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Old 04-16-2020, 05:13 PM   #4 (permalink)
Aero Wannabe
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Join Date: Dec 2007
Location: NW Colo
Posts: 718

TDi - '04 VW Golf
90 day: 50.21 mpg (US)
Thanks: 690
Thanked 209 Times in 162 Posts
E-On Coasting

In the TDI I use E-On Coasting because the Engine stays On and it seems to glide forever (for eons). Most of my trips are on 2 lane highways with other traffic so extreme Pulse and Glide would be rude at best and possibly dangerous with other cars around. I tend to drive at a steady state, usually a few mph below the posted speed limit if there are no other vehicles behind me. (Base Specific Fuel Consumption BSFC in this engine is around 1,800 rpm so driving closest to that rpm in 5th gear on flat roads is very efficient) However, I find I can get very good mpg numbers in rolling gentle hills and when coming into a town with lower speed limits by anticipating the road ahead and using an extended coast to the lower speed limits. If the road is wide open I will accelerate at the top of the hill and slip the gearshift into neutral and coast while getting between 350-400 mpg. This extends my coast times to at least 30 seconds or more which makes it more worthwhile.

DFCO- Deceleration Fuel Cut-Off. On the TDI the computer injects no fuel while engine braking. Mileage on the ScanGuage goes to 9999 or infinity. So why not do this all the time? The short answer is that it is going to slow the car down much faster than coasting in neutral. The trade off for using no fuel while engine braking is that you will use much more fuel in the long run, to get the car back up to speed. Should you use DFCO? Absolutely, but under the right circumstances. On long downhills where you would pick up too much speed? Yes! In fact I run the A/C full blast in the summer while engine braking to keep me cool and try to keep slowed down, or front and rear defrosters on high in winter. (Remember that part about diesels having no throttle plate? They don't engine brake the same as a gasoline engine. Now you know why semi trucks have a Jake Brake to create backpressure for engine braking) I use DFCO coming into stop signs and red lights. Otherwise, drive a little slower and coast, coast, coast on rolling terrain.
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun

Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 04-24-2020 at 06:45 PM..
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