Some info I've saved over time from TDR

Timing the VP44 Fuel Injection Pump

The Cummins 24-valve engine was designed to meet

the tighter EPA federal emissions regulations of January

1998. An essential feature of this engine was the use of

electronically-controlled fueling events. The Bosch VP-

44 injection pump (see Figure 10) was already in use in

Europe for smaller engines, and was fully electronically

controlled with regard to injection timing and fuel quantity.

This pump delivers fuel at high pressure (1000 bar or

14,500 psi), almost as high as the P7100, to assist in

meeting emissions requirements. The size, weight, and

cost of the pump are much lower than the P7100, more

like the VE pump. However, the new VP44 pump differs in

several important respects from the older pump. In order

to develop the higher pressure it produces, it uses three

radial pistons to pressurize fuel instead of one axial piston.

While the engine mechanically rotates the pump, as with a

VE pump, the fueling commands are all performed via onboard

computer (fuel pump control module). While there

are different Woodruff keys for the VP44 pump shaft, you

cannot advance the pump timing with them. The computer

will normalize the timing to specification.

As soon as the 24-valve Cummins engine appeared

with our Turbo Diesels, in January 1998, some owners

of the new version of the Cummins B series engine

began complaining that they wanted more power.

Several aftermarket companies addressed the problem

and found that electronic solutions were the most

straightforward to develop and install. Some of the

power-adding products also added timing advance. The

VP44 injection pump is mechanical but is surrounded

by three computers. First is the Dodge computer on the

firewall, second is the engine electronic control module

(ECM) on the driver’s side of the engine, and third is

a computer on the top of the VP44 pump itself. The

ECM has proprietary software controlling the fueling

parameters, and the fueling commands are sent to

the VP44 computer through CAN-BUS communication

protocols.

The electronic enhancements made by

aftermarket firms have used one or more of the four

techniques listed below:

1. Intercept the CAN-BUS communications to the VP44

computer at the multi-connector that plugs into the

pump. This process entails unplugging the connection,

and putting in a Y-connector that goes to the aftermarket

“black box” computer. This add-on computer then

replaces some commands from the ECM with new

ones. One brand (example) that uses this technology

is the BD Plug-n-Power.

2. Add new instructions along the CAN-BUS using the data

link/diagnostic connector at the engine wiring harness.

This connector is used by Dodge and Cummins

technicians to access the ECM for engine diagnosis,

and to reprogram the ECM. The Edge Products EZ

box uses this system, and their Competition Box uses

both this technique and Technique #3.

3. Intercept the fueling signal coming out of the VP44

computer that holds the fuel solenoid of the pump

closed. This signal determines the time duration that

high pressure fuel is available to the injection line

and injector. The insulation of this wire is pierced

by a Scotch-Lok or similar connector so the addon

aftermarket computer box can receive this signal

and add another immediately afterwards to hold

the solenoid closed longer. The percentage of the

original signal’s time duration that is added to it by the

aftermarket computer box will determine the power

increase. This technique was introduced by Blue Chip,

then followed by a similar approach from TST, and later

Edge Products.

4. Reprogramming the ECM fueling and/or timing advance

curves.

Techniques 1, 2 and 3 require an additional wiring harness

to the manifold absolute pressure (MAP) sensor on the

side of the cylinder head at the intake plenum, if they

are to provide large power (fueling) increases. The ECM

generates defueling commands when turbocharger boost

goes too high (reportedly, over 20.5 psi). The aftermarket

computer harness puts a Y-connection into this harness

at the MAP sensor. The box intercepts the boost signal

and replaces the signal going to the ECM with an adjusted

voltage that indicates to the ECM that boost is within the

acceptable range, even when higher boost is actually

present. In this way, sufficient boost becomes available to

burn the additional fuel efficiently.

Add-on “boxes” that use Technique 3 take the engine rpm

and ECM-generated fueling level signals from the pump

wire. Boxes that receive CAN-BUS signals, including the

Edge Comp box that uses both Techniques 2 and 3, take

rpm and fueling commands from signals along the CANBUS.

Electronic power enhancement “boxes” that also add timing

include, among others, the Edge Mileage Max and the Juice

module with Attitude gauge and control readout box.

The Smarty programmer gives the option of adding timing

in its re-program of the ECM (Technique 4).

Well I can give you this much for food. Weather around here jumped up to about 85-95*F and I unplugged my rheostat on the IAT and hooked up the IAT sensor again to play with ideas. My last trip to Boise, ID I pulled 24.5 MPG round trip with hot weather. Then today I had a take trip up to Donnelly, ID weather was cold 44*F and light raining off and on. Well the rain pretty much stopped and still the weather continued to be cold 44-48*F most of the day. My MPG now fell from 24.5 from the Boise trip to 20.5 on today's trip. Cold air tend to degrade MPG's when using the IAT... Time to get my switch built...

hmmmm, Rheostat on the IAT? Could you expand on this? I am also looking to increase the economy of my truck, so this might be something I would like to do. Also Thank You for the Site. Great informatation

Ummm... Product will be out very very soon... http://www.dieselautopower.com/product_p/high-idle-switch-98-02-cubby.htm