[DML] Re: Failed emmissions AGAIN

["Harold McElraft" <hmcelraft@xxxxxxx>]

The ping is the result of a premature burn in the combustion chamber. 
Either too rapid or started too early. Modern car technology can 
compensate for this with knock sensors. Performance can be 
significantly affected by ping and/or sensor compensation. Octane is 
the means of dealing with this in engines and different octanes are 
recommended across varying performance types. The higher octane equals 
less chance of ping or knock. The ping is noticed at the higher 
compression demands of the engine, i.e. higher throttle openings, and 
especially WOT.

I have found that with age, my DeLorean engine has developed a ping 
around 3-4,000 RPM under WOT using "regular" gas (87). I have traced 
the issue to what I believe to be the spring on the spark advance 
weights in the distributor (I have clean intake valves and no carbon 
buildup). I figure the spring is weakening over the years (50,000 
miles when I noticed it)and giving me premature advance as the timing 
light shows the advance slightly out of spec. I found the premium gas 
stopped the ping and have observed no other performance issues. So, I 
have not bothered with the weight spring and the cost of gas, given 
the limited miles I drive, is not an issue.

Harold McElraft - 3354



--- In dmcnews@xxxxxxxxxxxxxxx, "tuxr" <tuxdarby@xxxx> wrote:
>
> Thanks very much for the info on this, I've been using 93 for this 
> car and my previous, will switch to 87 tomorrow.  Since I put 650 
> miles a week going back and forth to work, this is a real cost 
> savings.  The forum is great for stuff like this to those of us that 
> aren't very mechanically inclined.  But I had what might be a stupid 
> question: What do you mean by "less chance for detonation"???
> 









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