Re: New Engine Build
Posted: Sat Feb 17, 2018 10:24 am
Finally found time to put the Elan with the new engine on the Dyno. It had run OK at the last race meeting on Avgas but was clearly not quite right and i want to tune it now to run on pump fuel. This engine was a bit of an experiment as I was dropping the compression ratio from 12.5:1 to around 11:1 to run on 98 Octane premium unleaded pump fuel rather than Avgas ( In Australia quoted fuel octane is RON+MON / 2 like in Europe ).
I went to a longer duration and higher lift inlet cam of 0.46 lift and 300 degrees seat to seat to try to compensate while leaving the 0.44 lift 285 degree exhaust cam.
Spent a day on the dyno and did many runs, trying many things. I had used 36mm chokes previously but ended up trying 38mm chokes which gave more top end with no loss of mid-range torque. Also found my fuel pump was not keeping up at the top end and losing pressure so did the dyno work with a temporary set up - new pump and fuel line to go in next weekend !
Dyno curves for the best 36mm choke result and the final 38 mm choke are attached. 141 HP at the back wheels is not bad for a 1600 twink in an Elan with a 3.77 diff in top The curve drops off at 7400 rpm but this is the dyno safety cutoff setting, it would have pulled with similar power well over 8000 rpm
Also have one noisy exhaust tappet that I need to have a look at, must have got the clearance a little big
cheers
Rohan
I went to a longer duration and higher lift inlet cam of 0.46 lift and 300 degrees seat to seat to try to compensate while leaving the 0.44 lift 285 degree exhaust cam.
Spent a day on the dyno and did many runs, trying many things. I had used 36mm chokes previously but ended up trying 38mm chokes which gave more top end with no loss of mid-range torque. Also found my fuel pump was not keeping up at the top end and losing pressure so did the dyno work with a temporary set up - new pump and fuel line to go in next weekend !
Dyno curves for the best 36mm choke result and the final 38 mm choke are attached. 141 HP at the back wheels is not bad for a 1600 twink in an Elan with a 3.77 diff in top The curve drops off at 7400 rpm but this is the dyno safety cutoff setting, it would have pulled with similar power well over 8000 rpm
Also have one noisy exhaust tappet that I need to have a look at, must have got the clearance a little big
cheers
Rohan