AstroRig57
near Tehachapi, CA
Senior Member
Joined: 01/15/2009
View Profile
|
pnichols wrote:Speaking of V10 Class C gas mileage ... here's an interesting angle I'd REALLY like to get to the truth on regarding gas mileage for V10 Class C motorhomes late enough to have the 5-speed transmission with TOW/HAUL mode:
For "V10 motorhome travel under average contitions" (whatever that is), in which mode does one get the best mileage - TOW/HAUL mode, or standard mode? 
I'll guesstimate that it might be with TOW/HAUL mode always engaged because a Class C motorhome is always hauling around quite a load ... unlike delivery trucks which oftimes are empty or nearly empty. When hauling, the transmission's torque converter is slipping less during acceleration in TOW/HAUL mode so overall average efficiency should be higher.
I'm considering leaving the transmission always in TOW/HAUL mode when traveling to perhaps get slightly improved gas mileage.
I think your premise is absolutely wrong.
Tow/Haul mode "Raises the shift point RPMs and internal trans shift pressures for a given engine load."
That means you will remain in a lower gear, with higher engine RPM's, for longer under any given load. Higher engine RPM's, and lower gearing, translates into higher fuel consumption and lower gas mileage. "The intention of having overdrive gears is to improve fuel mileage. To get that improved fuel mileage you need to get into that overdrive gear as soon as possible, and stay there as long as possible." Tow/Haul mode delays the "up shift" into a higher gear or overdrive.
Tow/Haul mode also, "Engages the “coast clutch” and uses other internal trans clutch/band application strategies in order to achieve engine braking through all gears as the transmission coasts down."
Using engine braking, "in all gears", and under all conditions is also going to equate to higher RPMs, greater fuel consumption, and lower gas mileage.
Intermotive Tech Tip August 06 pdf
2005 31' Coachmen Freelander 3150SS, Stargazer II - Mobile Astronomy Unit
Do you remember when the sky was dark, and the stars were bright?
The International Dark-Sky Association
American by birth...Scottish by the Grace Of God.
|
AstroRig57
near Tehachapi, CA
Senior Member
Joined: 01/15/2009
View Profile
|
joe&julie81 wrote:A friend told me that they are getting 13-18 mpg with a V10 Ford engine in a 29 ft class c. That kind of blew me away for a minute, but this person is trustworthy if they're calculations are correct. So can somebody tell me if this sounds reasonable? Or what do these units get with gas engines and a length somewhere around 29 ft? Thanks
As others have noted, I think your friend is either dreaming or very poor at practical math.
In addition to our Ford V-10 powered Class-C, we also have a V-10 powered Ford Excursion (4WD). Yes, it too is a big vehicle but nowhere as large, or as heavy, as our 31' Class-C. Nor does it have the demonstrably non-aerodynamic, air catching, flat front end of the motor home.
Our 8,900 lb GVW Excursion averages 12 mpg in a mix of city and highway driving, and 15-16 mpg, (depending on how hard I push it) on the freeway. There is no way that a 14,500 lb GVW Class-C, with dual rear wheels, and a wind catching front end, can do better than that.
Don't ask me what kind of mileage I get with my Class-C. I don't know. I don't care. When the tank gets low, I put the nozzle in the filler spout, close my eyes, and I fill it up.
|
pnichols
Santa Cruz Mountains
Senior Member
Joined: 04/26/2005
View Profile
Good Sam RV Club Member
|
Quote:Using engine braking, "in all gears", and under all conditions is also going to equate to higher RPMs, greater fuel consumption, and lower gas mileage.
Do you mean that taking your foot off the gas, letting the engine idle, and then using your brakes while going down a hill uses less gas than taking your foot off the gas, letting gravity rev the engine for vehicle hold-back, and not using your brakes does? Any additional gas usage from this is not intuitive.
Granted that the engine is revving but it's not burning more gas that's causing it. It's my understanding that modern fuel injection engines suck in no gas above idle maintainance - even if downhill runs are "force spinning it" - unless the gas pedal asks for more gas above idle. (This was probably not the case with carbureted engines, which draw gas based on spinning engine vacuum.) When in TOW/HAUL mode going down hill I many times do not depress the gas pedal at all, as I am letting engine braking entirely control speed.
