11sORbust

The Stoichiometric constant has been known to do little(in the past). BUT there is new infomation out that is shedding some light on that contant. Which gives me a chance to ask some questions, considering that the definition of stoichiometeric constant has changed since I started tuning. I know that rbob answered this in another thread. But I still have some questions.

I'll explain my tard logic. I'm basing this off the idea that 14.7:1=128blm/int . So the ecm has to be told that 14.7 a/f ratio=128blms otherwise it wouldn't know what stoich means. I think that the stoichiometric constant is how the ecm knows what stoichiometric means. If that is the case then I have a potential tuning method. If it's not the case then how does the ecm know what stoichiometeric means..

Rbob explained that the stoich constant is for different type fuels. Which I kind of understand. For example certain states have oxygenated fuel that effect measureable a/f ratio. So changing that constant will compensate for different types of fuels. The question is, if that is all that the stoich constant is for then why is it set the same for different bins. From what I understand all bins have that table set at 14.7:1 . That confuses me because different calibrations are all set the same(for that constant).

RBob

iTrader: (1)

They all use the same fuel, gasoline? Oxygenated fuels come and go. In PA they start in October and end in April (or May?). The O2 sensor feed back allows the ECM to compensate as the fuel oxygen content varies.

RBob.

11sORbust

ok forget about that, I understand. What about the rest of my thread?

TRAXION

Here is what I know.

What RBob said.

What I gained going through the assembly with my CSH on was what RBob stated. That is to say: Changing the stoichiometric AFR will initially change the BPW. In my previous post I showed how AFR is related to the BPW ... BPW=GMS of Air/(AFR * Injector Flow). Thus, decreasing the AFR will result in an initially HIGHER BPW. Notice my use of the word "initially''. However, this BPW should then very soon change back to the normal BPW you previously had. Why? Because the stoichiometric AFR does not control the BLMs. It controls the BPW. The O2 voltage points control the INT. It's when the INT swings a particular amount that the BLM then changes. So, what it all comes down to is the O2 voltage points (which RBob has clearly pointed out on numerous occasions). In short, decrease the AFR and the initial BPW will increase. The O2 voltage swings will increase too. However, since the INT is based off of predefined O2 mV swing points (constants), then the INT will decrease in order to stay in line with those O2 constants. Thus, the BLM will decrease and the BPW will return to normal even though you specified a lower AFR.

This explains A LOT. People noticed the same BPW in closed loop when changing the AFR. I noticed this too! I changed my AFR to 16:1 and my BPW was basically the same. I never thought to look at the BLMs and compare them.

Tim

11sORbust

So the constant work the way I thought. That's untill the integrator drags the blms to bring the ecm back in line with 14.7:1.

The blm value of 128 is not related to the stoichiometric constant?
The Integrator IS directly related to O2 millivolts?


It would be nice to have something like 14.0:1 or 13.x:1 as the commanded part throttle a/f ratio. I play with hotrods not stockers. Throttle response and engine life is more important that emissions. All the cars I work on doesn't have emissions. No ccp, a.i.r., catalytic converter, etc. They tend to respond to slightly richer a/f ratios for part throttle.

I'm not ready to run in open loop,yet. I like how the ecm works. I think it has saved a million engines. It seems like the stoich constant should be the only thing that controls commanded part throttle a/f ratio. The problem is the integrator will "take control" and bring the a/f ratio back to stoich(as pointed out to me). I think that is a good thing, in general.

The integrator is based of O2 constants then .450mv=128 int,right?. Then why couldn't the constants be changed to .500mv or whatever to get the int to "swing" at the new commanded a/f ratio? I know that the NB o2 is not acurate when it strays from .450mv . I could use a wideband, there is a way to get one to replace the stock o2. Then if I command a new a/f ratio, the ecm will be more acurate.!?

So does this mean I can set the stoichiometric constant to XX.X:1 a/f ratio and it'll keep the ratio IF I set the "o2/int constants" to match?

TRAXION

First, I don't know if you necessarily want to run richer at idle. This gets complicated. Granted, some motors do like richer at idle. Hear me out.

