Hannibal wrote:
I agree with you 4x4ord but what's wrong with a gas engine running 3200rpm? Back before O/D was implemented not for towing or the faint of heart but instead for CAFE requirements, we used to run 3k~ rpm or more everywhere we went on the interstates. 3k rpm is nothing for those run forever 4cyl Hondas and Toyotas. My '98 12v 5spd/4.10 Cummins used to run 2500rpm at 70mph towing or not. 74mph was against the governor and that was all it could do. Didn't and won't hurt a thing. Higher rpm puts less stress on the engine, not more. Turbo chargers force more air into the engine increasing the compression ratio which makes more torque. That's a good thing. They also allow rpmaphobes to lug their engines when higher rpm would be better for the engine.
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.
