4x4ord wrote:
The problem with running a 6.2 gasoline engine at 3200 rpm while cruising down the highway and only making 100 hp is this:
The 3200 rpm is dictating how much air the engine is desiring to pump through it; roughly, 3200rpm x 6.2 liters = about 20,000 liters per min. To make 100 HP the engine can only use roughly 14,000 liters per min so the throttle plate will be run partially closed to restrict the amount of incoming air and therefore fuel .... in a way the throttle plate is performing the job of an exhaust brake, only restricting the intake air instead of the exhaust gas. Ideal for this gas engine would be to slow the engine down more so that it is not working against the throttle plate so hard...it needs more gears.
With the turbo charged diesel engine running at 1600 rpm the turbo will not push an excessive amount of air into the slow running engine but will attempt to ensure there is at least enough air to burn the fuel required to make the necessary HP.
Bottom line is that although 3200 rpm is not necessarily hard on the engine it is hard on the engine's efficiency.
If we're talking about the Corvette cruising 70mph, nowhere near 100hp is necessary. If we're talking about a 6.2L pickup towing, we're all aware of the mileage probabilities. I remember the old F250s with C6 and 4.10 rear ends. They weren't known for efficiency but the 300cid I-6 was known for longevity even with the old technology and inferior oils of that era.
