idea, 4 cylinder to 2 cylinder engine conversion
 

I am thinking about changing my 2.2L 4 cylinder engine to a 3 or maybe even 2 cylinder. The car at the moment can accelerate with plenty of energy to spare, I could easily drive without any issue with ¾ the power that I currently have.

I have seen one or 2 posts about the idea on here and I have done some general research but I am trying to see if anyone has actually done this before as there are significant risks that I can see at the moment and if I do it wrong I may damage the engine and have to get a new car.

From what I have found a 4 cylinder engine is balanced so that during each piston stroke there are 2 pistons going one direction with 2 pistons going the other direction essentially cancelling out any motion that would unbalance the engine.
So going down to 3 cylinders would have the issue of 2 cylinders going up while 1 goes down in which case due to the inertia change the engine will vibrate. Standard 3 cylinder engines get around this a bit by having different angles and firing timing which would be very difficult for me to do on an existing engine. I could try it out just removing one cylinder and see how it goes but im likely to have a very shaky car and vibration may damage things.

The other alternative is converting my 4 cylinder to a 2 cylinder. There are some 2 cylinder cars around not very popular though. My car can apparently generate 115 hp with the 4 cylinder so it would make sense that a 2 cylinder would give 57 hp which I figure would be enough to run a car on, wouldn’t accelerate too quickly though.
There is something I am concerned about though, the 2 cylinder engines are inherently unbalanced because although 1 cylinder goes up and 1 goes down which cancels out the inertia but it then creates a rotating force because the 2 cylinders can’t be in the same location and any offset causes rotational forces.
Another possible issue is that with 2 cylinders which have cylinders going in opposite directions is that the firing sequence will be uneven. A 4 cylinder engine fires all cylinders in 2 rotations so 720 degrees. Each cylinder will then fire every 180 degrees, when deleting 2 of the cylinders AND making sure each cylinder goes in the opposite direction the only way to do this causes one cylinder to fire at 180 degrees then the other to fire at 360 then for angles 540 and 720 (or 0)there will be no cylinders firing 0 power. I am worried this will mean the engine will have to idle faster to cause enough inertia to keep rotation going while the engine rotates from 360 to 720 degrees.

So my question to the group is, has anyone tried this since I still want my car to work when im done I’d like to know if anyone has tried and failed or succeeded.
If anyone has tried it or if anyone has a 2 cylinder engine do they have significant engine vibration?

Can't really help with real world experiance on this but given that 4 stroke engine fires on every other TDC. on standard 4 cylinder a firing is happening at each 180 interval (every time a piston comes up, one of them fires as 2 are up and 2 are down).
Now with only 2 working its going to be very rough running IMO and have real low TQ (hp is not a factor really as you need to get going from a stop) .I think 626 is to heavy for 2 cylinder, maybe 3, I think it be better to just use smaller more efficient 4 cylinder , tuned for long stoke, low rpm .

Whats the weight on 626 , around 2800 Lb ?
engine is 2.0 liters if memory is ok .

Edkiefer, thanks for the info,
I had assumed fairly low torque but i am assuming it will be half the torque at all RPMs assuming i get rid of the friction of the unused cylinders. I can test if the torque and power will be enough by simply unplugging the injector connectors of the appropriate 2 cylinders and test it out on the road.

I agree about the smaller more efficient 4 cylinder, ideally i would drop in a 1L 3 cylinder engine and be done with it but I am going for 0 cost mods and the interfacing to existing parts could be problematic as well.
So my aim here is to modify what i have in the car already unless i can get very cheap engine from a wrecker but the local wreckers charge a very high price for engines even if they are from really old cars and worthless to most people.

I have not looked up the weight recently enough to remember, ill have to have a look on the name plate. But i have reduced the weight a bit, took out AC, power steering pumps, condenser, carpeting, mirrors.

I think when i am able to in the next few days ill run the test with fuel only being injected into 3 and 2 cylinders and see how that goes. If that works well then it is only a question of balancing if i take out the pistons which will reduce overall friction.

