When the MAF detects hotter air or less dense air what is the ECU's normal reaction? Advance timing, add fuel? both? Lets consider high altitude conditions like Denver or high temps 95-100F like AZ.
Are any other sensors considered before making the timing/fuel change? O2 specifically?
air density
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Mayhem_J30
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Q45tech
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The MAF cannot differentiate between hot air and thin air or humid air............it just weighs the air in grams per second.Newer engines have an air intake thermistor and fuel temp sensor.The ecu gets a clue wthether it is summer or winter by a signal from HVAC computer [AC on, ambient temp sensor] and primarily from the coolant temp sensor.
Just as the cruise has a 20% fine adjust range from O2 switching rate, the WOT tables are trimed by the MAF vs rpm vs TPS vs coolant temp.
The coolant temp is ignored in the range of 170-194.9999F. The TPS is assumed to be wideopen above say 3.9 volts.
The summer signal primes the ecu to watch the knock sensors better and increases the decay time after knock detection [time to return to what ever full advance was preprogramed .The coolant temp reduces the full programmed advance by 1 degree for every 5F step above 194.9F to a max of minus 5 degrees less than calculated.
Since x grams of air per sec are flowing at y rpm there is only one correct injection pulse to maintain a certain exhaust excess air ratio [I am not using A/F ratio because thats not what the O2 actually measures] plus the O2 is very very inaccurate when you get away from the 14.7 it was designed to measure.
So really what was measured on the dyno in the factory lab is where the numbers come from........the factory made the injector pulse extra rich to protect against summer heat and extended WOT operation to cool the cylinders.
I assume you are asking if more air flows thru the MAF than possible by the engine design what would the injectors do.......good question........my guess is there are a few steps higher than has ever been seen in normal use as the engine might be subjected to WOT at say 0F ambient where the air would be ........150-0=150/11=13.6% denser than at 150F.
I have tested [with Consult ] and it appears that the max open time is 11.5 milliseconds at 4,000 rpm [where by definition it would be max] regardless of temperature however since the normal max is already 20% excessively rich what happens in cold weather is the mixture becomes less and less excessively rich as the temperature drops.........good.This explains why the colder the air is, the more power the engine produces.
When JWT leans the mixture by 10% the power goes up across the board [3500-7,000 rpm] so their still is some safety left [10%].
The unanswered question is what if anything does the short /long term [relative as it changes in 60 seconds] fuel trim do probably nothing since the ecu cannot trust the source [the o2 sensors] at WOT!
Just as the cruise has a 20% fine adjust range from O2 switching rate, the WOT tables are trimed by the MAF vs rpm vs TPS vs coolant temp.
The coolant temp is ignored in the range of 170-194.9999F. The TPS is assumed to be wideopen above say 3.9 volts.
The summer signal primes the ecu to watch the knock sensors better and increases the decay time after knock detection [time to return to what ever full advance was preprogramed .The coolant temp reduces the full programmed advance by 1 degree for every 5F step above 194.9F to a max of minus 5 degrees less than calculated.
Since x grams of air per sec are flowing at y rpm there is only one correct injection pulse to maintain a certain exhaust excess air ratio [I am not using A/F ratio because thats not what the O2 actually measures] plus the O2 is very very inaccurate when you get away from the 14.7 it was designed to measure.
So really what was measured on the dyno in the factory lab is where the numbers come from........the factory made the injector pulse extra rich to protect against summer heat and extended WOT operation to cool the cylinders.
I assume you are asking if more air flows thru the MAF than possible by the engine design what would the injectors do.......good question........my guess is there are a few steps higher than has ever been seen in normal use as the engine might be subjected to WOT at say 0F ambient where the air would be ........150-0=150/11=13.6% denser than at 150F.
I have tested [with Consult ] and it appears that the max open time is 11.5 milliseconds at 4,000 rpm [where by definition it would be max] regardless of temperature however since the normal max is already 20% excessively rich what happens in cold weather is the mixture becomes less and less excessively rich as the temperature drops.........good.This explains why the colder the air is, the more power the engine produces.
When JWT leans the mixture by 10% the power goes up across the board [3500-7,000 rpm] so their still is some safety left [10%].
