Fuelly Forums - 2+2=4... But If you -2 Then??

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2+2=4... But If you -2 Then??

Hey everyone MY First Post !@ @

I have a standard 150,000km 4 Cylinder Engine 132hp 2000 Dodge NEON !
(best car in the world!) Its Red too@

Anyways I hate paying for gas so, while I was bored messing with my car I just happen to unplug my cars Number 2 cylinder fuel injector just to see what happens, and it started running a little ruff on one end, so I unplug the number 4 cylinder fuel injector to even it out, it ran ruff and die when I tried driving it LOL. I idle it for about 1 minute and then the engine started running smoother and smoother, so I got into it again and the f-ing thing moved! So I said sweet! and backed out of my driveway and began driving on 2 cylinders, ran not that bad, it did feel alittle rougher then normal. I started up the street got to 10km then 20km, then all the way up 60km with no problems, only 25% throttle and got there pretty fast, 70km acceleration slowed. 80km was the highest and couldn't pass it, I didn't want to push the gas pedal to much. so I thought not bad! then I had to go see my girlfriend, plug everything back together and thats it, I was just wonder...

Is it bad to run on 2 cylinders?
Do you think my car gets better fuel economy?

Because it wouldn't be hard to make a switch to shut down 2 cylinders for city and to start them up for highway or 60km+?

When you said you disconnected the cylinder, how did you disconnect it? Please describe in detail what you did because if you didn't do it right, you could seriously screw up your engine and not save a drop of gasoline.

People on this forum have experimented with cylinder deactivation before, but nobody has had any real success. That's not to say that you won't, but it is pretty complicated to do it and actually run well / save gas.

Most often you hear of V-8's being converted into 4 cylinders. I had read articles published in the 70's on doing this. What they were doing then was removing the pushrods and exhaust valves on one bank of cylinders, and putting bushings in to hold the intake valves closed. I think this would only work with a carbureator or throttle body injection (With the deactivated bank's O2 sensor moved) though...

Quote:

Originally Posted by Jay2TheRescue (Post 137597)

Actually it'd be easier on a FI car because you could disconnect the electrical to the fuel injector and spark plugs, no spark and no fuel means you can leave the valves alone, unless you want to reduce the losses incurred from having them open, close and compress for nothing.

Additionally, you want the valves closed so it's not pumping air through them. You'll be opening the throttle more and running higher RPM, so if you don't close them you'll be pushing a lot more air through your intake and exhaust -- probably enough to lose some efficiency (vs. low RPM with closed throttle when you've got all your cylinders running).

Quote:

Originally Posted by theholycow (Post 137605)

But for the sake of simplicity, it'd be easier to not even take off the head because if you do decide to want the extra power and or fuel economy, you don't want to have to replace the head gasket, drain the coolant, etc. You'll obviously not get the benefit of less frictional losses but you will get the benefit of less fuel being burned. If you really want a 2 cylinder engine, you'd probably want to redesign the crankshaft, remove two cylinders, remove the valves and associated stuff, plug up the oil holes, etc.

Nobody has had any real success with cylinder deactivation??? Why? I pretty sure some people reading my post don't believe me that I did drive with 2 cylinders, so I made a video, show you how I did it, note that its really hard to drive a standard and record at the same time.
P.S all I did was disconnect 2 fuel injectors
"Video Link"
https://www.youtube.com/watch?v=LelL8OfCYQ0

Thanks
Love to here what you think.

Another thought would be that if you don't keep the valves closed on the unused cylinders, the O2 sensors will read more oxygen than normal. Causing more fuel to be dumped in.

No one said it could not be done. I have pulled cattle trailers with an injector that was unplugged before.

The issue at hand is it worth it in the long term? You haven’t posted your gas mileage for before and after. I think about the long term issue. IMO I think you will get a build up of carbon on the valves and possibly the piston if it’s run for to long like that.

Quote:

Originally Posted by Jetta90GL (Post 137609)

Another thought would be that if you don't keep the valves closed on the unused cylinders, the O2 sensors will read more oxygen than normal. Causing more fuel to be dumped in.

You make a good point, I guess a very simple thing he could do is get a cam that doesn't actuate the valves on the cylinders he doesn't want to run, it wouldn't require a head rebuild and wouldn't be too difficult though he would have to pony up some dough.

Unplug two injectors, the oxygen sensor reads lean and increases the fuel to the working injectors. The excess fuel is then pulled into the cylinders with dead injectors and the engine still runs on 4 cylinders but not very good.

Seen it on a Maxima with one dead injector, idled fine, slightly rough on acceleration.

regards
gary

Quote:

Originally Posted by Diabloflash (Post 137608)

Nobody has had any real success with cylinder deactivation??? Why?

