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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.

Frank Lee 01-20-2010 07:17 PM

And lots and lots of welding. You know, for the nuclear debris benefits.

Christ 01-20-2010 08:02 PM

Quote:

Originally Posted by Frank Lee (Post 155568)
And lots and lots of welding. You know, for the nuclear debris benefits.

If the weight of the weld medium exceeds that of the engine....









You might drive an old ass subaru...

user removed 01-20-2010 08:06 PM

59 Bugeye Sprite with two burnt exhaust valves was seriously gutless.

35 PSI compression on those two cyls.

regards
Mech

ahab13 01-21-2010 04:23 PM

On my 91 Geo Storm 2 of the fuel injectors simultaneously went out, and even with the ECM in limp mode and the unnecessary drag of 2 useless pistons and everything I was still able to drive home about 25 miles using going about 50 on the freeway and almost stopping when going up hills. The Storm has speed density EFI so it goes off of RPM and TPS, and MAF which could be tricky with 2 cylinders. I'm not too sure about tricking it, but If you can figure that out then you should have a 800cc fuel sipper. If not you can just throw the carb on there, and still get really good mileage.

Christ 01-21-2010 10:16 PM

Quote:

Originally Posted by ahab13 (Post 155780)
On my 91 Geo Storm 2 of the fuel injectors simultaneously went out, and even with the ECM in limp mode and the unnecessary drag of 2 useless pistons and everything I was still able to drive home about 25 miles using going about 50 on the freeway and almost stopping when going up hills. The Storm has speed density EFI so it goes off of RPM and TPS, and MAF which could be tricky with 2 cylinders. I'm not too sure about tricking it, but If you can figure that out then you should have a 800cc fuel sipper. If not you can just throw the carb on there, and still get really good mileage.

Thanks for this post, and informative for a first post here. There is a thread on going about this over here, please add your input there, as well! :thumbup:


Welcome to EM!

guillermoariast 02-06-2010 11:19 AM

Killing individual cylinders in carburated engine
 
Hello, i have a Chevrolet K5 Blazer 4x4 truck with a 6 cyl, 250 ci engine.
It is a carburted engine with electronic distributor.

I would like to know how to kill 2 cylinders when i'm on a plain road at constant velocity.

Thanks

stonebreaker 02-06-2010 12:16 PM

Just deactivating the injectors won't work. The problem is you're still pumping air through the engine, which requires work. The way the OEM's do it is they shut off the valves to the deactivated cylinders, so that the trapped air simply acts as a spring and you don't have the pumping losses. Even so, the OEM's are seeing only about a 15% increase in fuel economy with cylinder deactivation.

guillermoariast 02-06-2010 03:04 PM

Quote:

Originally Posted by stonebreaker (Post 159484)
Just deactivating the injectors won't work. The problem is you're still pumping air through the engine, which requires work. The way the OEM's do it is they shut off the valves to the deactivated cylinders, so that the trapped air simply acts as a spring and you don't have the pumping losses. Even so, the OEM's are seeing only about a 15% increase in fuel economy with cylinder deactivation.

Hi, thanks for answering. My engine is carburated. How could i (with help from my mechanic) do it?

stonebreaker 02-06-2010 04:11 PM

You can't. The engines with cylinder deactivation have to be designed that way from the factory. For example, the way GM does it in their LS series engines is by turning off oil flow to half the lifters, which causes them to collapse, thereby deactivating the valves. You'd have to get a brand new unmachined engine block and drill the oil passages yourself, fit electric solenoids in place, and program a computer when to activate it or not, in order to do that on a version of the engine you have now; you're better off just buying a junkyard motor that has it already.

A couple of places you CAN look for fuel economy improvements in your current setup might be in friction reduction. Is your motor an overhead cam engine or a pushrod engine? If it's a pushrod engine, look into roller rockers. These reduce internal engine friction. If an overhead cam, maybe check into camshaft roller bearings.

Another area to think about when you have to rebuild your engine is with new design pistons. get hypereutectic pistons with anti-friction coatings on the skirts and heat reflective coatings on the tops. Get the pistons that use the thinnest rings available. We've seen horsepower increases by as much as 20 hp just by going with these; all they do is reduce internal friction and keep more heat in the combustion chamber.

Maybe look at porting your exhaust ports. The faster the cylinder blows down after the exhaust valve opens, the less work the engine has to do pumping the exhaust out of the cylinder. I doubt intake porting would help much, but pocket porting the exhaust, especially to increase low lift flow, would certainly help make the engine more efficient.

You said your engine was carberated. If it is a pushrod engine, see if it has roller lifters. If not, think about converting. It will not only reduce internal friction but increase reliability, as well.

I realize you're never going to save enough gas to justify the more radical mods, but I'm coming at this from a performance viewpoint rather than a cost standpoint.


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