The unanswered question is what if anything does the short /long term [relative as it changes in 60 seconds] fuel trim do probably nothing since the ecu cannot trust the source [the o2 sensors] at WOT!
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Q45tech
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But water injection [10% by volume of the amount of fuel] only solves the preignition problem at the expense of reduced BTU in the cylinder.The water displaces the gasoline [without direct injection after the valves close].
Remember that the excess gasoline is just used to cool the cylinder [and slow down the burn] as the correct AF is 14.7 [chemical decomposition] not the 10-12 AF that is normally found in WOT.The importance of never allowing your coolant temperature [as presented to ecu] to rise above 194.99F nor below 176F is paramount!!!!!!!!!!!!
The biggest problem is the natural lack of homogenity in the charge. Every charge varies [scatters] in exact composition as gasoline is a mixture of 100's of compounds.........each cylinder wants a different ignition advance and the amount varies from cycle to cycle............by up to 3 degrees [+-1.5].
Remember that the excess gasoline is just used to cool the cylinder [and slow down the burn] as the correct AF is 14.7 [chemical decomposition] not the 10-12 AF that is normally found in WOT.The importance of never allowing your coolant temperature [as presented to ecu] to rise above 194.99F nor below 176F is paramount!!!!!!!!!!!!
The biggest problem is the natural lack of homogenity in the charge. Every charge varies [scatters] in exact composition as gasoline is a mixture of 100's of compounds.........each cylinder wants a different ignition advance and the amount varies from cycle to cycle............by up to 3 degrees [+-1.5].
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Mayhem_J30
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thanks, good info
When I mentioned "hot air or less dense air" I didn't mean literally but it all affects what readings the MAF does measure, which if it's grams/sec...is almost like a density with a function of time. It will be measuring less grams on the hotter day or higher altitude, correct?But you did answer my question. Being more to the hot day than just a MAF is exactly what I needed.
The MAF cannot differentiate between hot air and thin air or humid air............it just weighs the air in grams per second.
When I mentioned "hot air or less dense air" I didn't mean literally but it all affects what readings the MAF does measure, which if it's grams/sec...is almost like a density with a function of time. It will be measuring less grams on the hotter day or higher altitude, correct?But you did answer my question. Being more to the hot day than just a MAF is exactly what I needed.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
MAF can be very accurate at high flows if hot film sensor is used vs Karman Vortex [which is more accurate at low flows [idle-low cruise]].
In theory the Nissan Q MAF is within 3% at 200 grams per second thus able to accurately provide a voltage number [1.0-5.0 volts...resolution to 0.001 volts]which when entered into the exponential equation derives an injector pulse accuracy of within 0.1 millisecs..........the normal steps are 2.000 millisecs to 11.000 millisecs~~~9,000 possible injection levels of fuel.............the Consult only shows the number to 0.1..........2.0,2.1,2.2,2.3 etc. making some think there are only 100 steps.Anyway 100 ,1000, or 10,000 is still pretty fine resolution.Also the CAS resolves to 0.1 degree even though the Consult only shows 1.0 degree increments.The CAS is the master clock for ecu showing it where TDC is [except the CAS is feed from the exhaust cam so slack, whiplash, error etc can make the clock off by 1,2,3 degrees from the real position of the piston.At 7,000 rpm the cams are turning 3500 rpms and 360 degees is 21,000 pulse per second from the CAS [fine 1 degree wheel].21kHz.........there are also [4] 90 degree slots as a fail safe back up incase the 360 wheel or sensor fails.
In theory the Nissan Q MAF is within 3% at 200 grams per second thus able to accurately provide a voltage number [1.0-5.0 volts...resolution to 0.001 volts]which when entered into the exponential equation derives an injector pulse accuracy of within 0.1 millisecs..........the normal steps are 2.000 millisecs to 11.000 millisecs~~~9,000 possible injection levels of fuel.............the Consult only shows the number to 0.1..........2.0,2.1,2.2,2.3 etc. making some think there are only 100 steps.Anyway 100 ,1000, or 10,000 is still pretty fine resolution.Also the CAS resolves to 0.1 degree even though the Consult only shows 1.0 degree increments.The CAS is the master clock for ecu showing it where TDC is [except the CAS is feed from the exhaust cam so slack, whiplash, error etc can make the clock off by 1,2,3 degrees from the real position of the piston.At 7,000 rpm the cams are turning 3500 rpms and 360 degees is 21,000 pulse per second from the CAS [fine 1 degree wheel].21kHz.........there are also [4] 90 degree slots as a fail safe back up incase the 360 wheel or sensor fails.
