Apologies for the delay in producing this newsletter! With examinations and uncertainty in what was happening at Manchester, I was waiting for some concrete news before writing.
By the end of their project, the students had just managed to get the engine running and two of them, Victor and Ahmed, were offered one month internships to continue the testing after their examinations. In the event, broken crankshaft bolts and a limit on technician time resulted in only two hours of tests. However, these were sufficient to give an insight into our problems. Since then, I have been negotiating with the MACE department at Manchester to agree a way forward.
The tests were run by Victor, one of the students, Prof. Yates, Dave Houghton (Technician) and me. The results surprised us all and suggest a more detailed phase of testing is required to answer the questions and find solutions.
We tested three fuels: Avgas, the 1960 – 70’s equivalent as a control fuel, Esso 95 octane from a local garage and Supermarket E10 obtained in France. Running over a range of engine revs for each fuel, we measured torque, air fuel ratio, exhaust temperature and investigated changes in ignition timing. Tests were performed with a wide open throttle and part throttle producing about 80% of the maximum torque.
On the full throttle tests not only did the engine run almost exactly the same on the three fuels, we found the standard advance curve produced by the Distributor Doctor’s distributor produced the optimum power. What differences we did see could easily be explained by the physical differences in the fuel and the “enleanment” effect of ethanol in the E10.
The part throttle tests gave a different story, which is not obvious when you look at the torque curves. To achieve these values we had to WEAKEN the mixture of the Avgas by 2 flats on the carburettor relative to the full throttle setting and RICHEN it by 6 – 7 flats from the Avgas setting for the Esso and E10.
In other words, fuels that behaved identically on full throttle ran differently on part throttle – modern fuels running significantly weaker than Avgas, our control fuel.
This effect is very worrying. Have your car tuned on a rolling road, at full throttle, then drive it away on part throttle and it will run weak and hot! The problems we are experiencing with modern fuel are real and elusive.
There are two possible explanations, evaporation in the carburettor, changing the mixture or differences in combustion. Unfortunately, the measurements we took were insufficient to give the answers, hence the need for further test.
Ed’s Note: Very worrying indeed! In discussion with Paul I have said that lack of money should not be a bar to further research. Further research is potentially costly but the funding must be found. Whilst I have pledged further financial support on behalf of readers there are other funding avenues which need to be explored. You can be assured that Paul is ‘on the case!’