Fixitsan says the chain wear changed the timing by 2 degrees. Out of interest would a worn chain advance or retard the ignition?
The ignition timing stays the same relative to the crank position. The valve timing is retarded, later opening and later closing
It is easy to think of the TDM engine as a bit agricultural, however if two were grafted together you would have a 4 cylinder 20-valve engine with an output of over 170HP, which for a normally aspirated engine is pretty hot, by anyone's standard.
At those performance levels most tuners consider cam timing to be an important parameter. On a single cam low state of tune engine it isn't so important, but this engine is much more than that, and I consider valve timing to be important.
One thing I've observed from tests is that the fuel injectors fire before the inlet vale opens. This is done for a variety of performance related reasons. The engine has a cylinder identification sensor which runs from one of the cam, but I haven't been able to establish if injector timing is run from the crank position sensor or the cam position sensor.
Ignition timing should always be tied to crank position, and I'm inclined to think that injector timing is also timed to the crank with this engine..
Retardation of exhaust valve opening can cause a loss of power because of the resistance presented to the rising piston when the exhaust valve doesn't open soon enough.
The 3 inlet valves open at different times, the middle valve opens slightly earlier than the two outer ones (per cylinder) if this is delayed by a worn chain then the early opening of the middle valve, often done to cause acceleration of the air in the intake tract before the partner valves open, is not as beneficial due to the changed timing.
From observation the inlet sound especially around 3500-4000rpm is more raspy now since changing the chain. I have no idea if there is any increase in power, I do think it is a good idea though to run the engine with valve timing most like that which it was delivered with from the factory, because they seemed to know what they were doing.
Edited by fixitsan, 15 August 2018 - 09:55 am.
