Vk45de and vk56de

[lebanesepathy]

Something confuses me about these engines, how come the way smaller displacment produces much higher horse power. Talking about 340 vs 310. And why use the 5.6 in the first place ? Is the higher torque really that important ?

[smj999smj]

When you are talking about a 4000+ pound truck which may be used for towing, "yes," higher torque IS that important!

[skinny2]

The power curve peaks considerably lower on the 5.6L as well. It has about the same torque at 2,500rpm as the 4.5L at 4,000rpm.

[smj999smj]

Sometimes it's just a matter of cost to manufacture or a matter of a particular design being better when it comes to passing emission standards. For example, the SR-series is a fantastic, 4-cyl. engine, so why replace it with the QR-series, which has shown to be less reliable and have less performance potential? The cost of manufacturing for the QR is a lot less. The bottom line has a lot to do with the decisions manufacturers make.