i just had an idea pop into my head...
on a cold day, when you start your car, it runs rich to heat up quickly, right?as opposed to running lean, which runs cool????
iv'e heard everywhere that running lean will overheat an engine and melt something, well then why don't cars run lean for a short time at startup?
these two ideas contradict each other:
"running rich warms up an engine""running lean can melt something"
can someone offer insight?
Logic contradiction
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smockers83
- Posts: 3889
- Joined: Sat Oct 28, 2006 12:07 pm
- Car: 2006 G35 Coupe
Re: Logic contradiction (600hppot)
No not really. When you start your car, no matter the temperature, it has to get a bunch of fuel to all 6 cylinders because it has no idea where its at in the timing and it has to start turning on its own. So at that point I guess you could say it runs rich, but after that its all based on the accelerator and airflow as far as I know.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: Logic contradiction (smockers83)
The problems are 2 fold" cold cylinders [bore]/heads which tend to allow gasoline vapors to condense and to quickly light off the precats and cats.
Extra unburned gasoline is burned [reacted] in cats..... too much and you can flood the cats lowering their temperature where the reaction stops.
Rich conditions are stepped down and are limited to 90 seconds by which the cats begin to come on line and reduce HC to acceptable levels. On newer engines with wideband O2, the warm up idle is controlled to 14.7AF as soon as a stable rpm can be maintained after the 30-90 seconds.
On older [heated narrow band] O2 sensors the AF ratio is just preprogrammed and O2 are not consulted until the O2 starts switching steadily, usually 3-5 minutes.
http://society.kisti.re.kr/~Ek...4.pdf
Now if you are really interested:http://vehicle.me.berkeley.edu...s.pdf
Extra unburned gasoline is burned [reacted] in cats..... too much and you can flood the cats lowering their temperature where the reaction stops.
Rich conditions are stepped down and are limited to 90 seconds by which the cats begin to come on line and reduce HC to acceptable levels. On newer engines with wideband O2, the warm up idle is controlled to 14.7AF as soon as a stable rpm can be maintained after the 30-90 seconds.
On older [heated narrow band] O2 sensors the AF ratio is just preprogrammed and O2 are not consulted until the O2 starts switching steadily, usually 3-5 minutes.
http://society.kisti.re.kr/~Ek...4.pdf
Now if you are really interested:http://vehicle.me.berkeley.edu...s.pdf
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zozoka1212
- Posts: 5533
- Joined: Wed Mar 14, 2007 7:54 pm
- Car: 08 Infiniti G35x
- Location: Winter wonderland
Re: Logic contradiction (Q45tech)
I love reading your comment.
zozo
Re: Logic contradiction (600hppot)
The reason cold starts run rich is because of really cold cylinder walls. A big fraction of fuel might enter the chamber as liquid droplets, and not enough of fuel will be atomized / vaporized. Droplets don't burn as good, and since most of the fuel is in this form, your engine might stall. In addition, some of the fuel in liquid state will never make it into the combustion chamber, making it the problem even worse.
Easy solution: put as much fuel as you can to maximize the amount of atomized/vaporized fuel, that way there is something to burn and keep your engine running.
Easy solution: put as much fuel as you can to maximize the amount of atomized/vaporized fuel, that way there is something to burn and keep your engine running.
Re: Logic contradiction (adren77)
much obliged.