2 cyl civic test?
 

Hi I'm new to the website and have been trying to play catch up on all the mpg tips. I have a luxury that many do not in that I will be changing the motor in my daughters 1.5 93 civic while the old one still runs well. It has 150,000 miles on it but has just recently blew an oil ring. I found a used low mileage motor that will be cheaper to put in than going through the old one. But before I pull it out I thought I'd play a little. I plan on seeing the difference in mpg by disconnecting cylinders. I do not have a scangage but the plan is simple. Fill up run 80 miles or so straight highway. Refill and check mpg. Take it in my shop, remove the rocker arms on the bad cylinder placing a hose clamps with rubber over the oil holes to maintain oil pressure and disconnect the fuel injector. The reason for removing the rocker arms is to keep from confusing the oxygen sensor. Retest mpg. Do the same test again, this time pulling out the spark plug to see the difference between the "air spring" affect and no air spring. Once these tests are complete and I can see which is better - air spring or not, then I will proceed with unhooking another cylinder, the one that is 180 degrees from the one already disconnected making it a two cylinder motor. I know the power loses will be great and the vibrations incredible but why not? What do you all think? Am I missing anything?

Many ppl here have tried unplugging the injectors with little or no gains but only a few have disabled valves.

Go for it, but try just disabling 1 cylinder first. Speaking from my own experience, acceleration really suffers on a 1.6 liter Honda engine when you disable 1 cylinder.

Put your car in the "garage" and start a gas log and show your valve disabling results for all to see.

So this has been tried before? I know others have tried disconnecting the injectors but disabling the valves and pulling the plug has been done? I don't want to reinvent the wheel or waste my time if no gains are expected. Can you provide me with a link to the tests?

If I'm understanding correctly, you disconnected the injector, rocker arms on both intake and exhaust valves? Did you pull the spark plug or leave it in? I know hp would be greatly affected but what happened with the mpg? What car was it on?

Disabling the valves and pulling the plug will be what makes this worthwhile.

Please take a look at this thread:
https://www.gassavers.org/showthread.php?t=7400&page=2
There's an intense discussion going on in there about very similar stuff, and real experimental data from you could answer and close it once and for all.

I can only forsee getting worse mileage. Even if you were to disable the valve acuation of those 2 cylinders (I would attempt #2 and #3), you will still have pumping / friction losses from those cylinders (even with the spark plugs out).

I just don't see where you are going to benifit, perhaps reducing pumping losses past the throttle plate? (As it should require to be opened more)

Hmm...I wonder what would happen if you entirely removed those pistons and connecting rods. Would the resulting extreme imbalance cause stuff to fly apart?

I don't understand your last question. If you are asking why disconnect the valves the reason is simple in my way of thinking. If you don't disconnect the valves air will be pumped into the exaust instead of carbon monoxide. This air mixing in with the cylinders that are still running would make the exhaust appear to run lean. If that were the case I think the computer would compensate by richening the mixture defeating the desired goal.

I thought about that too. If there was a way to remove the piston without pulling the head I would love to try it. One would have to cut the connecting rod short to the crank and leave it installed to maintain oil pressure. Yes, it might be out of balance but I would not be too concerned as the motor will be discarded in the end. I really don't think the frictional loses will be that great though. If you have ever pulled a high mileage motor apart, the pistons really slide easily. Seeing as there will be no heat generated by combustion in these cylinders I would think the loses would not be that bad. Is there any other threads in the archives that I could read where someone has done what I am attempting?

If I'm unhooking two cylinders in the end why #2 and #3? These cylinders are not 180 degrees apart are they? I would think to even have a shot at success it would have to be 1 and 3 or 2 and 4 or vibrations would be much worse.

If I remember right, the firing order is 1-3-4-2, so you're going to want to disable either 1 and 4 or 2 and 3.

My question was, by disabling 2 cylinders, how will that improve your FE? As far as I can see, you aren't really reducing weight, pumping losses, friction losses, thermal losses, etc. Maybe there is something I'm missing?

Would still be fun to try! Nothing wrong with a glorious explosion.

