View Full Version : Optimal speed for FFH
07-19-2011, 02:22 PM
I have had my FFH for a little over a year now... Currently at 16,000 miles.
My average over the 16,000 or so miles is currently 51.4, but on my way to work, I can get 53-58 MPG, on the way home, it's 48-55 (more uphill).
I keep reading how people are driving 60 MPH on the highway in their FFH. I can't seem to keep my speed up enough for that. I am usually driving the speed limit minus 5-10 MPH.
How do you keep your speed up? I think I'm gonna have to re-learn how to drive my car...
07-19-2011, 03:23 PM
45 55 and 65 MPH yields the same MPG from my tests (anything over 65 MPH and the MPGs fall) Cruse control is great for maintaining the same speed (not good if its hilly)
07-19-2011, 05:04 PM
I don't go up that high ( 65 mph) unless i'm coasting downhill, 40 to 50 is usually the range @ highway and 15 to 35 city with nice results to date....
Right Lane Cruiser
07-19-2011, 09:37 PM
I definitely get better highway numbers in my wife's car by keeping the speeds down, but that's true of any vehicle I drive. I have done long stretches using DWL around 60mph and with the tires aired up in warm dry conditions (even with AC running) the car is capable of right around 50mpg.
The last time I did this was a drive up to my in-laws' cabin (~150mi) and though there is a slight elevation gain I ended up with 49.6mpg. The temp was in the low 80's, I had the AC on the whole way, my wife and daughter were on-board with the seat behind the driver also filled with kid stuff and the trunk crammed to capacity.
07-19-2011, 09:47 PM
I dont really know what numbers I will get on the highway. I dont want to find out since it will likely bring my TANK average down from 49.9mpg.
2010 Ford Fusion Hybrid at the May 2009 MiHG - Second 1,000 mile tank in progress (http://www.cleanmpg.com/forums/showthread.php?t=22218)
07-22-2011, 09:30 PM
I thought that 1000 tank will be easy but, 60mpg avg on a tank looks a little hard for my daily driving, but that will not stop me to try and try on every new tank... :):);)
07-25-2011, 12:32 PM
The Advanced Vehicle Testing Activity ( AVTA ) of the D.O.E.s Idaho National laboratory reports 45 mpg. at 40-50 mph in a FFH in commercial document delivery service in Phoenix in the AVTA testing fleet: http://avt.inl.gov/pdf/hev/2010Fusion_4757_June2011.pdf.
My tests confirm 45 mpg at a steady state speed of 50 mph, 60 d. F. temp. and 38 psi. tire pressure. I found the steady state speed mpg. to be almost exactly inversely linear vs. speed with a slope of -0.6mpg./mph. 30 mph yielded 57 mpg., 70 mph yields 33 mpg. The temperature co-efficient is + 0.2 mpg./ d. F. Thus 90 d. F. at 50 mph. yields 51 mpg. Combining the two factors always puts me within a 1 mpg disregarding the many other effects
Far less than what we have seen during the RT loop unfortunately with tire pressures at 51 all around. Temps were provided in the link.
07-25-2011, 05:34 PM
The FFH ride is a little harsh over tar strips so I've been hesitant to go that high on the PSI. I suspect that the PSI/mpg gradient is pretty significant. My figures were on level roads with CC on; no P and G or other hypermiling techniques. I found a 2 mpg loss for a steady state AC at 50 mph, 72 d. F. interior temp and 85 d. outside temp. and a 4 mpg loss at 30 mph. The fuel used for the AC shows a little increase per hour at 30 mph. The radiator fan may be coming on and there is less airflow cooling on the body which was exposed to strong sunlight. The AVTA FFH's are being driven about 50,000 miles/yr. and have accumulated almost 100,000 miles each. Their mpg figures show they are probably driven hard with no hypermiling or driver massaging of the hybrid system and probably a heavy HVAC load all the time. It's obvious the HVAC load is a real killer in attempting 50+ mpg. I see that Honda and others are exploring absorption automotive AC systems that use the ICE exhaust waste heat for energy. The biggest problem there is the high AC requirement of a heat soaked car and the delay of several minutes getting the exhaust heat working. They have some refrigerant storage ideas as solutions. This would be a big boost as the US driver is pretty hooked on AC.
There were no other techniques other than driving with CC on in most cases. That is how we arrive at the steady state numbers.
Anything over the EPA is hypermiling so maintaining strict discipline to the local PSL’s is one of the best techniques one can follow while on the road.
If you throw the book at your FFH, it has pulled as high as 88 mpg on a RT loop and over 80 with just 40 psi in the tires over an entire tank.
Keep it in mind the next time you take her out as it will offer numbers far in excess of any study, any calibrators results and even what most consider “good” FE. The drive train is that well designed.
Regarding A/C, most manufacturers are chasing more efficient solution because of the new 5-test cycles incorporating a Hot test. The waste heat to A/C conversion has its flaws but you will find that the electric A/C included in the FFH allows decent efficiency with segments in the 50's and 60's quite easily as well.
07-25-2011, 09:56 PM
These are exciting times in automotive design. The Prius is still the standard but the FFH is more fun.
08-24-2011, 08:31 AM
Sorry it took so long to reply... this website is not on my regular rotation...
I don't use cruise control, but I do coast whenever possible. My tires are at 50 PSI, and I average 45-60 mph depending on if there are people behind me. If someone is behind me, I tend to speed up a little. I don't use the AC, which is a considerable effort since we are over 100F (~40C) and have been for the last 2 months straight. If I run the AC, it's at 83F (~28C), but usually, that's only when my wife is in the car. I do crack the rear passenger window and open the rear of the sunroof. When I'm driving in traffic, I do put the windows down...
I drive around 70 miles a day (35 in both directions), and I average 53-58 MPG.
I too, strive for that 1,000 mile tank. I think my personal best is around 870 miles per tank.
I do strive to drive the best I can, but my lifetime average (with over 18,500 miles) is currently 51.8 MPG...
I guess I will have to try the cruise control bit... Does it disengage when you shift into neutral to coast, or do you have to turn it off, then shift?
08-27-2011, 02:55 PM
That is a nice avg. mine is 43.9 with 1,800 miles... and still looking for that K tank, but the long drives to my hometown are killing it..:(
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