Best air/fuel ratio
10-31-2007, 07:59 PM
#1
Best air/fuel ratio Hi guys,
I have a question for the tuners here. I have a 95 a4 z28 with mild ported stock heads and cam. The car is currently running 11.90s at 113 with the stock fuel system (pump and injectors). Injectors are near max duty cycle so I just purchased a new LM-1 wide band set up to verify what was going on in there. My car reads 12.5 or so wide open until the last 400 rpms right before it shifts it will spike up to 13.0-13.2, i know this is lean but how bad is that? I have 7 1/4 mile passes in this current tune and i am hoping i wasnt to hard on my pistons.
I have a question for the tuners here. I have a 95 a4 z28 with mild ported stock heads and cam. The car is currently running 11.90s at 113 with the stock fuel system (pump and injectors). Injectors are near max duty cycle so I just purchased a new LM-1 wide band set up to verify what was going on in there. My car reads 12.5 or so wide open until the last 400 rpms right before it shifts it will spike up to 13.0-13.2, i know this is lean but how bad is that? I have 7 1/4 mile passes in this current tune and i am hoping i wasnt to hard on my pistons.
10-31-2007, 08:30 PM
#2
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12.5 a/f is not lean.. it's rich. Anything under 14.7 is rich, anything above 14.7 is lean. You need to upgrade your injectors and a 255 lph walbro fuel pump would be good.
I'm no tuner, but I've heard that around 13.0 A/f is good for performance.
I'm no tuner, but I've heard that around 13.0 A/f is good for performance.
10-31-2007, 08:37 PM
#3
First thing would be to check the fuel pressure underload to see if its dropping off. If it drops then you need a fuel pump. Once the pressure is good then adjust your tune for A/F. My car likes 12.8 Then see what the injectors are at for duty cycle.
10-31-2007, 08:52 PM
#5
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the monitor doesn't have a logging ability? Based on what I've read, for N/A cars 13.0 is pretty darn ideal when wideband tuning on the street. Obviously tuning on the street and dyno will show differences.
11-01-2007, 06:26 PM
#7
Hi Jason, 13.0 is IDEAL. You NEVER want it at 14.7 with your foot to the floor. When you are cruising or idling, 14.7 or higher is fine, but WOT you want it as close as possible to 13.0. 12.5 is not too shabby, but certainly can be improved.
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11-01-2007, 07:59 PM
#8
Keep it at about 14.7 at idle and cruise... Better gas milage and any richer is just a waste, leaner is dumb idea of course.
When WOT 13/1 is about perfect. A little rich is never too a bad thing (though way rich is). Lean it anymore than 13/1 while WOT and your asking for trouble.
With a turbo car you want to aim for 11-11.5/1 while WOT. If I see a 12 on my gauge i'll get out of it. Holes in pistons aren't cool!
11-03-2007, 07:30 AM
#10
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open loop.... I've also seen and heard the trend that 13:1 is a good AFR
I'm no tuner and definitely am just listening-in but had to ask : You guys mention 14.7 AFR fior cruising,... Isn't that what the car will automatically try to find in closed loop under casual driving conditions? I was under the impression you can only tune our cars AF mixture for the open loop mode -- Which, if thats the case then it would only be when your putting the pedal to the floor (unless you're keeping it in open loop all the time somehow). I'm only referring to the stock GM computer as well.
I'm no tuner and definitely am just listening-in but had to ask : You guys mention 14.7 AFR fior cruising,... Isn't that what the car will automatically try to find in closed loop under casual driving conditions? I was under the impression you can only tune our cars AF mixture for the open loop mode -- Which, if thats the case then it would only be when your putting the pedal to the floor (unless you're keeping it in open loop all the time somehow). I'm only referring to the stock GM computer as well.
11-03-2007, 09:56 AM
#11
I'm thinking you might still be on the stock fuel pump. A 24lber at 100% is enough to handle a 400hp motor. When I went to nyirp last year, my car was leaning out on the top end, and i was running 12.4's. The injectors were fine, but the pump couldn't keep up for 12 seconds straight at full throttle.
11-03-2007, 01:03 PM
#13
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I've also seen and heard the trend that 13:1 is a good AFR
I'm no tuner and definitely am just listening-in but had to ask : You guys mention 14.7 AFR fior cruising,... Isn't that what the car will automatically try to find in closed loop under casual driving conditions? I was under the impression you can only tune our cars AF mixture for the open loop mode -- Which, if thats the case then it would only be when your putting the pedal to the floor (unless you're keeping it in open loop all the time somehow). I'm only referring to the stock GM computer as well.
I'm no tuner and definitely am just listening-in but had to ask : You guys mention 14.7 AFR fior cruising,... Isn't that what the car will automatically try to find in closed loop under casual driving conditions? I was under the impression you can only tune our cars AF mixture for the open loop mode -- Which, if thats the case then it would only be when your putting the pedal to the floor (unless you're keeping it in open loop all the time somehow). I'm only referring to the stock GM computer as well.
yes the car in closed loop will try and go to 14.7 unless the BLMS are off.
