"basskisser" wrote in message
om...
"Calif Bill" wrote in message
ink.net...
"Bob" wrote in message
...

My Volvo AQ130C 4 cyl/130 hp engine (a factory rebuild with about 85
hours on it now) pings when I am at sea level and running above about
4400 rpm...not a real bad ping but a ping none the less that concerns
me...this despite using 91 octane gas with octane booster added to it.
It does not ping at all at on Lake Tahoe (6200') using the same
gas/octane booster. I checked the ignition timing today while out for
a cruise on Lake Tahoe and it was right on spec, which does not
surprise me since the engine was installed and tuned at Lake Tahoe.

My question is this...does altitude affect ignition timing? I guess
one way to find out is to put the timing light on it next time I have
it down at sea level.

Any other ideas why it might ping at sea level?

Thanks!

You can run more advance at altitude. We use to run about 6 degrees
more
advance on the race car when running at Stead AFB.
Bill


Learn to read. He asked, simply, whether altitude changes ignition
timing. Answer is also simple...no.

At altitude there is less oxygen, or rather the max pressure at ignition in
the cyl is less than at sea level. Less pressure means cooler and no
preignition ping. Less pressure at ignition means the fuel may not
completely burn unless ignited sooner (advance timing).
Shaving heads causes the heads to be closer to the pistion increasing the
pressure in the combustion chamber causing a more complete burn but can
cause preignition (ping) thus you need higher octane.

Larger loads on an engine cause the higher pressure from normal ignition to
be sustained for a longer time (the piston isn't as free to move becasue of
the load), ALSO more air is in the cyl before ignition because the
butterfly valve (throttle) is open thus more pressure at ignition.

If the global warming people are right then we can all use lower octane in
our cars as the carbon dioxide levels increase. Less oxygen in the mix and
engines run richer thus eliminating ping. Our gardens will also grow
better. More plankton in the water, faster growth of our forests, whoops,
that means the CO2 level will eventually decrease.

Green house gas producers in order of their effect on the environment:
1) Termites
2) Cows
3) Powerplants
4) Cars
5) Cooking and heating fires in third world
6) Heating (fuel oil) in developed countrys

Mercury and lead emissions from industry and Coal Fired power plants are the
most dangerous environmental factors by FAR. Mother nature can adjust to
higher co2 levels in a couple of decades but mercury will take thousands of
years. Clinton should have addressed this issue. The EPA under Bush, by
direction of Congress is finally starting to do something.

One of the reasons we are using more oil is that powerplants are under
pressure to reduce emissions, using oil which has less sulphur and mercury
is one answer. But less is not none! Alternative energy sources including
nuclear need to be used.