Idle Issue

[907DAVE]

I was leaning towards using the 400DD program as my starting point , I will be pulling some ICP out of it though.

I know the 200DD has faults and even though I don't plan on using it, I was just curious why it was acting this way. I am weird like that........ always asking why, gotta figure stuff out even if it really doesn't matter much.

Can you further explain the ICP duty cycle map?

My understanding was that it I like a rough estimate for duty cycle, and then further refined with the ICP map.

[907DAVE]

Originally Posted by soutthpaw

did I miss something? where do I get a 200HP DD

Whoa......new mod in town.

Have fun parting it up hardcore with the other mods.

[cleatus12r]

Ok......

The relationship between the injection pressure regulator and the actual/desired injection control pressure goes a lil' sumpin' like 'dis.

1. The PCM bases an initial injection pressure regulator duty cycle using the IPR map to attain a desired injection control pressure.

2. The PCM looks at the actual injection control pressure data from the ICP sensor.

3. The PCM makes fine adjustments in the IPR duty cycle to get the desired injection control pressure reading from the ICP sensor.

Every varying load/RPM will start with an initial duty cycle commanded by the PCM and constantly tailored adjustments by looking at ICP sensor output.

This entire system is called a "feedback loop". It's very similar in operation to how the oxygen sensors relay to the PCM about how accurate the air/fuel correction is.

When the base IPR duty cycle is off, then the initial duty cycle for a desired injection pressure is off and if it's off too far in a certain operating range, then the PCM cannot correct it and maintain a stable RPM because the actual pressure desired varies too much from the desired and the PCM basically fights itself because the map is no longer valid. I recognize that as a run-on sentence but I'll leave it that way because that's how it came out of my head.


I know what I want to say but I don't think it came out right.

[907DAVE]

Came out fine.

Thanks, it makes more sense now. The duty cycle map is a bit more involved than I originally thought.

How would a guy fine tune this map, besides in the low ICP range with BO is it even necessary?


oops....BO= big oil.

[cleatus12r]

Actually, data logging can be a great tool when fine tuning the IPR map. I was doing some testing/tuning last night for my extreme towing program (which really doesn't make much more power over stock) to get some things just right. Remember how I said about a week ago that I had something to test? Well, I was working on that.

If you see certain trends in your IPR DC% that cause you to wonder.....

I'll post some datalogs and screenshots one of these days in the near future. I didn't set out to do any IPR changes, but I ended up making a few.

........and if your BO is that bad, then I think you need more help than just some fine tuning.

[907DAVE]

Cant wait!

I think I need to get the emulator stuff so I can get some actual live tuning done. I think this will be a great learning experience for me.

[907DAVE]

Well it worked, I "layed down" the PW in the lower MFD/ ICP ranges, and changed the ICP duty cycle to be more like stock. Also I dropped the ICP to around 550psi in the idle range, and it runs and idles super smooth.

I love it.......... still smokes a little if I lug the engine in OD but I am real close to a fix for that.

[cleatus12r]

Good to hear. You'll be making the truck run EXACTLY like you want it to in no time!