idea, 4 cylinder to 2 cylinder engine conversion

[Frank Lee]

Whoa- so much misinformation all in one thread! I've almost blown a vessel for how many days now?

el: dozens have tried the injector cut-off, and failed. Dozens more will try it again in the future... and still fail. The reasons why it doesn't work have been discussed. It revolves around pumping losses... always has. If a simple injector cut-out worked, everything would have displacement on demand since the late '80s. The pumping losses have to be reduced for this thing to work, either as a permanent conversion or as a dod setup. That means no air in/out of the cylinder.

If A-B-A testing is gonna happen then none of the mods can be permanent in nature i.e. no grinding off lobes and whatnot.

saand: you only have to look a few posts up to see that the pistons on a parallel twin rise and fall in UNISON.

Originally Posted by oly

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.

What? Piston speed is related to loading how? Stroke and rpm, with a lil rod angularity effect too. That's it, and the geometry of all that isn't changing. Loading is not a factor.

Change the spark advance why? Each individual cyl works as hard or as little as required, no matter how many more are helping it.

Re: epoxying dead intake man ports: with closed valves on the ends of the runners the worst thing that could happen is maybe some sort of helmholtz resonant phenomema- which tends to dampen pulses right? Who knows, maybe that would help?

phantom: removing an ex valve and venting the cyl to the atmosphere eliminates pumping loss? We gots a piston going up with an open port so it's gonna expel what's in the cylinder. That's pumping. Then the piston will go down and it'll draw charge back in. More pumping. In and Out and In and Out; I.E. pumping losses.

Originally Posted by ed

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 .

That may be; I wonder how detrimental it really is vs optimized? After all, much of the time stock engines are operated outside of the narrow rpm band where any sort of in and ex tuning helps flow.

...

Perhaps ideally what we'd want is a home-made displacement on demand system. I do think it's doable. There is a lot of field experience with them now so we know what to expect performance-wise, econo-wise, NVH-wise, and longevity-wise.

Perhaps less ideally, perhaps not, is the more or less permanent disabling of cyls. If the reduced hp is tolerable there should be efficiency benefits vs dod by totally eliminating- not just reducing- pumping losses and internal friction.

Oh, maybe I'll get to the rest later...

[saand]

shadetree reduction of the o2 sensor output is a good idea but im not sure it will work as intended. as the exhaust wont have double the o2 if 2 cylinders are deactivated it will likely have a higher ratio as o2 is burnt up in combustion of the o2 in the working cylinders.
There might be a good way to do this with a wide band o2 sensor (mine i assume is only a narrow band) but the ideal way would be to ensure the deactivated cylinders dont exhaust into the section with the o2 sensor.

Also i have no doubt some incorrect opinions are on this thread but thanks to all that have contributed even if they are wrong. Ultimately id like to test things out and actually see what happens but until i can test its good to see all the possible angles. The ideas that have come from this thread have given me some good direction

[Frank Lee]

If 2 cyls are disabled i.e. completely offline then the O2 sensor will function correctly as is. Why wouldn't it?

[saand]

Frank agreed the o2 sensor would work fine if 2 cylinders were completely disabled.

still looking at other options which may still involve the deactivated cylinder pumping but not doing useful work. in which case the o2 would flow through the cylinder. The only reason to go down this route is if going to 2 cylinders causes the engine to be unbalanced or if i try deactivating cylinders on the go.

[Frank Lee]

OK how's this for a thought experiment:

We know what factory DoD returns (7-20%), and we can safely say shutting down cylinders w/o shutting down the valves as well would not work as well as that, otherwise why would the factory go through all the effort?

So is it worth it for a possible fe improvment of up to likely less than 20% and maybe even an fe decrease? (Your car 29 x 1.2 = 34)

Check this out: http://ecomodder.com/forum/showthrea...ssion-968.html

[elhigh]

Originally Posted by Frank Lee

el: dozens have tried the injector cut-off, and failed. Dozens more will try it again in the future... and still fail. The reasons why it doesn't work have been discussed. It revolves around pumping losses... always has. If a simple injector cut-out worked, everything would have displacement on demand since the late '80s. The pumping losses have to be reduced for this thing to work, either as a permanent conversion or as a dod setup. That means no air in/out of the cylinder.

That's why I recommended only interrupting the injectors for his early testing. It doesn't sound to me like he wants to make any major alterations to the engine, and installing a break on those is pretty cheap and easily reversed.

