New Ram/Cummins vs GM/Duramax on the IKE

FishOnOne wrote:


If this new cummins HP is understated then one can say that about the Duramax used in this test.

Not exactly. There is nothing in the rule books saying that you can report lower power numbers than the SAE test. There is, however, rules stating you cannot advertise above it. We seen this during the 90's and early 2000's when all of the Japanese car makers had a "gentlemen's agreement" not to advertise their cars over 276 hp even though many of their sports cars were making well over that. - Japan Dumps 276-hp Pact


A manufacture can add additional stipulations to their power ratings such as altitude which will lower advertised ratings. There is also the factor that not all turbochargers are alike. Some may loose more power at higher elevations than others depending on their efficiency map. I know Cummins made the HE351VE on the small side specifically to work well in high elevations which reduces max power allowed and is a big restriction for someone at sea level like me, but it is a huge plus for those at live at higher altitude because it is not so laggy and you don't loose as much power. I don't know enough about the PSD or DMAX turbos to comment on them.

FishOnOne wrote:


How could a lower compression engine make the same fuel economy?

By increasing fuel pressure. Higher fuel pressure means greater atomization of fuel for a better/cleaner burn to get more out of each drop of fuel. Basically smaller droplets under pressure will mix with the air better. It also allows you to inject more fuel withing a given amount of time for more power. You are only given a certain amount of time to inject fuel and the higher the pressure you have, the more an open injector can inject within that window. This is why increasing fuel pressure will generally allow you to increase power in a diesel.