If you are dealing with a high performance motor then it is going to be cammed. This means more overlap. A Lot of overlap will mean that some of the FRESH unbrunt intake charge (O2 and Fuel) will be dumped into the exhaust. The O2 sensor will register a lean condition even if you are dead nuts on target. This is a perfect example where any O2 sensor (including a wideband) doesn't tell the full story. It is doing exactly what it is suppose to be doing ... registering O2 content. HOWEVER, the basic premise of O2 sensors is that they are measuring the results of combustion. With a high performance cam with a lot of overlap this is just NOT true at idle. It is also measuring some of the unburnt charge. What does this mean? This means that even if you are dead nuts on at 14.7:1 at idle ... the O2 sensor is going to see something leaner (even with a wideband). Thus, the INTegrator will raise and fuel will be added until the O2 sensor registers 14.7:1. However, at this point the real AFR will be LESS than 14.7:1. The problem with performance cams is that the excess overlap really wreaks havoc on O2 sensor readings because the O2 sensor was designed to read the results of combustion and now it is reading the results of combustion ALONG WITH fresh oxygen that is being pulled through due to the overlap.

I'll address the other questions later. Time for some lunch

Tim

11sORbust

FYI, I'm not talking about idle. The issue you raised is different than what I'm talking about. Not sure that all "fat" cams have alot of overlap. I do think you raised a unresolved tuning issue though. The current solution to that is run open loop, right? I did notice that before, the wb was showing a very lean idle. So I richened it up untill I could smell raw fuel out the exhaust. It still was reading lean.....

11sORbust

Long *** lunch????

3.8TransAM

So since we are discussing o2 limits and ridh/lean hysterisis.. what would be an adviseable attack strategy to use this parameters to our full advantage? I played with these at one point and never got to far with them(plan to repeat with operational wideband) but i could not quite deduce what benefits this would give me...............
Later and thanks

TRAXION

ahahahahaha. I leave work early on Friday's. I didn't have enough time to work on a reply to this before I had to leave. Patience danielson. Patience. Or, you could always rip out the same assembly that I am doing and work through it too? Gotta start sometime right?

Tim

11sORbust

Tim,

I'll give the stupid corvette hack a look. I say stupid because it's not a AUJP . BUT couldn't you just help me out a little bit. Me need resolution. I think there is at least one valid question in my previous post.

I thought you went for lunch and quit.


Grasshopper.

jeepguy553

Question from Grasshopper larva...
If you DID change the AFR constant and left the rest of it alone, what would the final effect on things like INT and BLMs be? This finally came to light as I was reading the previous posts in the thread. I see how the INT helps move the BLM values, but if the initial AFR was set at...say...13.5:1...wouldn't that tend to move the BLMs down in value for the same mV on the O2 sensor?
I downloaded the VEPHD spreadhseet setup and I am wondering if it would apply to a TBI (8746 ECM, ANLU base BIN). Maybe I could take a scan from the system and put the values into the table and come out with a really close new VE table.
Just a little speculation/conjecture from a complete newbe here trying to learn all this...
TIA

TRAXION

Tim,

I didn't give up on this post. Just took a little break. I would have gotten to it Friday if I didn't have to troubleshoot something before leaving early. Maybe I'll get to it later today while the kid is napping

Tim

TRAXION

Another cut and paste from my first post to this thread

"In short, decrease the AFR and the initial BPW will increase. The O2 voltage swings will increase too. However, since the INT is based off of predefined O2 mV swing points (constants), then the INT will decrease in order to stay in line with those O2 constants. Thus, the BLM will decrease and the BPW will return to normal even though you specified a lower AFR."

11sORbust

Tim,
Thanks for keeping with this thread. I have a few more questions

What are the constants that control the o2 "swing points" ?

I would ASSume the O2 swing point is .450mv.!?

Is the o2 constants defined in any editing software or hack?

