[Mgs] Timing adjustment on an 18GK engine

[PaulHunt73]

If you change to a lower octane then it is more likely to ping/pink, and this is more likely to happen in a high compression engine than a low.  If you must use that fuel - is it cheaper? - just back the timing off until you can't hear pinking at any combination of throttle opening, revs and load.

The factory specs on original fuel were conservative to take account of engine component tolerances and many engines can run more advance without problems and give better acceleration and cruising economy - BT, DT back in the day.  Haynes agrees and says to run at full throttle between 30 and 50 in top gear and set the timing so that faint pinking can just be heard.  For me that's too aggressive, like you I've had part-throttle pinking on hills that goes at full throttle, hence my modified recommendation.  I also found that the change to unleaded increased the tendency to pink, so on this engine that never could run more advance than book on leaded has to be slightly retarded from book on unleaded.  E5 hasn't made any difference, E10 will be arriving here this year but only in the lower of the two octanes usually available, so I will continue to use the higher in the roadster, and change to that in the 'low compression' V8. 

PaulH.
  ----- Original Message ----- 




  It appears to run well enough, but I have had a couple of issues come up where there was a low-speed but high load situation, like going up a short hill with a 15 mph speed limit. I could hear it pinging some. 
  ...
  I expected the timing to be too far advanced at that RPM, but if anything, it was slightly retarded.
  '''

  Does anyone else run 87 in a high compression engine, or have I gone off on a fool's errand here?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/mgs/attachments/20210710/da5e98d7/attachment.htm>