Another method i could pursue is to not remove any pistons which will keep the balance but i could deactivate one cylinder by removing one injector connector and open up the input and output air valves so the only loss in the deactivated cylinder is friction of the piston going through the cylinder. Not sure if there will be much gain from that though

Ok, how about a 323 1600cc if my memory is right, same yrs as yours (late 80's, early 90's)

Ok, the problem of removing piston an rod is your oiling system needs rod bearing being in place or oil presure be 0 .

You might be able to do something like disable injector, then disable intake value rocker and leave exhaust working,

But that said I doubt you will like the running of the vehicle after you pull the 2 injectors .
I am saying this from being a mechanic for 25+ yrs and driving vehicles (4 cylinder) that had dead cylinder .

Give it a test and see .

I think a smaller engine working harder could use just as much fuel but maybe it could work. A simpler approach may be to look at other Mazdas of the same era and see if any of them share parts - especially the gearbox. If they do then you could relatively easily swap the engine for another Mazda unit - say from a 323 (1.3-1.6).

There was also the Mazda 626 Diesel which had a supercharged (instead of turbo) engine. I don't think they sold many though. I think you (Australia) had it as something else, Capella ?

right, If you go to small on engine mpg won't go up, at least not in city mpg, highway probably would .

Thats why i said originally to use smaller engine but one with long stroke to help with TQ . problem is finding this. while the 1600cc 323 is smaller I am pretty sure stroke is down too, I can't remember if bell housing are same between 626 and 323 , probably not, my guess .

Ok it seems Mazda made a 626 2.0l SOHC in late 80's and in early 90 a 626 1.8 and 2.0L DOHC . these later would probably do better in mpg but my guess you might need ECU which would complicate any upgrade .

The older 2.0L looks like destroked 2.2 as bore are same on both (86mm)

i have already thought this out and said it is unjustifiable for pricing and parts..

what you would need to do to achieve this.

1. plug up the intake and exhaust ports on the head, and grind off the lobe on the cam on cylinders 2 and 3.

2. get the bottom end balanced as it will be extremely offset to the side with the pistons and rods, as the piston and rods on cylinders 2 and 3 would be removed.

3. weld up the rod journals on the crank in cylinders 2 and 3.

4. pull the 2 injectors and plug wires as needed.

5. tune car based on these things.

problems with this setup would be:
rotating a crankshaft 360* with the amount of reciprocating weight had on most engines is a LOT for smaller displacement engines, idle speed would have to be set higher to compensate. higher idle speed is, the higher your gas bill would be.

balancing an engine wouldn't be cheap, adding parts to the mix wouldn't keep it cheap either, expect to spend 1k+ on any setup...

intake manifolds are designed to use the venturi effect to pull air into the engine to make power, removing 2 cylinders will remove part of that venturi effect and could cause problems with laminar airflow into the engine.

exhaust manifolds do the same effect but if i can remember correctly it is called the bernoulli effect with exhaust gas pulses.


time is money, thus if you're wasting time, you're wasting money...

trying to remove piston an rod and get it balanced is not worth it .
cars that have cylinder deactivation still have piston going up and down but modify the value opening with rockers .
Most disable the intake valve operation .

Here info on Honda V6 modes

http://www.honda.com/newsandviews/article.aspx?id=4106

VCM Operation
""To help improve the fuel efficiency of the V-6 engine available with the 5-speed automatic transmission, a new generation of Honda's VCM is used. This is the first application of VCM on a non-hybrid Accord model. Unlike previous VCM systems that switched between three- and six-cylinder operation, the Accord's system can operate on three, four or all six cylinders.

During startup, acceleration or when climbing hills - any time high power output is required - the engine operates on all six cylinders. During moderate speed cruising and at low engine loads, the system operates just one bank of three cylinders. For moderate acceleration, higher-speed cruising and mild hills, the engine operates on four cylinders.