I want to try and change the stoichiometric table to have it actually control the target a/f ratio. If these o2 constants can be changed to match then it should work, right? I know the fatal flaw is that the narrow band o2 is not acurate anywhere but .450mv. I solved that by using a wb O2...


Grasshopper Larva.

TRAXION

As far as I can tell ... no. The BLM is initialized to 128, but it has no direct relation to stoichiometric. The BLM changes based on INT changes. As far as I can tell, the INT isn't related to stoich either. Stoich is basically used for calculating BPW. BLMs and INTs are applied to this BPW to bring them back in line with what the ECM thinks they should be. It appears that this is done according to O2 mV thresholds.

I don't know if I would call it 'directly related' but it is related due to the fact that the ECM changes the INTegrator due to O2mV.

You've hit my wall where I debate about saying anymore. Not because I don't want to ... but because my limited knowledge of assembly is starting to show. This is one area where somebody really good with assembly (like RBob) and the motivation to poke through the code could shed A LOT of light on how this is done. There's so much stuff that goes into this that it cornfuses me. Let's see, we have ...

Integrator Delay vs. Air Flow
Fast O2 Rich/Lean (R/L) Threshold at idle
O2 Upper Zero Error at Idle
O2 Lower Zero Error at Idle
Fast O2 R/L Threshold vs. Map (not at idle)
R/L offset vs. Coolant
Upper Zero Error Reference for Slow O2 R/L Threshold
Slow O2 Filter Coefficient vs. Air Flow
AIR Managment R/L Difference
Filtered A/D O2 Value
Old Filtered A/D O2 Value
mV Diff for R/L Window
O2 Crosscounts (ALDL R/L counter?)
Mult Gain factor for POS Errors
Mult to Closed Loop Gain Factor
Proportional Step Duration vs. Error Table
Proportional Step Size Gain vs. RPM Table
Proportional Step Size Gain vs. Air Flow
Integrator Delay Mult vs. Error Table

This is definitely not easy to explain and figure out for someone with my limited knowledge. I know my limits and right now this is one of them. The first thing that we have to do is to have others jump in and help explain what everything above actually is/does. I would suggest that we actually step through the code together. This is important enough to start a new post entitled "How does the INTegrator work and how is it related to O2mV in $8D?". I'll create it and make the first post.

I think this can be done. Notice my use of the word think. It's more than just changing a constant though ... and this is a GOOD thing. There is a constant that is used for Idle and then there is a table that is used for not at Idle. This is awesome because this will actually allow those of us with big cams to run one AFR at idle and normal AFRs while driving.

You could, but since the stock GM code for AIR uses a subtraction of 100mV and relies on that non-stoich mV reading I think we can deviate from that stoich mV and be reliable. GM thought it was reliable. I guess the real question is 100mV from stoich is approximately what AFR?

I think so I'll start that other post. We've pretty much answered how the stoichiometric constant affects part throttle BLMs. Now we're getting into how O2mV is handled by the ECM and how the INT is dependent on them.

Tim

onebinky

iTrader: (1)

So is this like a secondary AE then, only with less adjustability???

RednGold86Z

iTrader: (1)

One slick but expensive way to actually have closed loop target any air fuel ratio is to buy an Innovate LM1 wideband, and run the analog output into the O2 wire. You can set the analog output to act like a normal O2 switch at any air fuel ratio you want. I've run my car with it switching at 14.7 and it works.

I've found it marginally worthwhile to target higher O2 voltages and play with the lean vs rich step and jump sizes with our efi system's closed loop with a standard O2 sensor.

rooster433

Really old thread that caught my eye.

The stoich AFR constant is simply a part of the formula determining fueling.. Exact same thing as the injector constant or displacement.. Try changing it to 16:1.. the car will be initially really lean but as soon as it hits closed loop the BLM's will run up and chase it back down.



I've been able to do alot with plotting on car wideband AFR out with O2 mv to see exactly what is happening and where.. Afterall a INT is just a integration around a cross over point.

