99 L29 454 build

[BeXtreme]

So that screen shot shows the afr at 14.18 all the way across except at wot. That's not right is it?

Unless you are running ethanol free premium and have calibrated your wideband as such, stop looking at AFR. Log and think about all of this in Lambda. Stoich for any fuel will always be lambda = 1. AFR will change depending on what mixture of ethanol is in the fuel, but the computer is changing fueling based on lambda. The LTFT and STFT are percentages of error from Lambda.

PE will not really there to add any power. It's there to protect the engine under heavy loads. If you are doing short duration stuff with lighter loads, like drag race cars, you might want PE in the lower range... like 1.10-1.12 lambda to maximize power while sacrificing some safety. 1.20 is usually where heavy, long duration load guys live in order to maximize engine protection at the loss of a little bit of power. The extra fuel helps keep everything cool and keeps you from melting pistons and valves.

 

[L31MaxExpress]

Unless you are running ethanol free premium and have calibrated your wideband as such, stop looking at AFR. Log and think about all of this in Lambda. Stoich for any fuel will always be lambda = 1. AFR will change depending on what mixture of ethanol is in the fuel, but the computer is changing fueling based on lambda. The LTFT and STFT are percentages of error from Lambda.

PE will not really there to add any power. It's there to protect the engine under heavy loads. If you are doing short duration stuff with lighter loads, like drag race cars, you might want PE in the lower range... like 1.10-1.12 lambda to maximize power while sacrificing some safety. 1.20 is usually where heavy, long duration load guys live in order to maximize engine protection at the loss of a little bit of power. The extra fuel helps keep everything cool and keeps you from melting pistons and valves.

PE does add power though. At stoichiometric there is not enough fuel for the engine to fully utilize the air in the combustion chamber. On paper you would be lead to believe it should, but in an actual running engine that is not the case, especially with air/fuel mixture variations in every cylinder. At a richer mixture all the air is used up in every cylinder, thus creating more cylinder pressure and torque. The difference is substantial. Many vehicles have long PE fuel delays and eliminating that delay gives a large improvement in performance. I had a 4.7L Dodge that would not enable PE until it hit 3rd gear at nearly 80 mph. Getting it into PE on the WOT throttle stab knocked 3 tenths off the 1/8 mile times and added nearly 2 mph to the trap speeds alone. It added a lot of low-midrange torque. Most of the 8-lug GM trucks have a similar PE fuel delay and some are up to a minute delay. To keep the engine from having detonation, the timing advance is neutered while the engine is at full load and at stoich. The GM tune adds a lot of timing advance once it is richer than stoich, some as much as 8* in places. Just getting them into PE when the skinny pedal hits the carpet wakes them up alot. The biggest gains I have ever seen on a naturally aspirated engine was an 8100 in a bus. GM neutered that 340 hp engine down to 265 hp electronically.

The added fuel in PE on the heavier GVW trucks does offer increased cooling for the pistons, exhaust valves and cats for towing at higher power levels as you state. On E10, I typically shoot for 12:1 at peak torque and 12.5:1 at peak HP. If it is a dedicated tow pig, 11.8-12:1 through the whole curve offers added protection and will not make a 5 hp difference.

 

[Scooterwrench]

PE does add power though. At stoichiometric there is not enough fuel for the engine to fully utilize the air in the combustion chamber. On paper you would be lead to believe it should, but in an actual running engine that is not the case, especially with air/fuel mixture variations in every cylinder. At a richer mixture all the air is used up in every cylinder, thus creating more cylinder pressure and torque. The difference is substantial. Many vehicles have long PE fuel delays and eliminating that delay gives a large improvement in performance. I had a 4.7L Dodge that would not enable PE until it hit 3rd gear ant nearly 80 mph. Getting it into PE on the WOT throttle stab knocked 3 tenths off the 1/8 mile times and added nearly 2 mph to the trap speeds alone. Most of the 8-lug GM trucks have a similar PE fuel delay and some are up to a minute delay.

The added fuel in PE on the heavier GVW trucks does offer increased cooling for the pistons, exhaust valves and cats for towing at higher power levels as you state. On E10, I typically shoot for 12:1 at peak torque and 12.5:1 at peak HP. If it is a dedicated tow pig, 11.8-12:1 through the whole curve offers added protection and will not make a 5 hp difference.

