A/F Mixture adjustments
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Car: 1992 Z28 Camaro w/70k
Engine: 427 w/4" Mufflex Exhaust
Transmission: 700R4 3500 stall
Axle/Gears: 4.10:1
A/F Mixture adjustments
I had dyno'd my 92 Z28 last night, came up with 282 RWHP @ 6200 and 282 RWTQ @ 4200. My Fuel Mixtures were as follows:
13.5:1 at idle
12.5:1 between shifts
10.2 - 10.9:1 at WOT.
The Dyno guy had suggested that at WOT it is much too rich, and recomended me changing that to 12.5:1 but NOT MORE THAN 13.0:1. How much HP do you suppose that can gain? Anyone had any input on that, its greatly appreciated. I have a fellow thirdgen member here who had been working with my chip & tuning it for me with his equipment.....any feedback is appreciated, thanks!
-Mike
13.5:1 at idle
12.5:1 between shifts
10.2 - 10.9:1 at WOT.
The Dyno guy had suggested that at WOT it is much too rich, and recomended me changing that to 12.5:1 but NOT MORE THAN 13.0:1. How much HP do you suppose that can gain? Anyone had any input on that, its greatly appreciated. I have a fellow thirdgen member here who had been working with my chip & tuning it for me with his equipment.....any feedback is appreciated, thanks!
-Mike
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Car: '91 Z28 L98 G92
Engine: Modded L98
Transmission: Modded 700R4
Axle/Gears: Modded 10-Bolt
Re: A/F Mixture adjustments
My car, with the mods in my sig, picked up 15rwhp when the WOT a/f ratio was corrected to ~13.0:1 from ~10.5:1.
Bill
Bill
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Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: 5.7 TPI, LG4
Transmission: 700R4, 700R4
Axle/Gears: 3.27, 2.73
Re: A/F Mixture adjustments
Are you running open loop idle?? Only ask because of the 13.5:1 reading.
With the variation from cylinder to cylinder on these engines, I'd recommend keeping it in the mid 12's for AFR.
You do seem to be a bit low on power though (and torque). Might be from the driveline though.
If you had some EGT probes, you could aim leaner, if you're careful. Your combo might like it.
Definitely make sure you're not knocking. Some cylinders may be too quiet for the one lonely knock sensor to hear, so check your plugs for specks after a few 1/4 mile passes. Also, after one or two passes, avoid idling for more than a few seconds before you turn it off. Pull ALL the plugs and see if any are grey ish. That'll be your lean cylinder and will dictate whether you need to make it richer overall, just to keep that one (or more) cylinder in the safe zone.
With the variation from cylinder to cylinder on these engines, I'd recommend keeping it in the mid 12's for AFR.
You do seem to be a bit low on power though (and torque). Might be from the driveline though.
If you had some EGT probes, you could aim leaner, if you're careful. Your combo might like it.
Definitely make sure you're not knocking. Some cylinders may be too quiet for the one lonely knock sensor to hear, so check your plugs for specks after a few 1/4 mile passes. Also, after one or two passes, avoid idling for more than a few seconds before you turn it off. Pull ALL the plugs and see if any are grey ish. That'll be your lean cylinder and will dictate whether you need to make it richer overall, just to keep that one (or more) cylinder in the safe zone.
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Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: 5.7 TPI, LG4
Transmission: 700R4, 700R4
Axle/Gears: 3.27, 2.73
Re: A/F Mixture adjustments
How do I delete a double post??
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Car: 1992 Z28 Camaro w/70k
Engine: 427 w/4" Mufflex Exhaust
Transmission: 700R4 3500 stall
Axle/Gears: 4.10:1
Re: A/F Mixture adjustments
Are you running open loop idle?? Only ask because of the 13.5:1 reading.
With the variation from cylinder to cylinder on these engines, I'd recommend keeping it in the mid 12's for AFR.
You do seem to be a bit low on power though (and torque). Might be from the driveline though.
If you had some EGT probes, you could aim leaner, if you're careful. Your combo might like it.
