Engine/Transmission (1998.5 - 2002) Adding timing to HO engine

[KLockliear]

actually I lost a lot of bottom end when I switched to the SO pump, but now that I have the 275's and the EZ, I gained it back and have more top end to boot. I made the swap though cause my old VP was going out, and I have plans for over 500hp someday.



Darkhorse, your exactly right, its got bigger plungers than a HO, so it pushes more fuel, but it does so at a lower pressure, so i've been told anyways. I just wasn't sure if the module on the pump itself controlled timing or if the engine ecu did.



So in other words, the module on the inj. pump is basically just a "middle man", right? It makes the pump do what the engine ecu tells it too.

That's because even though the plungers are larger in the SO pump, the cam ring isn't as aggressive. The hot ticket is to add a SO rotor head and plungers to a HO pump with HO cam ring. About 40rwhp.

 

[blacksheepdiesel]

Keith,

Would that make it the famed "hot rod" pump?

Godspeed,
Trent

 

[KLockliear]

Keith,



Would that make it the famed "hot rod" pump?



Godspeed,

Trent

Nope, the SO plunger size was ~10% smaller than the DD HRVP44 plunger. :-laf

 

[Jdonoghue]

So in other words, the module on the inj. pump is basically just a "middle man", right? It makes the pump do what the engine ecu tells it too.

Correct. The engine ecu sends it a message containing a timing value and a fueling value. The PSG (pump module) takes those numbers and does what's necessary to obtain them. I have yet to 'decode' the fuel part of the message. I don't think it's as simple as an encoded form of mm3/stroke, though. Time will tell... .

 

[darkhorse]

Thanks to the last few posts,I just learned several new things about the amazing but finicky VP44

 

[Jdonoghue]

Update

Well, I've been running around with a 1* advance in timing for a couple of days now, I'll have to wait and see if it does anything for my fuel economy...