A couple of suppositions and a question...

I understand that the ECM uses a set of base parameters burned into a chip to set fuel mixture (injector pulse width). It uses O2 sensor readings to tweak the settings richer or leaner than the base settings. There are long term and short term adjustments that the ECM makes. Right?
I also understand that at WOT the ECM instead uses sensor readings (MAP, TPS, RPM?) and "lookup tables" to calculate the correct pulse width, for the correct fuel mixture. AT WOT, the O2 sensor is not a part of the equation. Right?

The first part of the question is, which parameters are used to calculate WOT pulse width? The base parameters? Or the modified parameters, based upon how the ECM has adapted?

The real question: I'm going to be scheduling some dyno time, hopefully this week. I've got five chips that I'd like to dyno.
After I'm done with one chip, can I just pop in the next one, and have at it? Since dyno runs are made at full throttle, where the O2 sensor is out of the picture, do I still need to let the ECM learn before I hammer it? If so, how long do I need to drive it?

Any help would be appreciated.

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Raydar
88 3.4 coupe...........

Coming soon...
88 Formula, presently under the knife.
Read Nealz Nuze!

[This message has been edited by Raydar (edited 03-12-2005).]

hey; this sounds like a really good thread and topic; I look forward to some input here. I for one will be learning something.
One comment tho' based on things you said; if the O2 sensor is 'out of it' on WOT runs (which is "I think" all you would do on a dyno...), then what about the wide band vs 'narrow' (?) band O2 sensor recommendations that people make?
Is the O2 used at some part of the rpm range maybe? I don't know; simply raising this one point.

Looking forward to some good info and discussion, no doubt, here! Thx Raydar!

quote Originally posted by fiero308: then what about the wide band vs 'narrow' (?) band O2 sensor recommendations that people make? Is the O2 used at some part of the rpm range maybe? I don't know; simply raising this one point.

From what I understand, the stock (narrowband) O2 is more like a binary switch. It toggles back and forth between "rich" and "lean" with no values in between. At least that's how the ECM interprets it.
The wideband varies continuously, and can interpret any value between "full rich" and "full lean". At least that's what I've gotten from all the previous discussion.
I could always be wrong.

[This message has been edited by Raydar (edited 03-12-2005).]

The wide band vs narrow band O2 sensor question is easy to answer. Narrow band sensors only measure meaningfully right around 14.7:1, so effectively they are used as a rich/lean switch in most cars. At wide open throttle you want a 12:1-13:1 air/fuel mixture, but that's way outside the range that a narrow band sensor can sense reliably. The answer is to ignore the O2 sensor at WOT and use pre-calculated fuel maps, which is what Fieros use. I don't know if the WOT maps are affected by short and long-term fuel trims, I suspect that they aren't.

Now, a wide band O2 sensor can measure reliably all the way down to 10:1, which means that an ECM can be designed to actively control fuel mixtures at relatively lean and rich conditions. Sensor types can't be interchanged, even with different programming in the ECM, because the circuitry for the two different types of sensors is radically different. There is no way to adapt one sensor type to work with the other ECM design.

Typically, the wide band is used during testing, and then new programming is done to the ECM and testing is repeated until the WOT mixture reaches the desired ratio.

JazzMan

Thanks, James!

quote Originally posted by JazzMan: I don't know if the WOT maps are affected by short and long-term fuel trims, I suspect that they aren't.

Cool. I hope that you're right.

Anyone else?

when WOT, the ECM goes strictly open loop, by the tables, no adaptive learning parameters should enter the equation. Typically this is very rich so you don't burn anything up As long as the engine's warm, I'd say pop the chips in and hammer away. (On the car that is, not the chips )

What are the major differences between the chips?

Wheelie here. This right up my alley.I was looking for a good airfuel ratio tester to use on my dynojet motorcycle dyno. I also have a load dyno. I seem to have found one. It is the LM-1 This should work on my dyno and my fiero(3.4 dohc with obd2) This thing is really amazing it .Acts like a dyno when on the car and can be used with a dyno.It uses a wide band sensor and can record up to 5 inputs for up to 44 minutes. Connects to any pc and graphs out all the stuff you need to tune.
On my 750 kawasaki turbo. the fuel injection did not have an o2 sensor so it just ran off the supplied maps in the computer. This was tuned for wide open throttle with an adjustable fuel pressure regulator. More pressure- richer less leaner. Easier than changing jets or remapping really.Most na engines are designed to run rich at WOT to save the engines.turbos need more fuel when adding boost.You can also adjust some other things like the tps resistance? iat (intake air temp) yes we have all seen that majic chip on ebay!! I did the same thing on my bike and it can be used for tuning. I will be ordering this tool soon and I will be experimenting to do on my swap. Nobody likes obd2 but I think it can be made to work.Sorry for rambling!
wheelie

quote Originally posted by Cooter: What are the major differences between the chips?

I have three chips that were burned by Troy, to work with the new intake manifold. They are various stages of "lean to rich".
I also have the chip that Jeremy burned for me, to go with my 3.4 with the stock Fiero intake system.
Just for grins, I'm going to throw a stock 88 chip into the mix. I expect it will be hugely rich with my injectors, but I'd like to see it, anyway.

ok so just for the sake of learning here, at what point does the ecm decide it is at WOT? 100% at the tps? 90%? is it adjustable or dependent on anything else (like a vacuum signal and/or rpms etc)? And does the 'rate' of opening have anything to do with it; I guess what I am getting at is the "accelerator pump' function on a carb.... I believe that gets duplicated but how, exactly?

anyone know for sure?
great thread!
gp

quote Originally posted by fiero308: And does the 'rate' of opening have anything to do with it; I guess what I am getting at is the "accelerator pump' function on a carb.... I believe that gets duplicated but how, exactly?

