Just something that I have noticed whilst mapping recently that a map done for Tesco 99 that is completely knock free will, if left in the car for a period of time unused will then start knocking a couple of degrees here or there.
I havent noticed the same with Shell vpower.
I know that fuel loses its octane gradually and that race fuel is particularly prone to this.
does Tesco 99 go off more than vPower?
I only spotted it the other day Gerry then looked back through logs.
When the map was done it was knock free (say on a saturday am)
But consistently logs from mid week (the week after) showed a couple of points where there was some knock. Not much.. but retardation all the same.
I wonder whether the ethanol in the Tesco has a shorter in tank life and the octane of the 99 reduces.
I will see if I can properly replicate the test with vpower.
[geek mode]
I have noticed that there is a 3% difference in closed loop fueling between the two as well which carries forward into open loop.
ie.
if mapped on 99 and it wants to take out 3% fuel if run on vpower.
if mapped on vpower - it wants to add 3% more fuel for tesco 99 because it considers it is running too lean.
I now have two maps - one vPower with injectors at 867cc and a tesco99 at 842cc to account for the stoich differences in fuel.
[/geek mode]
When the map was done it was knock free (say on a saturday am)
But consistently logs from mid week (the week after) showed a couple of points where there was some knock. Not much.. but retardation all the same.
I wonder whether the ethanol in the Tesco has a shorter in tank life and the octane of the 99 reduces.
I will see if I can properly replicate the test with vpower.
[geek mode]
I have noticed that there is a 3% difference in closed loop fueling between the two as well which carries forward into open loop.
ie.
if mapped on 99 and it wants to take out 3% fuel if run on vpower.
if mapped on vpower - it wants to add 3% more fuel for tesco 99 because it considers it is running too lean.
I now have two maps - one vPower with injectors at 867cc and a tesco99 at 842cc to account for the stoich differences in fuel.
[/geek mode]