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Rainh2o 01-19-2010 07:02 PM

Killing individual cylinder ignition
 
I did a search on the website but I wasn't able to come up with exactly what I am thinking here. Found all sorts of posts talking about removing cyld and such but thats not what I am thinking. Sorry if this has been discussed before.

I know some of the larger V-8's kill cylinders when in cruising mode to improve mpg. I know they do it with the valve train and computer combination.

What I am thinking is killing only the injectors to 2 of the cylinders (out of 4). Now I know it will probably upset the oxygen sensors so I would also have to take a reading of the sensors in normal running mode and maybe also switch in some sort of voltage source or resistor in place of the oxygen sensors, maybe only the #2 sensor since it would see the most increase in oxygen. Maybe this would trick the ecm that nothing is different and not to dump more fuel into the remaining 2 cylds?

Sounds too easy. What Am I missing here?

RobertSmalls 01-19-2010 07:11 PM

You'd barely save any gas. Air would still need to be pumped through all four cylinders, and engine friction would remain the same. Noise, vibration, and harshness would be a serious problem. You'd gain a little economy because you'd open the throttle plate wider, but:

You'd need to spin an elaborate web of lies to keep the ECU from throwing a check engine light and going into "limp home" mode. You'd need fake fuel injectors for the ECU to look at, and the front O2 sensor would pick up O2 all the time, rendering it useless. I think you'd need two O2 sensor simulators, which are more elaborate than a voltage source.

BTW, Honda does the variable displacement thing on its V6's. I'd like to see it on their hybrid 1.3L L4, using the electric motor to smooth out the uneven power production that results from having only two cylinders.

Christ 01-19-2010 08:30 PM

I'm about to turn my '91 Geo Storm into a 2 cylinder parallel twin... we'll see how it works out, if I can fake the ECM into thinking that all's well or not. If not, I'm probably going to go with a side-draft carb.

RobertSmalls 01-19-2010 09:43 PM

With valvetrain mods? Does that make it a 660cc engine?

I just realized another problem any OBD-II ECU will pick up on: the variation in crankshaft velocity will result in a check engine light with Cylinder 2 & 4 Misfire codes.

If the Geo Storm has a similar misfire monitor, you may need that carb, or MegaSquirt. Or drive with the Check Engine light on and see if it runs lean enough despite the light.

Christ 01-19-2010 09:48 PM

Quote:

Originally Posted by RobertSmalls (Post 155370)
I just realized another problem any OBD-II ECU will pick up on: the variation in crankshaft velocity will result in a check engine light with Cylinder 2 & 4 Misfire codes.

If the Geo Storm has a similar misfire monitor, you may need that carb, or MegaSquirt. Or drive with the Check Engine light on and see if it runs lean enough despite the light.

I'm fairly certain the Storm is OBD-0, if not, it's OBD-1. It's not as advanced.

I was thinking that I'd still allow the ECM to provide fuel to the dead injectors, but pipe them into a return line instead of letting the fuel into the cylinders.

I'm also physically removing two pistons, so there will be no extra flow in the exhaust for the O2 sensor to pick up on, it will only get the flow of the 2 cylinders that are running. Defeating the injectors without throwing a CEL is the only thing I really have to worry about in this case.

I'm also going to be removing the springs and dropping the valves so the cam has less work to do, albeit marginally. I'm going to have to put something into the valve guides to prevent oil from leaking down through them, too.

Christ 01-19-2010 09:56 PM

Also, the ignition timing is electronically controlled, I think... I'll probably need some sort of compensation for that, unless it's only based on RPM/TPS settings...

Even then, it won't be as good as it could be, I think...

bgd73 01-20-2010 12:52 AM

the theory you inline four runners are running in the counterbalance category is getting a crazier theory by thinking of shuttin down cylinders.

my share of crap four cylinders and down to 3 rods two cylinders spewing headgaskets and on and and and on... there is only one four cylinder in my history of four cylinders that can run on two of the four...and it is a 3 main boxer with two sohc cams...one timing belt removed. (I even maintained highway speed)..the rest is flunking tragedy.

inline fours can't do it. don't bother, it is all down or all up, variable valve bs aint even gonna help it.

a inline four diesel may get away with it if stroke is deep..like tractor four cyl, not rabbit deisel four cyl.

Christ 01-20-2010 01:06 AM

Quote:

Originally Posted by bgd73 (Post 155407)
the theory you inline four runners are running in the counterbalance category is getting a crazier theory by thinking of shuttin down cylinders.

my share of crap four cylinders and down to 3 rods two cylinders spewing headgaskets and on and and and on... there is only one four cylinder in my history of four cylinders that can run on two of the four...and it is a 3 main boxer with two sohc cams...one timing belt removed. (I even maintained highway speed)..the rest is flunking tragedy.

inline fours can't do it. don't bother, it is all down or all up, variable valve bs aint even gonna help it.

a inline four diesel may get away with it if stroke is deep..like tractor four cyl, not rabbit deisel four cyl.

Do you have any idea what you're talking about?

I want some of whatever you're on, dude...

Rainh2o 01-20-2010 11:30 AM

Quote:

Originally Posted by bgd73 (Post 155407)
the theory you inline four runners are running in the counterbalance category is getting a crazier theory by thinking of shuttin down cylinders.

my share of crap four cylinders and down to 3 rods two cylinders spewing headgaskets and on and and and on... there is only one four cylinder in my history of four cylinders that can run on two of the four...and it is a 3 main boxer with two sohc cams...one timing belt removed. (I even maintained highway speed)..the rest is flunking tragedy.

inline fours can't do it. don't bother, it is all down or all up, variable valve bs aint even gonna help it.

Not sure what your talking about, I have had an inline 4 before that had a broken spark plug, brok it late one night putting it back together, other then runnig a bit rough and a bit underpower, it ran fine for 2 days until I got around to replaceing the plug.

MadisonMPG 01-20-2010 01:00 PM

Quote:

Originally Posted by Christ (Post 155409)

I want some of whatever you're on, dude...

me too

I want a 3 main boxer engine too.


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