With three operating modes, the VCM system can finely tailor the working displacement of the engine to match the driving requirements from moment to moment. Since the system automatically closes both the intake and exhaust valves of the cylinders that are not used, pumping losses associated with intake and exhaust are eliminated and fuel economy gets a further boost. The VCM system combines maximum performance and maximum fuel economy - two characteristics that don't typically coexist in conventional engines.

VCM deactivates specific cylinders by using the VTEC (Variable Valve-Timing and Lift Electronic Control) system to close the intake and exhaust valves while simultaneously the Powertrain Control Module cuts fuel to those cylinders. When operating on three cylinders, the rear cylinder bank is shut down. When running on four cylinders, the left and center cylinders of the front bank operate, and the right and center cylinders of the rear bank operate.

The spark plugs continue to fire in inactive cylinders to minimize plug temperature loss and prevent fouling induced from incomplete combustion during cylinder re-activation.""

So the easest would be remove the 2 rockers on the cylinders that want to no fire and unplug injector .
Another way would be remove intake rocker (intake valve always closed) , then on exhaust adjust lash so valve is never closed and if you wanted make a header with the 2 disabled exhaust ports being connected (not going out the tail pipe) the exhaust would just go back and forth in the dead cylinders. honda claims no pumping losses with both valves closed , hmm .

Even VW's 3 cylinders run notably rougher than their 4-potters.
2 cylinder bikes also run rougher than 4 cylinders.
And those are purpose-built.

Don't get your hopes high, I'd expect it's going to start reluctantly, run very rough, and hardly make any power.

A 1.1L engine is really too small for a car the size of the 626.
It's going to be very thirsty when accelerating - you might not gain as much as you'd hope.

VW may be putting a 1.2L cylinder in the Gof Variant (station wagon), but that's got 105 HP ...

right, to be honest, I am not even sure it would start up ok with 2 cylinders disabled, especially in colder climates .
I think best hope is smaller engine if one is available that fits with little work(bellhousing, axles, electrical/ECU .

while that might help I still think it will be extremely rough and hard starting .

For a test disable 2 injectors and pull the 2 spark plugs, that will take compression out of the equation .

See how it works . IT going to be way to much work to get it to work and even if it works the out come won't be good IMO .

Thanks for all the replies, looks like this mod may not be the best idea. Lots of work, and id get a very unreliable engine at the end. I am still going to try out pulling the 2 injectors see how it runs anyway. Maybe when the car is about to die ill try it out the full mod just for the curiosity.

I may try out deactivating one cylinder by pulling the injector connector, and deactivating the valves, I guess if honda does it for efficiency then there might be some gains hopefully the mod works and they just aren't doing it for marketing. Ill have to research this a bit and read through the replies properly when I have more time.

Edkiefer just out of interest how have you found info about compatibility of parts between different cars. I have never known how to find out if a part from one car is suitable for mine.

hi , On the vehicles with deactivation cylinder mods , just remember they start out with all cylinders firing and go into various mods when cruising .

Well I don't know that much on compatibility, I did work on many Mazda back in 85-95 timeline, mostly Rx7, 323 and 626 (ones that were turbo mostly) .

There a lot you can find online, like parts catalogs or even Google it just takes some searching and reading time .

I now have a 08 Accord so I read up on there features .
Thats about it.

I would say the engine maybe not even run if you pull just one injector and spark plug. Have you even driven a car with a lost cylinder? It doesn't end well. Especially if you keep driving.

You would have to do two, and even then the engine management system will know something is wrong. You'll get misfirecodes and with only half the cylinders firing your O2's and emissions system would most likely end up showing codes. And as I remember most cars dump into a preset mode once you have the CEL for emissions. The settings are not the most efficient but a generic default for the car. This is done incase the engine management losses single from vital components.

So long story short, it won't work. You would have better luck pulling a large motorcycle 2 cylinder and going from there. But even at that rate the build cost will be $$$.

What mileage are you currently getting versus your goal? Even if you could acheive a 60HP engine in a 626, I doubt you're going to break 35-40mpg. Simply power/weight/gearing. And 60hp in car that size would pretty much be unsafe on the highway.

