turning off deceleration fuel cut off

Two40sPlease · Post by **Two40sPlease** » Mon Jan 26, 2009 3:31 am

I'm going to calibrate my Z32 maf translation and I wanted to know what table and what inputs I would have to make to turn off the (DFCO).

Matt · Post by **Matt** » Mon Jan 26, 2009 7:16 pm

Adjust the "Fuel cut" table

Two40sPlease · Post by **Two40sPlease** » Tue Jan 27, 2009 2:41 am

Thankyou for responding Matt,
Where exactly is this "Fuel Cut" table located, I see no table in the lists to the right on Nistune by this name. I see "TP load limit", "Increase fuel","ttp max/min" But no "Fuel cut".

MichaS14a · Post by **MichaS14a** » Tue Jan 27, 2009 9:21 am

The table you search is "TP load limit" or "Theoretical Pulsewith (Lad) Limit".

It is short described in the document: http://www.plmsdevelopments.com/files/n ... basics.pdf at page 16 (15 is shown in the footer of the doc).

Matt · Post by **Matt** » Tue Jan 27, 2009 5:49 pm

which vehicle/engine do you have? perhaps your address file doesnt have those entries (and needs them added?)

Two40sPlease · Post by **Two40sPlease** » Wed Jan 28, 2009 2:17 am

I have a Red Top Sr20det that is installed in my s13 240sx. I'm using the real time type 3 board for it.

Two40sPlease · Post by **Two40sPlease** » Wed Jan 28, 2009 2:38 am

I just looked at TP load limit and I'm not sure how that would turn off my deceleration fuel cut. I want a table that allows the engine to maintain set primary fuel mixtures when I let off the accelerator to decelerate.

datsunboy · Post by **datsunboy** » Wed Jan 28, 2009 6:40 am

why would you want to turn it off anyway?

it will backfire a lot......is that why you want it off?

Two40sPlease · Post by **Two40sPlease** » Wed Jan 28, 2009 7:09 am

I want to take it off so I can better tune my maf translation when reading logs.

I want to modify my maf translation that way when I command an afr number I get that number or close to that when I'm driving. Otherwise its just an arbitrary number in the map to get a desired afr. Most professional tuners using HP tuners or efi live etc. almost always calibrate the maf. My Friend tunes LS1s for a living and he couldn't believe I wasn't doing this at the time, said something about hack tuning lol.

There seems to be some misconception that because nissan presents a maf translation (for a z32 maf in my case) that it is accurate for every (z32)maf. When in fact if you have two of the same mafs they'll never be exactly the same. Which is why I have to command a 10.0 in my fuel map to get an 11.6. This is B.S. when I could calibrate the maf to be more exact. Why should I have to work in filtered values when its easier to just put in a desired afr in the map and get it when I'm driving.

MichaS14a · Post by **MichaS14a** » Wed Jan 28, 2009 7:44 am

Two40sPlease wrote:deceleration fuel cut

Sorry, in this case I am wrong. I thought that you mean the "real" fuel cut which comes in when the readings from the maf goes over the programmed limit and then the engine cuts the fuel injection.

Two40sPlease · Post by **Two40sPlease** » Wed Jan 28, 2009 9:14 am

Matt wrote:which vehicle/engine do you have? perhaps your address file doesnt have those entries (and needs them added?)

So how can we get those added?

Matt · Post by **Matt** » Sat Jan 31, 2009 5:47 pm

I've spent a bit of time just then looking through the code

All the address files based from 8 bit ECUs have the FUEL CUT/RECOVER but none of the 16 bit stuff does

The closest I can find on S13 SR20DET is
FUEL_CUT,&H0350,16,1,16,1
FUEL_RECOVER,&H0360,16,1,16,1

If you edit your address file and add these two lines, see if it works for you?

Those are both temperature based lookup tables and they are next to each other. There is a speed check before using them and they are just after the RPM/Speed limiter checks in the code, similar to J30 VE30 code which I was comparing against

So those are the closest I can see which match upto the ones in the 8 bit ECUs. No guarantee they are the right addresses but I'm pretty sure they will work

Two40sPlease · Post by **Two40sPlease** » Sun Feb 01, 2009 11:09 am

c:\program files\NIStune\address\s13_sr20det_256_E_test fuel cut recover.txt
You don't have permission to save to this location.
Contact the admistrator to obtain permission.

Would you like to save to documents folder instead?

this is what it tells me when I try and enter those two lines and save them in notepad.

Matt · Post by **Matt** » Sun Feb 01, 2009 10:27 pm

dont know whats going on with your computer there

i've attached the modified file here, save this onto your PC and the tables will show up with this version

Two40sPlease · Post by **Two40sPlease** » Tue Feb 03, 2009 1:47 pm

Ok awesome, this seems to add quite a few tables to the mix including,
Decel loss ratio
Decel loss RRM
Decel loss temp
Closed loop Cut
Injection response
Low AFM volt enrich

If anyone has experience adjusting some of these and cares to share their findings please let me know.