What is the limit and why????

[CumminsPuller]

Just curious what the limiting factor with the EZ, An Aaken, etc. that you can only get 60-65 HP out of them. Or is it the limiting factor of the truck? The only way to get more out of a box is to tap the pump wire?



Jason

 

[RustyJC]

Any box that doesn't tap the pump wire cannot force the VP44 to deliver any more fuel than the maximum fueling limit programmed into the ECM and VP44 itself. All these boxes do is intercept the fueling command from the ECM to the VP44 and tell the VP44 to deliver more fuel than the ECM is calling for, but the maximum fueling limit programmed into the VP44 can never be exceeded.



Boxes that tap the pump wire take control of the fueling solenoid in the VP44 away from the VP44, so they are not limited by the maximum fuel limit programmed into the VP44. This can be good... or bad.



Rusty

 

[CumminsPuller]

Just getting back to this Rusty... ..... Had to run to Montana on Monday and got back home here early Friday morning. So how does the EZ give us an extra 65hp without tapping the pump wire?



Jason

 

[Sticks]

I think that it both adjusts the timing (starts pushing fuel a microsecond earlier and a microsecond longer than normal), and tricks the VP into flowing the maximum fuel allowed immediately rather than when all the OEM criteria is met.



Or I could be completly wrong, but this is how it was explained to me.

 

[RustyJC]

If you look at the dyno chart for the EZ, it doesn't give 65 more maximum BHP. Rather, it gives 65 (or whatever the advertised number is) more BHP at around 2100 RPM. I think the BHP increase actually seen on the dyno is around 40 peak BHP with the EZ.



Looking at the stock torque curve of, let's say, the ETH (Cummins HO), you'll notice that it reaches a maximum of 505 lb-ft around 1600 RPM and is perfectly flat to (as I recall) around 2500 RPM. This isn't an engine characteristic - it's a "safety" programmed into the ECM by Dodge that controls fueling through this RPM range to protect the clutch, transmission, etc. and to minimize warranty expenses. The EZ overrides this safety by calling for increased fueling and produces a more normal torque curve that peaks around 2100 RPM and then starts falling back toward the stock values as the difference between maximum fueling rate and the stock fueling rate decreases.



This is great for towing, but with the EZ and stock injectors, I could feel a great mid-range "kick" in torque output, then the engine seemed to fall on its face over 2700 RPM. It turns out this is apparently a fuel flow limitation of the stock injectors, as the engine will now pull strongly to 3200 RPM with the EZ and DD2s.



Insofar as the ability to obtain slightly more than peak rated BHP is concerned, the diesels our company builds have fuel systems set up to allow the engine to produce 110% of rated BHP for 2 hours out of each 24 hour day - this is called a DEMA (Diesel Engine Manufacturers' Association) rated engine. In the same manner, the VP-44 is apparently able to provide more fuel at 2700 RPM than is called for by the ECM - the EZ takes advantage of this unused capacity by calling for maximum fueling.



Hope this helps.



Rusty