Nissan ECU Tuning

xtensive · Joined: 19 Nov 2003 Posts: 200

I know there isn't a lot known about the feedback control, but I am curious about the differences between JDM and USDM feedback. The JDM feedback control value is set to 100 (64h) as is the EURO feedback control, but the USDM is set to 75 (4Bh). Anyone know why?

Mike

Ryan · Joined: 24 Nov 2003 Posts: 86

as far as I know feed back control is at what egine water temp the ecu starts to look at the O2 sensors for feedback (IE arfter warm up) to D-50 = C. so 100-50 = 50C for jap, and 75-50 = 25C for USDM.

Im not sure on the -50 part, but thats what the consult uses for temps, so I guess its the same for feedback control.

Cheers
Ryan

xtensive · Joined: 19 Nov 2003 Posts: 200

Excellent info, thanks! I changed the JDM Auto TT bin to reflect this value for feedback, and I also changed the data at 7FBB, 7F0C and 7F2E. Not sure what those are for but it didn't seem noticable when driving around. Those three values are all the same for JDM/EURO bins, and different for USDM bins...I'm going through the ASM code right now trying to figure out how they are used.

Is there any commented code running around anywhere by chance?

Mike

noss · Posted: Mon Feb 09, 2004 9:54 am Post subject:

i know this is kinda an old thread, but i stumbled across this on the net..

ProZ · Joined: 21 Nov 2003 Posts: 48 Location: Sweden

The feedback value is at what temperature the ECU is supposed to go into closed loop. It is compared to the current value picked from the water temp conversion table wich is simply a scale from 0C to 100C where 0 is 0C and 255 is 100C...
To calculate Celsius from a certain value use the formula (C = (x/255)*100) or simplified (C = x*0.392) where x is the temp conversion value, wich makes 100 = 39C and 75 = 29C. The reason for the difference is simply because of different emission-regulations, in US the ECU has to go into cloosed loop faster to pass the cold start emission test and to save the precats...

The cooland temp sensor in a Z32 is NOT capable of meassuring below 0C and mot much above 100C, so I don't understand where this "-50" comes from but maybe the one who came up with it just happen to test it around 34C where the tempvalue is around 84, but that is the only temperature where value-50 is correct, or the Consult-interface spits out a modified value and not the raw temp-conversion value...

/Niclas

Eric · Joined: 17 Nov 2003 Posts: 258 Location: Holland

the temperature value, when requesting either the coolant or fuel temp from the ECU is then obviously modified.
You need to subtract 50 from the value that is spit out to get the actual temp.

This is also how a real Nissan consult calculates the temp and I also verified the coolant temp with an analog meter and it matched.

If you'd use the val*0.392-formula then the engine's operating temp would be around 52 degrees Celcius and the water would start to boil at around 60 degrees celcius...

the highest (ecu) value I have ever seen was 180 (130 degrees celcius)
This was while the engine was overheating very badly and the coolant in the overflow bottle was boiling

-Eric

PS: I didn't know the sensor isn't able to measure below 0 and over 100 Celcius though ? How did you find out ?

ProZ · Joined: 21 Nov 2003 Posts: 48 Location: Sweden

Hmm, I think I'll have to eat my hat now... Embarassed

The tempsensor is a standard termistor so I just looked up a standard termistor that happen to have the exact same resistance at different temperatures as the coolant temp sensor, and the one I found just happen to be limited to 0-100 degrees C. As termistors and termocouples are very standardized pieces I assumed that the sensor had the same limitations and did my math based on that. But now, since you questioned my statement I tryed to find that spec sheet again and found that there are termistors that cover a wider temperature range that still fits perfect to the sensors resistans-curve/temperature. So you are probably right here, the water temperature conversion table defines a scale from -50C to +205C even if the practical range of the sensor is less than this. The termistors that I found now are rated (with defined precission) from -40C to +130C, and there would not be any problems defining the temp onversion table as C-50 all the way from -50 to +205 C...

Sorry if I made a mess, but the principal of the feedback value is still the same...

/Niclas

darkhalf

Digging up an old thread....

Calum · Joined: 11 Feb 2004 Posts: 226

0x8038 (on early 16-bit ecus) isn't a temperature value, but a set of flags. Bit 5 disables feedback (well, it turns off the whole O2 sensor, I'm not sure exactly what it does) and I think bit 4 disables the knock sensor.

Did I just tell you something you already know?

darkhalf · Posted: Mon Nov 05, 2007 1:30 pm Post subject:

Thats more than I knew before Smile

Guess I was also wondering if there is a temperature setting for the O2 sensor in the 16 bit ECUs in addition to the flags

Calum · Joined: 11 Feb 2004 Posts: 226

I don't know. Whats the stock temp with the Z32 ecu? I sat down a while back and made a list of all the spots in a FWD bin that compare the water temp to a value in the rom (its a bunch). Might start looking at the values that are close to what the Z32 used and see if anything jumps out at you. Want the list?

This would be handy on the later 77xx ecus with the funky two-part fuel maps. The amount of trimming that the self-learning does on those ecus is crazy compared to the older ecus.

darkhalf · Posted: Wed Nov 14, 2007 6:46 am Post subject:

Z32 file has different temps depending on EDM, USDM etc ECU