Tuners Inside, loaded vs. unloaded wot a/f ratios (long)?
06-22-2006, 07:39 PM
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Tuners Inside, loaded vs. unloaded wot a/f ratios (long)? Discussion that myself and a friend had on this issue.
Me:
"Well if your clutch is slipping you'll find that you'll end up richer then you would normally be as the motor is not loaded as much. Get that clutch in and give me a yell, i'll put my wide band 02 sensor on it and tell ya exactly where it's at!"
Him:
"......the computer is dumping fuel in according to the amount of air going through the MAF so the amount of load on the engine doesn't matter for fueling on my setup "
Me:
"......In either event the amount of air drawn into the motor will not change weather it's loaded or unloaded which is all the maf measures based off of how cool the wire element gets in the maf reporting a frequency to the computer. But what will change is the force against the piston on the power stroke which will cause differences in the burn characteristics according to my understanding of the fuel injected ICE motors. This in turn will cuase differences in air fuel ratios.
For instance, the dyno jets typically use 3000lbs of resistance to get a measure of hp. But when you have a heavier then 3000lbs car, like an fbody, the wide band readings taken from a dynojet are often richer then what's seen on the street/track/real world under the fool load of the car! "
Basically i'm looking for actual descriptions of what's going on in the internal combustion engine (ICE) in loaded and unloaded situations that causes the difference in wot air fuel ratios. If this is a myth then don't be afraid to pipe up and say so.
Me:
"Well if your clutch is slipping you'll find that you'll end up richer then you would normally be as the motor is not loaded as much. Get that clutch in and give me a yell, i'll put my wide band 02 sensor on it and tell ya exactly where it's at!"
Him:
"......the computer is dumping fuel in according to the amount of air going through the MAF so the amount of load on the engine doesn't matter for fueling on my setup "
Me:
"......In either event the amount of air drawn into the motor will not change weather it's loaded or unloaded which is all the maf measures based off of how cool the wire element gets in the maf reporting a frequency to the computer. But what will change is the force against the piston on the power stroke which will cause differences in the burn characteristics according to my understanding of the fuel injected ICE motors. This in turn will cuase differences in air fuel ratios.
For instance, the dyno jets typically use 3000lbs of resistance to get a measure of hp. But when you have a heavier then 3000lbs car, like an fbody, the wide band readings taken from a dynojet are often richer then what's seen on the street/track/real world under the fool load of the car! "
Basically i'm looking for actual descriptions of what's going on in the internal combustion engine (ICE) in loaded and unloaded situations that causes the difference in wot air fuel ratios. If this is a myth then don't be afraid to pipe up and say so.
06-22-2006, 08:12 PM
#3
You're both wrong.
MAP sensor values also dictate where the computer is in the VE table thus changing fuel control based on load. There is also a O2 sensor conrolling short term fuel trim as a check and balance.
Him:
"......the computer is dumping fuel in according to the amount of air going through the MAF so the amount of load on the engine doesn't matter for fueling on my setup "
The computer is also controlling fuel based on the MAP sensor and O2 sensors as stated above. Target AFR varies based on load.
Me:
"......In either event the amount of air drawn into the motor will not change weather it's loaded or unloaded which is all the maf measures based off of how cool the wire element gets in the maf reporting a frequency to the computer. But what will change is the force against the piston on the power stroke which will cause differences in the burn characteristics according to my understanding of the fuel injected ICE motors. This in turn will cuase differences in air fuel ratios.
You are correct (for the most part) that the amount of air will not change with the exception that Volumetric Efficiency may change at varying levels of RPM and thus changing the amount of air an engine consumes. The force pushing down on the piston varies because the AFR is changing to a more powerful level at WOT under load.
For instance, the dyno jets typically use 3000lbs of resistance to get a measure of hp. But when you have a heavier then 3000lbs car, like an fbody, the wide band readings taken from a dynojet are often richer then what's seen on the street/track/real world under the fool load of the car! "
Doubt that. The computer is controling injector pulse width based on MAP and O2 values.
