[revetec]

We are using wideband for programming and then narrow band for control.

Hightower: I know how a Lambda sensor works and we didn't expect the sensor to read in the way it does. But purely it does give a reading as I have described. This trait has been consistent on multiple lambda sensors. Motec set up our first engine management system in 2001 and it was then we all discovered that the Lambda was showing the combustion effectiveness rather than the actual air/fuel ratio. We spent a lot of time trying to work out why we were getting such a reading, because we actually want to know the actual air/fuel ratio of what we are using, but as it turns out we can only use it as a tuning guide.

In reference to piston height. At 4,000rpm let's say at an ignition point of 30deg BTDC a piston is 10mm from the top of the stroke, our piston is about 5mm from top. This means that the firing volume is half it would be normally.

We have found that our combustion fires richer than normal with a normal injection amount. If we use a normal type injection map the engine chugs black smoke, poorly performs and the Lambda is off the scale in the rich side at higher RPMs. Note: We are injecting roughly the same amount per cycle as we were at 2,000rpm which we had a Lambda reading of 14.7:1. Normally at 4,000rpm we would be injecting slightly more to reach a 14.7:1 ratio (I'm sure you have seen a normal injection map). We had to lean the mixture off to about half of the injection amount to bring the Lambda down to read correctly.

As an example on our RHL4 engine (full throttle) at 2,000rpm our injection was 12ms and at 4,000rpm was 7ms. Fuel pressure was consistent, manifold vacuum was consistent, power output was almost double while torque remained reasonably consistent and at both RPM ranges we had a Lambda reading of 14.7:1. The fuel usage was measured by weight and the engine was using roughly the same amount of fuel in both rev ranges. This was tested in an independent test facility.

We came to only one conclusion from this test. The fuel per firing cycle reduced as the revs increased, although the Lambda was reading the same.

Note: We have changed the piston position profile in the latest tests.

What is your view on this data? And what is anyone's view on this data? Input would be much appreciated.