Thread: Nismotronic SD factor

The problem I have run into is that my car has 1000cc injectors and the base tune that was on it was driveable, but the sd factor was incorrect and did not allow revs over 4k. It acted like fuel cut but it was actually leaning out really bad. I increased the sd factor by 25% and this opened up the top end completely. However, I am working on dialing in my cruising AFR's and I it generally bounces all over the place. It seems like small deviations in the TIF's and mulitipliers greatly affect the TFF. A problem I have been having is when the a/c fan comes on with the defroster, my idle afr's jump to 16+:1. But it never does that when the rad fans come on.

Does anyone know how to set the sd factor? Is there a calculation?
Does anyone know how I would upload my TCD and TCL?

Otherwise, everything with this ecu has been stellar.

You can adjust (reduce) CURRENT INJECTOR SIZE to increase fuel across the map, which will allow you to reduce the SD factor, which will increase the resolution of the values in the fuel map. You want to use the minimum SD factor that still gives you the proper fuel map values (IPW) across the fuel map.

You should be able to increase the fuel map value at the higher fuel map load cell when the A/C comes on.

In advanced post edit mode, there is a "Manage Attachments" button for uploading TCL and TCD files.

John can probably add more detailed info and certainly look at your TCD and logs.

Dave

So if I am understand correctly, 1000cc are out of the nemus tuning capability due to vast resolution required to properly set fuel values against the map load?

So, if I were to cut the injector size 1/3, reduce the sd factor, I would gain the neccesary resolution to tune?

I guess my mistake was trying to run such large injectors with 93 when the build was designed for e85. Now, would it just be simpler to convert to e85 since doing so would require decreasing the injector size?

No, not at all. You simply use the current injector size factor to scale the entire fuel map up so you don't have to use the SD factor to do the same. The larger injectors require less IPW, so setting the current injector size to 1000 reduces IPW. If that requires you to now increase SD factor, then just use a smaller current injector size to increase the fuel instead.

Then how was I running out of fuel value when the sd was set and the injector were set to 1000? I mean literally the values were set to 255 and it would still lean out. It wasn't until I increased sd that this problem went away.

Use a smaller current injector size. That will increase the fuel (IPW).

The problem isn't that I am not getting enough fuel, it's that small changes in the map greatly affect the cruising afr's. I'm really not looking for a work around on the injector sizing issue either.

I dont have time to post a long detailed answer right now, but I can definitely help you get things more dialed in.

Send me your current tcd and TCL and I can take a look!

I have never ever had to max out the SD factor and I have used up to 2200cc injectors with the SA firmware without any issues like this.

Also. Check the help section for a more detailed description.. and if you are boosted definitely make use of the boost fuel trim!!

I wrote a small explanation of how the SD factor works and some ways around what you are experiencing.

http://www.sr20-forum.com/nismotronic/71143-sd-fuel-factor-effect-fuel-map-resolution.html