Cold Start Question
Thread Starter
Instructor
Joined: Jun 2024
Posts: 117
Likes: 135
Cold Start Question
Is there any way to know when the engine is cold enough for the car to initiate the cold start sequence? For example, lets say you meet up with some friends for lunch and when leaving they'd like to hear the cold start. Any ideas?
Race Director
Joined: Aug 1999
Posts: 13,280
Likes: 2,509
From: Bluffton SC via Canton Oh
Depends a lot on weather…..but better to carry a video! Won’t hear it at a lunch break unless there’s a lot of drinking going on! As I understand it… It occurs when extra fuel is used to heat the cats. The cats stay fairly warm esp in hot weather. Here in sc with the recent weather….those cats are cooking like a bbq.
Race Director
Joined: Mar 2007
Posts: 11,373
Likes: 8,531
From the 2020 version of the Service Manual that I have, it says this:
Conditions for Meeting a Cold Start
The ignition voltage between 11-18 volts.
The barometric pressure (BARO) is more than 75 kPa.
The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
The difference between the IAT and the ECT is less than or equal to 6°C (10.8°F).
The ambient air temperature is between 4-30°C (39-86°F).
The fuel level is between 15-85 percent.
Conditions for Meeting a Cold Start
The ignition voltage between 11-18 volts.
The barometric pressure (BARO) is more than 75 kPa.
The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
The difference between the IAT and the ECT is less than or equal to 6°C (10.8°F).
The ambient air temperature is between 4-30°C (39-86°F).
The fuel level is between 15-85 percent.
Race Director
Joined: Mar 2007
Posts: 11,373
Likes: 8,531
By the way, while looking for the conditions for cold start, I ran across this that I did not know about:
"During a cold start, the ECM commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the injectors are energized twice during each injection event."
As others already mentioned, the cold start strategy also affects timing, air fuel mixture, and idle speed. If you have NPP, the muffler valves are all open during a crank event, but that is true for all starts, not just cold starts. Folks without NPP report the start up bark as well at a cold start, so its not all about the muffler valves.
"During a cold start, the ECM commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the injectors are energized twice during each injection event."
As others already mentioned, the cold start strategy also affects timing, air fuel mixture, and idle speed. If you have NPP, the muffler valves are all open during a crank event, but that is true for all starts, not just cold starts. Folks without NPP report the start up bark as well at a cold start, so its not all about the muffler valves.
Safety Car
Joined: Mar 2014
Posts: 4,482
Likes: 668
From: Kilmarnock Va
Both with my C8 and now the Z06, I switch it to weather mode for a quieter start in the early morning to not bother my neighbors. For those who like a quieter start start I recommend it. Other times I put it in sport before I start it.
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