[hightower99]

Originally Posted by revetec

In the report we quoted the wide band high speed sensor from our dyno. We do close loop under 50% load from our narrow band but under the test of course are at 100% load.

As I expected

Originally Posted by revetec

We had not used a catalytic converter. We have a 5 gas analyzer measuring HC, CO, CO2, O2 and NOx which are pretty consistent with an engine with no emission control.

I am guessing you have low HC and CO emissions CO2 should be about normal (for untreated exhaust) NOx should be on the highish side? (maybe not OTT but definately you should still be seeing a good deal at WOT as you are running very lean). Does the O2 reading from the gas analyzer agree with the lambda readings? This is a great way to check the validity of the lambda sensor. If the gas analyzer agrees then gas oxygen is being used to produce something else and the Lambda sensor is working properly. If it doesn't agree then it could mean two things. If it reads more O2 then the lambda sensor measured then the Lambda sensor has a problem, if it reads less O2 then the lambda sensor then there is a really big problem.

Originally Posted by revetec

Our engine likes a higher ignition timing from idle and it varies little during all operational conditions. Usually there is only 10degrees variation throughout all operational conditions. Our test figures on the X4 were produced with a fixed timing of 24deg for the whole dyno ramp. Advancing and retarding from this figure dropped performance slightly (we tested +/-5 deg) The whole engine management programming is totally different from a conventional engine.

the fact that you engine likes relatively advanced timing is not surprising as it is firing in a more dense mixture. The fact that timing doesn't vary much is overly surprising either as you are only going from idle to just over 4000RPM at WOT. It is odd that you seem to have hit the optimum timing and that you can run the whole rev range well with just that timing.

Originally Posted by revetec

Our dyno readout only displays when the sensor is at operating temp (displays "cold" when warming up) and the heater is always on when testing is on. This is part of the dyno, and the heater cannot be turned off while displaying.

I doubt that the heater is inadequet but it is something to test because if the sensor isn't hot enough then the readings can be all kinds of wacky.

Also I have been thinking about NOx in your engine. It is produced due to high combustion temperatures but if enough is made it will lead to cooler exhaust temps. However while traveling in the (relatively) cool exhaust, NOx performs an exothermic process where it reverts back to O2 and N2. However this does take some time so it would probably occur close to the end of the exhaust system. I wonder if you put in an exhaust temp probe close to the head and one closer to the end of the exhaust system if you will find that you exhaust starts cooler (than your average piston engine exhaust) when measured close to the head but ends slightly hotter (than your average piston engine exhaust) when measured close to the end of the exhaust system. Note: I am not saying that the actual temperature at the exhaust exit is higher than at the manifold but that your exhaust temperature doesn't drop as much as for a typical engine.


Matra: The raw output from the sensor (ie the input that the output is made from) is the pump current. I agree that there could be a null point but I doubt that that is what is causing the weird readouts.