At any rate, he pulled two pistons out because of a spun bearing on one journal so it would not shake so badly. He used a hose clamp and a strip of beer can around the journal to keep oil pressure to the other journals. The car took almost a half mile to get up to 55mph, but he drove it for over a year before the case studs gave up for good. It ran smoothly, idled fine and got well over 30mpg. Thanks for everyones efforts here...cheers.

This is pretty cool. I assume you are talking about a classic Beetle (pre-VW Rabbit). Can you remember which 2 pistons were removed?

Here's a stretch :

VWs are flat-4 air cooled "boxer" motors
Subarus are flat-4 water cooled "boxer" motors

I wonder if there is something in the balance of a flat-four that lends itself to stable cylinder deactivation.

This implies to me that you could :

- Take a classic VW bug
- Remove the body down to the belly pan
- Put on a super-light body shell (dune buggy or ?!?!?)
- Add light-weight bucket seats
- Remove 2 cylinders
=> Have thrifty 2 cylinder VW

Reference - Flat engine
http://en.wikipedia.org/wiki/Flat_engine

CarloSW2

[Snax]

Originally Posted by cfg83

I wonder if there is something in the balance of a flat-four that lends itself to stable cylinder deactivation.

This implies to me that you could :

- Take a classic VW bug
- Remove the body down to the belly pan
- Put on a super-light body shell (dune buggy or ?!?!?)
- Add light-weight bucket seats
- Remove 2 cylinders
=> Have thrifty 2 cylinder VW

Reference - Flat engine
http://en.wikipedia.org/wiki/Flat_engine

CarloSW2

Absolutely. Any buddy pair could be deactivated for balanced operation. That's one of the reasons Subaru has been such an advocate of the boxer motor. They don't have to reinvent the wheel every time they want to add or remove cylinders.

[cfg83]

theclencher -

Originally Posted by theclencher

Carlo-

Minnesota State University- Mankato did almost EXACTLY what you outlined around 1980! They put a 'glass baja kit on an old VW bug, took out two cylinders, and named it the "50/50" as in 50 mph and 50 mpg. Unfortunately all the data I had on it was stolen from me, and I can't find any mention of it online.

The e-vile petrol manufactures stole it!!!!!!! Why won't you believe me?!?!?!?!?!?! It's cool to know that someone already made it. It's a natural, I guess. I wish the Kit-Car market was still bug-based instead of custom-tubular-chassis-super-expensive-design-based. If it was a Master's thesis, it should be on file in the archives.

This is also why I wish Subaru would offer econobox 2WD cars. They have 4-banger cylinder-deactivation sitting in their lap!!!!!

Regarding lost cars, I have the same problem with the "Ford Gnat" I saw at an LA auto show in the late 70's early 80's. It was designed by Ghia and now that I think of it, was practically a pre-CRX, or a pre-Metro. It was maybe a little bigger than a Fiat 500 and it was super tiny cool. I couldn't even find it at the Russian concept car site you used in other threads.

CarloSW2

[Snax]

Originally Posted by cfg83

This is also why I wish Subaru would offer econobox 2WD cars. They have 4-banger cylinder-deactivation sitting in their lap!!!!!

What? You don't want to see this of Ferraris and Porsches?

As far as Subaru is concerned, they went to the AWD-only platform in 96 or so. There are definately some pre-96 FWD Imprezas out there that might be worth exploiting.

[cfg83]

Snax -

Originally Posted by Snax

What? You don't want to see this of Ferraris and Porsches?

The thought hadn't occurred to me, but whyyyyyyyyy not!?!?!?!?!

[I]
As far as Subaru is concerned, they went to the AWD-only platform in 96 or so. There are definately some pre-96 FWD Imprezas out there that might be worth exploiting.

I didn't know that. Subaru is so funny. They have their "niche", but if they want an MPG contender, they need a 2WD option. Econo-boxer-engines for the rest of us!!!!!

CarloSW2

[equate975]

Hmmm jumping in here late I guess, but I have a few things to add.

First off, unplugging the injector is just a bad idea all together for your engine. Your valves will still be opening and closing and believe it or not they need fuel to cool down. If you run it long enough like that you are going to burn your valves up.

Displacement on demand will actually stop the valves from moving so they don't burn out. Its also really lame (at least on SUV's) it more or less will only kick on when you coast, if you blow on the gas pedal it will go back into v8.