Once I found a happy AFR (notice I don't give a number here because its all relative, espeically when dealing with huge cams.. go for what makes the car happy, not a number you think should work.) I'll go back and plot that AFR against a running average of the o2's at that particular cell (fuel rim cell on some ECM's, MAP & RPM on others and some are even gm/sec on some speed density ECM's)

Then all you have to do is change your rich lean fast and slow tables to reflect these changes..

here are two examples.
Fast O2 Rich/Lean (R/L) Threshold at idle
Fast O2 R/L Threshold vs. Map (not at idle)

With this I've been able to get cars to actually chase the AFR I choose.. My own car for instance is definately not happy around 450mv. It likes around a 13.8-14.3 idle and I've gotten my threshold tables tuned in so that my O2's are actively trying to pull the car to that AFR.


I've been so successful with this I've actually thought about taking it to the next step and disabling PE mode and letting the car chase a AFR I'd like at wide open.. I'm missing some definitions for BLM and INT update rates but it would be something interestint to try.

Z69

The stock NB response curve at 12.5-13.0 afr makes the resolution so poor that even if you got it to work right this week. Whose to say about next month.
Or how well it would work with a different sensor or car.
And there are some who claim the accuracy at those voltages are suspect too. So you'd have to have a WB to even hope of getting there w/o damage. Or a low specific output engine.

Also, doesn't this work out so that the average voltage is equivalent to say 12.8 afr. What would the max and min voltages work out to be during the swings? 10 , 13 , 16???

Some effort on WB Cl code might be a better solution.

rooster433

While making it find the AFR you want at wide open might be a pipe dream I can tell you its got a pretty good range from 14.2-13.0

Try it and you'll see.. it actually works pretty damn well.

JPrevost

Just thought I'd remind everybody that you CAN run a different closed loop AFR with a narrow band and stock code. It just takes tweaking the O2 PID tables and constants. If the correction tables are lopsided you can get the average AFR to be whatever you want it to be. I've done this to pass inspection with a couple vehicles that had some cam, no EGR, not AIR, just a cat. The latest was my buddies zz4 truck, I can't tell you exactly what YOU should do other than to experiment and take notes. Maybe if I had a lot of time I could go into this with more detail but it's not difficult. Good luck, oh, and like Grumpy always says, "don't edit too much."

rooster433

I agree totally..

Even though the stock o2's aren't linear they are at least pretty consistant.

if I boot up my laptop I'll post the excel graph I made plotting my wideban AFR out and NB signal. I don't reccomend others using the values I came up with but instead it just a story to incite ideas of your own.

rooster433

Here a the graph I made of the NB vs WB out. The sensor is mounted adjacently in the same collector. I do not reccomend anyone to use this as a look up chart.. instead use it as an idea of how you can tune in your own 02 tables.

11sORbust

The graph you presented really just lends to my belief. Narrowband O2 sensors have one primary use, that is to osculate A/F ratio. I think this is to maintain proper catalytic converter operation. There must be a reason the catalyst doesn't function correctly at a constant stoichiometric a/f ratio. Maybe it's just heat buildup, or deposit formation. The only thing I know is that NB O2 sensors are useless if you are not running a catalytic converter (and provided the computer's operating system has been recalibrated). I think there is even a valid argument as to MPG difference between running an O2/cat and without. Maintaining a constant A/F ratio will average a lower total pulse width. Lower the average pulse width and fuel consumption goes down.

WHile you might be getting good results commanding different A/F ratio now, things can change with conditions. This means you will find actual A/F ratio varying from commanded as average exhaust temps change. Here in missouri, the weather can swing 30*f within hours. Situations like that is where you'll find the a/f ratio drifting. IMHO, you should do comparison testing of actual vs calculated A/F ratio under many types of conditions. Then go back and look at the data as a whole and ask some questions. How much did the a/f ratio vary during all the testing? What percentage of time did the narrowband O2 maintain the commanded a/f ratio, under each conditional test? The worst case scenario, how well did the NB hold the commanded value? HOw does rain effect the actual vs commaned a/f ratio while using a NB O2? What happens during sensor malfunctions? Without knowing anwers to questions like that, it's hard to say you are on to something "good".

rooster433

This isn't something I dreamed up and just posted without any trials nor have I only had success with this in only 1 car.

