So when the PCM is operating in closed loop and receiving a narrowband O2 signal does it learn any conditions? I've heard yes and no on this board. Do we have so called long term fuel trims and short term fuel trims? Does it learn spark adjustments in a similar way? Is there a way to clear these trims, such as unplugging the battery?
And what about when operating in Power Enrichment mode? Does it still adjust for say, intake air temperature, or does it just pretty much run on the hard-wired tables for PE?
Thanks for looking!
The tables adjust for certain conditions. There are long and short term fuel trims.
2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero
Yes there is long and short term fuel trims. Once in PE (Power Enrichment) it runs off of the tables in the tuning, and there is tables that adjust timing based on IAT temps, but O2 readings are out the window.
FU Tuning
in power enrichment, the ecu is non-adaptive fuel/ VE wise.
in PE mode, the ecu monitors throttle position, manifold pressure (for determining what spark advance to use), coolant temperature, knock, and intake temperature. if either of the temps get too hot, the ecu is supposed to pull timing (more timing is pulled depending on how over-temp the readings are). and also if it detects knock, it'll pull up to a maximum of 8 degrees of timing (stock figure)
there's also multipliers that further increase, or decrease these numbers depending on their behavior (too much to explain without physically seeing the tables)
they build upon eachother, so if IAT and ECT are over temp, and the IAT wants to pull 1 degree of timing, and ECT wants to pull 3 degrees of timing, it'll pull 4 degrees total.
the knock sensor also has several multipliers that work in the same way.
the ecu does not 'learn' changes in airflow, these must be programmed and flashed onto the ecu via HPT.
in closed loop, the ecu monitors the O2 sensor and trims the fuel in reaction for as close to stoich as it can get.
your trims will never be very close to zero unless you go through a very painful process of 'partitioning' the VE tables into sections of part and wide open throttle and deciding on where the engine will see typical hi and low loads, but my personal suggestion would to just tune the VE tables for WOT and let the trims do their thing.
the only truly adaptable part of the ecu is the spark tables, which reference the MAP sensor and can automatically compensate for pressure changes (up to 105kpa) which would arise from temperature fluctuations to elevation, and there's also a low and high octane spark table for PE and non PE situations (4 in total).
this is what I can gather from my tuning 'adventures' with HPT. however, I noticed all other things equal, if you have the car locked in power enrichment mode (which is necessary to tune the VE tables), if you change the desired WOT AFR and NOTHING ELSE it will radically change the AFR under WOT.. which I found sort of strange...
a few members have theorized that there are certain tables/parameters missing from the Jbody ecu on HPT and I tend to agree.. it seems like we still don't have complete control over all the parameters as of yet.
Edited 1 time(s). Last edited Saturday, September 13, 2008 1:42 AM
thanks that is what i was looking for and then some. It may not learn airflow changes, but the trims compensate to stoich during part throttle/outside of PE mode. Closed loop tables then become a "rough estimate" at best because of monitoring the O2 sensor.
Hmmm i wonder what that 8 degrees of pulled timing equates to in power loss? 20whp?
Now im just starting to learn the deatails of tuning, but isn't a non-adaptive fuel map under PE mode one of the most retarded things GM can do? So we should really at a minimum have a summer and winter tune if we want to maintain a consistent AFR in PE mode. If you tune in one extreme the AFR is probably off by almost an entire point in the other extreme...
Quote:
Now im just starting to learn the deatails of tuning, but isn't a non-adaptive fuel map under PE mode one of the most retarded things GM can do?
I have disabled open loop in my car. Yeah it's taken a lot of time to get the normal driving just right and every 10* in weather change I've got a different tune for it, but for me it's what I like. Full control of the pcm, well full to what we've got. Because of certain things I've got going on w/ my car it's actually been a lot easier for me to tune this way vs. running in an open/closed setting.
Non-adaptaive closed loop is how EVERY manufacturer operates in their respective "PE" modes. To say GM is retarded, well my friend, that would mean that all PROFESSIONAL automotive programers are retarded. We are not pros they are. To question their theories is one thing, to call it stupid is something completely different.
Like you said you are just starting to learn. Keep learning.
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
Skunk wrote:Quote:
Now im just starting to learn the deatails of tuning, but isn't a non-adaptive fuel map under PE mode one of the most retarded things GM can do?
