p055um5
Well-Known Member
It worked for me, Can now turn on A/C and the engine does not stall
How To Get A Great Idle With Your Electronic Fuel Injection System
Written by wolfems on September 10, 2009 – 11:05 am
http://wolfems.com/electronicfuelinjectionblog/2009/09/10/how-to-get-a-great-idle-with-your-electronic-fuel-injection-system/
You know, sometimes people talk about an idle control system, whether it be a stepper motor, or a pulse width modulated solenoid, as if it can overcome fuel and ignition tuning issues. That is not always the case.
BEFORE you start playing around with the idle control system on your ECU, you must make sure that the engine will idle as well as you possibly can, without the idle control system taking control.
Let’s talk for a minute about the most basic concept on how to set up your fuel and ignition maps so that you have the best chance of having a stable idle, even under varying load conditions such as when you turn the headlights on, or when the A/C comes on.
Let’s say for example that your engine idles at 20% load and at 1,000 RPM.
If your engine goes to stall, the RPM will drop and the load will increase.
So, you need to increase the amount of engine torque generated as the engine begins to slow down. This will then try to increase the engine speed, and hence this will stop the engine from stalling.
How do you do this?
Let’s say that at idle (20% load and 1,000RPM) your ECU is delivering 3mS of fuel and 10 degrees of ignition timing. We will assume the engine is running at an air fuel ratio of 14.2:1. As the engine starts to slow down (you will see the increase in load and decrease in RPM), you want to increase the amount of torque the engine is producing. So instead of 10 degrees of ignition timing, you might have 13 degrees at 875 RPM. This will increase the amount of torque the engine is producing and the engine will try to speed up.
As it speeds up it returns to the 20% load and 1,000RPM point where there is slightly less engine torque, so it will begin to slow down again.
Now, and this is the important bit. The idea is not to have the engine cycle faster, slower, faster, slower. The idea is that the engine ends up “sitting” on this new torque slope. Even though it may actually be going faster, slower, faster, slower, it may only be doing that by 20 -50 RPM, and you will not even notice that.
You can do the same thing with fueling, giving a little extra fuel as the engine slows down will increase engine torque, and help keep the idle stable.
NOTE: Don’t make these fueling and ignition slopes too steep, otherwise you will get cycling happening and the engine will not have a smooth idle.
Now that your engine is idling smoothly, you can activate the idle control system. The idle control system can now be adjusted to take up any slack caused by headlights and other loads that the fuel and ignition torque ramp cannot completely control.
How To Get A Great Idle With Your Electronic Fuel Injection System
Written by wolfems on September 10, 2009 – 11:05 am
http://wolfems.com/electronicfuelinjectionblog/2009/09/10/how-to-get-a-great-idle-with-your-electronic-fuel-injection-system/
You know, sometimes people talk about an idle control system, whether it be a stepper motor, or a pulse width modulated solenoid, as if it can overcome fuel and ignition tuning issues. That is not always the case.
BEFORE you start playing around with the idle control system on your ECU, you must make sure that the engine will idle as well as you possibly can, without the idle control system taking control.
Let’s talk for a minute about the most basic concept on how to set up your fuel and ignition maps so that you have the best chance of having a stable idle, even under varying load conditions such as when you turn the headlights on, or when the A/C comes on.
Let’s say for example that your engine idles at 20% load and at 1,000 RPM.
If your engine goes to stall, the RPM will drop and the load will increase.
So, you need to increase the amount of engine torque generated as the engine begins to slow down. This will then try to increase the engine speed, and hence this will stop the engine from stalling.
How do you do this?
Let’s say that at idle (20% load and 1,000RPM) your ECU is delivering 3mS of fuel and 10 degrees of ignition timing. We will assume the engine is running at an air fuel ratio of 14.2:1. As the engine starts to slow down (you will see the increase in load and decrease in RPM), you want to increase the amount of torque the engine is producing. So instead of 10 degrees of ignition timing, you might have 13 degrees at 875 RPM. This will increase the amount of torque the engine is producing and the engine will try to speed up.
As it speeds up it returns to the 20% load and 1,000RPM point where there is slightly less engine torque, so it will begin to slow down again.
Now, and this is the important bit. The idea is not to have the engine cycle faster, slower, faster, slower. The idea is that the engine ends up “sitting” on this new torque slope. Even though it may actually be going faster, slower, faster, slower, it may only be doing that by 20 -50 RPM, and you will not even notice that.
You can do the same thing with fueling, giving a little extra fuel as the engine slows down will increase engine torque, and help keep the idle stable.
NOTE: Don’t make these fueling and ignition slopes too steep, otherwise you will get cycling happening and the engine will not have a smooth idle.
Now that your engine is idling smoothly, you can activate the idle control system. The idle control system can now be adjusted to take up any slack caused by headlights and other loads that the fuel and ignition torque ramp cannot completely control.