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Q45tech
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http://www.installuniversity.c...0.htm
http://www.pro-flow.com/flow%20sheets/37ptflow.htm
Flow chart for 24 lb/hr injector flow meter calibration. STP IS 29.92 BARO 75 DEG. F. 65% REL HUMIDITY Volts LB LBM KG GMS SCFM APROX /MIN /HR /HR /SEC @STP* H.P. 0.400 0.52 31.3 14.21 3.95 7.1 4.5 0.500 0.63 38.1 17.27 4.80 8.6 5.5 0.600 0.76 45.8 20.77 5.77 10.4 6.6 0.700 0.91 54.5 24.74 6.87 12.4 7.8 0.800 1.07 64.4 29.23 8.12 14.6 9.2 0.900 1.26 75.5 34.25 9.51 17.1 10.8 1.000 1.46 87.8 39.86 11.07 19.9 12.6 1.100 1.69 101.6 46.08 12.80 23.0 14.6 1.200 1.95 116.7 52.97 14.71 26.5 16.8 1.300 2.22 133.4 60.55 16.82 30.3 19.2 1.400 2.53 151.8 68.86 19.13 34.4 21.8 1.500 2.86 171.8 77.95 21.65 39.0 24.7 1.600 3.23 193.6 87.85 24.40 43.9 27.8 1.700 3.62 217.3 98.61 27.39 49.3 31.2 1.800 4.05 243.0 110.27 30.63 55.1 34.9 1.900 4.51 270.8 122.87 34.13 61.4 38.9 2.000 5.01 300.7 136.45 37.90 68.2 43.2 2.100 5.55 332.9 151.06 41.96 75.5 47.8 2.200 6.12 367.5 166.74 46.32 83.4 52.8 2.300 6.74 404.5 183.53 50.98 91.8 58.1 2.400 7.40 444.1 201.49 55.97 100.7 63.8 2.500 8.11 486.3 220.65 61.29 110.3 69.8 2.600 8.85 531.3 241.06 66.96 120.5 76.3 2.700 9.65 579.1 262.77 72.99 131.4 83.2 2.800 10.50 630.0 285.82 79.39 142.9 90.4 2.900 11.40 683.8 310.27 86.19 155.1 98.2 3.000 12.35 740.9 336.16 93.38 168.1 106.4 3.100 13.35 801.2 363.53 100.98 181.8 115.0 3.200 14.42 864.9 392.44 109.01 196.2 124.2 3.300 15.54 932.2 422.94 117.48 211.5 133.8 3.400 16.72 1003.0 455.08 126.41 227.5 144.0 3.500 17.96 1077.5 488.90 135.80 244.4 154.7 3.600 19.26 1155.9 524.46 145.68 262.2 166.0 3.700 20.64 1238.2 561.80 156.06 280.9 177.8 3.800 22.08 1324.6 600.98 166.94 300.5 190.2 3.900 23.58 1415.1 642.06 178.35 321.0 203.2 4.000 25.17 1509.9 685.08 190.30 342.5 216.8 4.100 26.82 1609.1 730.09 202.80 365.0 231.0 4.200 28.55 1712.8 777.15 215.88 388.6 245.9 4.300 30.35 1821.2 826.31 229.53 413.2 261.5 4.400 32.24 1934.3 877.63 243.79 438.8 277.7 4.500 34.20 2052.3 931.16 258.66 465.6 294.7 4.600 36.25 2175.2 986.95 274.15 493.5 312.3 4.700 38.39 2303.3 1045.07 290.30 522.5 330.7 4.800 40.61 2436.6 1105.55 307.10 552.8 349.9 4.900 42.92 2575.3 1168.47 324.57 584.2 369.8 5.000 45.32 2719.4 1233.87 342.74 616.9 390.5 5.100 47.82 2869.2 1301.81 361.61 650.9 412.0
http://www.pro-flow.com/flow%20sheets/37ptflow.htm
