MPG - E450 - four summers

A few years back I installed a Scanguage on our 2007 E350 with V10.  I find it very interesting with the difference in down hill fuel economy.  With tow haul mode off, when I coast in drive down long grades, the fuel economy is in the 35 to 40 mpg range.  But if I roll down in neutral, the fuel economy shoots up to around 120 mpg.  The experiment concludes that a high reving V10 engine is injecting more fuel than an idle engine, even though the throttle is not touched.

Please don't misunderstand me.  I don't recommend coasting down hill in neutral to save gas.

Our Scangauge II reads 99.99 when coasting downhill in gear. Are you sure you have the Cutoff parameter set to the TPS value + 4?

I never set the tps.  Maybe that explains why my mpg reads poorly while rolling downhill in gear.  I really should read the Scanguage manual.

Thanks!

Our Scangauge II reads 99.99 when coasting downhill in gear. Are you sure you have the Cutoff parameter set to the TPS value + 4?

This is what the manual says:

Set the Fuel Cutoff Level
Some vehicles will turn the fuel injectors off while coasting – this is known as Fuel Cutoff.  ScanGauge attempts to detect the fuel cutoff condition by comparing the open/closed loop indicator and the throttle position.  If ScanGauge improperly detects fuel cutoff, then you may see fuel economy being reported as 9999 MPG or 0.00 LHK.

The CUTOFF parameter allows you to set the point at which ScanGauge can determine the throttle is closed and in the fuel cutoff condition.  The default value of 24 is usually correct for most vehicles but may need to be adjusted. This setting is not critical but is best at about 4 above the no-throttle TPS value. You can choose to disable the fuel cutoff sensing feature of the ScanGauge by setting the value of CUTOFF to 0.


I have left mine set at the default value of 24, because I don't know what the actual no-throttle TPS value is so that I can set it +4 above that.

Are you saying that you set yours to +4 above the no-throttle TPS value, if so, what is that value?

I may try setting it to "0" to disable the function since I am not sure what is happening here, or maybe I should call ScanGuage.

Thanks, Bob


EDITED TO ADD THE FOLLOWING:

I just sent the following to ScanGauge and will report back with their response:

I have had my ScanGauge II for three years and have always wondered about setting the Fuel Cutoff Level.  Can someone tell me what exactly is happening with that function?  I have left it at the "24" default setting because I don't know what the no-throttle TPS value is for my 2010 E450 V10 engine, so that I can set it at "+4" above that value.

How will the MPG readings be affected by either (A) leaving it at "24", (B) setting at the "+4" above the no-throttle value, or (C) setting it to "0" to disable the function?

Thanks for any help you can give me to understand this,
Bob


EDITED AGAIN TO ADD THE FOLLOWING:

Reply from ScanGauge:

Some vehicles will turn the fuel injectors off when coasting (also known as the fuel cutoff) which causes the fuel economy to go to 9999 MPG or 0.00 KHL. This shows when you are not using any fuel while coasting. The ScanGauge attempts to detect the fuel cutoff condition by comparing the open/ closed loop indicator and the throttle position. The cutoff parameter allows you to set the point at which the ScanGauge can determine the throttle is closed and in the fuel cutoff condition. To tell if the throttle is closed, the throttle position is checked against the CUTOFF value. CUTOFF is the value the throttle has to be below in order to indicate a fuel cutoff and show 0 fuel flow. The default (24) is right for most vehicles, but it can be adjusted. The setting is not critical, but is best if about 4 above the no-throttle TPS value. If the cutoff value is set to "0" it disables this method of fuel cutoff sensing and therefore eliminates the 9999MPG reading. To check your no throttle TPS value, pull up the TPS in the GAUGE screen while idling. Please let me know if you have any questions.

Seems simple now that it was explained further.  The no-throttle value is simply the TPS (Throttle Position Sensor) value at idle, when the throttle is obviously closed, and it can be found by by looking at the TPS value in the GAUGE screen.  Then add 4 to that value to set the CUTOFF value.

Bob

I assumed the throttle was open slightly at idle so I used the TPS value displayed while coasting downhill. For me that value plus 4 is 18. Your vehicle may be different.

I assumed the throttle was open slightly at idle so I used the TPS value displayed while coasting downhill. For me that value plus 4 is 18. Your vehicle may be different.

I think the throttle is considered closed by the TPS whenever your foot is off the gas pedal, whether at idle or coasting downhill.  I will check this next time out in the RV.  You had a better understanding of the ScanGauge than I to know to look at the TPS value, I never thought to do that.  Now I get it and will proceed accordingly.

We are heading out in the PC next week, headed to Moab and Ouray to do some Jeeping, I will check the ScanGauge then.