Cold start video
05-06-2020, 06:08 PM
#1
Melting Slicks
Thread Starter
Cold start video
I posted up a vid over in the Canadian section:
https://www.corvetteforum.com/forums...old-start.html
Any idea what the smoke is out the exhaust when it fired up and during the rev?
https://www.corvetteforum.com/forums...old-start.html
Any idea what the smoke is out the exhaust when it fired up and during the rev?
05-07-2020, 01:14 PM
#2
Le Mans Master
My LT1 smoked a bit at start up when it was new. I was consuming 3/4 Ltr of oil a year. Since then i dont consume any oil.
My understanding is the engine was breaking in. My dealer showed me a GM bulletin stating some oil consumption is normal for a new engine. Monitor your oil level and keep it on record with your dealer.
My understanding is the engine was breaking in. My dealer showed me a GM bulletin stating some oil consumption is normal for a new engine. Monitor your oil level and keep it on record with your dealer.
The following users liked this post:
NofakeJake (05-07-2020)
05-08-2020, 07:57 PM
#4
Le Mans Master
05-09-2020, 09:48 PM
#7
Pro Mechanic
Pro Mechanic
(sigh)
....Oil smoke is a sort of bluish white–it's just that...well...maybe some Canadians' eye sight is just are a little less sensitive to certain parts of the spectrum. Rich mixture gets you black smoke which has a slight blue tinge. Coolant being burned gets you smoke that's almost completely white.
If you log some data from the DLC using HPTuners VCM Scanner or similar application you can easily see that the engine is rich at start-up by the commanded EQ ratio number. It's 0.63λ, BTW–well-rich enough to puff a little black smoke immediately after start-up. Once cranking is over and the engine is running the Cmd. EQ Ratio, goes up to 0.85λ–not enough to make black/bluish smoke.
Now, "RedZ4Me"–you get to solve the mystery for us...
Why are LT5s rich just at start up?
Last edited by Hib Halverson; 05-09-2020 at 09:54 PM.
06-04-2020, 02:43 PM
#8
Melting Slicks
Thread Starter
Nothing's changed other than AWE X pipe (and a cleaner car and polished exhaust tips):
Last edited by Cman01; 06-04-2020 at 02:45 PM.
06-04-2020, 03:19 PM
#9
Melting Slicks
when you start any engine there is water in the exhaust because burning gasoline creates water as a byproduct. So While the exhaust is cold the water collects the same way it does on a cold glass. Thats why you see water flicking off the tail pipe and why all those exhaust systems seem to rust in a way that looks like water was dripping/draining (it is)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
06-04-2020, 08:47 PM
#10
Le Mans Master
when you start any engine there is water in the exhaust because burning gasoline creates water as a byproduct. So While the exhaust is cold the water collects the same way it does on a cold glass. Thats why you see water flicking off the tail pipe and why all those exhaust systems seem to rust in a way that looks like water was dripping/draining (it is)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
06-06-2020, 01:03 PM
#12
Le Mans Master
Spot on.
I jumped the gun on this one. After careful reading I found no factual errors. My apologies!
Catalytic converters are more efficient at higher temperatures. Dumping extra fuel in during warmup helps to reach operational temperatures quicker.
I jumped the gun on this one. After careful reading I found no factual errors. My apologies!
when you start any engine there is water in the exhaust because burning gasoline creates water as a byproduct. So While the exhaust is cold the water collects the same way it does on a cold glass. Thats why you see water flicking off the tail pipe and why all those exhaust systems seem to rust in a way that looks like water was dripping/draining (it is)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
As the exhaust warms up the water leaves and turns to white visible smoke... "boils water"
That said, if the conditions are right you won't even see the white smoke leaving. Just like sometimes a window can fog or not depending on temperature there are situations where you wont get the water vapor cloud visible.
moving on. The dark black soot smoke is a rich condition. Engines ever since the old days (chokes on carbs) tend to be run rich during cold starts to improve performance. This is because liquid fuel will not burn and there isn't enough heat in the engine parts yet while it is cold to fully vaporize all the fuel that is being injected, so extra fuel must be injected to make up for the non-vaporized quantities of fuel.
If you try to run a cold engine with 'warm engine' fueling it will run lean, probably poorly, response will suffer, etc... but it isn't physically harmful to the engine. It might actually stay cleaner that way. I run and tune all my own personal engines to have barely any cold-start fueling for this reason... because i dont care about cold performance (I would never run a 700hp engine while it was cold) and have to wait for it to warm up a bit anyways, so I just let it run lean. Theres nothing detrimental or dangerous about a lean-running engine, coughing sputtering and spitting, misfires, etc... if we are talking idle speeds and lazy conditions.
And then there is one more thing to consider, catalytic converters often need some kind of extra-rich warmup feature I hear. I don't bother with cats so I can't give any advice about them but, the most likely cause for a 'black smoke soot' during cold start is a factory programmed cat-warming up feature... if not the cold start enrichment (which shouldn't necessarily be so rich that it shows up as black smoke)
06-10-2020, 08:43 PM
#13
This article explains why the outer tips are black.
https://www.caranddriver.com/feature...ect-injection/
https://www.caranddriver.com/feature...ect-injection/