When I was looking at the .bin in the 7427 that I bought to upgrade my 7747 I noticed that long PE delay and wondered why would they delay PE.
Seems I read that you initiate PE at 50% throttle. Do you run any delay?

 

[L31MaxExpress]

When I was looking at the .bin in the 7427 that I bought to upgrade my 7747 I noticed that long PE delay and wondered why would they delay PE.
Seems I read that you initiate PE at 50% throttle. Do you run any delay?

I run a slight delay in mine. It has to be over the TPS threshold for 8 seconds or the engine has to be above 2,500 rpm to bypass the delay. It prevents PE from coming on and off with slight changes of pedal position near the transition point at cruising speeds. if I hammer on it though, it is near instant PE with the converter I have stalling nearly 3K.

The 7427 has an bit weird PE in most stock tunes. It is progressive, the initial PE is delayed and can come in at a lower throttle position. It also starts out fairly lean and richens up over time. There is also a setting for fast PE, which is set at a higher throttle position and gives more fuel as soon as the throttle opens past it. The PE logic continues to richen up a bit in either case if the throttle remains open long enough. I feel like GM was trying to save a bit of fuel yet still protect the engine on a long hard WOT pull.

I use the catalyst overheat logic in the 0411s and P59s to accomplish the same thing. Start out a bit leaner and richen it up over time. The 383 in my van can run as rich as 11.28:1 if it is run hard for a longer period of time.

 

[Supercharged111]

Unless you are running ethanol free premium and have calibrated your wideband as such, stop looking at AFR. Log and think about all of this in Lambda. Stoich for any fuel will always be lambda = 1. AFR will change depending on what mixture of ethanol is in the fuel, but the computer is changing fueling based on lambda. The LTFT and STFT are percentages of error from Lambda.

PE will not really there to add any power. It's there to protect the engine under heavy loads. If you are doing short duration stuff with lighter loads, like drag race cars, you might want PE in the lower range... like 1.10-1.12 lambda to maximize power while sacrificing some safety. 1.20 is usually where heavy, long duration load guys live in order to maximize engine protection at the loss of a little bit of power. The extra fuel helps keep everything cool and keeps you from melting pistons and valves.

I'll 2nd L31 here as I took have observed substantial gains with PE fueling engaging even without the associated timing adder. My truck's exhaust changes tone when I cross over to PE mode and it lurches if I'd been hovering near the threshold before crossing over. The first 6.0 I ever tuned was a night and day difference just changing the PE timer from 60 seconds to 0. Of course I went in and bumped up the high octane timing map then reshaped to add more down low for a more effortless cruise.

 

[BeXtreme]

I'll 2nd L31 here as I took have observed substantial gains with PE fueling engaging even without the associated timing adder. My truck's exhaust changes tone when I cross over to PE mode and it lurches if I'd been hovering near the threshold before crossing over. The first 6.0 I ever tuned was a night and day difference just changing the PE timer from 60 seconds to 0. Of course I went in and bumped up the high octane timing map then reshaped to add more down low for a more effortless cruise.

I agree with what he was saying. I mispoke in my comment. What I meant is anything past about 12.5-13 depending on the engine and application, isn't meant to gain you power. Anything past that will actually usually show a drop in power(but not much), but more than makes up for it in engine safety and longevity. He was asking if 11.8 was too rich, so that's why I was commenting that it wasn't that rich for power, it was that rich to protect the engine and cats.

 

[L31MaxExpress]

I'll 2nd L31 here as I took have observed substantial gains with PE fueling engaging even without the associated timing adder. My truck's exhaust changes tone when I cross over to PE mode and it lurches if I'd been hovering near the threshold before crossing over. The first 6.0 I ever tuned was a night and day difference just changing the PE timer from 60 seconds to 0. Of course I went in and bumped up the high octane timing map then reshaped to add more down low for a more effortless cruise.