I've been able make large cams happier by moving the AFR a touch to the left or the right depending on conditions.

For instance in my own car I needed to move the AFR about .5 of a point to the rich side and it worked flawlessly.. The BLM's are chasing a 13.9-14.3 AFR. The car is driving really smooth with VE I've tuned in solely on a wideband and desired AFR lookup and I've even got to where I'm able to shoot a little fatter (mid 13's) in heavier loads (70- till PE comes in)


Look at the oscillations at .450 mv compared to say .750 besides a few hair noise points the swing gets much tighter (the moving average depicts this also).. Something to think about..

rooster433

BTW.. you can always try it yourself to see how it works for you. Set the begining of all your threshold tables to say 750 and end them at around 830

Then datalog it with wide band and plot the average AFR vs RPM vs MAP on a table and see how the AFR changed to a consistant 14-13.0

Its important that you take an average when doing anything like this as an attempt to filter down all fo the transients

JP86SS

iTrader: (1)

Great info, thanks for sharing that.
I am led to believe that this is a good operating theory because of shifting the o2 constants require the BLM to follow. Weather and baro changes are handled already in the code for CL operation. The key to it all as you said above is that the sensor is "repeatable" not accurrate (sp?).
For CL "normal" conditions on any different vehicle the constants and AFR setting WILL need to be tweaked for the application but "should" still be repeatable until the sensor begins to shift with age/contamination.
Do you have any comparison info on shifting over time that might verify the long term effects?

I believe the switching R/L is to keep the cat temperature changing to avoid fouling/buildup by maintaining high temperatures. If there is nothing to burn in it, it may cool down or overheat if too rich. Just the way I've heard it needs to operate. RednGold86Z probably can confirm/deny the operation better.

Z69

I don't have an issue with you running 13.8 cl. Plenty of people can attest to doing it already.

My comments were directed to your running 12.8 at WOT using the NB. More than one person has seen evidence as to the NB not being repeatable at that voltage. The slope of the output is just too high in that area. I work on industrial process controls.
That sensor would get thrown in the round file if I had to try and actually control something at other than about 450.

All you have to do is look at the voltage response curve of a NB.
It acts looks similar to a switch with a little dead band at 450.

rooster433

I'm not arguing with you.. I mearly said it woudl be interesting to try.

RednGold86Z

iTrader: (1)

Basically, if a cat is operated at steady state, it (the cerium in it) will "fill" up on Oxygen, or empty, depending on if you're a touch lean or rich respectively. Switching allows to fill some oxygen when lean, then use that Oxygen when rich to oxidize with the CO and HC. Just keep it from completely filling or emptying to get always clean emissions. Keeping it averaged a touch on the rich side keeps CO and NOx in there to reduce the NOx that is produced. It can take lots of time on a dyno (trust me) to get it clean in most places. And then it can take some fudging (in the closed loop maps and transients) especially for the emissions test drive cycle to keep it clean through the test.

But if you have a wideband with programmable outputs, and code with a Voltage target map and a tightened "window", then you can do whatever you want for a street application. Now you just need that Voltage target map.......

dimented24x7

iTrader: (2)

Another thing about a narrowband is that its cheap, doesnt need any special hardware, and provides a good signal to input ratio around stoich, which was origionally needed since the crappy hardware at the time didnt have much resolution. The origional ECMs where also slow and couldnt handle much code. The switching action provides an easy way to both control the AFRs without the need for super-sophisticated software and test the sensor to make sure it still works. No switching=dead sensor.

dimented24x7

iTrader: (2)

In linear terms, the response is nearly flat at .9 volts or so. Same problem would happen with feeding a WB controller into an ECM with an output over a broad range of AFRs. The response is just too flat for the 8-bit A/D converter to accuratly resolve. Probably could have broad control over the AFRs, but fine control would be difficult since the differences would be very small. So really, the whole system should probably be placed in the round file.

