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!

"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

"Bob" wrote in message
...

My question is this...does altitude affect ignition timing?

If you have the old fashion mechanical distributor then no, altitude would
not change your timing. If you have a totally electronic computer
controlled fuel and ignition system then it would be possible.

It is far more likely that the reduction in the amount of ping is due to the
lower atmospheric pressure. The lower air pressure will have the same
result as if your engine had a lower compression ratio, which is what
requires the higher octane fuel to avoid pinging.

Rod

Bob wrote:
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!

It's not the timing changing, it's the air density.

Rob

(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?

Is this a carburated or fuel-injected engine? If the engine was
"tuned" to run at 6200', the mixture may be set too lean for use at
sea level.

But yes, timing too far advanced can cause detonation too. And you
can get away with advanced timing at altitude if the mixture is too
rich.

Curtis CCR wrote:
(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?
:
:Is this a carburated or fuel-injected engine? If the engine was

Carbureted. Dual, single bbl Solex PA 44 PA1.

:"tuned" to run at 6200', the mixture may be set too lean for use at
:sea level.

When you say "tuned", is there anything I can relatively easily do to
tune it while at sea level in an attempt to stop it from pinging?

:But yes, timing too far advanced can cause detonation too. And you
:can get away with advanced timing at altitude if the mixture is too
:rich.

I checked the timing and it was essentially right on spec (27-29 BTDC @
2000 rpm) and the timing has not been touched since I got the engine in
the fall of 2002.

Replies to a post I made to boatered.com suggest that the carbs need to
be re-jetted for sea level operation. Sounds like a major job though
for a DIY'er, especially since I'm dealing with carbs that are 32 years
old.

Thanks.

Try a colder heat range plug. Are they the correct ones for the marine
motor? The carburator probably needs rejetting otherwise - just take it off
and take it to a carb shop.


"Bob" wrote in message
...
Curtis CCR wrote:
(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?
:
:Is this a carburated or fuel-injected engine? If the engine was

Carbureted. Dual, single bbl Solex PA 44 PA1.

:"tuned" to run at 6200', the mixture may be set too lean for use at
:sea level.

When you say "tuned", is there anything I can relatively easily do to
tune it while at sea level in an attempt to stop it from pinging?

:But yes, timing too far advanced can cause detonation too. And you
:can get away with advanced timing at altitude if the mixture is too
:rich.

I checked the timing and it was essentially right on spec (27-29 BTDC @
2000 rpm) and the timing has not been touched since I got the engine in
the fall of 2002.

Replies to a post I made to boatered.com suggest that the carbs need to
be re-jetted for sea level operation. Sounds like a major job though
for a DIY'er, especially since I'm dealing with carbs that are 32 years
old.

Thanks.

"Bob" wrote in message news:cagi3a$3c5

Any other ideas why it might ping at sea level?

Thanks!

I recall years ago having to advance timing approx 1 degree per thousand
feet to compensate for altitude. This was when relocating cars from around
sea level to Denver. I would think the opposite would hold true. If you're
set up properly for 6000 feet at Tahoe, try retarding about 5 degrees when
you go to sea level.

"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.

"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.