Basically i'm looking for actual descriptions of what's going on in the internal combustion engine (ICE) in loaded and unloaded situations that causes the difference in wot air fuel ratios. If this is a myth then don't be afraid to pipe up and say so. Unloaded engines will be close(r) to 14.7:1 where loaded engines will be closer to 12:1
Peak power 12.7:1
Peak Torque 12.9:1
Lowest emissions 14.7:1
Most engines are tuned with a margin of safety and closer to 12.0:1
Best fuel economy comes leaner and can be around 15:1
Originally Posted by DAPSUPRSLO
Discussion that myself and a friend had on this issue.
Me:
"Well if your clutch is slipping you'll find that you'll end up richer then you would normally be as the motor is not loaded as much. Get that clutch in and give me a yell, i'll put my wide band 02 sensor on it and tell ya exactly where it's at!"
Me:
"Well if your clutch is slipping you'll find that you'll end up richer then you would normally be as the motor is not loaded as much. Get that clutch in and give me a yell, i'll put my wide band 02 sensor on it and tell ya exactly where it's at!"
Originally Posted by DAPSUPRSLO
Him:
"......the computer is dumping fuel in according to the amount of air going through the MAF so the amount of load on the engine doesn't matter for fueling on my setup "
Originally Posted by DAPSUPRSLO
Me:
"......In either event the amount of air drawn into the motor will not change weather it's loaded or unloaded which is all the maf measures based off of how cool the wire element gets in the maf reporting a frequency to the computer. But what will change is the force against the piston on the power stroke which will cause differences in the burn characteristics according to my understanding of the fuel injected ICE motors. This in turn will cuase differences in air fuel ratios.
Originally Posted by DAPSUPRSLO
For instance, the dyno jets typically use 3000lbs of resistance to get a measure of hp. But when you have a heavier then 3000lbs car, like an fbody, the wide band readings taken from a dynojet are often richer then what's seen on the street/track/real world under the fool load of the car! "
Originally Posted by DAPSUPRSLO
Basically i'm looking for actual descriptions of what's going on in the internal combustion engine (ICE) in loaded and unloaded situations that causes the difference in wot air fuel ratios. If this is a myth then don't be afraid to pipe up and say so.
Peak power 12.7:1
Peak Torque 12.9:1
Lowest emissions 14.7:1
Most engines are tuned with a margin of safety and closer to 12.0:1
Best fuel economy comes leaner and can be around 15:1
Last edited by Katech_Jason; 06-22-2006 at 08:32 PM.
How can I be wrong?
06-22-2006, 08:52 PM
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Katech, this car is a VW and part of my discussion with him was cut out which asked if his car has a ve table and maf sensor like an fbody for which i'm not sure it does. Furthermore if you were answering me in the sense that it was setup like an fbody i'm pretty sure that at a certain percentage of tps (but maybe not and instead a certain gms/cyl value is referenced from the maf or kPa from the map sensor) that the oxygen sensors wouldn't be used for any fueling during close to or wot fueling hence negating the "MAP sensor values also dictate where the computer is in the VE table thus changing fuel control based on load. There is also a O2 sensor conrolling short term fuel trim as a check and balance" statement as there is a possibility that no MAP table exists for this VW and the 02 sensors and stfts would not be changing anything at wot unless posative ltfts were seen right before and through wot/pe.
"You are correct (for the most part) that the amount of air will not change with the exception that Volumetric Efficiency may change at varying levels of RPM and thus changing the amount of air an engine consumes. The force pushing down on the piston varies because the AFR is changing to a more efficient level at WOT under load." I think there's a misunderstanding here as well. I'm not quite sure what you're intending to say here but when I discuss the "force against the pistons" I don't mean the force caused by the power stroke but mean the force against the power stroke (i.e. the force against the power stroke will be much greater at full load vs. against a slipping clutch or revving the motor with no load).
