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

[Maim Menu]

That's pretty interesting, I'm looking forward to see what others think about it.

[Eye8Pussies]

that is very interesting, and it seems as though you've thought this through...

I'm not sure about the wear and tear on the engine without combustion...but...I think that oil and coolant worries shouldn't be a problem...theoretically...

but just a couple of questions....are you going to disable the spark in the cylinders too? and also...what do you mean by "pre-programmed" values in limp-mode? if the ecu throws the car into limp-mode, the pre-programmed values are to pull timing about 15degrees and dump fuel....if you want to save gas, you'll have to prevent the ecu from throwing any codes at all.

also, are you planning on being able to turn the cylinders on/off on the fly? or only when the car is off? I could see some problems arising if the cylinders are already moving at high speeds and the fuel and spark is added all of a sudden...

[Kevin89AllTrac]

Originally Posted by v6camrydriver

-Fuel economy gains offset by engine overcoming pumping losses

Don't variable displacement engines hold a valve (exhaust?) open on the disabled cylinders? I seem to recall Cadillac doing that with electro-magnetic actuators back in the 70's or 80's, and I assume that current variable displacement engines have variable valve timing which are modified to hold a valve(s) open. I would think that without removing compression from the disabled cylinder you wouldn't gain much fuel economy, but I don't know if/how current engines do that.

[xtremeskier97]

I thought the 94 V6 started the 1mz-fe...not the 3vz-fe?

Correct me if im wrong?

[Kevin89AllTrac]

The opposite...both valves are kept closed. From Wikipedia:

In order to deactivate a cylinder, the exhaustvalve is prevented from opening after the power stroke and the exhaust gas charge is retained in the cylinder and compressed during the exhaust stroke. Following the exhaust stroke, the intakevalve is prevented from opening. The exhaust gas in the cylinder is expanded and compressed over and over again and acts like a gas spring. As multiple cylinders are shut off at a time (cylinders 1, 4, 6 and 7 for a V8), the power required for compression of the exhaust gas in one cylinder is countered by the decompression of retained exhaust gas in another. When more power is called for, the exhaust valve is reactivated and the old exhaust gas expelled during the exhaust stroke. The intake valve is likewise reactivated and normal engine operation is resumed. The net effect of cylinder deactivation is an improvement in fuel economy and likewise a reduction in exhaust emissions. General Motors was the first to modify existing, production engines to enable cylinder deactivation, with the introduction of the Cadillac L62 "V8-6-4" in 1981.

[bigbird]

sounds cool, seems like the biggest worry would be burning oil do to the lack of cyinder pressure. but a DIY DOD would be somthing good.

[v6camrydriver]

A few points:
The spark will not be disabled to keep the control system simple.
The cylinders will be deactivated on the fly, all 6 for acceleration, and 3 or 4 for cruising.
I’m hoping that by leaving the Oxygen sensor connected on the running bank that this will keep the ECM in closed-loop mode and running as normal.
The reason for deactivating the de-activated banks sensor and the sub-oxygen sensor is to stop the ECM thinking the engine is running lean, because the deactivated cylinders will essentially be dumping large amounts of oxygen into the exhaust stream.
Not sure if this will work, but will find that out in testing and economy runs.
My main concern is weather the engine will be able to handle the mechanical loads.
My system is vaguely modeled on Hondas VCM system. http://www.honda.co.nz/hondaV6/about-vcm.html
The main deference is in four cylinder mode two cylinders on the same bank will be deactivated, as opposed to one on each side. This I have found smoother. The other difference is of course the valves on the deactivated cylinders will keep going as normal.
I’m thinking that if that engine can handle the loads then so should mine.
Also, does anyone know the role that fuel plays in cooling the intake valves? I’ve heard someone mention it to me but not sure if it’s true otherwise every-time the engine’s on the overrun and the fuel is cut that would mean the valve’s could potentially burn if say engine braking down a long hill.
Bigbird raises a good point…does anyone know how other stock cylinder deactivation systems get around the lack of sealing pressure problem?
Finally, I’m sure xtremeskier97 is correct that the American ’94 Camry started the 1MZ-FE but mine is an Australian built Camry and definitely is a 3VZ-FE...I would put it down to regional differences.