UFO gas milage

[-Gramps-]

For those interested, our coach averaged 7.5 mpg at 62mph on I-95 with 2000 miles on our trip to Florida.
Not bad and with a 100 gallon tank I didn't stop for gas much.

[DriVer]

-Gramps-, Given the 6.13 gear set, GVW and that a toad is being pulled along, I believe that this can be considered to be very good fuel economy. The 6-Speed Allison with its 2nd overdrive gear, in cruise, is no doubt the single most most beneficial property of the UFO powertrain.

What was your cruising speed on average? Just guessing; I would say that you were probably flirting with 62 to 65 MPH. Am I close?

[CraigA]

Quote:

Originally posted by -Gramps-: For those interested, our coach averaged 7.5 mpg at 62mph on I-95 with 2000 miles on our trip to Florida. Not bad and with a 100 gallon tank I didn't stop for gas much.

Interesting this comes up, since new, and before the FCA failure, our mileage was not so good, 6.1mph average, and driver you are right on with your average speeds. After updated FCA replacement, we are around Gramps figures of 7.2mpg.

Keith from RTS and I spoke at the FMCA rally in Indio about the FCA failures. He mentioned that if a FCA would stay engaged, to whatever degree it was, it would rob horsepower, I'm no mechanic, but maybe lower mpg's, and I know there are a lot of variables with that, could be a sign of a FCA that might need attention. Just a thought.

[CraigA]

oops, MPG's not MPH sorry!

[DriVer]

Quote:

Originally posted by CraigA: He mentioned that if a FCA would stay engaged, to whatever degree it was, it would rob horsepower, I'm no mechanic, but maybe lower mphs, and I know there are a lot of variables with that, could be a sign of a FCA that might need attention.

CraigA, On front gas units we are more in tune with whether or not the FCA is engaged. My problem last year was that it didn't engage and I was having over heat issues. When the FCA clutches up or the clutch remains engaged as Keith observed it does take more energy to keep spinning the fan over.

Once the cooling has been achieved the FCA no longer needs to be clutched up so it should free wheel.

At very high RPM and without the need to additionally cool the engine the FCA is doing a lot of work for nothing and it should de-clutch and allow the engine to spin without a clutch load. When de-clutched the process saves fuel.

[-Gramps-]

Dirver, my avg cruising speed was between 59 and 62. I set my cruise control to 62. When I hit cruising speed, the rpms were just at 1800.

[CraigA]

Quote:

Originally posted by DriVer: <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by CraigA: He mentioned that if a FCA would stay engaged, to whatever degree it was, it would rob horsepower, I'm no mechanic, but maybe lower mphs, and I know there are a lot of variables with that, could be a sign of a FCA that might need attention.

CraigA, On front gas units we are more in tune with whether or not the FCA is engaged. My problem last year was that it didn't engage and I was having over heat issues. When the FCA clutches up or the clutch remains engaged as Keith observed it does take more energy to keep spinning the fan over.

Once the cooling has been achieved the FCA no longer needs to be clutched up so it should free wheel.

At very high RPM and without the need to additionally cool the engine the FCA is doing a lot of work for nothing and it should de-clutch and allow the engine to spin without a clutch load. When de-clutched the process saves fuel. </div></BLOCKQUOTE>

I do understand all of that. I guess what I was referring to was that when the FCA engages to allow cooling, it is supposed to de-clutch when that is accomplished. As it was told to me by Jesse WCRSM, the reason for the FCA failures and additional damage, was because the FCA didn't de-clutch, and was engaged, while not needing the cooling operation, thus creating vibrations and excessive stress causing the failures, and not to mention the loss of some power due to the load.

I don't know how long that had been happing to my coach until my failure, but from the onset of ownership I never got more than the 6.2mpg's or around there. I guess what I was trying to say was, the lack of it de-clutching could have been the reason for my poor MPG's, and maybe any UFO owners that are getting less than average MPG's might have a FCA that could be suspect to the failure that some of us have had. As I mentioned after the updated FCA was installed my mileage has gotten close to Gramp's mileage. It is possible that Workhorse, while my coach was there because of the failure, might have reprogrammed some parameters, but I asked, and was told they changed noting other than the FCA, waterpunp, and belt.

[max49]

Quote:

Originally posted by -Gramps-: Dirver, my avg cruising speed was between 59 and 62. I set my cruise control to 62. When I hit cruising speed, the rpms were just at 1800.

62 MPH @ 1800 RPM with a heavy vehicle like the UFO. Are you sure? My little 18,000 LB rig with the same engine is right about 2200 RPM @ 60 MPH. It also gets about 8 MPG on avg.
I'm surprised it could pull a level road being geared that high.

[-Gramps-]

I remember my Bounder's 8.1 ran around 2200 at 60 mph which would put it in 5th gear. The UFO is in 6th at 400 rpms less. Shouldn't that be about right?

CraigA, my friend Charlie who also owns a 38plt told me he never got much better than 5.6 average mpg Before his water pump failed. It went up after replacement but I never thought that there might be a connection. You seem to be on to something there.

[max49]

Not necessarily. The gear ratios could/ should be all different. And the engine needs to have enough torque to pull at a given RPM. Theoreticaly, they could gear it where it could go 60 MPH at 1000 RPM, but the engine would'nt have the power to pull this high gearing unless you were going downhill.

My P-32 only has the 4 speed and 80 MPH is about 2950 RPM . If it had another ( and it could use another) I certainly would hope they would change all the gear ratios and not just slap one on top.
Mine will go 40MPH in first gear, that's why I need first where some of you say you use 2nd on the same moutains. Your 1st gear is probably a granny gear, and I don't get one of those with the 4 speed.

[-Gramps-]

Next time I am at 60mph, I will double check the rpms.

[dieselclacker]

Max49, the Allison in the UFO chassis is a six speed, with 5th and 6th both being overdrives. Sixth gear is pretty "tall" but the chassis is also equipped with a better than 6:1 rear end ratio to allow the engine to pull the tall trans gearing. Don't own one, and don't ever expect to, so don't know what the final RPM would be at 62. (Can I say that?
Final drive on my 5 speed is about the same as your GM 4 speed, 2200 RPM at 62 MPH.

Dieselclacker

[Lash]

In our trip to California from Houston over I-10/I25/I40, our gas mileage for the entire 4500 miles we put on the coach was 7.0 mpg. We set the cruise for 63 mph but those who have traversed this routing know that there are some grades to work thru.

The rpm's on our coach were also in the range of 1850 to 2000 during the transit. On some grades we would tach 3100 in D3 with 4000 in D2 sometimes going thru Flagstaff. (These rpms are approximate but close to reality as I did not log the readings)

The six speed makes a sweet setup for cruising and towing for sure.

Regards

[The Bull]

Rear differential gearing is based on many factors. A few are engine torque curve, tire size, transmission gear ratios, weight, perceived usage of the vehicle. I have ran gear ratios in the same race car that range from 5:59 to 7:33 depending on where I was racing. I am sure that Workhorse tested and put the best all around ratio in the UFO. We get around 7.5 mpg and have been on all kinds of roads and terrain. Also you are correct in the assumption that the FCA robs power and lowers mileage when it is engaged. Other power/mpg robbers are misadjusted brakes, wrong tire pressure, wrong octane fuel which could be to high or to low, air conditioning, and overloading.