As many of you know, Stinky is having a bad hair day and I'm looking at every nuance of his operation. I suspect something, but I don't have a frame of reference to work off of (oddly enough for me). Since I installed single-shot injectors, I expected my oil demand to drop - but I don't know by how much or if it will even register a difference at idle. To seek out a reference to work from, I'm asking the members with AE and single-shot injectors here:

If everything on your truck is dialed in and running good, what is your ICP and ICP DC (IPR%) at idle?

 

AC Codes w/stock nozzles. Idling ICP right around 500psi and DC about 8% at operating temp.

My injectors have 50k miles on them and 'stock' HPOP has over 200k miles.

Fwiw, at WOT I see a steady 2400-2500psi and DC never exceeds 40%.

Here ya go:

 

160 cc 30% nozzles. ICP 475...DC 6.64. Pretty dialed in, but still a couple issues.

Rich email sent.

 

Sorry, I have splits in all my trucks....

Did the replacement injector arrive yet?

 

It's in, but I have so much air in my oil that it's impossible to tell if I fixed it or not before I get a few miles on it. I was running with the VC off and I could see a lot of bubbles in the oil, but #1 is spewing oil pretty strong now. I'm just watching my IPR and it is so different from the old IPR numbers... I don't know if they're good or bad. Sure, I have ICP numbers to tell me what the HPOP is doing... but I'm not sure I trust the sensor.

 

If you want to double check the ICP conversion value then select ICP voltage and use the look up table. Here you go....

 

ICP can be all over the place and DC will tend to be high with air in the oil.

 

Thank you for that.

I don't have a separate pressure gauge to measure my ICP, but I finally stumbled onto something interesting in the library:

• If RPM is unstable, disconnect the ICP sensor.
• If the RPM stays unstable, IRP is suspect.
• If the RPM smoothes out, ICP sensor is suspect.
• Pulling the ICP plug defaults to 725 PSI on a stock engine.

The manual doesn't state if the ICP reading "says" 725 when unplugged, or if the IPR is defaulted to what would make 725 PSI, but my modified and tuned truck does not say 725 PSI the last time I pulled the ICP connector. I'll try it again the next time I work on the truck.

This procedure is said to address fluctuating RPM, but I don't know about other symptoms.

 

Kinda both....
Page 5-42 of the PC/ED manual that I attached earlier says that the PCM will go to open loop control and estimate the pressure. So, with the ICP sensor unplugged, the voltage reading should be zero while the IC pressure as reported by AE will be an estimated value. In short, the IPR duty cycle will be set at a percentage that should provide around 725 psi....a value that could be checked with a mechanical gauge connected to one of the oil port gallery plugs. If you drive the vehicle with the ICP unplugged then the reported pressure will change value according to the PCM's estimated figure.

It's fairly common to have at least two general states of operation when it comes to engine/power train management. Open Loop and Closed Loop. Basically what Open Loop means is the PCM commands an action via a regulator or solenoid(relay) and does not validate the results. Closed Loop means the PCM validates the results via a sensor of some kind and then continually makes adjustments to the commands to obtain the desired effect. From time to time the PCM will also verify if the sensors are working properly, either by adjusting the regulator command (and then watching for a corresponding change in the sensor reading) or measuring sensor voltage or even a 'ping' in the VREF signal. If the ICP sensor is unplugged, then IC pressure control will switch over to Open Loop and attempt to keep the engine running.

So, when working with AE, it's important to understand if the system is in Open or Closed Loop. There is a green dot on the display screen that is supposed to change to yellow or red if any system goes Open Loop when not expected.

To further complicate matters....
Some tuners and programmers will make changes to the look up tables or what I think is called 'transfer function'. At times that can be problematic because then Open Loop operation may be adversely affected. I always had to remove my Bully Dog stuff whenever I was using AE to diagnose most anything because some of the values were haywire. So far I have not discovered any issues with PHP calibrations as the transfer functions seem to be correct (as near as I can tell anyway...). I have not data logged any other brands of custom tuners so I can't really comment on what effects those may have (if any).

 

"Spewing oil pretty strong" is excellent news! If the new injector is in, and there is nothing obviously wrong except some air in the oil, I'd button it up and drive it around to work it out faster. I see no value in any AE numbers until the air is worked out. Get 'er rolling and blast onto a few freeway onramps, see if you can blow off a boot. Then see how she feels at idle and get your measurements.

 

SSJ: I am curious about your AC injectors with stock nozzles and will PM re same.

 

I'm glad its running. I feel you mit have a little remorse on the single shots. Button on and drive a while. You'll be fine. Keep track of MPG on your trip, that I'd like to see. 160/100's and the power you have, can't wait. Somewhere on the middle of the trip, hook up the AE and give it a good look. There's not to many guys on here that do that without a problem first. You should get so good number to compare.

Chet

 

1. Open loop - closed loop: I'll remember that! Thank you for taking the time to explain it. I feel all warm and fuzzy when I can get my head around what's going on in there.
2. I ignore many of the readings until the air gets worked out... for the reasons you suggest. It's still worth mentioning for any newb that may happen on this thread with a search.
3. The fuel economy stayed the same right after the initial set went in... no change at all. My overhead went kaberzerky though - about 10 MPG over hand-calculated. All I have to do is subtract 10 and it still works about as well as before.
4. Drive... Yup. Now that everything is buttoned up, Stinky's in for it.

A little something extra for those who chose to chime in... one way to say "thanks":

 

That is quite interesting. For comparison's sake, my overhead data actually improved when I installed the new (rebuilt) set of injectors. As best as I can tell so far, the fuel economy on the display is about 1 mpg higher than my hand calculated figures. Kinda early to tell for certain though....I need to burn through a few more fuel loads to get a better sample of data....

Of course you switched to 160cc singles where I simply remained with the original type of split shot so it's reasonable to expect your overhead to get very confused. Almost like giving Mydol to a dude...

 

Here's a good visual of the PCM-IPR-ICP closed loop signal/regulator/sensor operation.

The Pulse With Command regulates the IPR duty cycle.