Thanks for knowing the details of the Low gear and clearing up our questions. The Energi sounds excellent.

Here's a related question. Whether you're above or below the EV mode's top speed, is it better to slow down some by shifting from Drive to Low, or doing the equivalent slowing by using the brake pedal?

A friend who has a Prius uses his brakes in situations where I shift into Low.

 

Whether you're above or below the EV mode's top speed, is it better to slow down some by shifting from Drive to Low, or doing the equivalent slowing by using the brake pedal?

The 2009 and newer FEH software means there is very little reason to go into "L" as frequently as a hypermiling champion would have in the 05-08 FEH vehicles.

The Prius and FEH do not share the same software. The Prius has a greater "effective" range of SOC than the FEH's 40-53%.

 

I see no use for L in the '09 and newer hybrids. I managed to use my brake pedal to get as close to 100% of regen as possible. Like I said, in the '09 FEH, you can get complete DFSO (fuel-cut) during deceleration in D above 40mph. It helps to tap the brake pedal to bring on DFSO sooner. This is a trick to the trade of being a hypermiler.

Gary

 

Thanks. I have a follow-up on this subject that I have not seen discussed on FEH forums.

Where I live, and unlike Florida, we have mountains. We drive up and down them both on highways and old gravel roads. This means some descents are at highway speeds above the top "ev" mode speed, and the gravel descents often are below that speed. These descents can be as much as 4000' vertical in one go.

Obviously the energy needing to be dissipated on these descents often quickly exceeds the available capacity of the hybrid battery. Of course, once the battery is full, all speed retardation falls to the hydraulic/mechanical brakes. This causes brake wear. I thought I'd have a problem with overheating brakes, since the FEH has no effective engine braking at low speeds. Luckily the FEH's brakes seem to be well up to the task.

What I want to do is maximize the electricity generated during these descents. Any such additional energy should translate into less brake wear. The goal is to get the FEH working more like a diesel-electric train locomotive that brakes down long descents by generating electricity that is wasted through resistors mounted on top of the locomotive.

I want to pass some thoughts by you to see what you think. I assume the situation is different above and below the ev top speed.

For descents below that speed, I'd suggest keeping it in Drive, and turning on as much electrical load as suitable. This would include the main lights, rear window defroster grid, and heated seats and a/c as suitable. (I'm not going to lean on the horn.) I'm thinking that below the ev speed in Drive the engine should shut down and any energy lost to electrical accessories should translate into more resistance and speed reduction due to regenerative braking. In turn this should reduce brake wear. But I can also see it's likely doing so will just force the gas engine to come on sooner to replenish the traction battery which in turn supplies the 12V battery.

The highway situation is different because above the ev top speed, the engine will be running anyway. Any electrical energy used up by accessories will just put more load on the gas engine resulting in more gas consumption with no additional speed retardation. But this could be different in Low gear compared to Drive, and at this point I have no idea what would be the best configuration to minimize using the friction brakes during long steep descents at highway speeds.

What do you think?

 

Xspirit, do you have a SGII? I have never driven my '09 in your type of conditions, so you must determine your best course of action. The '09 FEH was the last year with the aux. battery A/C, this means you have an excellent way to cool the battery while fast charging with regen. The EV max speed and the speed above EV are programmed to work differently.

Understand how DFSO works and how to see it on the SGII. First, your Instant MPG will go to 9,999, and you will see Open-Loop just like in EV. The difference is the wheels will generate power to MG1 to spin the engine at an idle speed. Spinning the engine also means spinning the A/C compressor for the cabin or the aux A/C when needed. You need to determine with your Charge/Assist gauge how much regen you get in D and L while descending to determine the mode you should be in. In L, the engine should be spinning higher than an idle which will give you more engine braking.

The 12V battery is only used to stabilize power when the DC/DC converter's power is exceeded. Therefore running other accessories may not be of much use saving the brake pads. Concentrate on the use of D and L while descending and use as much battery climbing in EV. My goal is shutting off fuel whenever I can.

Gary

 

Well, I don't use L that much, as I said. In traffic, on hills, and to assist braking. But I'm not that into hypermiling.

But I'm enjoying your posts on the CMAX.

 

I don't have an SGII. (I tried to set up an ELM-27 bluetooth connection to an OBDII app on my phone, but I wasn't able to come up with a PID for SOC that would work on the only customizable app that's compatible with Symbian. I'll try again some day when I replace the phone.)

If I reset the avg. fuel consumption before I start the descents, I know it reads 0 at the bottom. So I'm not using fuel, but I'd like to also minimize brake wear.

I will keep an eye on where on the most common descent the charge meter goes to the center position. That's where I've run out of battery capacity and the speed starts picking up so I have to use the brakes. Past that point the speed increases more slowly if I'm in Low than in Drive, so this FEH has some sort of residual engine braking in Low.

For the same descent, at the same speed, with the same load, varying Drive/Low and having accessories on or off may/should be reflected in where the charge meter goes to center. Short of installing an SGII, I'll be more careful noting what's going on.

 

I love that the discussions on the use of "L" are still ongoing all these years later.

While I've certainly never done the extensive testing that Gary has done with his, my experience is that using L doesn't cost me anything in mileage and in fact, I seem to do better in L. Mine are never in D unless I am on the highway and I remembered to shift it back.

Really looking forward to the weather warming back up. I had a couple tanks in the high 20's this winter and am finally above 30 mpg again. Looking forward to 50° or more so I can get a couple 38-40 mpg tanks to restore balance to my life.

 

I guess that many of the early FEH buyers participated keenly here and eventually had little to talk about. Then us johnny-come-lately's arrive on the scene with our newer FEH's and want to learn about the same things. Thanks to the "old timers" for being patient.

I want to again thank GaryG for clarifying that the '09 FEH's implement the Low gear differently from earlier models.

I too look forward to warmer weather, summer tires and gas with more energy per unit of volume.

 

The other day I was able to drive several km's at a steady 50kph (30mph) on a totally flat road with no wind or traffic. The engine stayed off most of the time, and the average mileage was 3-4L/100km. This would be about 60mpg US. Unfortunately around where I live, driving like that is possible once a year at the most.