There are other ways of getting more MPGs. What else have you tried?

You must disable the intake valve or the sensors like MAF or even MAP will be reading the suction of the disable cylinders , which for sure would pull code .
The 626 I don't think measure crank movement for misfire code (as AFAIK is a distributor ignition system ),but if it does that would be a issue .
But your right I can't see it being drivable in 626 or worth while in long run.

Thanks all,
I agree with the MAP or MAF sensor issue, so if i do deactivate a cylinder i will leave just the exhaust port open and close up the inlet port which should stop any issues with the ECU.
As Edkiefer suggests the 626 91 year may not have crank movement measurement, it is relatively old and it has had some problems in the past and no codes have come up so im not too worried about this one.

my car currently gets about 28 mpg or something close to that, i do not have an MPG goal i more take the approach that i will do anything i am physically able to do to help the MPG of the car and when i have nothing else i can change ill stop.

Looks like ill just have to test out a few things and see what happens, ill try to run the tests tomorrow and post the results.

Did they ever import the diesel versions in Oz ?

I tried out some tests tonight, disconnected 1 and then 2 injectors and the car still ran. I moved around the plugged in injectors to ensure that I got the worst case firing sequence (2 on then 2 off) and the car still started to my surprise.
The engine did however vibrate around a lot, I do have the RPM turned down so I guess that is expected and can be improved a little.
If I was to remove the piston the vibration would only get worse as it would have the uneven firing which was causing vibration in my test tonight and it would have the unbalanced pistons.
During my previous research one of the websites mentioned a 2 cylinder would sound like a Harley and it definitely does, not sure I mind though. makes it sound like it has a bit of guts even though it will take off really slow.

when I get some more time and there aren't so many cars around I shall have to take the car out for a spin on 3 and 2 cylinders only see how it goes.

Euromodder, Im not sure about the diesel version in Oz, I got this one second hand and I didn't really look around at alternatives at all but I haven't seen all that many diesels until recently in the last few years so doubt there would be many in 91.

When you take out the pistons you could cut the conrods off near the big-end bearings, them bolt then back around the crank. That would plug up the oil holes in the crank so you don't have to weld it and put some of the mass back on the journals so that it wouldn't be so unbalanced.

AFAIK your firing order is 1342 , so if you started with 1 firing the next one would be 4 , (2 an 3 disabled) , I think that would work best .

The problem is when driving will you be much more into throttle than before driving around , I think in city driving with weight of 626 and only half the engine, plus the fact the ECU is not optimized anymore (the sensor data will be way out of normal ranges) there be good chance of using more fuel .

To bad you can't hook up SG2 and do quick check of mpg driving around (before after) .

Patrick thanks for the suggestion, I dont have a great understanding of all the terms and the details of how an engine works but i think if i cut off the connecting rods on the pistons near the big end i would have issues. The big end which i think is the part of the piston that goes up and down the shaft (please correct me if im wrong) is used to guide the connecting rod so if this was cut the connecting rod would just rotate freely and likely smash into things in the motor.
I think there are counter balances for the pistons so if there are i could remove the counter balances which would stop some of the vibration but wouldn't stop it all. I think i have to deal with the fact ill have vibration, i can counteract vibration caused by lack of balance on the shaft but the vibration i will get from 2 cylinders which are offset from each other and will cause rotation is unavoidable unless the engine was completely different. Also i will have vibration from the no so ideal firing order

Edkiefer thanks for the firing order i was going to find this out by experimentation or when/if i open up the engine.
i agree there is risk of more fuel being used but i think without the loss of 2 cylinders the fuel used will be much less idleing and at highway speeds as a large part of my losses while coasting is just the engine rotating away at very low energy output levels.
Some things that may cause issues with this assumption is the ECU being untunned due to the changes but i think if it relies on keeping the O2 sensor happy and at stoic then shouldn't be too bad, in open loop though it will probably just burn lean which i guess is a good thing for efficiency.
Another thing is if the engine now has to run at higher RPMs to get the energy to accelerate and coast.

