Series III 2.25l ignition timing riddle
#1
Series III 2.25l ignition timing riddle
Here is one for true engine geeks
What ignition timing is best for a 1982 LR with 2.25l engine (all original)?
Ok, the label in the engine bay says: 6° ATDC at idle speed.
I remember the manual said TDC and 6° ATDC for low octane fuel.
On the internet I find three choices: TDC or 6° ATDC for engines with emission control and also 6° BTDC for 7:1 compression engines.
Mine has no emission control, at least I can't see anything I could identify as emission control (by the way it's an Australian-made model).
My mechanic says he normally sets it to 6° BTDC (for whatever reason).
The engine definitely idles faster at some degrees before TDC. At 6°ATDC it runs not so well.
Questions: Any reason to set the timing after TDC at all? How can an engine have best performance when the ignition misses the first 6 degrees of the working cycle?
And does anyone know about this emission control thing and why it would require such a late ignition?
In essence I want to know what timing is the best, and I can't believe that 6° ATDC as per the label is the final wisdom.
Thanks for any well-founded advice.
Marc
What ignition timing is best for a 1982 LR with 2.25l engine (all original)?
Ok, the label in the engine bay says: 6° ATDC at idle speed.
I remember the manual said TDC and 6° ATDC for low octane fuel.
On the internet I find three choices: TDC or 6° ATDC for engines with emission control and also 6° BTDC for 7:1 compression engines.
Mine has no emission control, at least I can't see anything I could identify as emission control (by the way it's an Australian-made model).
My mechanic says he normally sets it to 6° BTDC (for whatever reason).
The engine definitely idles faster at some degrees before TDC. At 6°ATDC it runs not so well.
Questions: Any reason to set the timing after TDC at all? How can an engine have best performance when the ignition misses the first 6 degrees of the working cycle?
And does anyone know about this emission control thing and why it would require such a late ignition?
In essence I want to know what timing is the best, and I can't believe that 6° ATDC as per the label is the final wisdom.
Thanks for any well-founded advice.
Marc
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