Flow chart for 24 lb/hr injector flow meter calibration. STP IS 29.92 BARO 75 DEG. F. 65% REL HUMIDITY Volts LB LBM KG GMS SCFM APROX /MIN /HR /HR /SEC @STP* H.P. 0.400 0.52 31.3 14.21 3.95 7.1 4.5 0.500 0.63 38.1 17.27 4.80 8.6 5.5 0.600 0.76 45.8 20.77 5.77 10.4 6.6 0.700 0.91 54.5 24.74 6.87 12.4 7.8 0.800 1.07 64.4 29.23 8.12 14.6 9.2 0.900 1.26 75.5 34.25 9.51 17.1 10.8 1.000 1.46 87.8 39.86 11.07 19.9 12.6 1.100 1.69 101.6 46.08 12.80 23.0 14.6 1.200 1.95 116.7 52.97 14.71 26.5 16.8 1.300 2.22 133.4 60.55 16.82 30.3 19.2 1.400 2.53 151.8 68.86 19.13 34.4 21.8 1.500 2.86 171.8 77.95 21.65 39.0 24.7 1.600 3.23 193.6 87.85 24.40 43.9 27.8 1.700 3.62 217.3 98.61 27.39 49.3 31.2 1.800 4.05 243.0 110.27 30.63 55.1 34.9 1.900 4.51 270.8 122.87 34.13 61.4 38.9 2.000 5.01 300.7 136.45 37.90 68.2 43.2 2.100 5.55 332.9 151.06 41.96 75.5 47.8 2.200 6.12 367.5 166.74 46.32 83.4 52.8 2.300 6.74 404.5 183.53 50.98 91.8 58.1 2.400 7.40 444.1 201.49 55.97 100.7 63.8 2.500 8.11 486.3 220.65 61.29 110.3 69.8 2.600 8.85 531.3 241.06 66.96 120.5 76.3 2.700 9.65 579.1 262.77 72.99 131.4 83.2 2.800 10.50 630.0 285.82 79.39 142.9 90.4 2.900 11.40 683.8 310.27 86.19 155.1 98.2 3.000 12.35 740.9 336.16 93.38 168.1 106.4 3.100 13.35 801.2 363.53 100.98 181.8 115.0 3.200 14.42 864.9 392.44 109.01 196.2 124.2 3.300 15.54 932.2 422.94 117.48 211.5 133.8 3.400 16.72 1003.0 455.08 126.41 227.5 144.0 3.500 17.96 1077.5 488.90 135.80 244.4 154.7 3.600 19.26 1155.9 524.46 145.68 262.2 166.0 3.700 20.64 1238.2 561.80 156.06 280.9 177.8 3.800 22.08 1324.6 600.98 166.94 300.5 190.2 3.900 23.58 1415.1 642.06 178.35 321.0 203.2 4.000 25.17 1509.9 685.08 190.30 342.5 216.8 4.100 26.82 1609.1 730.09 202.80 365.0 231.0 4.200 28.55 1712.8 777.15 215.88 388.6 245.9 4.300 30.35 1821.2 826.31 229.53 413.2 261.5 4.400 32.24 1934.3 877.63 243.79 438.8 277.7 4.500 34.20 2052.3 931.16 258.66 465.6 294.7 4.600 36.25 2175.2 986.95 274.15 493.5 312.3 4.700 38.39 2303.3 1045.07 290.30 522.5 330.7 4.800 40.61 2436.6 1105.55 307.10 552.8 349.9 4.900 42.92 2575.3 1168.47 324.57 584.2 369.8 5.000 45.32 2719.4 1233.87 342.74 616.9 390.5 5.100 47.82 2869.2 1301.81 361.61 650.9 412.0
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
http://www.pro-flow.com/main.htm
The above chart is NOT for any Infiniti MAF just the closest one I could find............the 4.4 volts is probably closer to 300HP than to 278 as show by the Mustang chart.
Actually about he best you can hope for is a 3% accuracy.
The above chart is NOT for any Infiniti MAF just the closest one I could find............the 4.4 volts is probably closer to 300HP than to 278 as show by the Mustang chart.
Actually about he best you can hope for is a 3% accuracy.