I do have a home made scan gauge (which uses the injector pulses for fuel info) which will tell me how much fuel i have used so i can do a before and after test. But i dont think it will work for the test that involves just pulling the injectors because air will still be pumped through the unfueled cylinders so if the car tries to keep stoic it will just put more fuel in the working injectors causing those cylinders to burn rich and inefficiently. Ill take some measurements anyway, if i get an improvement it will give me an idea.

The "big end" is the "big end" of the connecting rod--the rod that connects the piston to the crankshaft. The notion being that you just leave the round part of the rod that goes around the crankshaft, and that's it. You have to be careful, though, as I'm not sure how much clearance there is around the crank throws. It'd be bad to have the left over bit of rod smashing the inside of the engine...

-soD

Here a link on balancing that may give some info for those not familiar with the process .

Understanding Crankshaft Balancing: Engine Builder

There really not a lot of room around the rod ends on many engines (bottom of cylinder wall come down close to crank so so do the block walls , all to make block strong ) .

Your really going to have tough time removing rod/piston .

Thanks edkiefer, good link explains balancing well. If others dont know if a 2 or 3 cylinder engine is "balanced" as described in the link in the last post by edkiefer it doesn't mean the engine will be free of vibration as other modes of vibration occur.

Well i tried out removing the injector signal to 1 and 2 injectors and it was an interesting ride. The car lugged a lot when accelerating up but if i was sitting at 70 kph it was drivable. I believe the lugging is because there is a dead spot in acceleration during a quarter of the cylinder cycle so less power therefore require higher revs to go to the next gear. My automatic car obviously didn't know this so every time it went up to the next gear it would lug. So i don't think i can go any further until i see if i can make a manumatic out of my auto.

In general besides the lugging it wasn't too bad i think when actually moving at speed i would barely notice the missing cylinder.

Not sure about vibration though which could compromise the life of engine parts.

So at this stage im going to look into changing my car to a manumatic and ill have to think about if i can deactivate a cylinder on the fly from the cabin. This would let me get up to highway speeds, deactivate a cylinder and reduce some fuel usage. The issue i have to think about is how to stop the pumping losses of the cylinder on the fly

For sure 2 cylinder made from manufactures are balanced , like all the motorcycle engines , but that not going to stop them from vibrating Harley's are good example .

Your problem is you have 2 counter balance weights on the crank that you would not want (plus the rod journal )

Going from AT to MT would probably be much better improvement and easier . I forget, what speed is the AT on 626 , 4speed ? . If 5 speed MT is available that would be nice improvement .Better performance with improvements in mpg due to extra gear and less drivetrain losses .

Harleys are a BAD example. Any decent motorcycle with 2 jugs runs smooth as silk. Harley has a crank that would be great if there were 3 cylinders, instead there are 2; ie, the rods are opposed by 120 degrees instead of 180 degrees.

A properly balanced 600 cc 1 cylinder can run perfectly smooth. And I've had a 6 cylinder Ford 4.0L and a GM 3.8L both running on 3 cylinders, and while they lacked power, they were smooth since it was every other cylinder in the firing order that was disabled.

If you want to disable half your engine, find out your firing order. On many 4 cylinders, it is 1-3-4-2. The outside cylinders are both at top dead center at the same time that the inside cylinders are at bottom dead center. Since you are going for economy, disable cylinders 1 and 4 and you should have a non stumbling engine.

I apologize I haven't read the whole thread, but one thing to watch for is if you are doing this to a fuel injected car, you need to consider what the o2 sensor is going to do when it detects 2x the o2 it should be seeing; ie it will detect a highly lean condition and the ECU will dump fuel in an attempt to correct it. There will be so much excess fuel in the 2 running cylinders it will wash past the piston rings into the crankcase and dilute the oil. I had a Explorer I did just that to; I disabled half the cylinders remotely from the drivers seat. But I noticed the oil level going up (it had a slow leak, so it was something I checked on regularly.) A little bit too late I realized the problem and the engine quit on me.