I have disabled open loop in my car. Yeah it's taken a lot of time to get the normal driving just right and every 10* in weather change I've got a different tune for it, but for me it's what I like. Full control of the pcm, well full to what we've got. Because of certain things I've got going on w/ my car it's actually been a lot easier for me to tune this way vs. running in an open/closed setting.
Non-adaptaive closed loop is how EVERY manufacturer operates in their respective "PE" modes. To say GM is retarded, well my friend, that would mean that all PROFESSIONAL automotive programers are retarded. We are not pros they are. To question their theories is one thing, to call it stupid is something completely different.
Like you said you are just starting to learn. Keep learning.
Don't you mean you have disabled closed loop operation? Open loop is when the car runs off the settings in the table. Closed loop is when it uses the sensors.
If that is what you meant you run around daily in open loop every day? Why? You are wasting gas. For tuning yes run in open loop, but once tuned no reason to.
FU Tuning
Did I get that confused again? Damnit I always do that lol.
As for wasting gas...w/ afr's in the upper 14's to lower 15's I'd think not, as a matter of fact I've tracked it, highway I'm around 32 or so and city it's in the mid 20's. I also don't sweat mpg's too much. As much as I'd like to claim daily driveability it really isn't. I drive my truck to work 3 days outta 5. I might put 30 miles a week on my car. I also use 110 race fuel in the car which is $6.50 a gallon around here.
Edited 1 time(s). Last edited Sunday, September 14, 2008 6:06 PM
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
oldskool wrote:Hmmm i wonder what that 8 degrees of pulled timing equates to in power loss? 20whp?
8 degrees is a lot based on what a buddy of mine said about his car pulling 5 degrees. he has a 2.0 liter turbo charges Toyota MR2. He runs about 15 psi daily. When his AEM EMS sees knock, and retards 3-5 degrees, he said it's like the pwor is just shutdown. HUGE loss in power he says. He has about 300 hp on it now, and based on what he's saying its more like 50 hp lost, from just 4-5 degrees. So, 8 degrees would be a lot of power loss. I would assume that is, i'm sure someone else can chime in with experience on the J-body.
I always think of it like this... a closed loop is a completed circuit, in other words the ecu IS using the O2 sensor.
an open loop is an uncompleted circuit, and is ignoring the O2 sensor.. like an OPEN switch (when a light is turned off, or a sensor for instance) that's how I remember.
oldskool wrote:
thanks that is what i was looking for and then some. It may not learn airflow changes, but the trims compensate to stoich during part throttle/outside of PE mode. Closed loop tables then become a "rough estimate" at best because of monitoring the O2 sensor.
Hmmm i wonder what that 8 degrees of pulled timing equates to in power loss? 20whp?
Now im just starting to learn the deatails of tuning, but isn't a non-adaptive fuel map under PE mode one of the most retarded things GM can do? So we should really at a minimum have a summer and winter tune if we want to maintain a consistent AFR in PE mode. If you tune in one extreme the AFR is probably off by almost an entire point in the other extreme...
for engines pushed to the edge, yes it would be imperative.. but a stock engine's AFR isn't too important when you have lower power outputs, and the ignition maps ramp out advance a lot in order to limit internal stresses and account for the seemingly high AFRs (stoich).
lack of adaptability is the severe limiting factor with alpha-n fueling maps. it only reads your throttle and rpm. It can, in no way shape or form compensate for pressure changes (whether it be temperature related, elevation, higher boost, etc) or for that matter, load changes.
speed density (MAP vs RPM) can adapt to an extent by monitoring the MAP sensor, but overall the flow of the engine has to be programmed into the table for it to properly reference.
a mass-air flow setup would have the maximum amount of flexibility since it physically 'counts' every air molecule that goes past it in the intake stream, but in certain high-performance applications the MAF sensor itself becomes a restriction in airflow.
speed density and MAF systems are almost exclusively used in high horsepower boosted applications, while alpha-n usually reserved for highly modified all-motor setups which have weak or spiky MAP signals (like a car with high-lift/duration cams or ITBs)
Not to offend anyone (skunk), but newer PCM/engine management are leaps and bounds above that of the jbody (duh). Maybe I should have said that gm chose the absolute cheapest and least engineering-intensive method of running this powertrain. On some systems, the AFR, even in the respective PE mode, is adjusted for things like temperature and absolute pressure.
