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 Post subject: Does engine compression braking use more gas?
PostPosted: Mon Feb 18, 2008 10:45 pm 
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Does engine compression braking use up more gas? When traveling in the mountains I prefer to shut off my OD when going down hill so I don’t have to brake (as much) and also save my brake pads. But now I’m wondering if I’m decreasing my mpg when I do this?

If I’m doing 50 when I turn off the OD the RPM’s will go up to about 2,500 and I usually won’t let them get past 3,000. However, if I just left everything in D (automatic) the RPM’s will drop down to about 1,000 when I’m braking for a little bit.

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PostPosted: Mon Feb 18, 2008 10:50 pm 
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I'm not sure on this issue if your talking Deisel then yes it has great advantages, But when we talk of Gasoline powered Rides it doesn't matter what you do if your in drive and the engine is ingaged gas will be burned highly. If I'm incorrect I'm sure someone will jump in and verbally spank me. But thats the beauty of deisel is the fuel efficeincy Gas is expensive. Just a fact of life.
Sorry :wink:

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PostPosted: Mon Feb 18, 2008 11:29 pm 
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with an electronic engine, IDK... it may or may not turn off fuel if it sees that the tps is a 0%

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 Post subject: Re: Does engine compression braking use more gas?
PostPosted: Mon Feb 18, 2008 11:36 pm 
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scoobysnax wrote:
Does engine compression braking use up more gas? When traveling in the mountains I prefer to shut off my OD when going down hill so I don’t have to brake (as much) and also save my brake pads. But now I’m wondering if I’m decreasing my mpg when I do this?

If I’m doing 50 when I turn off the OD the RPM’s will go up to about 2,500 and I usually won’t let them get past 3,000. However, if I just left everything in D (automatic) the RPM’s will drop down to about 1,000 when I’m braking for a little bit.
No,the fuel is shut off until you level off or press on the gas pedal.


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 Post subject: Re: Does engine compression braking use more gas?
PostPosted: Mon Dec 08, 2008 2:31 am 
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tjkj2002 wrote:
scoobysnax wrote:
Does engine compression braking use up more gas? When traveling in the mountains I prefer to shut off my OD when going down hill so I don’t have to brake (as much) and also save my brake pads. But now I’m wondering if I’m decreasing my mpg when I do this?

If I’m doing 50 when I turn off the OD the RPM’s will go up to about 2,500 and I usually won’t let them get past 3,000. However, if I just left everything in D (automatic) the RPM’s will drop down to about 1,000 when I’m braking for a little bit.
No,the fuel is shut off until you level off or press on the gas pedal.


is this on the gas 3.7? off as in completely like some VWs?

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 Post subject:
PostPosted: Thu Jan 01, 2009 3:33 pm 
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Well, In my '03, When engine breaking down steep hills... the Evic shows the MPG as going down to 14-15 most of the time. It goes up to 99 if I throw it in N and just use my brakes.


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 Post subject: Re: Does engine compression braking use more gas?
PostPosted: Thu Jan 01, 2009 7:07 pm 
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tjkj2002 wrote:
scoobysnax wrote:
Does engine compression braking use up more gas? When traveling in the mountains I prefer to shut off my OD when going down hill so I don’t have to brake (as much) and also save my brake pads. But now I’m wondering if I’m decreasing my mpg when I do this?

If I’m doing 50 when I turn off the OD the RPM’s will go up to about 2,500 and I usually won’t let them get past 3,000. However, if I just left everything in D (automatic) the RPM’s will drop down to about 1,000 when I’m braking for a little bit.
No,the fuel is shut off until you level off or press on the gas pedal.


Yes, this is correct. If you are going downhill and shift to a lower gear - like if you lock out O/D you get DFCO......or Deceleration Fuel Cut Off - so no fuel is being used during that time. Both my EVIC and Scangage confirm this.

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 Post subject:
PostPosted: Thu Jan 01, 2009 10:57 pm 
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Robocody wrote:
Well, In my '03, When engine breaking down steep hills... the Evic shows the MPG as going down to 14-15 most of the time. It goes up to 99 if I throw it in N and just use my brakes.
You are using more gas in "N" and using your brakes on steep down grades,not to mention frying your brakes,then downshifting and letting the engine slow you down by using compression braking which uses no gas at all(and is much safer).


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 Post subject:
PostPosted: Sat Jan 03, 2009 11:49 am 
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Wow, That's good to know, Thanks.


Do I HAVE to shift into a lower gear before the gas is shut off to the engine? Many my problem is that when I tested it, I left in in OD...


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 Post subject:
PostPosted: Sat Jan 03, 2009 9:36 pm 
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Robocody wrote:
Wow, That's good to know, Thanks.


Do I HAVE to shift into a lower gear before the gas is shut off to the engine? Many my problem is that when I tested it, I left in in OD...
Yep it works better if you just push the O/D lock out switch on the trans shifter and lock out O/D.


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