Idle Issue

[907DAVE]

I have had a recent problem with my idle speed.

Idles fine normally and when I let it sit and idle for awhile it will roll up to a fast idle (normal). The problem I have is when I press the brake the idle will drop a few hundred RPM (from 1100 to +/- 950), then run rough and not completely return to base idle( I think it is set at 750). It WILL not return to base idle until I drop it into gear, or switch programs. Sometimes it will do this after a drive and I throw it into park, idle speed will jump up and run rough.

It only seems to do this in a certain program and not in the rest, I have compared programs to see if I could find the issue, but no luck.

Any thoughts?

[cleatus12r]

Which one does it and which ones don't?

[907DAVE]

It does it in 200dd, and doesn't do it in the rest........well I don't know about the hot files, haven't tried any of those yet.:hmmm:

[cleatus12r]

Three things Dave....

Min ICP (IPR) duty cycle at the top of "parameters".

Base PW map in the low ICP/MFD area (WOW, BIG DIFFERENCE)

IPR Duty cycle map in the low ICP ranges.

[907DAVE]

I see what you mean about the Base PW map, but don't quite understand the ICP duty cycle map/ min. parameter issue.

Can you please explain.:matt-roloff:

[907DAVE]

And why only when coming down off of a fast idle?:hmmm:

[soutthpaw]

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

[cleatus12r]

I see what you mean about the Base PW map, but don't quite understand the ICP duty cycle map/ min. parameter issue.

Can you please explain.:matt-roloff:


Well, I don't know for sure.....

But the IPR map is going to at least cause a couple issues. I can't say for sure WHAT will happen with the values you have there but remember how that map needs to be changed just a little bit even with an Adrenaline pump sometimes....

Heck, if you look at the tune I sent you (the one seems to have had an issue with breaking things :whistle1: ) look at the IPR duty cycle near idle......it causes things like near-stalls when coming back down to an idle and a slow recovery back to the correct idle speed.

I don't remember what pump you're using for your HPO, but having a "hard" (parameter set) MINIMUM duty cycle of >9% and commanding a minimum of <11% in the IPR map is very high (for big oil). You are holding a lot of HPO back (not draining). For comparison, your 400DD uses the stock IPR map which must work very well and is bypassing plenty of oil.

You are also running around TWICE the base commanded pulse width in the 200 vs. the 400 in the "idle range". I don't know what the 200 and 400 denote, but if you're using both of those tunes with the same injectors, there are going to be issues.

These are just the differences I saw and the issues that may come of them.

[cleatus12r]

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


Once you get injectors and compounds like Dave has.......:evillol:

[soutthpaw]

Heh, would have to change those lil' thingies in his Avatar pic first... Hoping to do an Adrenaline this summer, Injectors down the road but prob just single shots

[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.:disbelief:

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.:shrug:

[907DAVE]

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

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

Have fun parting it up hardcore with the other mods.:hehe:

[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.:D

[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. :evillol:

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]

:happy-dancing:

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