Think about it; on part throttle its taking info from the O2 sensor to at least adjust the AFR for present conditions. But when you floor it (when fuel is most important), it runs a hard-wired table and takes no environmental variables into account. Seems kind of backwards to me.
That said, I didnt expect it to be the most advance system on the planet. The LNF system, however, is one of the more advanced I've seen - map, maf, tps, two IAT's, WBO2 and calculated toque are all a part of the system. It makes things a bit more complicated in the background, but its a very effective system for modification, once the code is cracked that is
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I don't know, even if my car is pulling the full 8* because of being lean up top, I doubt its anywhere near 50whp lost, but time will tell.
So is closed loop operation bound to stoiciometric AFR, or can it be tuned richer?
oldskool wrote:Not to offend anyone (skunk), but newer PCM/engine management are leaps and bounds above that of the jbody (duh). Maybe I should have said that gm chose the absolute cheapest and least engineering-intensive method of running this powertrain. On some systems, the AFR, even in the respective PE mode, is adjusted for things like temperature and absolute pressure.
Think about it; on part throttle its taking info from the O2 sensor to at least adjust the AFR for present conditions. But when you floor it (when fuel is most important), it runs a hard-wired table and takes no environmental variables into account. Seems kind of backwards to me.
That said, I didnt expect it to be the most advance system on the planet. The LNF system, however, is one of the more advanced I've seen - map, maf, tps, two IAT's, WBO2 and calculated toque are all a part of the system. It makes things a bit more complicated in the background, but its a very effective system for modification, once the code is cracked that is .
I don't know, even if my car is pulling the full 8* because of being lean up top, I doubt its anywhere near 50whp lost, but time will tell.
So is closed loop operation bound to stoiciometric AFR, or can it be tuned richer?
As said Alpha-n and even speed density (GM reflash) have been used in many cars, and still used. Yes there is always something better. I would not expect J-body's to have anything better considering what they were designed for, but that did not stop us some fixing them up.
Closed loop is set at 14:7:1, no real reason to tune it richer anyways.
Also just because the LNF has map, maf, tps, 2 iat's, and a WBO2 does not mean it is all used in PE. I also believe J's have calculated torque, because there is tables in the auto tranny that used torque as the setting, but how the ECU gets that who knows.
FU Tuning
complexity does not necessarily make a system better.
most stand alone systems are actually pretty simple in comparison to stock management.. they do it mostly for emissions regulations, and from a performance aspect most of the stuff is just a PITA.
I can see where oldskool is going with this... and you cannot tune closed loop for anything other than stoich. At this point tho, I believe it is helping you because its adapting for the extra airflow from the intake manifold and I doubt you're getting much ignition retard, although I have seen up to 1 degree or so on my stock 1SV.
are you putting higher octane in it now? if 87, goto 89.. if 89, goto 91, etc
I run 93 in my 1SV now to get a bit more advance out of it (the tables can interpolate for octane.. although how it does it I'm not entirely sure).
have you HPT'd your jbodies ecu yet?
You got it 100% skwirl - but thats not the answer I wanted to hear
I'm running 89 octane since the full exhaust and LE5 manifold. They way it runs, its either pulling timing pretty extensively or hitting major lean AFR in PE, because part throttle is great, WOT and high RPM is flat. It should be a screamer when its tuned.
I do not yet have HPT. Hopefully within thirty days i'll have higher flow injectors, a WB and HPT.
I agree that complex is not always superior, but when you can simply and literally dial in an AFR and thats what you get back, its because you have a readout from many sensors so that you (and more importantly the PCM) knows its correct.
Quote:
but when you can simply and literally dial in an AFR and thats what you get back, its because you have a readout from many sensors so that you (and more importantly the PCM) knows its correct.
Can you explain more what you mean about this? Sounds like you are saying you can change the desired AFR and the ECU will give you that. This is not so. You still have to tune it to that AFR. For your set-up you can dail in the AFR with no problems.
FU Tuning
John Higgins wrote:Quote:
but when you can simply and literally dial in an AFR and thats what you get back, its because you have a readout from many sensors so that you (and more importantly the PCM) knows its correct.
