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Does altitude affect ignition timing?
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! |
Does altitude affect ignition timing?
"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 |
Does altitude affect ignition timing?
"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 |
Does altitude affect ignition timing?
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 |
Does altitude affect ignition timing?
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Does altitude affect ignition timing?
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. |
Does altitude affect ignition timing?
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. |
Does altitude affect ignition timing?
"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. |
Does altitude affect ignition timing?
"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. |
Does altitude affect ignition timing?
"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. |
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