Caterpillar C-18 RPM Operating Range

[lwaugaman]

Hi All, I have a pair of C-18 Acerts in my 2009 Grand Banks Aleutian 72'. We like running at 8.5-10 kts, for several reasons - we prefer the relaxed ride and also the fuel economy. To achieve this, we run the mains between 1000-1100rpm's. Every few hours I run @ 1800-2000rpm's for 20-30 minutes to exercise the turbos.

During a recent search of the CAT website it shows the operating range as 1800-2300rpm. My question; am I damaging anything by running at such low rpm's?

Thanks!

Lou

[skipperpete]

Cat run the C18 in gensets at either 1500 or 1800 so maybe.... just maybe its ok since you do a full noise burst every few hours. Cat guys refer to long periods of light load low rpm use as wet stacking but it sounds like you’re not in that category. Maybe look up “Adept ape” on youtube, he’s a dedicated cat mechanic and you’ll get trusted (and boring) info from a real pro on the C18 ACERTS

[thesaltytar]

We run two C-18s in parallel for power demands, so we're always at 1800 RPMs. That said sometimes the load is light, which may put us in the same ballpark as what you are asking. I will send an email to one of our techs and get their opinion. I have a good idea what his follow up will be, so I will ask you first.

Remember this isn't about RPM as much as engine loading, which is a product of your displacement, your prop pitch, and yes also your revolutions. An easy way to determine engine load is fuel consumption.

- What fuel do you consume for an hour at cruising speed for both engines?
- What is your typical oil consumption per engine?
- Has this changed appreciably?
- How many hours have you been running under these conditions?

Increase in oil consumption could indicate cylinder glazing, for example. A quick visual check behind the air filter would let you know how the turbo is doing, such as if a lot of soot is going out your exhaust, but I am also thinking you might have noticed this more directly by now if it were the case.

I consider a bit of smoke to be normal if you blow out the exhaust by increasing revs for a short while as you report doing, but then it should also clear up. Our main engine does that, but it's a slobbery beast (old EMD).

[rslifkin]

If they're coming up to temp at low RPM and not loading up (which would be seen as excess smoke when you power up for a high load run), I wouldn't worry about it.

Most modern electronic diesels do pretty well under light load (as long as they're not actually idling). The higher RPM / heavier load run every few hours should be plenty to keep things cleaned out.

[Lepke]

When Cat still supplied truck engines, C-18s and other engines often idled for many hours, even days.