Show whole topic
Aug 20, 2012 12:26 pm
Aug 20, 2012 12:26 pm
Subject: Re: Ignition timing ("be a little retarded")
Hello Peter,
A very good topic to kick off a technical discussion! Let me add my thoughts to David's great article.
My old 1925 12/24 Lagonda - now in the enthusiastic hands of Lagonda Club member P49 who calls "Connie" - has a very low compression ratio, along with an Overhead Inlet Side Exhaust (OISE) arrangement. Very Edwardian. The advance-retard lever is very handy on the steering column. First rule, as David says, is to ignore the timing marks, though in Connie's case, they are hopelessly retarded. This is because with a low compression engine, modern fuels burn too slowly and they need to be "lit" much earlier than fuels of the 1920's and 30's. This is even more of an issue with the 12/24 engine because the combustion chamber of the OISE engine is eccentric to say the least. The block has a non-detachable head with the exhaust valve set to one side, with the inlet valve above it. This is in a cage complete with the seat and whole unit screws in above the exhaust valve. The spark plug sits between the two valves which communicate with the cylinder via a slot. Distinctly odd but in 1913 was probably the latest thing!
Driving the car is fun. You have such modest power that the ignition advance lever has to be used all the time to get the most pull from the engine in certain conditions. What amazed me was that some times I had to ADVANCE to the ignition at low revs to maximise the power from the engine. Heaven knows what strange gas flows through the slot are taking place under these conditions but apparently the car ran very well on pool petrol during the war.
They stopped making the 12/24 in 1926. A mere 12 years later the V12 was born. What a huge technology change took place during this time - including fuels.
Cheers
Colin
Hello Peter,
A very good topic to kick off a technical discussion! Let me add my thoughts to David's great article.
My old 1925 12/24 Lagonda - now in the enthusiastic hands of Lagonda Club member P49 who calls "Connie" - has a very low compression ratio, along with an Overhead Inlet Side Exhaust (OISE) arrangement. Very Edwardian. The advance-retard lever is very handy on the steering column. First rule, as David says, is to ignore the timing marks, though in Connie's case, they are hopelessly retarded. This is because with a low compression engine, modern fuels burn too slowly and they need to be "lit" much earlier than fuels of the 1920's and 30's. This is even more of an issue with the 12/24 engine because the combustion chamber of the OISE engine is eccentric to say the least. The block has a non-detachable head with the exhaust valve set to one side, with the inlet valve above it. This is in a cage complete with the seat and whole unit screws in above the exhaust valve. The spark plug sits between the two valves which communicate with the cylinder via a slot. Distinctly odd but in 1913 was probably the latest thing!
Driving the car is fun. You have such modest power that the ignition advance lever has to be used all the time to get the most pull from the engine in certain conditions. What amazed me was that some times I had to ADVANCE to the ignition at low revs to maximise the power from the engine. Heaven knows what strange gas flows through the slot are taking place under these conditions but apparently the car ran very well on pool petrol during the war.
They stopped making the 12/24 in 1926. A mere 12 years later the V12 was born. What a huge technology change took place during this time - including fuels.
Cheers
Colin