Also note that when in TOW/HAUL mode overdrive still is available and active - so the gas savings are still there when cruising in TOW/HAUL mode. It's just that when getting up to cruising speed in TOW/HAUL mode, less torque conversion slippage is going on because the transmission is locked-up solidly in gears longer until cruising speed is reached.
From the .pdf link you provided, TOW/HAUL mode does considerably more than the previous "OD ON/OD OFF" switch on Ford's pre-2005 V10 E350/E450 vans.
My earlier post was just asking if any in the forum have compared mileage on long trips both IN and OUT of TOW/HAUL mode for solid proof one way or the other. Ford may have had delivery trucks running around in town in mind when they designed the TOW/HAUL mode, but for a continually heavy loaded RV under a variety of driving conditions and speeds, the TOW/HAUL mode may provide some surprising slight upside in mileage due to less overall torque conversions taking place.
Phil, 2005 E450 Itasca 324V Spirit
|
Off Pavement
SW Nebraska
Senior Member
Joined: 01/21/2003
View Profile
|
We recently purchased a new 2010 E450 chassis 25' bumper to bumper class C. I have not compared mileage with tow/haul vs standard shift points, I'd like to add my driving experience would indicate that prudent use of both is the desired result, not one over the other.
According to the Ford chassis owners manual, the best overall fuel economy will be achieved with tow/haul deactivated, and I believe this. My impression is tow/haul is not designed for around town much. The shift points are too high RPM wise for normal driving.
Additionally, the owners manual cautions against using tow/haul with cruise contol engaged. The cruise seems to override the tow/haul and frequent shifting is the result on long inclines.
On long declines towing a nearly 5K Jeep, the tow/haul was nice to hold the vehicle back without using the brakes.
So... my driving habits have evolved to hitting the tow/haul button at the botton of a hill and turning off the cruise. It will almost always pull the hill I'm climbing without downshifting IF I am careful with the throttle.
I'm with a previous poster... put the nozzle in the tank, close my eyes, and think of the next beautiful camping spot.
Please Support Multiple Use of our Public Lands!
Brian & Margie
www.rv-camping.org
'10 Sunseeker Class C - Gozer II
'97 Jeep TJ (Wrangler) - Blackie
|
skimask
ND
Senior Member
Joined: 04/06/2010
View Profile
 Offline
|
pnichols wrote:Quote:Using engine braking, "in all gears", and under all conditions is also going to equate to higher RPMs, greater fuel consumption, and lower gas mileage.
Do you mean that taking your foot off the gas, letting the engine idle, and then using your brakes while going down a hill uses less gas than taking your foot off the gas, letting gravity rev the engine for vehicle hold-back, and not using your brakes does? Any additional gas usage from this is not intuitive.
Granted that the engine is revving but it's not burning more gas that's causing it. It's my understanding that modern fuel injection engines suck in no gas above idle maintainance - even if downhill runs are "force spinning it" - unless the gas pedal asks for more gas above idle. (This was probably not the case with carbureted engines, which draw gas based on spinning engine vacuum.) When in TOW/HAUL mode going down hill I many times do not depress the gas pedal at all, as I am letting engine braking entirely control speed.
Also note that when in TOW/HAUL mode overdrive still is available and active - so the gas savings are still there when cruising in TOW/HAUL mode. It's just that when getting up to cruising speed in TOW/HAUL mode, less torque conversion slippage is going on because the transmission is locked-up solidly in gears longer until cruising speed is reached.
From the .pdf link you provided, TOW/HAUL mode does considerably more than the previous "OD ON/OD OFF" switch on Ford's pre-2005 V10 E350/E450 vans.
My earlier post was just asking if any in the forum have compared mileage on long trips both IN and OUT of TOW/HAUL mode for solid proof one way or the other. Ford may have had delivery trucks running around in town in mind when they designed the TOW/HAUL mode, but for a continually heavy loaded RV under a variety of driving conditions and speeds, the TOW/HAUL mode may provide some surprising slight upside in mileage due to less overall torque conversions taking place.
In addition to the above, most fuel injected vehicles have a "deceleration fuel cutoff" mode. When the engine revs are a bit off idle (say 2,000 rpm for arguments sake) and the throttle position sensor is at or near the idle position, the ECU assumes an engine braking condition, goes open loop, and cuts fuel to the injectors. Therefore, in most fuel injected engines, fuel consumption during engine braking conditions is ZERO.
