Power FC Power FC for dummies
03-16-02, 07:43 AM
#1
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Power FC for dummies
I'm a newbie to the power fc and I have some questions that I hope some of the PFC experts can answer.
1. My idle is very rich, around 0.87v @ 800RPM. How do I lean it out? (Air pump gone) Also my injector duty cycle is 6.8-7.2% @ idle.
2. When cruising on the highway my engine runs rich, constantly, with the old stock computer, my air/fuel gauge would cycle back and forth betwen lean and rich to obtain the right mix. Now it's pegged at rich.
3.I still cant figure out the pressure values. I know the rpm values, but how do you read the pressure. For exsample, lets use the fuel map. @800RPM, I see these values
Ne 1: 800rpm
Pr 1: 1000...
[1.214] [x.xxx]
Ok, what does the 1000... stand for? How does it relate to pressure? When I think of pressure, I think mm/hg. So, If I wanted to lean out the mixture at 800rpms, and 580mm/hg, what blocks on the chart would I use?
I hate to ask these questions, but the fc commander booklet leaves much to be desired. They show you how to change values, but don't explain the WHAT the values represent very well.
Thanks in advance.
1. My idle is very rich, around 0.87v @ 800RPM. How do I lean it out? (Air pump gone) Also my injector duty cycle is 6.8-7.2% @ idle.
2. When cruising on the highway my engine runs rich, constantly, with the old stock computer, my air/fuel gauge would cycle back and forth betwen lean and rich to obtain the right mix. Now it's pegged at rich.
3.I still cant figure out the pressure values. I know the rpm values, but how do you read the pressure. For exsample, lets use the fuel map. @800RPM, I see these values
Ne 1: 800rpm
Pr 1: 1000...
[1.214] [x.xxx]
Ok, what does the 1000... stand for? How does it relate to pressure? When I think of pressure, I think mm/hg. So, If I wanted to lean out the mixture at 800rpms, and 580mm/hg, what blocks on the chart would I use?
I hate to ask these questions, but the fc commander booklet leaves much to be desired. They show you how to change values, but don't explain the WHAT the values represent very well.
Thanks in advance.
03-16-02, 01:48 PM
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I'm not the most knowledgeable person here, but I'll tell you what I've learned.
#1 and #2: I wouldn't worry about O2 or Injector Duty at idle or cruising around. O2 is in open loop in those situations so you can't get too accurate of a reading. What you really care about is O2 and Inj Duty at WOT. You want O2 to be above .82 or so (low #'s = lean, high = rich), and Inj Duty under 90%. Of course, those #s are debateable.
If you really do want to pull out or add some fuel in any rpm range, the quick and dirty way to do it is via PIM: Settings -> PIM Volt -> Normal. But you shouldn't do this unless you've got some wideband data telling you that you really are rich or lean.
#3: check out my site for a better representation of the pressure values. It'll make more sense then. Click on the "US" in the top left corner to toggle between PSI and kg/cm^2.
The number you see on the commander (12000 for example) represents kg/meters^2. Divide this number by 10000 to get kg/cm^2, then subtract atmospheric pressure, which is about 1.033 kg/cm^2 (page 23 of the manual). This gives you 0.167. Multiply this by 14.22 and you get 2.374 psi. People use different conversion factors, so you'll see different #s floating around. I use http://www.onlineconversion.com/pressure.htm as a reference. Rounding differences also screw things up.
It seems a lot of people get tripped up because they think 1 bar = 1 kg/cm^2, which is not true. 1 bar = 14.5 psi, whereas 1 kg/cm^2 = 14.22 psi. Subtle difference, but good to know.
Hope this helps clear it up for you. Someone let me know if I'm off.
-Scott
#1 and #2: I wouldn't worry about O2 or Injector Duty at idle or cruising around. O2 is in open loop in those situations so you can't get too accurate of a reading. What you really care about is O2 and Inj Duty at WOT. You want O2 to be above .82 or so (low #'s = lean, high = rich), and Inj Duty under 90%. Of course, those #s are debateable.
If you really do want to pull out or add some fuel in any rpm range, the quick and dirty way to do it is via PIM: Settings -> PIM Volt -> Normal. But you shouldn't do this unless you've got some wideband data telling you that you really are rich or lean.
#3: check out my site for a better representation of the pressure values. It'll make more sense then. Click on the "US" in the top left corner to toggle between PSI and kg/cm^2.
The number you see on the commander (12000 for example) represents kg/meters^2. Divide this number by 10000 to get kg/cm^2, then subtract atmospheric pressure, which is about 1.033 kg/cm^2 (page 23 of the manual). This gives you 0.167. Multiply this by 14.22 and you get 2.374 psi. People use different conversion factors, so you'll see different #s floating around. I use http://www.onlineconversion.com/pressure.htm as a reference. Rounding differences also screw things up.
It seems a lot of people get tripped up because they think 1 bar = 1 kg/cm^2, which is not true. 1 bar = 14.5 psi, whereas 1 kg/cm^2 = 14.22 psi. Subtle difference, but good to know.
Hope this helps clear it up for you. Someone let me know if I'm off.
-Scott
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