Can you explain more what you mean about this? Sounds like you are saying you can change the desired AFR and the ECU will give you that. This is not so. You still have to tune it to that AFR. For your set-up you can dail in the AFR with no problems.
i'm pretty sure oldskool was going to try and used closed-loop to shoot for a richer AFR, like 13:1 or so instead of stoich.
so far as I can see in HPT tho, we don't have control over that parameter. So long as fuel trims are active, it will shoot for 14.7:1
not to mention, narrow band O2 sensors are programmed for the resistance around 14.7:1 AFR.
So even if you could tell the ecu to shoot for another AFR in closed loop, the stock sensor can't do the job you'd ask it to.
but oldskool, run your tank almost dry and fill up with the highest octane you can get your hands on from a gas station. It should help for any kR you might be getting. There's a very little known "flatspot" in the eco powerband I've heard rumors about, and running higher octane tends to get slightly more ignition advance out of it and eliminates said 'flatspot'
its worth a shot.. if it doesn't work, tuning the car with HPT is the only way and I'm sure it'll be a night and day difference for ya with the injectors and WBO2 tuning
John Higgins wrote:Quote:
but when you can simply and literally dial in an AFR and thats what you get back, its because you have a readout from many sensors so that you (and more importantly the PCM) knows its correct.
Can you explain more what you mean about this? Sounds like you are saying you can change the desired AFR and the ECU will give you that. This is not so. You still have to tune it to that AFR. For your set-up you can dail in the AFR with no problems.
I was referring to the PCM that controls the LNF. Because it monitors a WBO2 sensor, commanded AFR and actual AFR are very very close.
But anyway, thank you for the hints and advice for the jbody. HPT is in its future...
oldskool wrote: Maybe I should have said that gm chose the absolute cheapest and least engineering-intensive method of running this powertrain.
step back and look at what your really talking about here.... on the grand sceme this car does what it was made to do
oldskool wrote:
Think about it; on part throttle its taking info from the O2 sensor to at least adjust the AFR for present conditions. But when you floor it (when fuel is most important), it runs a hard-wired table and takes no environmental variables into account. Seems kind of backwards to me.
I know very little about tuning and am trying to learn more, but isn't PE on ecos not turned on until 6200 rpms? i have heard about people setting it to 0 but it would seem that a stock eco never uses PE since redline is 6200 so it would never see the hard-wired tables correct?
I was thinking about finding someone with hpt to at least set my PE to 0 rpm but maybe i shoulldn't, would that allow my computer more adjustibility when floored, over the hard-wired PE mode or is PE still better than the other tables?
Any idea if I would see any gains by just having PE set to 0 rpm's?
What about running a higher octane as well? I just have full bolt on's but have read that our cars have tables for higher octane could I see any gains from that?
PE is still better as long as its tuned for your mods. Closed loop, as I've learned from this very thread, commands 14.7:1 AFR, and that's not safe much less ideal for WOT conditions.
What I was trying to get at (and I was dreaming) was having closed loop adjusted to a richer AFR under certain conditions (high rpm, high load). If it knows what stoich is, it could make some calculation based on IPW or IDC and add a percentage of fuel beyond what yields stoich. It would not have been perfect, but it would have been constant regardless of ambient temp or pressure. But this is basically what you're doing with a WB when it comes to tuning VE tables anyway, if i understand it correctly.
I think setting PE enable to 0rpm would be a waste of fuel.
oldskool wrote:PE is still better as long as its tuned for your mods. Closed loop, as I've learned from this very thread, commands 14.7:1 AFR, and that's not safe much less ideal for WOT conditions.
What I was trying to get at (and I was dreaming) was having closed loop adjusted to a richer AFR under certain conditions (high rpm, high load). If it knows what stoich is, it could make some calculation based on IPW or IDC and add a percentage of fuel beyond what yields stoich. It would not have been perfect, but it would have been constant regardless of ambient temp or pressure. But this is basically what you're doing with a WB when it comes to tuning VE tables anyway, if i understand it correctly.
I think setting PE enable to 0rpm would be a waste of fuel.
What you were looking at doing (based on what you just said), is already done (or can be done), just a little bit differently. Our cars go in to PE if many different things happen. RPM is one thing looked at, and in most 2.4's I have seen 4500, in most Eco's I have seen 6200, but it is also a TPS reading to, just because you are at 6300 RPMS does nto mean it will go into PE. There is a table called " PE enable TPS vs RPM". You can select how much or little TPS reading it takes to get the car to go into PE.