The "accelerator pump" function is called Power Enrichment (or PE). I believe it's based upon the rate of opening. Could be wrong. If not that, then it kicks in at a certain percentage of full throttle. I think it throws in some more fuel and some spark advance.
Again, this is what I've been able to gather by talking with people. If I'm incorrect, I'm sure (or hope) that someone will correct me.

Thanks for everyone's contribution, so far.

quote Originally posted by Raydar: The "accelerator pump" function is called Power Enrichment (or PE). I believe it's based upon the rate of opening. Could be wrong. If not that, then it kicks in at a certain percentage of full throttle. I think it throws in some more fuel and some spark advance. Again, this is what I've been able to gather by talking with people. If I'm incorrect, I'm sure (or hope) that someone will correct me. Thanks for everyone's contribution, so far.

This is the wall I ran into when trying to learn how to reprogram my chips. Back in the carb'd days there was the accelerator function which squirted in extra fuel when the throttle was opened. This was needed because opening the throttle temporarily reduced air flow through the venturies which in turn reduced the amount of fuel drawn up from the jets. However, once the throttle stops opening the accellerator pump shot stops, and the engine air intake flow still is relatively too slow for good fuel draw. Holleys use a secondary fuel metering device called a "power valve" to meter addional fuel in under low vacuum conditions.

From a drivability standpoint, a carb'd car that fall flat on it's face as soon as the throttle is opened needs more accellerator pump, and a car with the proper accellerator pump shot but insufficent post-shot enrichment would have a good bump of power folllowed by lag that gradually went away as RPMs built up.

I don't know what parameter controls that secondary enrichment in the Fiero ECM.

JazzMan

(From my foggy memory...)
There is a setting for acceleration enrichment that acts like the accelerator pump in the carb- it responds to changes in throttle position and/or MAP sensor readings to add fuel while the throttle is opening or load is increasing.
Then, when you get past a certain throttle percentage/RPM, the ECM goes into power enrichment and has a look-up table for the air/fuel ratio vs. RPM.
Most of the time, I don't mess with the power enrichment AFR. Instead, I'll change the base pulse constant until I get the O2 at WOT to around 850 mV. After I am sure it is getting enough fuel on the top end, I'll start tweaking the main fuel table to get better driveability.

I can try to pass on what I know about this. Some background info. I have three main things. I have a burner/reader that can take the bin file (data information), from a chip so I can analyze it and it can burn/ put the data, onto the chip. I have an eraser that takes the chip and erases the data on it because you have to start out with a blank chip to burn it. I also have a program that I use to change all the parameters of the chip, within a given range. I can take a stock chip and download the data, change the needed parameters, erase the chip and then reburn the chip.

There are a couple of main things. First, there are switch tables called ECM constant tables. There are probably like 50-75 of these. Same examples are Fuel cut off and return rpms, desired A/F ratio, min inj pulsewidth, max inj pw, power enrichment thresholds (stock is tps 59.4% and map at 60kpa and pe rpm of 3600 and also pe af ratio set at 12.0 stock). Idle rpm, egr items, tcc items, prom id number and some other things.

The second major things are about 20-30 different maps. Example are map vs rpm vs spark advance. The other major thing is the open and closed throttle setting of % vol eff vs rpm vs map.

There is also a ECM switch table with 4 parameters to turn on and off. 2 bar map, egr present, trans type, and syn mode closed full throttle.

There is a lot more I can do but it would take me hours to write it all down here and explain it how it works. When I usually make chips I only change the rpm fuel cut off and on, fuel table under load and ignition table under load. If anyone wants to I can change other things but I usually like do that when the car is here and we can change one thing at a time to see how it reacts. When you start changing a lot of things and some parameter is not right it is hard to figure out which one might be wrong.

As far as the wide band goes, people usually use them only for testing. There are a couple of cars that came with them stock and I expect most cars to come with them stock in the future because they are more accurate. The only thing is most cars do not run as rich or even close to anymore as the 80's did. When in doubt dumb in tons of fuel and do not worry about it.

As far as the computer learning it does not do much as like the computers today. The IAC motor people see it as learning, but what is is doing to changing the step motor to meet the desired rpm amount at idle. Some people say you have to go to 25-30pm to get it to work, but I did not see that in the settings I can change. That my be set somewhere I can not see or set as a hard datapoint I can not change. I do not think it really has anything to do with speed as far as I have tested, but someone else might be able to comment on that. The newer OBD II computers have so much control over it you can add 50% more fuel and in about 2-3 seconds the computer would react quick enough to take all the fuel out to get the desired af ratio it wants. They take readings of the sensors and can adjust to settings in the computer to compinsate for sensors that are not working as well as they should. So when an O2 sensor starts going bad it does not dump in extra fuel thinking it is lean when it is not, the computer knows.

I hope that may help.
Troy

quote Originally posted by WHEELIE: ....I seem to have found one. It is the LM-1 This should work on my dyno and my fiero(3.4 dohc with obd2) This thing is really amazing it .Acts like a dyno when on the car and can be used with a dyno.It uses a wide band sensor and can record up to 5 inputs for up to 44 minutes. Connects to any pc and graphs out all the stuff you need to tune. ....

I love that product. I got one and have played just a little with it. I have three cars to tune so it is more economical than dyno time (as long as you can burn proms too)

Look it here: http://www.innovatemotorsports.com/products/lm1.php

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Palm Beach Fieros
http://pbfieros.tripod.com

What program are you using, Troymx576? I can only see a few tables and such with the program I'm using, and would like something that'll give me all of info in the EPROM.

JazzMan

this needs a bump