Stange Volvo d12 behavior...

2005 Volvo d12 VN day cab
Computer set at 400 hp
3.73 gears
10 speed
Blixxton power box

Trying to figure out something about this truck. When loaded 75000 pounds it it runs and pulls pretty #### good. But when I pull with a empty flat the truck does not have as much power as it does loaded.

Fuel mileage is great and everything checks out. I am starting to wonder if there isn't some parameter to govern power when there is load on it? The truck use to be a fleet truck with the speed limited to 65mph 1600 max rpm etc. but have been removed since.

 

That would make sense. I have been trying to get VCADS loaded on my computer hopefully this week then I can check it.

 

Well, found out that a couple exhaust manifold gaskets were leaking. Bought new ones, got home to install them and right away noticed a huge improvement obviously... found that "kick" when accelerating now. I actually had to turn down the setting on my blixxton today as it is too much.