Standard Cummins vs. HO Cummins ?

[4xquadrod]

Aside from the hp and torque differences, what mechanically is different. Is it just electronic tuning or what?

 

[David Muench]

You know, this would be an excellent question for Carlton. . Even if he couldn't answer it himself, maybe he knows someone who can. There's been a lot of speculation on the 03 engines, but no one has said authoritatively if it's just ECM or if there's physical changes.



I'm going to PM him to take a look at this thread. .

 

[Greg Boardman-RIP]

ECM programming only.

 

[Badunit]

It's more than ECM programming. The HO has oil galleries in the pistons that the non-HO does not. There may be other differences as well.

 

[Greg Boardman-RIP]

If we are talking 2003, I think that the engineers said that it was a programming change. Thats it

 

[Badunit]

Straight from the '03 factory service manual: "high horsepower pistons are gallery cooled and utilize J-jet piston cooling nozzles". The TDR magazine (one of the latest issues) has similar information on the pistons.



Who are "the engineers" and where are they getting their information? They contradict the service manual.

 

[OHale]

There is a 50 pound difference between the HO and SO. Where those fifty pounds are (other than pistons) beats me.



Dry engine weight HO: 1083

Dry engine weight SO: 1033



Compression is the same for the engines.



This is from a Dodge 2003 Dodge Truck Drivelines Engines sheet my local dealer copied for me.

 

[David Muench]

This is exactly why I am hoping we can get an answer from Carlton or one of his coworkers. .

 

[REndres]

As per cummins.com--- New software,fuel pump components and injectors for increased fuel delivery. New design pistons for higher 17:1 comp. ratio. Powdered metal valve seat inserts for improved durability. Larger flywheel for larger clutch.

 

[David Muench]

Is that specifically about the 2003's on cummins.com? Because that sounds more like the 2nd gen HO's.

 

[OHale]

I have the same question David has, because the 2003 spec sheet the dealer gave me says the HO compression is the same as the SO, FWIW.

 

[David Muench]

I asked Carlton this question in a PM, and hopefully he won't mind if I post the answer here (if you do Carlton, let me know). He said the only differences are the piston cooling and the flywheel. I have to assume that's in addition to the ECM.



I'd further speculate (this is just me guessing though) that the pistons are the same in both engines, the HO just has the addition of the J jets to spray them with oil. Since the compression ratios are the same, I don't see how it would be cost effective to engineer and produce 2 different pistion designs when one would work fine in both engines.



One could further speculate that if the need arose, those J jets could just be bolted on to the SO block...

 

[REndres]

I assumed original ? was in general and not specific to 03. For 03 they do mention HO has beefed up components including pistons to handle more power.

No xpert here just gathering info before I buy.

 

[Dean Upson]

This is from an email I got from Cummins today.

"Summary: ram isb 2003 250 vs. 305 hp



Solution:

Probably not a lot of difference, but there are some differences which preclude those with 250 hp from approve uprates. The HO engine has different (more premium) piston material and also a different style of piston cooling nozzle which also provides more oil cooling to the piston crown. "



Dean

 

[OHale]

Thanks, Dean.



I've had the dealers here in Maine where the HO is banned and the SO de-rated to 235hp tell me, "well, you could buy one here (SO 235hp) and 'up the power'," with a wink-wink. I always say to them, 'and you'll warranty that?' That is another story apparently.

 

[Dean Upson]

OHale,



From what has been posted on this thread it would seem that the SO is "close but no cigar". I think that is like being "almost pregnant". Many of the salespeople haven't a clue as to whats inside the truck. What is really criminal is when convince some poor devil that the truck he is looking at will "pull anything". The RV dealers are worse, when they tell a guy that his 1500 will pull a 12,000 fifth wheel. I'd run away from ole wink-wink as fast as I could.



Dean

 

[OHale]

Well said, Dean,



On the flip side of towing pitches, the same sales manager said I really didn't need the HO or even the non-detuned version of the SO unless I intended to pull over 10,000 pounds on a regular basis.



I am finally old enough that (I think) I'm immune to the old 'wink. '



I remember this dealership was sweating last year when they got the word they would never have HOs, but they have been selling lots of CA emission SOs. I have the feeling that, like you said, the customers have no idea what is being sold in the other 47 states. I think the SO would be a fine truck for a particular person but for $600 more I wouldn't go any other way.



Good old TDR forums. A great source of information.