Definitely make sure you're not knocking. Some cylinders may be too quiet for the one lonely knock sensor to hear, so check your plugs for specks after a few 1/4 mile passes. Also, after one or two passes, avoid idling for more than a few seconds before you turn it off. Pull ALL the plugs and see if any are grey ish. That'll be your lean cylinder and will dictate whether you need to make it richer overall, just to keep that one (or more) cylinder in the safe zone.
With the variation from cylinder to cylinder on these engines, I'd recommend keeping it in the mid 12's for AFR.
You do seem to be a bit low on power though (and torque). Might be from the driveline though.
If you had some EGT probes, you could aim leaner, if you're careful. Your combo might like it.
Definitely make sure you're not knocking. Some cylinders may be too quiet for the one lonely knock sensor to hear, so check your plugs for specks after a few 1/4 mile passes. Also, after one or two passes, avoid idling for more than a few seconds before you turn it off. Pull ALL the plugs and see if any are grey ish. That'll be your lean cylinder and will dictate whether you need to make it richer overall, just to keep that one (or more) cylinder in the safe zone.
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Car: 86 vette
Engine: 383
Transmission: 700R4
Axle/Gears: 3.07
Re: A/F Mixture adjustments
Air/Fuel Ratio Limits
6.0:1 Rich run limit
9.0:1 Low power, black smoke
11.5:1 Rich best torque at WOT
12.5:1 Safe best power at WOT
13.2:1 Lean best torque at WOT
14.7:1 Chemically ideal
15.5:1 Lean light load, part throttle
16.2:1 Best economy, part throttle
18-22:1 Lean run limit
9.0:1 Low power, black smoke
11.5:1 Rich best torque at WOT
12.5:1 Safe best power at WOT
13.2:1 Lean best torque at WOT
14.7:1 Chemically ideal
15.5:1 Lean light load, part throttle
16.2:1 Best economy, part throttle
18-22:1 Lean run limit
For educational purposes only! Every engine combination will be different!
Last edited by pandin; 03-12-2008 at 09:55 AM. Reason: readablility
Trending Topics
#8
Re: A/F Mixture adjustments
What are the drive ability issues that goes along with running rich at WOT? I could understand black smoke, but other than that are there any signs.
Will running rich actually cause the car feel like you are starving it for fuel?
Will running rich actually cause the car feel like you are starving it for fuel?
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Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: 5.7 TPI, LG4
Transmission: 700R4, 700R4
Axle/Gears: 3.27, 2.73
Re: A/F Mixture adjustments
American fuel seems to burn pretty cleanly when rich. The power drop off is slower than on the lean side. The engine may sound a bit more mellow even (not sure why, but maybe to do with the cylinder pressures at EVO). You'd have to be pretty stinking rich to WOT bog for a long time, where as lean may can stay at wot bogged forever if it doesn't stall. Lean will usually spit back into the intake too. Rich may pop or gurgle in the exhaust if it's extreme.
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Car: 1992 Z28 Camaro w/70k
Engine: 427 w/4" Mufflex Exhaust
Transmission: 700R4 3500 stall
Axle/Gears: 4.10:1
Re: A/F Mixture adjustments
Heres my dyno graph, its kinda hard to see, but maybe you can see.
![](https://www.thirdgen.org/forums/attachments/diy-prom/153495d1205842785-f-mixture-adjustments-dyno1.jpg)
Last edited by 25thannivZ28; 06-15-2009 at 11:18 PM.
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Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: 5.7 TPI, LG4
Transmission: 700R4, 700R4
Axle/Gears: 3.27, 2.73
Re: A/F Mixture adjustments
Maybe you're hitting a bunch of knock at 4300+???
Or you're dropping a cylinder?
Or could be verrrrry rich, but it wouldn't do THAT in my best guess opinion.
You drop 10% in a very quick fashion. And the power still goes up after the big drop. I'd guess A or B above.
Or you're dropping a cylinder?
Or could be verrrrry rich, but it wouldn't do THAT in my best guess opinion.
You drop 10% in a very quick fashion. And the power still goes up after the big drop. I'd guess A or B above.
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