Low rail pressure

[cerberusiam]

So if you where WOT at 2000 rpms, on you 03 with stock tuning) it would want 15954 psi. 50% throttle would be approx 70mm3 or 50% load.

John, my understanding is the left legend is engine load not APPS reading. Engine load is calculated based on environmental factors so WOT may be 100% or it may 60% depending on those factors. APPS and load are rarely the same.

The concpet is a table driven solution so only tables need updated. Parameters are used to look up values based on the conditions at that particular time to derive timing, pressure, duration etc. It inerpolates the signals and finds the closest match to the table value and uses it.

Pretty basic stuff.

 

[AH64ID]

John, my understanding is the left legend is engine load not APPS reading. Engine load is calculated based on environmental factors so WOT may be 100% or it may 60% depending on those factors. APPS and load are rarely the same.

Correct, it's just easier to explain as WOT being max load, as it generally is with a Smarty. But below WOT you are absolutely correct, 50% throttle at 1200 rpms may be 75% load, but 10% load at 2800 rpms.

Smarty UDC talks about load, but also says to think of it at throttle position for explanation terms.

Personally I find it easiest to tune with UDC if the truck has a OBDII gauge that displays load.

 

[cerberusiam]

That is interesting that engine load goes 100% at WOT with Smarty. My son and I have AutoEnginuity to do the logging but we spend hours wrapped in all the features and have not had time to log the vitals yet. I will have to check that on the stock and tuned runs the next time I get a chance.

Almost never think of the APPS as anything other than an input to a calculation anymore so was just making sure I understood what you were saying.

 

[AH64ID]

A stock truck, 04.5-07, will only go to ~94% load. Stock tables go to 140mm3, but fueling is limited to 132mm3. SW1 will stay at ~94%, SW3 to ~97, SW5 and up is 100%. Now at low and high rpms the load is different that WOT, but for the most part the boost:fuel limiting table lets full fuel happen easily, unlike stock.

I don't know how high a stock 03-04 will go, but they only go to ~67% on a tunes truck. It has something to do with the ECM.