Don't think I believe it to be impossible, but either through electronically halving the signal from the o2 sensor or rerouting the exhaust, it will need to be dealt with if you value your engine.

Something else to consider, a 100 hp 4 cyl running on 2 cylinders will produce less than 50 hp at the crank due to the pumping losses from the 2 dead cylinders. My best guess would be about 35 hp but that's a shot in the dark sort of guess.

Harleys are a good example of how NOT to make an engine. I pulled up next to one at a stoplight and the handlebars, seat, trunk, everything was shaking like crazy. Good if you're a lady, I guess. ;) I can't believe people still buy them. :confused:

yes, Harley was bad example as it is made to vibrate and sound the way it is but it still will always be as you go up in cylinders the engine smooths out 1, 2, 4 ,6 ,8, 12 they generally get smoother . Most motorcycles that run smooth are 4 cylinders (Honda, Yamaha ,Suzuki )
Also the size of each cylinder has a affect , thats why large 4 cylinder have counter-balance shafts .

Shadetreemech good to hear from someone that has tried to deactivate cylinders, I had not thought of the problem of excess fuel in the cylinders flowing past the piston rings. I will have to do something with the unused cylinder exhaust ports if/when i attempt this again.
Interesting to see you say there are 2 cylinder engines that can run smooth. Do you know what configuration that is in? a straight two, v twin or boxer twin (flat). I understand that a flat engine design can be perfectly balanced however if i was to convert my car into a 2 cylinder it would be a straight 2 and my initial concern was if it would be inherently unbalanced due to a pulsed firing order or from the 2 cylinders going in the same direction all the time and counter balances cant account for the piston movement up and down.
I guess the question is, has anyone driven a 2 cylinder engine that is a straight 2 and was it vibrating all over the place or smooth. If anyone can tell me it was smooth then this mod might be workable.

I am still going to have to convert to a manumatic before i can progress with this cylinder deactivation mod anyway, the lugging was very unpleasant when testing.

With two cylinders not producing any power, that leaves much more loading against the two that are producing power, which changes the transitional piston speed during the power stroke, and results in the lugging.
Spark advance would need to be reduced to match this increased work load and slower piston acceleration. You will also likely need to increase the stall-speed of your torque converter and/or up the stall-torque ratio inside the converter. That part is not usually easy or cheap unless you can find one that already fits your need, and fits your vehicle.

IMO, it's best to keep the ECM in open-loop mode when testing a drastic change like you're doing. Even if closed-loop functioned perfectly during your test, stoich just isn't going to cut it when you're trying to accelerate with only two cylinders. Also, if you're not data-logging, then there will be far too many unknown variables in your experiment and probably a little too much speculation when it comes to the results.

I think this is interesting and I don't want to sound discouraging, but you know if it were very easy to do, ...

I like the idea, but it's hard for me to imagine being able to pull it off on a shoestring budget. If I were trying this experiment, I'd want to go through the engine thoroughly before-hand, eliminating the cam followers, rods, and pistons on the dead cylinders, and epoxying up the dead ports in the intake manifold, - make sure all open oil passages were either plugged or rerouted as necessary, and add weight to the flywheel or install a looser converter.

As for the crank, I have had to lighten the counterweights for performance rods/pistons before. It's relatively easy, though a little more weight would need be ground off in this case. I have my V8 cranks balanced for usually $150 or less - usually less if they don't require added weight. Tapping and plugging the oiling holes in the crank pins would also be easy. Oil pressure and delivery to the remaining bearings would actually be improved, possibly allowing a reduction in volume from the pump.

I would use a stand-alone for engine management, or an older GM ECM in case the required tuning parameters were such that the code had to be patched. The increased pulsing in the intake manifold would probably require extra smoothing (filter routine) to calm down the MAP output at lower RPM. The throttle body would also need to be physically downsized in order to preserve any sort of part-throttle resolution in both the spark and VE tables.

