Cruisers Forum
Main Forum => General Discussion => Topic started by: dickreid1 on August 13, 2015, 04:11:49 pm
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For the record.
Total miles including flatland, hills, mountains, A/C no A/C, good gas, bad gas, idle time...
divided by...
total gallons used corrected for generator use by 0.5 gallon/hour.
2012 - 9,700 miles - 9.2 mpg
2013 - 12,500 miles - 9.6 mpg
2014 - 10.200 miles - 9.2 mpg
2015 - 9,400 miles - 9.2 mpg
We do not tow.
We cruise 55-58 mph on secondary highways
and 60-64 mph on interstate quality highways.
We avoid high rpm (>3000) cruise control downshifts.
We use long coasts with fuel injectors off whenever possible.
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I'm confused on avoiding cruise control downshifts? Why do you avoid them? Also I don't understand the coasting with fuel injectors off? Are you saying you shut down your engine when traveling down long grades?
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Left to its own devices, the Cruise Control will shift down to whatever gear is necessary to maintain the set speed. That can mean 3rd gear at 55 mph, or in our case 5K rpm. That wastes gas. Best to let the PC slow down on upgrades. Too bad the Cruise doesn't have an economy mode.
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When we're on a freeway in cruise control, I'll often let the transmission shift down once if it looks like the incline we're on is fairly short and know it will shift up soon. If the incline in long or the transmission shifts down again due to the steepness of the grade, I always turn the cruise control off and choose the gear myself. We do slow down some, but I hate to hear the engine race and waste fuel.
--Bruce
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I find the cruise control on the E-350/E450 less responsive to grade changes than other vehicles I have driven. On a roadway that is flat to rolling the cruise control works well. However, once steeper inclines are encountered the cruise control seems to rely more on downshifting than throttle control. I have found that once my speed drops 4 or 5 MPH below the cruise control set point the transmission starts downshifting one or more gears. I have also found that if I manually increase the throttle and keep my speed close to the cruise control set point I can climb most inclines without having the transmission downshift. I do not know if this saves any gas but it sure makes me feel better to the keep the RPM's down.
The other problem I have with the cruise control is the way it handles declines. When going downhill with the cruise control set if my speed increases 4 or 5 MPH the transmission will downshift and will remain in the lower gear far too long. I avoid this situation by disengaging the cruise control on long or steep down grades and manually downshifting as necessary.
Barry
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I'm not certain that the following is appropriate to a post on MPG, but since we've touched on downshifting, etc. here is another thought to share:
I totally agree with Barry on manually increasing the throttle a little to maintain the speed set point in cruise control as long as the RPM's don't drop too much. I also hate to see the RMP's jump up too much. I'd rather slow down some than try to stay at some previously desired speed.
On declines I rely heavily on the Tow/Haul mode to slow us down. A brief tap on the brake pedal releases the cruise control and a push on the Tow/Haul button before more brake is applied will usually be all we need to maintain a safe speed. I seldom need to select a lower gear myself. Of course on really steep declines more braking will be needed, but the automatic downshifting after a brief braking is all that is normally needed in our experience to get to an appropriate gear. I'd rather have the engine/transmission work together to keep us safe rather than using the break pedal.
--Bruce
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Bruce, Your method is exactly how I use the tow/haul as well. I relied on it heavily on my previous coach and use it the same way on the new PC with great results. (exactly)
John
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Please explain the "tow-haul" mode.
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We have only had our PC for a few months now and have only taken short trips. We almost always tow our Subaru and I have always had the PC in tow/haul mode when towing. Am I doing this correctly? I know the original post was about MPG and apologize for going in another direction.
Mike
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The Tow/Haul mode is activated by pressing the button on the end of the gearshift lever.
We always tow our Honda CR-V, but only use this mode for engine breaking on downhills or to come to a slowdown or stop quickly.
The Ford owner's manual contains a section under Transmission.
--Bruce
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jfcaramagno ......The engine downshifting,, (Engine braking as its called) doe not use gas. Engine braking uses the drive train to slow the vehicle to the selected speed, not fuel. Adding fuel will increase engine speed not decrease. Electronically controlled fuel systems shut down the fuel unlike the carburetors of yesteryear so in reality your actually using less fuel than coasting with the engine idling down the hill although the amount of fuel is not significant.. Also the v10 is designed as a high revving engine so your doing no damage. Its doing as it was designed to. What you are doing is saving on over heating your brake pads if your slowing using your brakes compared to the engine assisting in the braking.
However if your goal is to coast to a higher speed going down one grade to make headway on the next upgrade then there is that advantage.
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Ok everybody, time to cover what was not covered related to driving for mpg.
First, turning off your injectors. Injectors squirt fuel as needed. One for each cylinder. When, at speed, you take your foot the accelerator, fuel is no longer needed, the injectors tun off. The engine continues to turn which gradually slows the mph. This is the way to get "free mpg" as you approach a stop or go downhill.
Second. There is an injector technique that can be used in long rolling hills which I think of as "driving above the average mpg (Scangauge)". I find that rather than taking my foot off the gas to turn off the injectors, I can accelerate while driving downhill and still drive considerably "above the average mpg".
For example, the Scangauge shows the average mpg so far is 9.0 mpg. Rather than taking my foot off the gas to get "free mpg" on the next hill, I give just a little gas to hold at maybe 20 mpg and also accelerate to get a run at the next hill.
The result is that the speed build-up carries me farther up the next hill before a downshift occurs and the average mpg slowly but steadily gets better. This is more effective than just taking your foot off the gas on big hiils... and more interesting. Eventually, I catch up to the average mpg and cannot improve but only maintain the highest mpg. From this I determine the true mpg of the engine under those conditions with that specific gas.
Finally, I note that the mpg can be as much as 1 mpg higher or lower than normal with some gas. Ethanol free gas seems to do better a little more frequently.
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Dickreid.. I use a slightly different method. I fill up the tank and drive till I need more gas and repeat. :)(:
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Joseph! I like the way you think & drive. Other ways seem to be "over thinking" the task and interfere with the purpose of traveling in a motor home, namely to enjoy the trip! (exactly) :)(:
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Dick,
Thank you for the information and ideas you've put into these posts.
We don't have a Scangauge in our PC, but we do pay attention to our MPG each time we fuel up. We know it's not exact because of fuel used by our generator and variations in the amount of a "full" tank from one fill to another, but it's close enough for us.
I'm accustomed to using techniques you mention while driving our auto as well as the PC. It's nice to hear from someone who can measure the results. Those techniques make perfect sense to me and don't spoil the enjoyment of the trip at all.
Happy trails,
Bruce
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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.
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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?
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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!
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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
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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.
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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.