So for High RPM and high load things it can go into PE (which will probably be a richer AFR) easily. Hope this helps.
As for setting the PE Enable RPM to 0, I would not. Usually 2900-3200 is a good area. Also usually the TPS reading require for that RPM range is higher as well, like 65%. Gets lower as the RPMs go up.
FU Tuning
John Higgins wrote:oldskool wrote:PE is still better as long as its tuned for your mods. Closed loop, as I've learned from this very thread, commands 14.7:1 AFR, and that's not safe much less ideal for WOT conditions.
What I was trying to get at (and I was dreaming) was having closed loop adjusted to a richer AFR under certain conditions (high rpm, high load). If it knows what stoich is, it could make some calculation based on IPW or IDC and add a percentage of fuel beyond what yields stoich. It would not have been perfect, but it would have been constant regardless of ambient temp or pressure. But this is basically what you're doing with a WB when it comes to tuning VE tables anyway, if i understand it correctly.
I think setting PE enable to 0rpm would be a waste of fuel.
What you were looking at doing (based on what you just said), is already done (or can be done), just a little bit differently. Our cars go in to PE if many different things happen. RPM is one thing looked at, and in most 2.4's I have seen 4500, in most Eco's I have seen 6200, but it is also a TPS reading to, just because you are at 6300 RPMS does nto mean it will go into PE. There is a table called " PE enable TPS vs RPM". You can select how much or little TPS reading it takes to get the car to go into PE.
So for High RPM and high load things it can go into PE (which will probably be a richer AFR) easily. Hope this helps.
As for setting the PE Enable RPM to 0, I would not. Usually 2900-3200 is a good area. Also usually the TPS reading require for that RPM range is higher as well, like 65%. Gets lower as the RPMs go up.
by setting the RPM delay to 6200rpm, you effectively disable PE because both criteria must be YES in order for PE to be enabled.
for example, say on a stock eco ecu you mash the gas pedal. delay is set to 6200rpm but the ecu sees this:
TPS = YES
delay = NO
PE= not engaged
since a majority of people have upshifted by 6200rpm, or those who hold it the 300rpm gap to the limiter is over so quickly the ECU doesn't have time to richen things up.
By setting the RPM delay to zero, you won't be in PE all the time, just the instant your TPS threshold is exceeded.
TPS = NO
delay = YES
PE= not engaged
TPS = YES
delay = YES
PE= engaged
by doing this, you re-enable the PE feature of the ecu, and on wide open throttle, you'll get a bit more fuel and run richer than 14.7:1. how rich, I'm not sure, and the stock injectors are maxed out anyway, on my daily driver with completely untouched VE tables, I've logged the stock injectors at 87% duty cycle on WOT.
the easiest way to confirm this is by hooking up a simple air/fuel gauge (not a wideband). You can see the sweep even when mashing the gas pedal in an eco equipped J-body. But when you set delay to 0, whenever the TPS threshold is exceeded, the sweep will go rich and stay there.
I'm not sure of the reasoning behind the delay being set so high.. GM probably did it for MPG concerns.
I would not want a delay for power enrichment. If you have a specifically tuned vehicle and say you floor it below your threshold RPM (say 3500rpm for arguments sake), you have the ecu pulling fuel to shoot for stoich. During this period, the AFR can go as lean as 16:1 or further. That is way too risky in my opinion, especially for a car that is boosted. When you open the throttle plate to let in the maximum amount of air, the ecu should by all means give you the best AFR for power. There's no reason to put the pedal down and not expect the incoming air to be met with the proper fuel. Once the TPS threshold is exceeded, you should be in PE all the time. This is why I set my delay RPM to 0 in both the skwirl, and my daily driver.
I just filled up today, and averaged 32mpg in my daily. So setting the delay RPM to 0 really has no adverse effects, in fact is pretty much ideal. Is it bad for a relatively stock engine? no.. but when you start modifying things, its one of the first changes via HPT I make.
So would it be a good idea to pay someone with hpt for the credits and have my PE set to 0 with out further tuning? al least for the time being? if so anyone near KC, MO with hpt?
Will Paulman wrote:So would it be a good idea to pay someone with hpt for the credits and have my PE set to 0 with out further tuning? al least for the time being? if so anyone near KC, MO with hpt?
I don't think so. You need more than that done.
FU Tuning
