DIY displacement on demand system project

[v6camrydriver]

Thoughts and feedback welcome on the following scheme:
Engine: 1994 Toyota Camry 3VZ-FE CAT (3L V6 non-VVT-I)
Transmission: 4-speed automatic FWD transaxle with lock-up Torque Converter
Odometer: 340,000Km
Fuel injection system: Sequential multi-point fuel injection EFI
Oxygen sensors: 3 total: 1 on each engine exhaust manifold and 1 sub-oxygen sensor mounted downstream of the Catalytic converter (CAT)
Firing order: 1-2-3-4-5-6
Current average fuel economy: 10L/100Km
The plan:
Through testing of the engine I have found that it still runs reasonably well on 3 or 4 cylinders for cruising.
I intend to have three modes of operation:
Normal (all 6) for start-up, warm-up and acceleration
V4 (4 cylinders) for high-speed cruising
I3 (3 cylinders) for low-speed cruising.
For 3 cylinder mode I will deactivate cylinders 2, 4 and 6 (the front bank) and for 4 cylinder mode I will deactivate cylinders 2 and 6. I have found these configurations the smoothest.
I also intend to deactivate the oxygen sensor for the disabled bank and the sub-oxygen sensor. The sensor for the running bank (cylinders 1, 3 and 5) will remain untouched.
The reason for this is it will either:
A: trick the control computer (ECU) into thinking everything?s normal and not just dumping more fuel into compensate, negating any economy gains; or
B: put the ECU into ?Limp-home mode?, which will cause the ECM to substitute pre-programmed values for the turned-off sensors, which since my engine is well maintained should run like normal when at operating temperature.
The method by which I will deactivate the cylinders/oxygen sensors is by rigging up a bank of centre-console switches to turn off power to the appropriate fuel injectors and Oxygen sensors.
The intake and exhaust valves will not be deactivated so the deactivated cylinders will act like air pumps.
The idea is to rig everything up and then do fuel economy tests in various modes to find out what effect it has on fuel economy. But before I do I want to make sure the engine will handle everything (i.e. by not blowing up), both short and long term, so would like opinions/constructive abuse on whether it?s a good idea.
Potential worries to consider:
-uneven wear
-uneven cooling
-deactivated cylinders not being lubricated properly
-burning intakes valves due to no cooling fuel passing over them
-extra oil consumption due to lack of sealing pressure on deactivated piston rings
-shorting or arching when flicking the switches, at best blown fuse, at worst blown ECU
-mechanical failure of connecting rods, pistons, bearings, engine mounts
-Fuel economy gains offset by engine overcoming pumping losses

[suspendedhatch]

Limp mode unfortunately defaults to very rich mixture and very conservative timing. You are confusing limp mode with open loop. Open loop is when the ECU ignores the O2 sensor and runs straight off the fuel and ignition tables. This happens any time you mash the gas to the floor and wait for the RPMs to climb past a certain point. It also happens any time you are below operating temperature or before your O2 sensor has had enough time to warm up.

Whether you're burning fuel or not, the cylinders will receive the same lubrication. All your injectors stay closed every time you let off the pedal in gear above 1000 RPM. They turn back on when you drop close to your idle RPM. So lubrication on deactivated cylinders is not a problem. Oil circulation is mechanical. You could turn the crank by hand and it would pump oil.

When a cylinder compresses air without burning fuel it decelerates. I'm not sure but it seemed like you were assuming that since there's just air flowing in and out of the combustion chamber there's no resistance besides drivetrain losses and the friction of the wheels.

You can't deactivate an O2 sensor with a simple switch. The ECU will sense something wrong and throw a CEL. Instead what you want to do is emulate an O2 sensor with normal readings. This is not easy but there may be products on the market that do this. The signal from a narrow band O2 sensor is constantly bouncing from one voltage to another, approximately .4 volts to .9 volts. That is what your ECU wants to see. If it sees nothing at all, or one constant voltage, it's going to throw a CEL and go into limp mode.

If you don't want electric spikes across your switch you simply bridge the terminals with a diode facing backwards. You could also switch relays and put diodes on the relay terminals facing backwards.

[v6camrydriver]

If one or two oxygen sensors ?stop working?, would the ECM use the remaining one to control the engine normally, or go into open loop mode or ?limp home? mode?
For example mine has three?two on each engine exhaust manifold and one after the CAT (the sub-oxygen sensor). I would switch off the sensor on the deactivated bank plus the sub-oxygen sensor and keep the sensor on the running bank connected.
I ask because I have disconnected the OS on the front exhaust manifold, with the engine running, without the CEL coming on.
Also I knew there would be drag from the deactivated cylinders, but there may still be fuel economy gains to be had which I may or may not find during test drives.

[v6camrydriver]

Another idea I've brainstormed is to disconnect permanently 2 of the oxygen sensors (OS) and leave the one on the running bank connected.
I would then split the siginal from that sensorl into three to feed all the OS inputs into the ECU.
Would this work?

[GasSavers_RoadWarrior]

Well, that's probably the way I would go about it. I'm plotting DOD on my V6 voyager, and wondering if I would add 2 O2s to do the same thing.

[theholycow]

Now THAT's a good idea...if you couldn't split the signal from one, just install a second one next to it and use that one to read the active side and feed the ECU that data for the inactive side. Neat idea!

[v6camrydriver]

I think I'll just wire the one Oxygen sensor into the three inputs. May do this in the weekend and see how it affects performance/economy before I go any further.
Another thing I've been concerned about is uneven loads on the crank with one bank shut-down. I've read that my engine model started off Toyota's trend of overbuilding thier engine blocks, cranks and rods but all the same I don't want to do this if it's going to destroy my engine. Also, when cruising, the Honda VCM system shuts down an entire bank of cylinders so obviously it can be done...
Does anyone think this will be a problem?

[DRW]

"The intake and exhaust valves will not be deactivated so the deactivated cylinders will act like air pumps."

This will be a difficult problem to solve. Perhaps add a valve that blocks off the intake tract to one bank of cylinders? This way the cylinders will be working in a vacuum.

[v6camrydriver]

Another thing I've been concerned about is uneven loads on the crank with one bank shut-down. I've read that my engine model started off Toyota's trend of overbuilding thier engine blocks, cranks and rods but all the same I don't want to do this if it's going to destroy my engine. Also, when cruising, the Honda VCM system shuts down an entire bank of cylinders so obviously it can be done...
What is everyones' thoughts on this?

[theholycow]

Look at a picture of how the pistons/rods line up on a crankshaft in a V-type engine, you'll get a better feel for the answer to your question.

My gut feeling: In I-3 mode the imbalance shouldn't be too bad. In V-4 mode it might be a bit much.