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Old 09-11-2010, 07:23 AM   #1 (permalink)
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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?

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Old 09-11-2010, 09:59 AM   #2 (permalink)
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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 .
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Old 09-11-2010, 11:15 AM   #3 (permalink)
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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
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Old 09-11-2010, 12:11 PM   #4 (permalink)
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Quote:
Originally Posted by saand View Post
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 .
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Old 09-11-2010, 12:24 PM   #5 (permalink)
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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 ?
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Old 09-11-2010, 01:14 PM   #6 (permalink)
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Quote:
Originally Posted by Arragonis View Post
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)

Last edited by EdKiefer; 09-11-2010 at 01:34 PM..
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Old 09-11-2010, 01:39 PM   #7 (permalink)
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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...
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Old 09-11-2010, 02:42 PM   #8 (permalink)
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Originally Posted by Frank Lee View Post
The thing is to not have pumping losses. That means no air in/out of the cyl. That means NO valves working in that cyl. Yes I think removal of the unused pistons/rods is vital to reduce the internal friction. The unused crank journal oil holes will need to be plugged somehow. Disabling injectors alone does nothing good.

I've considered this mod for quite a long time. Only reasons I haven't done it already are 1) Inertia... laziness 2) My M.O.: If it ain't broke, don't fix it 3) The car gets pretty decent fe already.
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 .
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Old 09-11-2010, 03:35 PM   #9 (permalink)
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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 ...
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Old 09-11-2010, 03:41 PM   #10 (permalink)
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Originally Posted by euromodder View Post
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 .

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