Z69

Extra speed and resolution are always nice to have.
But it also depends on how fast you need to adjust the system and the volume of code to process.

Linear WB's are, well linear. 0-5v = approx 10-20 afr.
I've never seen the raw sensor response.
But in Innovate's case, I don't think it would be of much use.
I don't recall the specifics of how they do it.
But you can speed them up and hook their calc'd output to a HS logger to see what's going on.
0.1 AFR resolution is sufficient for a non CAT equipped app.
So 25 counts/afr is fine when you consider that the afr will always be swinging a little around the desired value.

I just wanted people to see both sides of the NB and WOT use.
People by nature like to draw conclusions from incomplete pictures. Some aren't aware of their blind spots or are to young to process the info into a risk/reward thing. How else did our ancestors take on a Mammoth the first time.

dimented24x7

iTrader: (2)

My innovate unit has a linear, programmable output on it. I looked at doing wideband control, but the fact that theres going to be some error involved, and it takes a good deal of code to actually implement full PID control for WOT corrections sort of makes it so theres alot of maze without much cheese at the end. Could probably achieve better results by having more accurate open loop models in the computer.

It would be worth it for P/T lean cruise, though, since theres a much smaller dynamic range then whats needed with full control over all ranges. With high gas prices this could save a good deal of money at the pump.

rooster433

I'll probally open a whole new can of worms by saying this but I've had at least 3 different innovative widebands on dynojet dynos and they where all off. I trust my dynojet wideband because I get consistant results out of it from car to car. Prehaps someone else who has watched a innovative on the dyno will speak up w/ thier experiences.

The worst one I've see so far was a AEM. I don't know what the hell was wrong with it but the shorts/longs where on 0%, the dynojet wideband was 14.6-14.8, the nb sensors where switching nicely but the AEM read 12.0 a idle. Under load it cleared up and read along the lines of the dynojet wideband. It was mounted the downpipe of a turbo.

69 Ghost

iTrader: (1)

I have a question regarding this issue? The R/L switching is supposed to be to keep the CATS happy. Has anyone that does not use CATS like myself figured what to use here? Since I don't have to comply to any emissions I have no CCP or EGR. It would seem to make sense to narrow these down so that the ECM is not trying to go back and forth with the AFR's but to approach the desired steady state. I am fine with the CL constant of 14.7 at least I think so.

dimented24x7

iTrader: (2)

The switching really exists in the old computers because the O2 control routine is proportional-integral only and is prone to ocillations. In order to get a reasonable response time, they set the whole thing up to intentionally ocillate around stoich. You can tighten it, but the switching is a necessary function. Without this, the response would have to be reduced to prevent ocillations. Also, if it where set up to target and not switch, the computer could flood the engine with fuel if there was a fault with the O2. With the switching, the computer can simply exit closed loop if the O2 hangs around .45 volts and doesnt switch.

dimented24x7

iTrader: (2)

Interesting.

A neat experiment would be to get two seperate make units, calibrate them, and mount them on the same car at nearly the same location and see how they compare to eachother, and to the dynojet.

rooster433

I'd like to further this point by saying that normal switching on the o2's is really not that big of a jump in REAL AFR when you watch it with a wideband. For instance.. if you have a car that is spending most of its time jumping from 250mv to 750mv your still pretty solid in the 14's which is small potatoes in real world as far a fueling goes.

Havnig a car that sat on 14.7 exactly all the time is not a realistic senerio

That same dead band of AFR vs. Performance is what I think helps alot of people get away with NB tuning.. especially in the days before widebands where avaiable and affordable.. just a few years ago the only way to have one was to order a printed circuit board and build it yourself.

What i mean by AFR and performance is if you take a 300rwhp car and run it at 12.5 then go back and run it at 13.2 you'll likely see about 5rwhp give or take a pony or two.

rooster433

You know I'll probally take alot of heat about that but I work on a dyno a few times a week and its just an observation I've made over the years.. I have 2 of the orginal LM1's and I've pretty much come to terms with dailing a car in at say 12.0 with it and expect 13.0 when I put it on the dynojet wideband.