"Doubt that. The computer is controling injector pulse width based on MAP and O2 values." Well once again once the computer is in open loop pe mode no 02 values come into play unless the 02s right before wot/pe cause a posative ltft value dumping more fuel over top of the pe multiplyer in the fbods which is added over top of the maf value as in wot the maf seems to be used exclusively (unless in SD) and in the VWs case once again i'm not sure as i'm still unclear as to their architecture.
"Unloaded engines will be close(r) to 14.7:1 where loaded engines will be closer to 12:1" This would simply depend on the calibration of the ve or maf or both tables I think and is not describing what actually goes on in the combustion chamber itself. Tell ya what, think of it in the sense of a carb, how would you explain it then?
Remember, there is more to the performance of the ICE then the ls1 This is a hard question to answer in terms of the ls1 or any fuel injected vehicle considering the maf table/ ve table is simply corrected by you the user. A better question to ask in regards to ls1's would be "how does wot from 4500-6800 vary as far as time spent at each map pressure or gms/second in regards to loaded vs. unloaded conditions"???
.
"You are correct (for the most part) that the amount of air will not change with the exception that Volumetric Efficiency may change at varying levels of RPM and thus changing the amount of air an engine consumes. The force pushing down on the piston varies because the AFR is changing to a more efficient level at WOT under load." I think there's a misunderstanding here as well. I'm not quite sure what you're intending to say here but when I discuss the "force against the pistons" I don't mean the force caused by the power stroke but mean the force against the power stroke (i.e. the force against the power stroke will be much greater at full load vs. against a slipping clutch or revving the motor with no load).
"Doubt that. The computer is controling injector pulse width based on MAP and O2 values." Well once again once the computer is in open loop pe mode no 02 values come into play unless the 02s right before wot/pe cause a posative ltft value dumping more fuel over top of the pe multiplyer in the fbods which is added over top of the maf value as in wot the maf seems to be used exclusively (unless in SD) and in the VWs case once again i'm not sure as i'm still unclear as to their architecture.
"Unloaded engines will be close(r) to 14.7:1 where loaded engines will be closer to 12:1" This would simply depend on the calibration of the ve or maf or both tables I think and is not describing what actually goes on in the combustion chamber itself. Tell ya what, think of it in the sense of a carb, how would you explain it then?
Remember, there is more to the performance of the ICE then the ls1
This is a hard question to answer in terms of the ls1 or any fuel injected vehicle considering the maf table/ ve table is simply corrected by you the user. A better question to ask in regards to ls1's would be "how does wot from 4500-6800 vary as far as time spent at each map pressure or gms/second in regards to loaded vs. unloaded conditions"???.
Last edited by DAPSUPRSLO; 06-22-2006 at 09:12 PM.
06-22-2006, 08:56 PM
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Originally Posted by ATVracr
We ALWAYS had to add a good amount of fuel in my car coming right off of Heffners dynojet. Not so with Jeff's Mustang dyno. 
This is what i've come to see as well (that is the heavier load cuases leaner wot a/f ratios). My question is why, why in the sense of what's really going on inside of the ICE outside of "02 sensors do yadda yadda yadda".
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06-22-2006, 09:03 PM
#8
Originally Posted by DAPSUPRSLO
This is what i've come to see as well (that is the heavier load cuases leaner wot a/f ratios). My question is why, why in the sense of what's really going on inside of the ICE outside of "02 sensors do yadda yadda yadda".
"How does posi traction on a plymoth work? .... It just does! "
I think its just more load on the car means it has to work harder which = more fuel........
I just wrench on it and drive it 
06-23-2006, 04:09 AM
#9
I have personally seen a .2 difference in AFR from the street to the Dynojet, .2 leaner on the Dynojet with comparing my LM-1 WB02 on the street and on the dyno.
Driving a car on the road or at the track is the best load you can get, it's real world, not simulated.
Driving a car on the road or at the track is the best load you can get, it's real world, not simulated.
