Yep, those figures would be good Brad. Ken.
Misc: Ignition ET48AS (ATD Assembly)
- Thread starter Bradley Burt
- Start date
I see this claim often, but never any evidence cited to substantiate it. Does anyone know of any?
I'm not a petro Chemist although I did dable in the test equipment some decades ago. But, I have the experience. I built my Norvin and put it on the road in 1978 and ride it daily. Super petrol was at all the pumps back then. I built it with 9.5:1 pistons, as was the done thing in the seventies and avance by the book at 38 degrees BTDC. In about the late eighties early ninties unleaded petrol started to come in. It didn't come in over night but was phased in and I continued to mostly use Super right up to the end. When I started to use unleaded I noticed the the engine would ping when accelerating. I put up with it for awhile but then took out the 9.5:1 pistons and replaced them with pistons measured at 8.2:1. This helped but the pinging was still there. Slowly I bought the advance back to 34-35 degrees BTDC. This I still run it at today. As an aside the unleaded petrol did cause be a BIG problem but thats a bigger story for another thread.
I'm not a chemist either but it was discussed in a thread here about 4 years ago. Whether I am correct or not I don't know and can't prove. I opined that ignition timing is a balancing act between flame speed of the fuel and resistance to detonation. The thread lasted 6 pages before petering out and was I thought interesting reading.
E: Engine - Modern Fuel & Ignition Advance
Recently I've seen recommendations to set ignition advance at 34 degrees, as against the factory figure of 38. This is said to be necessary because of the difference between modern fuel and what was available c. 1950. Given that advance allows the mixture time to burn, so the pressure peaks...
www.vincentownersclub.co.uk
Strewth thats complex! Yes, combustion chamber shape is a factor in it as well. Vncent one not as bad as some. The combustion chamber we are stck with and fuel for the most part as well so the only option is to tune the ignition advance.I'm not a chemist either but it was discussed in a thread here about 4 years ago. Whether I am correct or not I don't know and can't prove. I opined that ignition timing is a balancing act between flame speed of the fuel and resistance to detonation. The thread lasted 6 pages before petering out and was I thought interesting reading.
E: Engine - Modern Fuel & Ignition Advance
Recently I've seen recommendations to set ignition advance at 34 degrees, as against the factory figure of 38. This is said to be necessary because of the difference between modern fuel and what was available c. 1950. Given that advance allows the mixture time to burn, so the pressure peaks...