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is there any performance to be gained by doing this? or is the programming different? what exactly makes the SO pump different than an SO pump? It seems like when your SO pump died, you could replace it with an HO unit for an easy horsepower gain
 
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You can swap a SO for a HO and vice versa, but the results are not good. The trucks will run rough and you loose power. As for the injectors I believe the HO injectors have more holes, a different spray pattern, and operate at a lower pop pressure than the SO injectors. Although I am not going to say that is the correct answer.

I know Mkoth or Smokem has went through this on here several times before and if you do a quick search you could probably turn it up fairly easy.
 

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Discussion Starter #3
ok, I just figured that ince it was more or less an eventuality you might as well upgrade while your at it, but since the compression ratio's different on the HO and the SO, it wouldn't owrk right, oh well
 

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HO pumps don't respond as well to electronics as SO pumps...
 

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SO pumps pump more fuel that a HO pump.

All the HRVP44 are built from SO pumps!

Just something to consider... I'm glad to own a SO engine...LOL
 

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It works either way, for low hp ie: small injectors and a 65hp fueling module on a "98-00 the HO pump would benefit, however this is not the case if it were a "01-02. The SO pump uses 7.5mm plungers vs the HO @ 7mm plungers, the advantage of the HO being the pressure and timing advance.
 

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Bouncer said:
As for the injectors I believe the HO injectors have more holes, a different spray pattern, and operate at a lower pop pressure than the SO injectors.
They have the same amount of holes, but I don't know for sure on the spray pattern. The pistons are different so that'd lead me to believe the spray pattern could be different. If they are different, it shouldn't be too different, people use injectors for the SO/ETC in the HO/ETH engines and don't seem.... to have problems.
 

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Smokem said:
Spray pattern and pop-off pressures are the same, hone size is different.
That makes perfect sense, but I still don't see what's giving the HO/ETH pistons so much more compression.

Anyone got a visual comparsion?




Also here's what MKoth posted about the ETH/HO once upon a time:

* Electronic Controls: New ECM calibration and fueling algorithms.
* Fuel Pump: Increased fuel flow in the Bosch VP44 injection pump.
* Injectors: Designed to provide increased fuel flow.
o Injector note posted to the TDRoundtable by tgbol:
+ ETH injectors (3946306) flow 600cc at 100bars for 30 seconds
+ ETC injectors (3944828) flow 640cc at the same test.
* Turbocharger: Revised wastegate setting for 26psi at the turbocharger outlet.
o Manifold boost specification is 43.5 inches Hg / 21 psi
* Head: Valve seat inserts for added durability.
* Pistons: New pistons with higher 17:1 compression ratio.
* Flywheel: New flywheel with 330 mm diameter clutch (vs. std. 310 mm).

The HO pump is limited to around 500-550hp max, and will not gain power by using any injector larger then 150-160hp. They also respond to electronics less.
 
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