Effects of killing one injector - 4 cylinders
 

Odd thought as my googling was unsuccessful. With a lot of real world experience with friends running Hondas basically tractoring down the road with one dead cylinder, two dead cylinders, and one time an amazing three cylinders down. What would killing one cylinder do? I assume if you killed the injector to keep the fuel from pumping instead of just killing the spark like what typically happens... Could you three cylinder it and get better mileage?
DIYactivecylindermanagement?

The 'dead' cylinder would pump fresh air into the exhaust, so the lambda sensor will sense an overage of oxygen and the EFI computer will try to compensate by injecting extra fuel into the other cylinders.
So just disconnecting the injector is no good.

However, if you close off the intake port of the dead cylinder that will be drawing a vacuum instead of pumping air. That way it has as little friction as possible. Then it would run more or less smoothly.
The vacuum will draw some oil into the cylinder head. Maybe it seeps back into the oil pan when the engine is at rest, otherwise the buildup may cause trouble.

Should be simple enough for you to pull the wire off an injector and run it. If the CEL freaks you out stuff a resistor in the connector.

It only works in engines with hydraulic lifters.

For cylinder deactivation to work you need to keep the valves closed on the deactivated cylinder. If you don't close the valves you increase the pumping losses of the engine. (You are essentially using that dead cylinder as an air compressor.) Pumping air also causes all kinds of problems with the engine management as noted by RedDevil



Plenty of overhead cam engines have cylinder deactivation. They use two piece rocker arms with a pin connecting them. When the cylinder is in use oil pressure keeps the two pieces pinned together allowing the valve to open in close. When the cylinder is deactivated the pin is disconnected so the cam is not longer connected to the valve.

EDIT: Eaton's overhead cam cylinder deactivation
http://videos.eaton.com/detail/video...tion-with-lash

That alone would stop me from trying this on a Prius, since the 2010s and 2011s are already known to be prone to developing oil-burning issues as they age.

My Fit lost an injector a year and a half ago. It was scary, I didn't think I'd make it up a couple hills no matter what gear I was in. Maybe it was the limp mode, but I don't want to see that again.

One of my wife's previous cars (Holden Gemini from many years ago) snapped the camshaft in half so it only operated the valves on the front two cylinders.
It ran on the flat, but wouldn't go up hills. Living in the mountains as we do, it meant getting the car towed home.

My FIAT runs great on 2 cylinders. I have had it on one cylinder (coil pack failure) and it still went well enough.

Yeah I'm not one to try it on the Prius. Car is too nice to be doing hanky mods. Makes me want wanna do a catch can but my car only burns like 1/2 to 3/4 quart over 10k. Considering what most of my American cars have used over 7.5k that's fantastic. 😂
What about your car? I mean on the worst end of the scale I went 12k on walmart syn and never had to add any oil. Still up halfway on the stick.

No oil consumption yet, at almost 80,000 miles....

My Fit lost almost 1/2 quart in a few days last week.

Turns out you need to put the 710 cap back on if you want the stuff to stay inside where it belongs.

and, there is no need to do it on a prius, since it has the best working point managment one can imagin.

A V8 will shake quite a bit if you lose a cylinder.

That's funny, my Cruze doesn't burn any oil.

I had a cylinder misfire in my 1997 Saturn SL with a 1.9 (1.8?) L 4-cylinder engine during a road trip. I disconnected the injector so as not to be dumping raw fuel and drove another 500 km or so. Fuel economy for that leg of the trip was around 6 L/100 Km as I recall, which was typical for that car on 4 cylinders under similar conditions.

I think you would have three methods for doing it and having the computer play nice.

1. Get a O2 spoofer these are usually are used to make the car think the CAT is still there or used when you do not want to spend the money on the post cat O2 sensor.
Wire up a switch so you can turn on the fake O2 when you turn off an injector. With some work you could possibly use one switch to do both.

2. Depending on how the exhaust is routed move the O2 to read only one bank so it does not see the deactivated injector. This would take more work and would not be able to adjust for unbalanced fueling on half the engine.

3. Depending on how the PCM/ECU operates it might be possible to change the tables it uses by adding a switch. That is only easily possible if it had something like "sport" mode available that already does that. IIRC some GM engines like the 3800 you could move the programming to Speed Density mode by disconnecting the MAF and I believe the system ignored the O2 for fueling and only went on MAP and RPM. The down sides not all PCMs had decent fueling tables in SD mode and you could not get back to standard fueling without turning the car off.

"Three-cylinder Ecoboost petrol engine gets the ability to run as a twin under light throttle loads, improving fuel economy by up to 6%"

I swear a Ford fiest 1.0 ecoboost swap in an insight or civic crx would be a cool swap. Drop the frontal area about 40-50%. With a stage one tune you could have a 160hp triple and a 50hp twin good for ~55 mpg on the interstate.

I don't think that would work, the O2 sensor in the manifold and the post cat O2 sensors are very different creatures: The post cat only determines if there's a difference fore and aft of the cat, whereas the one in the manifold actually gets a fairly precise stoichiometric reading.