This is all bench-racing though. I have a couple of spare four cylinders, but no time for such an experiment in the near future.

What could be done to help eliminate the issue of additional pressure/pumping loss from the deactivated cylinder is:
Remove the exhaust valve
Reroute the exhaust on those cylinders to open air

If you cant keep the spring in place to push back on the rocker this will not work and would not allow you to turn them on and off. By opening the exhaust side to open air it eliminates the compression of air and prevents it from slowing the expansion stroke of the firing piston. Also this will prevent the O2 sensor from seeing the extra air.

Plus it could sound cool.

I've driven an older Suzuki GS500 and newish BMW F800, both parallel twins.
The Zuki is rather rough, especially at lower rpm.
The F800 is smoother, because of the fake 3rd pistonrod acting as a balancer, but still not as smooth as a 4-inline.
http://www.motorcycle.com/gallery/ga...ngine_imge.jpg


(Didn't ride these : )
Another reasonably smooth parallel twin is the Kawasaki 650 (W650, ER-6 range).
With more vibes - could have been designed in or simply not ironed out - there's the Triumph 865cc (Bonneville Thruxton America Speedmaster).

So in m/c applications, the inline twin is a well-proven concept.

Euromodder thanks, good to know there are some 2 cylinder parallel twin out there that are smooth enough for production.
These are both on bikes though so i assume the RPM is higher at idle from a quick search about 1300 rpm so that might help reduce the vibration. Maybe if i go to 2 cylinder i do need to up the idle RPM so the engine doesn't shake itself apart and if i remove 2 cylinders and all their losses and increase the RPM by less than double i will have a fuel saving anyway.

Olympiadis thanks for all the good suggestions, given me a few ideas for when/if i try this out. I am hoping i dont have to change the ECU or get a custom one but will see how i go.

have you tried disabling cylinders 1 and 4 or 2 and 3? You'll be suprised at how the ECU will adapt to the new idle requirements. Most good ECUs will raise the idle requirements to compensate for the lack of power.

Earlier, you mentioned you disabled cyl 1 and 2. So your power order was no power, power, power, no power, no power, power, power, etc.

If you'd disabled cyl 1 and 4 or 2 and 3 it would have been power, no power, power, no power, power, no power, etc. Something tells me an intelligent chap as you will see the advantage of the second pattern adverse to the first.

My "experiment" in cylinder deactivation.
 

I had a 1962 VW beetle, the original air-cool horizontally opposed 4 cylinder boxer engine. It had a lot of miles. One day I'm driving along, and the engine suddenly makes this horrendous banging sound for about ten seconds. Then the horrible noise quits, but the engine runs very rough.

The top of the piston basically broke off at the ring groove, and the main part of the piston, hammered the piston crown up into the chamber until it couldn't hit it any more. This had several effects:

1. No pumping losses, since the top of the piston is effectively missing.
2. Less balance problems than the OP is considering. Just the top of one piston is "missing", not entire pistons and rods.
3. In 1962, there were no monitoring electronics or computers, just a carburator.


The original engine made some pathetic low number of horsepower, like 50, and with the one cylinder deactivated, it could barely get out of it's own way. And the vibration, particularly at certain speed was...ominous.

I drove it that way for a couple months while I built a new engine. I don't recall any improvement in FE.

troy

There a lot of things working against ya, the whole intake and exhaust system is optimized for 2.2L , running only 1.1L and intake manifold plenum and TB are to large along with exhaust system pipe diameter .

While the ECU will try to keep idle rpm at 800-850 (whatever stock spec is ) a 2 cylinder would probably need at least 1000 -1200 to get flow velocity up a bit .

Hey saand, a few thoughts:

I've seen this tried a few times, esp. with VW engines cut down to two-cyl opposed units, that was especially to fight the unbalance problem. It didn't double the mileage. Mileage did increase, but only because the incredibly underpowered engine was pushing a custom super lightweight car.

