MPG Reality Check

[Chuck Wheeler]

BOB,

HP is a function of Torque and RPM. 
Without knowing the RPM that is used for two motors to compute HP there is not
enough to run a fair comparison.  Up to a point torque will increase as the
timing is retarded but mileage will decrease.  The peak combustion temp will
decrease but the average will increase and this will reduce emissions.  The newer
motors can decrease emissions and increase efficiency but this was not the case
for most of the power plants produced in the 80s.  At that time they were just
trying to meet the emission regulations and did not have time to re-engineer
the motors.

The two things that helped our mileage
were getting a valve adjust, having the timing set, and solving the problem of
hot air from the radiator entering the intake system.  Some folks have had
improvement adding more area to the air intake but I used a very sensitive
device used to measure HVACs duct pressure and could not measure any negative
pressure in the existing setup for our 3208NA.  Makes me wonder if possibly
they just solved the heat problem in a different way or turbos do have a issue.

I believe, especially after our accident,
that we have one of the softest units out there.  I know we pay a mileage penalty
due to the weight, but given a choice I will take the lower mileage.  Walk
around a repair facility and you wouldn’t ride around the block in most
new motor homes.

Our FC31 happens to have a diesel
generator, 12.5kw for what ever reason as I can power everything on ½ of that!

- Chuck
Wheeler-

1982 FC 31SB Fort Worth TX

---

From: WanderlodgeForum@yahoogroups.com [mailto:WanderlodgeForum@yahoogroups.com] On Behalf Of freewill2008

Sent: Monday, February 15, 2010
8:09 PM

To: WanderlodgeForum@yahoogroups.com

Subject: [WanderlodgeForum] Re:
MPG Reality Check

Chuck - Thanks for those observations. The fuel in
this case was pumped in Brookings,
Oregon and the route was from
there to Q.



If our California
turbo really makes more power than the 210 NA, it surely does get used when
climbing the very frequent west coast hills. More power is more fuel.



The genset in this FC31 is gas, so genset operation does not affect the diesel
tank.



I'm sure the setup is unique to the California
motor. For example, the torque is more than a 225T even though the HP is less.
Cat has a manual with all the details but I haven't purchased it yet.



The posts to this thread are much appreciated. I intend to buy a GPS and start
keeping better track of miles and gallons. As Chuck says, tracking fuel
consumption is one way to monitor engine condition.



Meanwhile, sitting here in the Arizona
desert soaking up sun uses zero diesel fuel! )



Bob Griesel '84 FC31 WLII WA



--- In "WanderlodgeForum%40yahoogroups.com",
"Chuck Wheeler" .> wrote:

>

> Several things could be affecting Bob's mileage.

>

> 1. He is towing.

>

> 2. I don't know where he is in WA, but there is a lot of it that is more

> like mountain running. I can run 800 miles and not change over 600ft

> elevation.

>

> 3. Do they pump a "winter blend" of diesel in WA? My mileage in
the truck

> has always been lower on "Winter Blend"

>

> 3. He has more power than I do and when the power is there we tend to use

> it. My cousin followed us on a trip with his Monaco and he gained almost

> 2mpg driving the way we have to. (He said it wasn't worth it!)

>

> 4. We do a lot of winter traveling and so it is not necessary to run the

> generator.

>

> 5. I believe that a "California"
engine runs with different injection timing

> and advance curve.

>

> 6. I usually run with Gray and black water tanks empty, about ¼ tanks of

> fresh water and on the bottom half of the fuel capacity to keep my weight

> down. That's why I have to compute mpg over a many miles to get an idea of

> what milage I am getting.

>

>

>

> I track milage mainly to keep an idea of how the bus is running.

>

>

>

> - Chuck Wheeler-

>

> 1982 FC 31SB Fort Worth
TX

>

> _____

>

> From: "WanderlodgeForum%40yahoogroups.com"

> [mailto:"WanderlodgeForum%40yahoogroups.com"]
On Behalf Of ebirder2000@...

> Sent: Monday, February 15, 2010 2:39 PM

> To: "WanderlodgeForum%40yahoogroups.com"

> Subject: Re: [WanderlodgeForum] MPG Reality Check

>

>

>

>

>

> Bob, I don't dispute your method or your finding at all. My only comment

> is, that mileage seems too low. I would expect that your mileage would be

> closer to 8mg. But, that's only based on other folks bragging including my

> own,that I have observed.

>

>

>

> Steve (at Painted Rocks campground). Temp 80 degrees with absolute clear

> blue skies.

>

>

>

> In a message dated 2/12/2010 12:22:01 P.M. Pacific Standard Time,

> sundance101@... writes:

>

>

>

> Finally, after 7 years, I filled the fuel tank to the top, drove 1015
miles,

> and filled it again. The 167 gallons calculates to about 6 MPG.

>

> The method has plenty of potential for error. The odometer reads low and I

> don't have a GPS. I used the Google mileage plus 5% to account for wrong

> turns, finding RV sites, etc. The route was Brookings, OR
to Q by way of Hwy

> 101 and Malibu, CA.

>

> The tank is so big that I figure the fill could be off by as much as 10%.
If

> the fill-up were 10% low, the MPG would have been 6.7. If the fill-up were

> 10% high, the MPG would have been about 5.5.

>

> Other details: 1984 FC31 with California
210HP turbo 3208. Road speed about

> 58 MPH. 4.89 gears. 11R22.5 Michelins at 105 and 95 PSI. Towing a Honda
CRV.

> Air filter has about 5000 miles. The air intake is the enlarged version

> designed for the 250HP turbo engine. Never blows any black unless I make
an

> operator error.

>

> To achieve the 10 MPG sometimes suggested for the FC, my mileage estimate

> would need to be off by almost 700 miles, or the fill-up would need to be

> off by almost 70 gallons.

>

> I'd be interested any anyone else's MPG observations and the method used.

>

> Bob Griesel '84 FC31 WLII WA

>