The AEM was really close once you got some load across it and my twin tech has been really close. I don't know what type of sensor the AEM uses but the twin tech uses the same honda/NGK that the old DIY wideband called for. I also have a austrailian tech edge WB (my first) but never had a chance to compare it against anything.

But in the end it all boils down to just a relative number.. what are we shooting for anyway? A AFR number or best power/torque.



I'd say we are pretty far off topic by now huh?

RBob

iTrader: (1)

Yep, and yep. Don't use closed loop. Leave the ECM in open loop. Closed loop is only for keeping a CAT happy, and I don't mean the furry kind.

With running open loop the commanded (and resultant) AFR can be changed according to the engine coolant and load. Works out real nice. Try it.

RBob.

rooster433

How about those who use closed loop for what its for? Keeping the fuels inline.. year round, all kinds of weather, and conditions..

I've been a open loop guy just because the emmissions friendly stock closed loop thresholds was way to lean to keep a roots blown, 2 bar hacked car happy.. but open loop presented some problems like the tune changing with weather/conditions. Yesterday it was 70 and I was in shorts. Today it was 40 and I was freezing in heavy coat.. you can't tell me the tune isn't going to get a little quirky with changes like that.


Now I use closed loop to KEEP a friendlier 13.8-14.4ish whenever.


For those who question the switching.. Let me ask a question.. can you feel your car switching the AFR at a idle? Of course not... Can you watch the AFR switch on a wideband more than a couple tenths? no.. Its not looking to switch as far as a mv value goes.. it just goes a hair rich, hair lean back and forth. Making the running integration around the threshold point near 0 is all the computer is concerned about.

RBob

iTrader: (1)

Only if you don't tune the CTS/IAT blend, or, what is available, correctly.

Another way to look at it, how many years did carb's fulfill the AFR requirement ? Don't see many complaints there. . .. (ducking LOL).

RBob.

rooster433

One thing I hear from just about everyone with a carbed fox or carbed third gen is man.. I wish I could just hop in it and go.

One of the biggest advantages of fuel injection in my eyes of fuel injection is how it can to some degree take care of itself.

RBob

iTrader: (1)

Yep, that is the best part of EFI, isn't it?

As mentioned, closed loop is to keep the cat happy, nothing more, nothing less. Much is to be gained by staying open loop. . .

RBob.

]

69 Ghost

iTrader: (1)

OK so OL you have to start somewhere what would you recommend as a starting point for the AFR? I thought I was happy with CL. I assume the tuning is much the same get the VE and spark tables in line then the PE and AE then just keep it from going CL by setting the CL temp to the max temp. Would it be better to run CL and then just have a small delta tps to force it into OL? Lots of questions and maybe not appropriate for this thread.

rooster433

If thats your opinion


What do you think block learns and fuel trims are doing? When you have a bad tune and they are sitting at 110 are they not pulling the AFR back up. It hardly seems like the only reason for that is to keep the cat happy.

Fast355

iTrader: (2)

My current tune is as close to OPEN Loop as I can get it and still have a functioning catalytic converter. My A/F ratio changes about 1/2 point rich and lean. It continually goes from about 14.5-14.9 and back. Constantly crossing 14.7:1 (Wideband will let you do this via a Narrow Band Output). Under heavier load and higher MAP I change the ratio to about 13.6-14.2:1. WOT=11.5:1 to kill O2 to the cat and keep it from becoming a Blowtorch and overheating.

The OEM ECM even when tuned would go between 14.0-15.5:1 in closed loop and caused a slightly erratic idle.

RBob

iTrader: (1)

If all you have is a NB sensor then use closed loop to get the VE table as close as possible. If you have a WB then adjust the VE table so that the WB reported AFR matches the commanded AFR. Do this while in open loop and the BLM's cleared to 128.

Where to start with open loop AFR? Use what is already in the calibration, and adjust from there. I like to taper the AFR richer as the load increases. This prevents the sudden transition into PE mode.

RBob.