'03 HO vs. SO question

[Rosco]

As alot of you know I been privelaged enough to have owned a '03 SO and HO and I have a question for the few others who also have shared this experience.



Do you feel that the HO is louder than the SO. I think mine is louder in the respect that it seems to "rattle" more than my SO did. Do you think this has to do with a different injection process or is it something else. The "rattle" is more pronounced under light throttle as WOT acceleration sounds about the same as my SO. It's not that I dislike the noise I am just curious as to why their is a difference.

 

[mr plow]

just a guess...

my y2k got louder when i added a pnp to it. the ho is different than the so by programming, and cooled pistons being the bigger differences, right? that said, i would speculate that more fuel and changed timing would probably contribute to more noise, at least it did on my y2k.



??????????

 

[Steve M]

I can hear my SO change it's tune if I'm getting on it to blend in with interstate traffic. It sounds like my '01. 5 did when it was changing it's timing according to rpm load. Almost like it's pinging. The '03 is just quieter about it. My '03 does the same thing but it must be changing timing electronically as it fires the injectors instead of advancing or retarding the VP44. The HO/48RE I drove did the same thing but it did seem to be a tad louder than mine. It only had 32 miles on it. Mine is at 4500 now. My two 12v trucks didn't do this but if memory serves, timing is fixed in the P7100 pump?

I thought all Cummins engines had piston cooling nozzles aimed at the bottom of the pistons. Back in '92 that was an issue with Wix filters clogging them up an causing catastrophic engine failure. Then it was Fram causing the same heartache.