Zero'd PE timing adder tables drive me nuts when I look at tunes some so called professionals have been into. The engine will want less timing under load outside of PE due to the hotter combustion temps. When the added fuel starts flowing in PE, the engine will want more timing. I watch these tuners zero out the PE timing adder table, then tune for the highest output on a dyno. When the vehicle gets out on the street, heavy part throttle and not in PE, the engine starts spark knocking and the knock sensor pulls timing. At 80-100 KPA outside of PE I find most engines want 4-6* less timing at stoich than they do in PE, especially the richer PE settings used for cooling stuff. When you are running a PCM with dual spark maps with a functional knock sensor and low octane spark map, that knock activity in closed loop at higher part-throttle loading will cause the PCM to interpolate the spark timing toward the values in the low-octane timing map, costing power and efficiency because someone was too lazy to work around the values in the PE spark adder table. Not knocking how you tuned yours, but definitely some meat being left on the bone when the PE adder is disabled 99.95% of the time. I have never seen an engine not want more timing in PE than at stoich so to me it makes no sense doing away with the adder because the overall WOT timing will be reduced either way from spark knock at part-throttle. If it is not removed from the spark map to prevent spark knock at part-throttle, the knock sensor will remove it for you. Either way costing power the next time the engine is in PE.

 

[Supercharged111]

Zero'd PE timing adder tables drive me nuts when I look at tunes some so called professionals have been into. The engine will want less timing under load outside of PE due to the hotter combustion temps. When the added fuel starts flowing in PE, the engine will want more timing. I watch these tuners zero out the PE timing adder table, then tune for the highest output on a dyno. When the vehicle gets out on the street, heavy part throttle and not in PE, the engine starts spark knocking and the knock sensor pulls timing. At 80-100 KPA outside of PE I find most engines want 4-6* less timing at stoich than they do in PE, especially the richer PE settings used for cooling stuff. When you are running a PCM with dual spark maps with a functional knock sensor and low octane spark map, that knock activity in closed loop at higher part-throttle loading will cause the PCM to interpolate the spark timing toward the values in the low-octane timing map, costing power and efficiency because someone was too lazy to work around the values in the PE spark adder table. Not knocking how you tuned yours, but definitely some meat being left on the bone when the PE adder is disabled 99.95% of the time. I have never seen an engine not want more timing in PE than at stoich so to me it makes no sense doing away with the adder because the overall WOT timing will be reduced either way from spark knock at part-throttle. If it is not removed to prevent spark knock at part-throttle the knock sensor will remove it for you. Either way costing power.

I don't have an adder in the 1500 but I do in the dually. What I found was that those values in the main table cannot be hit outside of PE anyway, so it was a bit of a moot point. But then again my map doesn't make a big jump right at that fringe, so probably leaving some on the table. I've been wanting to just start over with timing since getting the MAF dialed in anyway since that pushes you around globally and kinda takes a dump on any pre-existing nuance out into the table. Do you typically leave the PE timing adder stock and work around that or do you find it necessary to screw with it as well?

 

[L31MaxExpress]

I don't have an adder in the 1500 but I do in the dually. What I found was that those values in the main table cannot be hit outside of PE anyway, so it was a bit of a moot point. But then again my map doesn't make a big jump right at that fringe, so probably leaving some on the table. I've been wanting to just start over with timing since getting the MAF dialed in anyway since that pushes you around globally and kinda takes a dump on any pre-existing nuance out into the table. Do you typically leave the PE timing adder stock and work around that or do you find it necessary to screw with it as well?

I usually find it necessary to tune the adder as well. Most of the time I do the spark map on the street with PE all but disabled, then use either timed acceleration or a dyno to do PE. The 383 in the van has seen 5,000+ rpm in closed loop at WOT during tuning. The spark map is dialed in outside of PE to run detonation free. With the aluminum heads on it, I also found it benificial to mess with the coolant temperature compensation tables. It wants a lot more timing when the engine is cold than it did with iron heads. At say 120*F, timing maxes out at ~42* off-idle for it to drive nicely.

Also do not assume that because it is not spark knocking, that more timing advance is not costing you power. Many engine combinations will fall off power wise before running into detonation.

 

[Scooterwrench]

I always thought the best timing curve was to run it up against the KS then back off 2deg. Let the engine determine how much timing it wants.
Yes,No?