If you're going to run on just two cylinders, run on the middle two. I think that will reduce shaft whip along the crank vs. trying to fire the outside two. It separates the firing to every 360 degrees for a nice even beat. And the two adjacent hot cylinders help keep each other warm for better combustion.

I don't think there are many advantages to be found in removing the pistons in the disconnected cylinders. Obviously there are frictional losses, but leaving them in place means you can have your full engine output at a moment's notice - perhaps literally if you simply interrupt the injector controls with a dash mounted switch. Don't bother with cutting down the cam lobes either, for the same reason.

Weight reduction is key. Drag reduction is key. The more load you can take off the engine, the closer you can get to an optimum level of power output with your minimized engine.

But what everybody else is saying is also true. Your engine was built to work properly as a four banger. All the parts are intended to work together; taking a few parts out of the loop like this throws everything off. You may see some improvement after all's said and done. But once you've got the vehicle weight down to the minimum, and changed your driving habits to the thriftiest you can make them, hook the two cylinders back up. See if the mileage changes.

Shadetree the firing order you mentioned has its benefits for more regular power and therefore should reduce lugging compared to the alternative. It does however have the disadvantage of worse balance as 2 cylinders will be going up and no cylinders will be going down.
There are trade offs for both methods and if i do progress with this mod (after changing to a manumatic) i will have to attempt both methods.
Also the ECU i have is from 1991 or probably designed a bit earlier so it doesn't appear intelligent enough to compensate the idle for the lower power. I can however tune the idle myself, i have been considering overriding the computer idle control as well as im an electronic engineer and i think i can give it a better response than the ECU does after i have made a few changes to reduce the idle level for the car in its current 4 cylinder state.

If i am just deactivating the injectors and opening up the air intake of the deactivated cylinders but leaving the pistons then definately the firing order you mentioned is the best as the unused cylinders will balance out the powered cylinders and the more regular firing order will help lugging.

elhigh your point about weight reduction and drag reduction is definately important. I had only considered this mod after reducing weight and drag (not as much as id like though). The car can accelerate with plenty of power to spare and it can maintain highway speed with power to spare. if i didn't then i wouldn't consider this mod.
I also like the idea of using the cylinders in the middle for localized heating keeping each other warm for good combustion and reduction in shaft whip

solarguy interesting to hear you were driving a 4 cylinder deactivated to a 3 cylinder for a few months must have been a wild ride. I have a friend at work that had the exact same experience of the piston breaking at the shaft only a month or 2 ago. You mention that you would have bad vibration at certain speeds, i assume this was due to vibration at a natural frequency of the engine since the removal of one of the piston heads caused a serious loss of balance rather than the engine lugging at a low RPM like i saw with mine during my very brief test drive.

with half the cylinders dectivated on my 4 L v6 the idle did kick up a bit for certain.

I would plan on making deactivating half the cylinders an objective that can be activated or deactivcated in the cabin. Honestly, you need all 4 clylinders for take off and acceleration, but for cruising you only need to maintain speed, which on the flat land requires only cutting throught the air. According to my scanguage cruising only requires less than 50 hp of the possible 200 hp of the engine. This played out when I would deactivate half the cylinders once I got to speed in my explorer. SUre it worked, but if I had been a bit more ingenious with making the ecu "see" only half the o2 content present it would have worked absolutely awesome.

To make the ecu see only the relevant data concerning the activated cylinders had a plumbing or electrical solution. The ECU depends on the 02 sensor to detect the oxygen content in the exhaust stream. If you make the ecu detect only half the signal of the 02 when in cylinder deactivation mode, it won't "know" you have 2 cylinders deactivated. If the ecu only detects the o2 content of half the cylinders from the o2 sensor when in 2 cylinder mode, it will not "know" 2 cylinders are deactivated and the 2 running cylinders will be running at normal efficiency. Sure you will lose a bit of fuel moving the worthless cylinders (although it would help cool the engine) but you will be using less fuel per rpm.