If you have some serious spare time, you could attempt to cut out those 2 cylinders, and then weld the crank, block, cam, head, manifolds back together. =)

You are correct about the firing order and which cylinders to disconnect. I just verified it in my service manual. I know I'm not reducing weight and am decreasing hp. There will be a little less work done by the motor as it does not have to open and close the valves and yet I realize the frictional loses of the non productive cylinders. The test is to see if the fuel is cut to one less cylinder would the power loss be enough to negate any mpg increases? Where is the main difference between what I am doing and some production vehicles are made to do automatically? I know they close the valves too. Again, I'm doing this for the fun of it. It's not a ton of work and in the end the motor is going to be swapped out anyway.

Cut both ends of the connecting rod and shove the piston up to the head.

I didn't realize that the connecting rod is required to maintain oil pressure, but wouldn't it need to remain pointing up? If you cut it short, isn't it going to spin around freely?

I haven't been inside a crankcase since I did a 5hp Kawasaki in high school so it's hard to remember some of this stuff...

Yes, it can spin freely but this shouldn't be an issue if its cut really short (it won;t hit th pan/block if its cut really short. Be sure to use a punch or something to knurl up some metal in the cylinder bore so the piston doesn't side back down out of the cylinder and fall onto the rotating crankshaft.

You guys are on the same track I was. This would take more time and I would not want to try it unless I could get some mechanism in the cylinder to lock the piston in place and I don't know there is room from the bottom side to do it. This motor would be shakin like crazy to that piston would drop pretty easy. If there was time after all the other testing was done maybe I would try it.

Remove the rockers to the pistons you want to disable and pull the plug., disconnect the injectors of course.

No valve activity will eliminate and intake or exhaust. The only pumping losses you would still have would not be related to air moving in or out of the engine. There would be a slight restriction to airflow through the plug holes, so you could open the holes up some. if you added a tube between the two dead cylinder plug holes it would keep the noise down.

I had a 59 Austin Healey Sprite (bugeye) that had two burnt valves (think they were exhaust). Compression was less than 35 psi per cylinder with about 1/5th of the valve head gone.

It ran but it didn't have enough power to climb any kind of significant grade.
My brother managed to blow the tranny before I figured out whether the mileage was better that the normal 32 mpg. This was in 1968 but I do remember I could get it up to a decent speed. 1 liter engine in about 1200 pounds of car, normally it would do about 82 MPH max.

regards
gary

Here you go.

https://www.gassavers.org/showthread.php?t=6137

I should have held the cam followers up with hose clamps so they did not contact the cam. Maybe next time. ;) The V8 on 4 cylinders was a lot more practical.

As for leaving rods off of an engine you can do that and cover the hole in the crank with a hose clamp. In this case you would want to make an odd fire engine for best balance. That is leave off 1 & 2 or 3 & 4. I am not recommending this just saying that is the way I would do it.

By all means have some fun if you want to.

No pain no glory. :)

he if its anything like my s-10 when 2 of the cylinders were misfiring a few times last winter, you will NOT want to try to pull out on a busy road... i suggest taking it around your neighborhood and gunning it to see how much power you have left, i could barely get going and had to pull over and rev it to evaporate moisture that condensate on the ign module...

I'm thinking that the dead cylinders need to be opposing to minimize out of balance issues. That means both would be coming to TDC at the same time, one normally on the exhaust stroke and one normally on the intake therefore I could not connect a hose between the two cylinders as they will both compress at the same time. I don't think there would be very much restriction from the spark plug holes. I live in a rural area and will just put up with the noise for the test.

Could you explain how odd fire would make balancing better? Every two full revolutions of the crank will normally fire all four cylinders so I would think if you were to remove two it would need to be every other one to give it the smoothest possible outcome.

I only meant this for if you were actually removing rods and pistons and was referring to the vibration characteristics not the torsional aspects of the problem. A parallel twin has the vibration characteristics of a big single. A 180 degree odd fire twin vibrates a bit less. An old John Deere tractor twin is a 180 crank twin unless you go way back in years. Something only 40 years old would be the Honda 305 scrambler motorcycle. They truly vibrated less than the 305 Dream which was almost identical but was a parallel twin engine. This is all pretty academic and really doesn't matter cause I don't think anybody is going to do if for more than a few hours at most.