Engine/Transmission (1998.5 - 2002) Need info on VP44

[JeffWhite]

I have a lot of questions, want to know as much about how the stock

system works as possible before doing any mods. I'm looking at injectors

and/or a box of some sort. First, what things cause the Bosch to de-fuel?

rpms? 2700? over XX boost? how does it defuel and is it a progressive

curve or just a sharp drop off? Am I correct in my assumption that my

wastegate is primarily why I only see 20-21 lbs. boost and that modifying

it for more is of no use until I increase fuel? It will set a code if I do it

without fooling the MAP, right? Does the EZ or Marco ECM address this?

I only get 1000 deg EGT max most of the time, maybe closer to 1100

if I really crowd it on bad hill. I operate at 400-550 feet of elevation.

Marco- am I misunderstanding this- my truck would have to sit in driveway

while my ECM goes to Italy and back? Sorry so many questions, but after

being fully into gas engines and fuel injection/O2 systems it bugs me bad

to love truck so much and understand so little about what makes it tick!

 

[Gary - K7GLD]

It's my understanding that fueling dropoff is controlled be one or more engine sensors as monitored and controlled by the VP-44 - and that fueling dropoff occurs pretty rapidly up close to 3000 rpm. Aftermarket boxes like the Edge Drag Comp apparently alter those sensor inputs, and defeat the defueling. Only basis I have for the above, is that Marco, with his CATCHER ECM modification is unable to change defueling within the ECM itself - at least last I knew...

 

[Beast2B]

The Mad ECM defueling is up in the air right now, I'm trying to determine the same info. Some users say it doesn't defuel (2700rpm is the factory setting), but last I read was that the new ECM did not defeat that setting, it took a fueling box to accomplish that. I would not call the defueling immediate or rapid, my experience is a fairly gradual decrease from ~2700 to ~3000.

The wastegate is two-fold. Mechanically, the wastegate opens/closes to keep boost ~20psi. Electronically, the ECM defuels about the same time to keep boost down. A boost elbow alone will cause an overboost code. The ECM or the EZ eliminate the electronic fueling control, a boost elbow would be required to mechanically alter the signal to the wastegate head.

I went through Bob Wagner for my Mad ECM and paid a core charge to keep my truck running until the ECM arrived. I haven't decided whether I'm gonna keep my stocker for spare, or get my $250 core charge back.