Engine/Transmission (1998.5 - 2002) What makes 24v H.O motors different?

[darkhorse]

It should be noted that the HO VP44 does generate higher pressure than the SO. That will result in better atomization of the fuel. You get better power & efficiency up to the point where it "tops out". So it would seem that unless you are aiming at more than say, 450 to 500 hp, the HO pump will out preform the SO.

 

[Hohn]

^^^ That is my opinion as well. The higher CR and the higher injection pressure are better, imo, right up until you hit the limits of HG and fueling.

 

[JBAndersen]

Why are SO 98-2000 autos advertised at 215hp and manuals at 235hp? Different ways to measure on auto vs manual? Later HO's are 245hp both auto and stick right?

 

[Hohn]

The manual trannys were the only ones strong enough for the more powerful rating.



The 245hp HOs were only available with the 6-speed trans in 2001-2002. There was no HO before 2001.



Standard SO ratings in 01 and 02 were 235/460 for both manual and automatic. That's the impression I'm under.

 

[tgbol]

Holysmokes

No body answered your question. I see by your signature you have an automatic. You have an SO engine. The HO's came only with 6 speed manuals.

 

[Hohn]

LOL... ... Yes you get the power from the EZ, just not the full potential of any box that taps the pump wire. The rev 29 pump will not work on your truck unless you change out the ECM... ... ... ... ... sorry

What's this "rev 29" pump?



I thought the SO was -027 and HO was -028. What's the 29 used on? And what ECM do you need for it?

 

[justinp20012500]

The HO motor only went in front of the NV5600. So if you have a 5 speed or auto, then you have a SO.

True to a certain extent...



I have a buddy that has a 99 with a SO motor infront of a NV5600.



It was not put in, it came from the factory that way. It even has a 12" clutch instead of the 13" clutch. (Smaller input shaft too)



I really need to get a boost guage on mine new 02. I moved my twins from my 01 auto and put them on my 02 and I can't accelerate past 80 mph because the truck defuels so bad its not even funny. It will pull pretty good up to 2200 rpms, then BAM no more fuel the ecm says!!!



O well, hot rod vp, huge edm's, fire ringed head, redline box w/ez sitting on the bench waiting for me to quite being lazy.



NOw to address the clutch. SBC 38?? DD??? Will that hold that much?

 

[Vaughn MacKenzie]

It should be noted that the HO VP44 does generate higher pressure than the SO. That will result in better atomization of the fuel. You get better power & efficiency up to the point where it "tops out". .

But here's another thought. . . fuel delivery into the cylinder is also faster on the HO, meaning more fuel is there before it lights off. This results in louder clatter (notice how HOs tend to be noisier?) and less efficiency since more fuel lights off in an instant instead of a smooth burn.



In reality I think the HOs & SOs are pretty camparable in MPG, with the SOs possibly having a slight advantage (the best MPG numbers from a 24v I heard of have been SO trucks).



Vaughn

 

[Hohn]

True to a certain extent...



I have a buddy that has a 99 with a SO motor infront of a NV5600.



It was not put in, it came from the factory that way. It even has a 12" clutch instead of the 13" clutch. (Smaller input shaft too)



I really need to get a boost guage on mine new 02. I moved my twins from my 01 auto and put them on my 02 and I can't accelerate past 80 mph because the truck defuels so bad its not even funny. It will pull pretty good up to 2200 rpms, then BAM no more fuel the ecm says!!!



O well, hot rod vp, huge edm's, fire ringed head, redline box w/ez sitting on the bench waiting for me to quite being lazy.



NOw to address the clutch. SBC 38?? DD??? Will that hold that much?

Well, that would be why I said that "the HO motors were only put in front of the 5600", NOT "The 5600 was only offered behind the HO"



So what *I* said was true in an absolute sense. Not "too a certain extent", but to EVERY extent.



Big difference.



It's pretty well known that the 5600 was first offered in '99 and 2000 on a limited basis, then withdrawn, beefed up, then offered to the buying public with the HO engine.

 

[nps]

Well, that would be why I said that "the HO motors were only put in front of the 5600", NOT "The 5600 was only offered behind the HO"

Justin,



Thanks for the defense, however justinp20012500 was quoting me.





justinp20012500,



What Hohn said. The guy was trying to find out if he had a SO or HO, and his sig says he has an auto. Your point?

 

[Texas Diesel]

I also remember something about piston cooling?

They all have oil spray on the botom side but I remember reading somewhere that the HO have a different design. Something to do with oil flow through the piston bottom.

 

[JaMan]

Does anyone know if the injector pop-off pressure is any different on the Ho's or the So injectors? If so what is it?



Jared

 

[Hohn]

The HOs and SOs should have the same popoff pressures. I think the higher pressure associated with the HO comes from the smaller injectors that are fitted.

 

[darkhorse]

The HOs and SOs should have the same popoff pressures. I think the higher pressure associated with the HO comes from the smaller injectors that are fitted.

I'm guessing it's the smaller diameter plunger in the VP44 that makes the higher pressure. Maybe it's both together.