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The Low Gear Advantage

Background

This is my second version of the LGA for the Ford Escape and Mercury Mariner. The original thread was started 9/19/05 on Greenhybrid.com when I first discovered the advantages of the use of low gear.

The first pioneer to discuss the advantages was a member here name Nitramjr (Ray Martin). It appears Nitramjr was driving most of the time in low gear and found his mileage increased from driving in Drive. Pravas Prime (Rich) also a member here, began to try Ray’s discovery and agreed that this did in fact improve mileage.

From the first day I got my FWD FEH, I drove as much as possible in EV by choosing routes with low speed limits. This brought my mileage to around 40mpg per tank, but this took a lot of hard work because recharging the battery was done with the engine (ICE) and the small generator. We all knew that using the brakes gave us limited added regenerative energy to the battery , but I didn’t think it added much at the time.

Finally, I got brave enough to try Ray and Rich’s driving in low gear and couldn’t believe Low Gear was the same as Drive. The exception was when you let off the accelerator, the traction motor worked as a strong generator (regenerative braking) from the wheels and charged the HV battery better than the small generator. There was no “Low Gear”, the traction motor was simulating a low gear by slowing the FEH down and generating energy for battery storage. One reason I thought Ray and Rich’s MPG increased while driving in “L”, was the fact that if you were below 40mph and let off the gas, the FEH would also go EV (Electric Vehicle) or ED (Electric Drive). They both (Ray and Rich) were getting better mileage because the engine would shut down more and the battery was being recharged at the same time.

With my 40+ mile city driving commute, this was a huge boost to extending my EV driving for improved mileage. Right away I was hitting mid 40's tanks using “L” only to slow down and charge the battery. At 43mph and below, I shifted to “L” to go EV at 40mph or lower speeds, and back to Drive (“D”) for coasting.. Of course I wanted to tell everyone about the LGA by starting that thread on 9/19/05.

Ecel ( Wayne Gerdes) wanted to know how I transferred to Drive without regen slowing me down in EV. The tach makes a bump before going EV at 40mph and lower, and this is when I made the change to avoid additional slowing for the coast in “D” at the highest speed possible.

Wayne had me do additional testing going to neutral instead of drive for coasting and we found you could coast 38% further than in Drive (“D”). This was like hitting the mother load in FE for the FEH. Neutral eliminates all regenerative braking, but let you coast 38% further. There is a higher idle in neutral with the ICE ON, but FE is still overall much better than “D” coasting.

The next FE increased came when I started using the Fake Shift (FS) in Low Gear to get a rapid charge in a very low battery State of Charge (SoC). Wayne advised me that the battery sucked up the juice with a low SoC, so I gave the battery all it would take with two fake shifts to get a charge to go a longer distance in EV. The FS’s in Low can cause the battery to get too hot for EV. I’ve found that running the cabin A/C requires the battery vent door to stay closed from the outside air. The battery A/C keeps the battery cool enough for the FS’s in Low with no problems.

GaryG

I hope you don't mind me adding V2 to the title. I think it will help people put this in perspective when they do a search.

Not at all, was thinking the the same but forgot.

GaryG

Gary,

I have a couple of questions--

With the battery range of 40-60%, does a low SoC mean at or near 40%?

How long do you "fake shift" for? 2-3 seconds? longer?

I was kinda expecting to see SoC go from 40% to 50% with one FS-- but it's more subtle, more like 40% to 41%.

Love that new scangauge.

Gary,

I have a couple of questions--

With the battery range of 40-60%, does a low SoC mean at or near 40%?

How long do you "fake shift" for? 2-3 seconds? longer?

I was kinda expecting to see SoC go from 40% to 50% with one FS-- but it's more subtle, more like 40% to 41%.

Love that new scangauge.

In the past when I did not have the X-gauge and only the Nav battery level, I really couldn't tell just how low in percentage I was working with. My main goal was to get one good FS in (2-5 seconds) without going EV, and another at the speed I wanted to maintain in EV. This often required the second FS at 35mph to maintain a speed of 30mph in EV and a speed of ~42mph to maintain the highest speed in EV possible. The ICE will kick on any where between 39.6% - 41.3% depending on EV load in my FEH. If the ICE kicks on close to 41%, I may only get one brief 2 second FS before going EV again. It all depends on the speed of traffic how I control when, where and how long I FS. Most of the time I maintain a SoC between 39.6-43%, and I consider that keeping a low SoC for the best MPG. My speed is generally between 25-35mph, but I can maintain a higher speed (up to 38mph) at a higher cost of FE in faster traffic with this technique.

One thing to remember is during a FS, you not only charge the battery faster, but you also get fuel cut back. So while the ICE is running and turning the generator (MG1), your getting that heavy charge in a FE mode. This is why I limit only 2 FS and go back to EV ASAP.

GaryG