Help with AFR
09-30-2004, 10:56 PM
#1
Help with AFR My AFR from my last dyno is practically a sine wave above 5000RPM.
I'm looking for the AFR to be about 12.6-12.7 on the street, so I guess I need to tweak the reported AFR's to account for the road load being higher than a dynojet? IIRC, road load is .2-.3 higher than dynojet load, so I'd want to alter these numbers to reflect 12.4-12.5 on a dynojet? Are these values changing too rapidly or should I be looking elsewhere?
I'm looking for the AFR to be about 12.6-12.7 on the street, so I guess I need to tweak the reported AFR's to account for the road load being higher than a dynojet? IIRC, road load is .2-.3 higher than dynojet load, so I'd want to alter these numbers to reflect 12.4-12.5 on a dynojet? Are these values changing too rapidly or should I be looking elsewhere?
Code:
Current PExRPM 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800 5200 5600 6000 6400 6800 7200 1.1172 1.1172 1.1172 1.1172 1.1172 1.1172 1.0872 1.1172 1.1143 1.0988 1.0872 1.0833 1.0950 1.0882 1.0620 1.0998 1.0543 1.0717 1.0717
Code:
Proposed PExRPM 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800 5200 5600 6000 6400 6800 7200 1.169 1.169 1.169 1.169 1.169 1.169 1.136 1.161 1.156 1.147 1.132 1.111 1.115 1.090 1.049 1.108 1.037 1.029 1.029
Code:
RPM AFR 2700 13.09 2800 13.01 2900 12.94 3000 12.94 3100 12.96 3200 12.99 3300 13.01 3400 13 3500 13.04 3600 13.05 3700 13.12 3800 13.17 3900 13.11 4000 13.01 4100 13.02 4200 12.98 4300 12.89 4400 12.86 4500 12.82 4600 12.81 4700 12.83 4800 12.75 4900 12.68 5000 12.66 5100 12.7 5200 12.52 5300 12.38 5400 12.3 5500 12.31 5600 12.33 5700 12.39 5800 12.49 5900 12.61 6000 12.71 6100 12.52 6200 12.38 6300 12.77 6400 12.14 6500 11.96 6600 11.94 6700 12.03 6800 12.11 6900 11.72
09-30-2004, 11:14 PM
#2
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Those PE table numbers are below normal (1.15 = 12.8:1
for the actuals you're getting. So something else is adding
enrichment (like an air or fuel metering error term). You want
to take away more from the top.
It looks like 1.09 is your number, why not try that as a flat
line value from 2400 on up and get another read? There's a
strange lump at 4800 too.
for the actuals you're getting. So something else is adding
enrichment (like an air or fuel metering error term). You want
to take away more from the top.
It looks like 1.09 is your number, why not try that as a flat
line value from 2400 on up and get another read? There's a
strange lump at 4800 too.
10-01-2004, 02:33 PM
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Presuming your Open Loop Fuel/Air table is some lower
value than the PE table, that would leave only the PE
adders/multiplers (IAT, ECT) or some sensor / table
scaling error, or residual trim from positive LTFTs.
Or COT but I don't see the abrupt onset that usually
gives that one away.
If you see the Fuel-Air Multiplier (FAM) PID coming up
with the PE table value then it has to be sensors /
tables biased rich. If you see FAM that is higher than
the PE value then it's adders or trims meddling.
value than the PE table, that would leave only the PE
adders/multiplers (IAT, ECT) or some sensor / table
scaling error, or residual trim from positive LTFTs.
Or COT but I don't see the abrupt onset that usually
gives that one away.
If you see the Fuel-Air Multiplier (FAM) PID coming up
with the PE table value then it has to be sensors /
tables biased rich. If you see FAM that is higher than
the PE value then it's adders or trims meddling.
10-01-2004, 02:50 PM
#6
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jimmyblue knows his stuff.
Set your O/L FAM to around 1.08 in the operating range. Then set your PE to say 1.10 flat from 2400+ and do another dyno pull. If the AFR is still all over the place, then one of your fueling tables is off or one of your sensors is off.
Edit: saw the comment about stock injectors. You are probably pushing the limits of those. What duty cycle are they running? Static injectors could explain fluctuating AFR.
Set your O/L FAM to around 1.08 in the operating range. Then set your PE to say 1.10 flat from 2400+ and do another dyno pull. If the AFR is still all over the place, then one of your fueling tables is off or one of your sensors is off.
Edit: saw the comment about stock injectors. You are probably pushing the limits of those. What duty cycle are they running? Static injectors could explain fluctuating AFR.
10-01-2004, 03:18 PM
#7
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Jimmy –
So you are saying that the displayed value of the Commanded AFR PID will change depending on what fueling table (PE vs RPM or Open Loop) is being used?
On my 98 that value is always the value that is based on the Open Loop table entry. In my case that is 13:1. The stock PE vs RPM value was calculated to 11.9:1.
***EDIT*** I was wrong about the above. My Commanded WOT AFR DOES follow the PE vs RPM table. Even though 12.9 might be commanded my WB shows 11.9-12.1.
