Cat C15 vs. C16 - found a horsepower stat that blew my mind

I was digging through old Caterpillar service bulletins last night, just killing time in the shop. Found a spec sheet from 2007 comparing the C15 and C16. The C15 maxes out at 625 horsepower from a 15.2 liter block. The C16 is only 0.6 liters bigger at 15.8 liters, but it cranks out 575 horsepower max. That's 50 less horses from a bigger engine. I always thought the C16 was the stronger motor, but the numbers say otherwise. Both are 6 cylinder, both use the same HEUI fuel system. So what gives with the lower rating on the C16? Was it a reliability thing or did they just never tune it right? Anyone else got old Cat power data that tells a different story from what you assumed?

3 comments

3 Comments

uma_nguyen241mo agoTop Commenter

Hmm, actually I think the C16 was rated higher in torque, not horsepower, so it had more grunt for pulling even if the peak HP was lower.

noah_webb9h ago

Yeah but even then the torque curve on the C16 was pretty peaky. I've seen dyno sheets where it makes decent grunt right off idle but falls off hard above 1800 rpm, while the comparable Cummins or Detroit would hold flat torque for another 500 rpm. That matters more for actual pulling than a single peak number. Also the C16's torque peak was at like 1400 rpm which is fine for heavy haul but terrible if you need to run at highway speeds with any kind of load variability. They tuned it for a very specific niche and it showed.

the_oscar1mo ago

Funny you mention that, I ran into the same thing with a couple Detroit diesels a few years back. Turned out the "weaker" one just had a more conservative tune from the factory (like they kept it under 600 for emissions or something). Could be Cat did the same with the C16 to keep it reliable for certain trucking applications.