I don't necessarily know why, I just know that I've read a few experiments and they all gave up when it didn't work for them and was too difficult. If you can make it work, that's great and I hope you'll document everything well.

Quote:

Originally Posted by theholycow (Post 137619)

Can you cite said experiments please?

Quote:

Originally Posted by ************* (Post 137603)

Actually this probably would make the engine stumble a bit, but most importantly disconnecting fuel injectors will set a trouble code in the computer, and force it to run in open loop.

Quote:

Originally Posted by Jay2TheRescue (Post 137623)

Actually this probably would make the engine stumble a bit, but most importantly disconnecting fuel injectors will set a trouble code in the computer, and force it to run in open loop.

Well that's what the op did. The problem with a carbureted engine is you'll get an accumulation of fuel build up behind the valves or on what ever you use to plug up the hole in the intake, but with a fuel injected car, you can simply not inject fuel into those holes at all, resulting in no fuel build up. This is one of the reasons why on the Vtec-E engines, under lower load low speed operation the second valve doesn't stay closed completely but opens a little, just enough so that fuel doesn't pool up.

Now that you mention it, I do remember them saying you had to block off half the carb... Maybe I'll look for that original article I read tomorrow morning. I remember it was published in Mother Earth News...

Carbed motors with deactivated valves might get a tiny little trickle of fuel down there, but there's no air movement to suck the charge that way, so it's not going to be particularly bad. Also The valve isn't going to be very hot on a deactivated cylinder, it will likely not bake crap on.

It has lately occurred to me that on normally aspirated engines, the amount of exhaust scavenging may have a bearing on the relative success of cylinder deactivation on a given engine. This would be because the active cylinders, would in fact "suck" harder than the inactive cylinders, and may leave the inactive cylinders a little less "full" in a slight vacuum relative to manifold pressure, than the active cylinders. In a well tuned fully active engine, charge robbing between cylinders with long intake durations is avoided by good runner tuning, insuring that runner momentum is enough to avoid backflow. However, with less runner momentum due to no exhaust blowdown to scavenge, this may not be enough to stop backflow from an inactive cylinder. In an extreme case, when exhaust manifold pressure is quite high, some amount of exhaust gas could be passing backwards.

In a case where you have both strong scavenging in the active cylinder at blowdown, intake valves overlapping between cylinders, and mid-late cycle higher exhaust manifold pressure, it's possible that "inactive" cylinders are almost "running backwards" in that they are getting (relative) positive pressure just before the exhaust valve closes and negative pressure just before the intake valve closes. This would mean that the "inactive" cylinders may in actual fact contribute net energy to the system, by recovering exhaust gas energy, or at least making up for the "huge" frictional losses that they apparently cause.

To purposely set up a motor to make the most out of this effect would be rather difficult. I think you'd need an undersized yet tuned exhaust system, meaning one that offers very little flow resistance due to shape, i.e. flows very well at lower speeds and volumes, but reaches a velocity threshold at higher speeds and backs up a little. It would probably need a "shorty" header or stock manifold. You'd also need to carefully balance intake runner volume.

Most likely way to be able to do this is if you had a block used in a limited capacity racing formula, like 1600cc, and you used the 1600cc racing parts and warm cam on a 2400cc version or something.

Whether you can take advantage of the above effect or not, the first question you really want to ask yourself for DoD experimentation is "Can I find a dyno graph for my motor that shows I have a max of about 75HP at 3000 RPM" This is a "rule of thumb" figure based on rough and ready calculations, if you have a particularly small, or particularly large vehicle it might be best to figure it out exactly yourself. Basically, you need to have around 30HP available to cruise at highway speed without being hugely affected by wind and slight grades, but you need it at less than 80% of the motors capacity or you will more than likely be out the top of the peak BSFC island, and using too much gas, most charts I've seen the best zone is in the 40-80% output area near torque peak. You don't wanna be too close to the bottom or top, and you wanna have slight reserve, hence about 30HP is good, even though you'll probably only use 20HP. So I figure for unmodified vehicles with stock aero and rolling resistance, you're gonna need about a 150HP motor before DoD is worth playing with. If you're starting with a 100HP motor, you're probably going to have to whittle down aero and RR until you're sure you're using a bit less than 12-15HP at cruise. Paradoxically, this might be where you're finding your rolldown tests indicate better aero and RR, but MPG tests are getting worse or no better, yeah, you've dropped out the bottom of the BSFC map and need to put it back in. That's why I guess the more modified vehicle drivers start to pulse and glide, the motor needs more load to be efficient.

I had a 59 Austin Healey Bug Eyed Sprite that had two burned exhaust valves. 35 PSI Compression on each so they were basically dead.
The car was completely gutless and would barely climb and grade above 4%.

regards
gary

Did you burn them on leaded or unleaded?