Jim-
My 98 was having the same WOT AFR issues that you are having. I ended up setting the PE vs RPM value to 1.062. This does calculate to 14.737/1.062=13.87:1 but my wide band O2 shows a consistent 12.6:1.
John
So you are saying that the displayed value of the Commanded AFR PID will change depending on what fueling table (PE vs RPM or Open Loop) is being used?
On my 98 that value is always the value that is based on the Open Loop table entry. In my case that is 13:1. The stock PE vs RPM value was calculated to 11.9:1.
***EDIT*** I was wrong about the above. My Commanded WOT AFR DOES follow the PE vs RPM table. Even though 12.9 might be commanded my WB shows 11.9-12.1.
Jim-
My 98 was having the same WOT AFR issues that you are having. I ended up setting the PE vs RPM value to 1.062. This does calculate to 14.737/1.062=13.87:1 but my wide band O2 shows a consistent 12.6:1.
John
Last edited by JNorris; 10-01-2004 at 10:37 PM.
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10-01-2004, 09:46 PM
#8
My OLFA table appears to be stock. How do I determine the operating range you're referring to?
Also, I thought the big tuners said the 98 injectors were good to ~450rwhp? Do injectors grow 'tired' after a long life?
Also, I thought the big tuners said the 98 injectors were good to ~450rwhp? Do injectors grow 'tired' after a long life?
Code:
OLFA table 1.670 1.483 1.329 1.270 1.214 1.138 1.060 1.043 1.080 1.070 1.050 1.030 1.020 1.000 1.000 1.000 1.000 1.000 1.000 1.623 1.483 1.329 1.270 1.214 1.145 1.065 1.046 1.080 1.070 1.060 1.040 1.030 1.013 1.013 1.013 1.013 1.013 1.013 1.623 1.499 1.334 1.270 1.214 1.145 1.073 1.054 1.125 1.110 1.070 1.050 1.040 1.020 1.020 1.020 1.020 1.020 1.020 1.623 1.517 1.339 1.270 1.214 1.146 1.076 1.069 1.140 1.139 1.070 1.050 1.040 1.020 1.020 1.020 1.020 1.020 1.020 1.646 1.536 1.354 1.276 1.218 1.157 1.100 1.090 1.140 1.139 1.080 1.060 1.040 1.027 1.027 1.027 1.027 1.027 1.027 1.670 1.558 1.371 1.290 1.229 1.170 1.146 1.123 1.140 1.139 1.080 1.060 1.041 1.041 1.041 1.041 1.041 1.041 1.041 1.670 1.558 1.394 1.317 1.259 1.202 1.175 1.148 1.140 1.139 1.080 1.060 1.057 1.057 1.057 1.057 1.057 1.057 1.057 1.670 1.575 1.411 1.332 1.271 1.214 1.186 1.157 1.140 1.139 1.080 1.064 1.064 1.064 1.064 1.064 1.064 1.064 1.064 1.694 1.579 1.423 1.339 1.280 1.238 1.207 1.176 1.140 1.139 1.080 1.080 1.080 1.080 1.080 1.080 1.080 1.080 1.080 1.694 1.597 1.440 1.354 1.294 1.252 1.228 1.203 1.150 1.139 1.088 1.088 1.088 1.088 1.088 1.088 1.088 1.088 1.088 1.719 1.619 1.458 1.376 1.320 1.278 1.255 1.232 1.176 1.139 1.113 1.113 1.113 1.113 1.113 1.113 1.113 1.113 1.113 1.719 1.619 1.458 1.384 1.334 1.296 1.275 1.255 1.178 1.139 1.121 1.121 1.121 1.121 1.121 1.121 1.121 1.121 1.121 1.745 1.623 1.471 1.399 1.344 1.303 1.281 1.261 1.179 1.139 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.745 1.623 1.471 1.399 1.344 1.303 1.281 1.261 1.179 1.139 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.745 1.623 1.471 1.399 1.344 1.303 1.281 1.261 1.179 1.139 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.745 1.623 1.471 1.399 1.344 1.303 1.281 1.261 1.179 1.139 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.745 1.623 1.471 1.399 1.344 1.303 1.281 1.261 1.179 1.139 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130 1.130
10-01-2004, 10:35 PM
#9
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The WOT operating range would be the bottom right quadrant of the table (MAP>75-80kPa and RPM>2400-3000). Those 1.13's are probably overriding your PE table at some point.
I have seen mixed opinions on the injector duty cycle issue. Some say above 80%DC can cause non-uniform fueling because the injectors are basically open all the time (static). Look at it this way - the intake valve is only open for a certain percentage of the cycle of one cylinder. If the injector is open all the time, you will end up with a puddle of fuel in the intake port waiting for the valve to open. Better to have a bigger injector spraying a properly atomized jet of fuel at the proper time.
I have seen mixed opinions on the injector duty cycle issue. Some say above 80%DC can cause non-uniform fueling because the injectors are basically open all the time (static). Look at it this way - the intake valve is only open for a certain percentage of the cycle of one cylinder. If the injector is open all the time, you will end up with a puddle of fuel in the intake port waiting for the valve to open. Better to have a bigger injector spraying a properly atomized jet of fuel at the proper time.
