Technical ecu question

[mellonman]

How does the OBD affect the O2 feedback then? its a straight voltage signal, thats the point of being able to skew the O2 feedback it makes the ECU see the expected O2 switch point as per normal, which allows you to run a richer AFR and the ECU is non the wiser.

 

Its becuse you have to match the voltage change on the o2 screw in the fuel map trim, other wise the ecu learns the change in the long term fuel trims and trim it back out, with the obd1 you cant read the short term fuel trims so you dont 100% know how close you are to a 0 short term, with the obd2 you can just look what voltage change does to the trim and put it in, then the long teams wont pick it up and it works, what I managed to do to get it close was, at idle see how much a map input affected afr, so I knew what sort of o2 voltage was to how much map input, but had to add move to compensate for boost that was built,but mine was more low down as I have a tt

Hope that makes sense the videos on youtube explain it better,

[scott87]

I'm going to get it mapped with an afr gauge anyway. Then get my own permanently in the cab shortly after to monitor it myself. Still gotta work out how to wire the unit in but at least I know or is a unit that is suitable to use.

[Tricky-Ricky]

Its becuse you have to match the voltage change on the o2 screw in the fuel map trim, other wise the ecu learns the change in the long term fuel trims and trim it back out, with the obd1 you cant read the short term fuel trims so you dont 100% know how close you are to a 0 short term, with the obd2 you can just look what voltage change does to the trim and put it in, then the long teams wont pick it up and it works, what I managed to do to get it close was, at idle see how much a map input affected afr, so I knew what sort of o2 voltage was to how much map input, but had to add move to compensate for boost that was built,but mine was more low down as I have a tt

Hope that makes sense the videos on youtube explain it better,

 

I see what you mean but there is an easy way to do that, just use a wide-band setup with logging then you can log a full RPM v load table of the std lambda trim/feedback so you then know just how much you need to bring it back to with the lambda skew, so it wont influence the short term fuel trim.

Its a sod to do this just using a wide-band setup by adjusting the narrow-band output side though, which is why I wished that Greddy had included this feature in the EMU.

[scott87]

I'm sure any mapper will know what u guys are talking about right?!

[mellonman]

I see what you mean but there is an easy way to do that, just use a wide-band setup with logging then you can log a full RPM v load table of the std lambda trim/feedback so you then know just how much you need to bring it back to with the lambda skew, so it wont influence the short term fuel trim.

Its a sod to do this just using a wide-band setup by adjusting the narrow-band output side though, which is why I wished that Greddy had included this feature in the EMU.

 

thats exactly it , its been a while since i played with mine to do the o2 correction but im not sure if you can actually get the std lambda trim from the fic ,As its controled by the stock ecu? maybe when logging but i didnt use that when setting it up ( i have now learnt its very usefull indeed).

this is why the obd1 and obd11 come into play the obd1 does not show fuel trims but obd11 does.

but still you will get it close enough with playing , i still reset my stock ecu every couple of months just in case .

 

 

scott

the problem with getting a mapper to do this is , they must know the ecu inside out as its time comsuming to get right. disconnecting the o2 sensors will make your car go into open loop and then the fic can be mapped very easily as there is no feed back from o2 sensors to adjust for your map , but you will run rich cruising and mpg will be affected

[scott87]

thats exactly it , its been a while since i played with mine to do the o2 correction but im not sure if you can actually get the std lambda trim from the fic ,As its controled by the stock ecu? maybe when logging but i didnt use that when setting it up ( i have now learnt its very usefull indeed).

this is why the obd1 and obd11 come into play the obd1 does not show fuel trims but obd11 does.

but still you will get it close enough with playing , i still reset my stock ecu every couple of months just in case .

 

 

scott

the problem with getting a mapper to do this is , they must know the ecu inside out as its time comsuming to get right. disconnecting the o2 sensors will make your car go into open loop and then the fic can be mapped very easily as there is no feed back from o2 sensors to adjust for your map , but you will run rich cruising and mpg will be affected

 

Thor have commented and know the ecu inside out and have fitted to many Supras, hence they have a set price for fitting so they must be confident. They have also fitted the unit i have in my possession to the last Supra that it was in.

 

There is also a way to take the voltage feed using the fic from the o2 sensors and modelling fueling based on a percentage from this. There is a huge section about it in the instruction manual.

[Tricky-Ricky]

I meant using a third party logger IE like the Innovate LM-1 or 2 (not sure if you can do it with the AEM series of gauges) but anyway its easy to run the car through the RPM/load range and compile a log/map of the std lambda feedback, then you know what it expects.

 

If you disconnect any std lambda sensor the ECU will default to a not ideal over rich map which also screws with the ignition timing as well, also not good, it doesn't go into open loop, its not a good point to map over IMO.

[scott87]

I meant using a third party logger IE like the Innovate LM-1 or 2 (not sure if you can do it with the AEM series of gauges) but anyway its easy to run the car through the RPM/load range and compile a log/map of the std lambda feedback, then you know what it expects.

 

This there is a huge section in the manual about different ways to do this..... And then a mapper will monitor with afr readings anyway or map with them in the first place.

[Tricky-Ricky]

Sorry Scott, we are high-jacking your thread, I am sure you will get more of a handle on things once you get it all installed and start to see what affects what when its running, it is a big subject but the basics are pretty straightforward once you get the gist of things.

[scott87]

Sorry Scott, we are high-jacking your thread, I am sure you will get more of a handle on things once you get it all installed and start to see what affects what when its running, it is a big subject but the basics are pretty straightforward once you get the gist of things.

 

Dont worry about it.

 

Highlighting things now is far better than me being stumped with a car that wont work.