If I really wanted to make a 4 into a 2, I'd want to change out the crank to a completely custom jobbie that only had the two middle throws, eliminate a lot of reciprocating mass/off center mass. Remove all the hardware for the outer pair of cylinders: pistons, rods, valvetrain, etc. I supposed a good machine shop could modify a crank for me if I wanted, cut out the extra throws and replace with straight stock. The cost gives me the shudders.

But once all of that work is done, wouldn't it have been cheaper/faster to build an adapter to run a nice, big motorcycle twin? Somebody's already done all the engineering, it's lighter to start with, and then you'd still have your unmodified 4 to bolt back in if you wanted to.

[saand]

frank thanks for that thread link, didn't catch it when i did my initial search.

To answer your question yes im happy to do all this work for a 20% gain. I am mostly doing it to see what happens, im in it for the engineering challenge so i dont mind if its not a great increase in FE. I would like to still be able to run my car after trying it though so im not ready to do anything completely crazy.

The motor cycle engine idea is great and probably the better way to go for cost/effort/efficiency. But the reason im trying this is to see what i can do with what i have.

[EdKiefer]

As long as the intake valve is closed IMO the O2 sensor will work ok . Cause even if you left exhaust valves open there no new air coming in (intake closed) . There maybe some reversal/turbulence depending on how you handle exhaust valve . As I posted before Honda says they close both valves to reduce pumping losses but while there no new intake change to compress there is still some back an forth compression/vacuum going on IMO .
Haven't look to see how other manufactures do it .

[ShadeTreeMech]

The reason I mentioned the NEED to change what the o2 sensor is seeing is due the the excess o2 from the disabled sensors. Of course it will work fine, it will read too much o2 and start to dump in the fuel to compensate. This isn't conjecture but fact based on experience and my understanding of engine electronics.

Frank, I've heard you refer to this idea as a guaranteed failure on many occasions, and while my own expirementation wasn't a complete sucess in that the fuel was getting dumped into the oil, I did manage to increase my mpgs by about 10 to 20%--had I not been wasting fuel by over fueling the running cylinders, I would have done better.

I'm in the same boat as saand, I have limited resources and have a strong desire to save money on fuel. The ideal solution would be a way to disable half the engine at the crank instead of the fuel, but that is much more complicated and pricey.

This bit here seems odd.....

So is it worth it for a possible fe improvment of up to likely less than 20% and maybe even an fe decrease? (Your car 29 x 1.2 = 34)

We've got people shaving off their door mirrors and removing windhshield wipers for much less than 20 or 10 or 5 percent increase. I don't understand why this particular mod rubs you the wrong way?

[EdKiefer]

Originally Posted by ShadeTreeMech

The reason I mentioned the NEED to change what the o2 sensor is seeing is due the the excess o2 from the disabled sensors. Of course it will work fine, it will read too much o2 and start to dump in the fuel to compensate. This isn't conjecture but fact based on experience and my understanding of engine electronics.

Frank, I've heard you refer to this idea as a guaranteed failure on many occasions, and while my own expirementation wasn't a complete sucess in that the fuel was getting dumped into the oil, I did manage to increase my mpgs by about 10 to 20%--had I not been wasting fuel by over fueling the running cylinders, I would have done better.

I'm in the same boat as saand, I have limited resources and have a strong desire to save money on fuel. The ideal solution would be a way to disable half the engine at the crank instead of the fuel, but that is much more complicated and pricey.

This bit here seems odd.....


We've got people shaving off their door mirrors and removing windhshield wipers for much less than 20 or 10 or 5 percent increase. I don't understand why this particular mod rubs you the wrong way?

I don't follow why you think O2 would dump more fuel in as long as no air is being drawn in. O2 don't know or care if its 2 ,4 ,6 or 8 cylinder, its the % that it reads not quantity . now if intake valve was open it be different story, it would "try" and compensate to keep 14.7 .

you sure you were in closed loop mode ?

I could understand when engine is cold or even hot under load with open loop . I have hard time seeing the MAF sensor (If memory right Mazda 526 has flap door type) would work right with only 2 cylinders , this type of sensor really needs smooth velocity airflow to work right , I could see the door might bounce at low speeds .

Edit: what sensor is being disabled ? , it only has 1 O2 on the manifold AFAIK