Is it the restricted intake? The restricted exhaust? or both?
The torque is the same.

 

Probably the intake due to the cramped conditions.

 

I'll go with Jimmy and say it's the intake and I'll add my theory of the slightly increased length of the exhaust. The engineers only lost 5 hp, could have been worse.

-Kerry

 

My experience is with the van 350 and 450 diesel powered ambulances....

I came across the same thing when comparing the van to the truck numbers. It aparently comes down to airflow, but not as the intake is concerned. From what I was told (forget the source right now), it has to do with the cooling. The airflow is less efficient at cooling the motor and making its way through under the hood. This being so, the motor is "turned down" via the computer.

If anyone can prove me wrong, please do so, but I thought it made sense..

 

It could be that. Engine ratings used to be done on a stand, and now are more accurate because they must be done mounted in the actual vehicle. Any number of things could account for the difference.

 

The torque is the same (I believe). I wonder what effect cooling has on torque?

 

The same as it does HP. This is why I stand by my statement of the intake air tube being more restrictive.
Similar to the late 90's Trans Am's vs Camaro's. The Camaro's had 5 more HP becuase the air intake was more restrictive on the T/A due to the hood clearance.

 

My dad's E150 had a football shaped baffle in the airbox that I've never seen on an f series. Granted, this was a 351, so the 5.4's might have a diff. setup. It came out easily and made a noticealbe diff. in acceleration (and noise). do the 5.4's have it?

 

I was reading a Ford magazine they put out for their salespeople at the dealership a few days ago, and it explained the reduced power of the diesel was due to "different" (afraid to say "less") grill area / airflow available. Sounds like a bit of de-tuning to keep it cool. This type of de-tuning would affect HP more than torque I would think, it would be at the higher RPM.