Of course this could have changed on newer cars, I mostly work on pre-2010.

Here's a strange thought. Run a pipe from the exhaust manifold to the intake of your chosen dead cylinder. Then, it would pump exhaust gas, just as if it were still firing. Don't forget to pull the wire on that injector, and block the intake air to that cylinder.

That would require a lot of fabrication on the intake and exhaust manifold.
Also it would compress the exhaust gas on the dead cylinders compression phase, which would entirely wipe out any possible gains.

So much easier to adjust the rocker arms to not open the valves at all, or leave one valve stuck open or even removed.

If you disconnect the 02 sensor with the car just run in Open loop? If in open loop disconnecting one injector might work OK.

If we are talking about a 2010 Prius, delaying the intake closing further would both lower power and fuel consumption, but why would anyone want to lower the power on a Prius?

How would you do that?

Cut the car in half.....:D

This is so dense. The awful vibes and exhaust note, and lack of power would have you BEGGING for that cylinder back, even if it halved the fe.

Exactly. The timing on a 4-3 conversion is not good and it will not run well at all.
A properly designed 3 cylinder would do much better.

The only way to disable a cylinder that will actually reduce fuel usage, would be to stop the valves from opening on that cylinder, either by removing rockers or grinding the lobe down or what not. You would also obviously want to disable the injector after you do that. There was a guy who had an old junky fiat that spun a rod bearing so his solution was to remove that rod and the one next to it, weld the oiling holes shut, then grind the cam lobes down. It was carbureted so nothing needed there. He said he picked up something like 15% fuel economy. There's videos of it running out there on the youtubes.

I DID test this on the 'Coupe by removing the push rods and unplugging the injector(s) for three and two cylinder modes. It wouldn't start on two, but it tried and nearly did. It started and ran on three but totally SUCKED as mentioned.

I think your ecm must have been mad about it or something, I've had more than a few 4 cylinders over the years with dead coils that are only running on two cylinders, and they still start, run and drive, albeit poorly. Vw 2.0 sohc's actually don't run that bad even on just 2 cylinders firing from bad coils, I'd imagine they'd be ok if the cylinders were actually disabled.

I seem to remember Cadillac selling a variable cylinder engine (the 4-6-8) that rotated the "off" cylinders so that they didn't end up with a single dead cylinder that filled with unburned oil. If one could program the Prius engine to four firings and one skip, (1,3,4,2,X,3,4,2,1,X,4,2,1,3,X,2,1,3,4,X,....), giving sixteen firings per ten revolutions, (or 80% the firings of a non-modified four cylinder) one might attain a 20% improvement in cruising mileage while not damaging the one cylinder.

Another rotating pattern might be to skip every third firing (1,3,X,2,1,X,4,2,X,3,4,X,....), giving eight firings per six revolutions. (66.666...% the firings of a non-modified four cylinder)


Taken to absurdity, firing one, and skipping the next two (1,X,X,2,X,X,4,X,X,3,X,X,....) would yield four firings per six revolutions,(33.333...%) rather than the normal twelve.

Might make sense on an older non-hybrid four, but it doesn't really make sense on a Prius.

Just disabling cylinders might get you 10-15% depending on the application and how it's driven. To get the most out of it, you would have to eliminate the drag of the dead cylinders by removing rods, pistons, valve trail components. Ford had a 300-6 that would disable half of the valves to make a 3 and it had some increased mpg, but nothing crazy because the pistons were still in there.

The 300-6 will run smoothly with the front/rear 3 cylinders only

Cylinder deactivation is a proven technology that exists even on 4 cylinders, but the gains are only in the 10-15% area from what I've heard. If we started rotating cylinders that are shut down, the balance of the engine would suffer and likely so would the economy gain.

I don't see that, over just the one cylinder every two rotations. Can you explain the difference to me, or point me to documentation?

The 10-15% I can see, as the car still weighs the same.

Engines are balanced by cylinder firings being even, if you have one cylinder shut down that, especially if it's not always the same one, then the firings won't be even causing significant vibration. There are engines that have unbalanced firing orders like odd-fire v6's and three cylinders to name a few, but those typically have flywheels, harmonic balancers, balance shafts and other means to tune out the vibration. If the source of the unbalance is a moving target, there really isn't any realistic way to counter it.

The mechanics of varying which cylinder is shutdown could be complicated... but otherwise I think it would be fine. I've driven a V6 with two dead cylinders, and though it shook like crazy at idle and under heavy load, cruising was fine, you'd have never known it had the issue other than the CEL.

I disconnect all 4 cylinders all the time using P&G, and deactivate all 4 of them regularly with EOC. Not a lot of wrenching or theory, just driving.

2960 miles with Active fuel management (these are known to burn upto 2qt per 1000 miles)

Zero oil consumption on this Wednesday engine

I do 3000-3500 oil changes I have an appointment to take it in on Monday for an oil change.. that will be 3150 miles or so