diesel truck help can't decide what to get

[hudr]

I understand the diesel having no intake control. Hence the vacuum pump (no buterfly valve, no vacuum) on a lot of diesels. Here is my hypothesis, I may be wrong, but hey [img]/forums/images/icons/grin.gif[/img]
Foot comes off throttle, pump goes to idle as far as fuel delivery, piston comes up against compression, no fuel to support increased burn so lots smaller fire, no acceleration. next piston comes up against compression, and so on and so on.
Just seem from my experience w/ diesel p/u (I started w/ a 5.7 chevy) that they slow down faster than their gas powered counterparts. Just an observation from having driven both engine types. Like I said in my earlier post, my P/U (6.5TD manual) slows down faster than my Brother In Law's P/U (6.5TD automatic) and I am sure it has something to do w/ the manual vs. auto BUT my P/U also coasts LESS than my gas powered suburban (auto) and less than my gas powered Bronco (manual). Maybe there are other forces at work here, but like I said that is just my seat of the pants, non-scientific observation/opinion. And you know what they say about opinions [img]/forums/images/icons/grin.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I drove the GM early diesels from day one, and those cars and pickups definitely did coast more than their gasoline-powered counterparts. A lot of what seems like engine braking is actually due to various parasitic loads both on the engine and in the drive train. Things like compressors, oil pumps, and vacuum pumps; it all takes HP to run and it does help slow the vehicle. I used to play the "no brakes" game in the mountains and use the air conditioning system as a grade retarder. I only cut in the compressor on downgrades so I got "free" air conditioning. [img]/forums/images/icons/crazy.gif[/img] PAT....did you know that before the advent of the Jacobs system the logging trucks had 11-inch brakes, two fifty-gallon barrels of water to drip onto the brake drums, and a lot of really nervous drivers? When those trucks went down a very long downgrade, the air through the engine often cooled it so much that if would not fire the fuel when the throttle was opened for the next upgrade. [img]/forums/images/icons/tongue.gif[/img]

[Pat]

hudr, I am at a loss to explain your experience.

As regards the effort that is required to push the piston up on the compression stroke. You get that back (minus frictional losses) when the piston comes back down on the power stroke. This is true even if ALL fuel is cut off, not just reduced as in coasting.

All I can say is that in my experience, your experience is unique. I have never known of a normally aspirated gasolline engine of equivalent displacement that would out coast a diesel. Goes back to my comment about exhaust brakes being offered from several manufacturers for diesel application but I have never heard of one for a gas engine. The reason is... diesels don't have significant engine braking without an exhaust brake (or jake brake.)

[img]/forums/images/icons/smile.gif[/img] PaT [img]/forums/images/icons/smile.gif[/img]