This is exactly how many engine manufacturers are squeaking that last bit of fuel mileage out of vehicles these days. They're setting the "deceleration fuel cutoff" mode to be more and more aggressive. In some cars, for instance Chevy's Cobalt "XFE" (extreme fuel economy), when you let off the gas to get off the highway, you can actually feel the engine "cutoff" and then kick back in as the revs get lower.
|
|
|
tarnold
georgia
Full Member
Joined: 03/01/2010
View Profile
Offline
|
Recorded every gallon of gas that we've used. 11.77 mpg going faster than we probably should w/o toad. Pulling Prius on a dolly, 11.45 mpg but keeping it just under or right at the speed limit. 98' Chinook.
|
crawford
Dandridge Tenn.
Senior Member
Joined: 03/22/2006
View Profile
Good Sam RV Club Member
Offline
|
tarnold Are we talking apples to apples didn't you post before you were around 24 foot? because we are talking 29 foot or larger.
|
pianotuna
Regina, SK, Canada
Senior Member
Joined: 12/18/2004
View Profile
Offline
|
Hi tarnold,
I thought the v-10 was introduced in 1999?
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
|
crawford
Dandridge Tenn.
Senior Member
Joined: 03/22/2006
View Profile
Good Sam RV Club Member
Offline
|
my 99 superduty have v10 which started on 98
|
AstroRig57
near Tehachapi, CA
Senior Member
Joined: 01/15/2009
View Profile
|
pnichols wrote:Quote:Using engine braking, "in all gears", and under all conditions is also going to equate to higher RPMs, greater fuel consumption, and lower gas mileage.
Do you mean that taking your foot off the gas, letting the engine idle, and then using your brakes while going down a hill uses less gas than taking your foot off the gas, letting gravity rev the engine for vehicle hold-back, and not using your brakes does? Any additional gas usage from this is not intuitive.
Granted that the engine is revving but it's not burning more gas that's causing it. It's my understanding that modern fuel injection engines suck in no gas above idle maintainance - even if downhill runs are "force spinning it" - unless the gas pedal asks for more gas above idle. (This was probably not the case with carbureted engines, which draw gas based on spinning engine vacuum.) When in TOW/HAUL mode going down hill I many times do not depress the gas pedal at all, as I am letting engine braking entirely control speed.
Also note that when in TOW/HAUL mode overdrive still is available and active - so the gas savings are still there when cruising in TOW/HAUL mode. It's just that when getting up to cruising speed in TOW/HAUL mode, less torque conversion slippage is going on because the transmission is locked-up solidly in gears longer until cruising speed is reached.
From the .pdf link you provided, TOW/HAUL mode does considerably more than the previous "OD ON/OD OFF" switch on Ford's pre-2005 V10 E350/E450 vans.
My earlier post was just asking if any in the forum have compared mileage on long trips both IN and OUT of TOW/HAUL mode for solid proof one way or the other. Ford may have had delivery trucks running around in town in mind when they designed the TOW/HAUL mode, but for a continually heavy loaded RV under a variety of driving conditions and speeds, the TOW/HAUL mode may provide some surprising slight upside in mileage due to less overall torque conversions taking place.
My reference was not referring to using Tow/Haul mode for descending steep grades. Injecting that into the context of the conversation is an obvious red herring and taking it completely out of context of the conversation. Of course, I too use it when descending grades. The conversation at the time referred to using Tow/Haul "all the time", and under all conditions, and whether this would equate to lower fuel mileage. No one in the immediate instance had said anything about whether or not you would use it descending grades. That's a given!!
It should be quite obvious that if you are using Tow/Haul mode all the time, and thus using engine braking at all times when you might otherwise be coasting to a stop under braking, your mileage is going to be decreased.
In like manner, using an engine/transmission strategy that is going to result in higher RPM's, more often, and for a longer period of time, is obviously going to reduce mileage.
Off Pavement wrote:According to the Ford chassis owners manual, the best overall fuel economy will be achieved with tow/haul deactivated, and I believe this. My impression is tow/haul is not designed for around town much. The shift points are too high RPM wise for normal driving.
That's what the manual says, that's what common sense tells me, and that's good enough for me.
|
|
|
|
