Variable displacement via Arduino
 

All, I have been doing some experimentation with variable displacement as described below. So far it's worked from a technical point of view but can't validate fuel economy with mpguino as this mod cuts inj pulses. One unexpected gain has been an improvement in throttle response/ pickup because there is less vacuum.

In essence the arduio watches a pulsed ground injector, counts and selectively interrupts the injection by driving open a solid state relay. I am experiememting on a 1.8l. 4cyl engine and the engine still runs smoothly with every 2nd pulse interrupted for all cylinders which is essentially 50% cylinder deactivation. My initial objective is to raise the manifold pressure from about 70kPaa to say 90kPaa, rather than convert to throttles altogether. My understanding is that approx a 10-15% FE improvement is expected without touching the valves as occurred in traditional deactivation.

One challenge is how to achieve closed loop control when inactive cycles pump air into the exhaust.

I'd be curious to know if anyone else has done any research or experimentation with cycle based cylinder deactivation.

I understand the GM/ Delphi commercialising the technology this year.

There has been quite a bit of tinkering with injector interrupts and it's a fail. 10-15% is what one can hope for with valve deactivation.

Interesting idea. 10-15% does seem like a lot since you are still pumping air. However, it would be great to see what you can do just with some electronics.

If you reprogrammed the arduino to sense cylinder deactivation, you could just cut your fuel use calculated by 50% when the cylinders are deactivated.

To monitor air fuel ratios when in cylinder deactivation mode, you'll probably need a wideband oxygen sensor. A narrow band sensor simply won't be able to monitor air fuel ratios outside its designed range.

Frank can you point me to any forum threads or reference materials where people have tried this. I haven't been able to find anything. Thanks

Daox, my understanding is that the majority of the pumping loss is at the throttle, since that has a 30-40kPa pressure drop at partload.

How would this differ from lean burn?

Alternate burn - still a stoich mixture in the hole but not every stroke. The main issue is the slow-ish response of the lambda sensor that will screw up the ST and LT fuel trims by enriching them to the point that it will probably use more fuel. This type of mod needs to be coded into the ECU so that the downstream effects can be allowed for or ignored as required.

Simon