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Thread: New MPG Technique Found
12-01-2008 01:09 AM #1
- Join Date
- Oct 2006
New MPG Technique Found
Desertdog (CarlD) has brought a new Hypermiler technique to the table which he first posted about on CleanMPG.com that I found remarkable: http://www.cleanmpg.com/forums/showthread.php?t=17097
I've confirmed his findings and wanted to pass this new technique to Hybridcars.com members and readers. Carl has an '05 FWD FEH and he is responsible for giving us the SoC gauge and many other codes to program the Scangauge for our FEH/MMH and other Fords.
The "Opposite Of The Fake Shift" was the title of his post. Since I came up with the "Fake Shift" technique originally, I thought we would call it the "Reverse Fake Shift" to shorten the name. This new technique works in all FEH/MMH and I have also confirmed it works in the '09 models. To my knowlege you must have a SGII (Scanguage 2) and have programmed Carl's SoC Code into the X-Gauge to take advantage of this new technique.
Background: It is a proven fact EV mode increases your overall MPG average, so the more time and distance your FEH/MMH is in EV the better. This makes the HV battery State Of Charge (SoC) management very important to improve MPG.
The Reverse Fake Shift is a technique to eliminate or reduce the amount of SoC it takes to restart the engine. Normally it takes between .3% - .7% of your battery SoC for a restart of the engine from EV mode. While this may seem to be a small amount of energy, it's not when you understand how EV mode increases your MPG. The least amount of time your engine is running, the more MPG you will average. The normal operating SoC of your HV battery is only 40% - 60%, but you rarely see the battery go higher than 53%. So if you let your SoC go to 53% which is where the generator stops charging, you only have a total of 13% of SoC to run in the EV mode. At a 30mph steady state speed, this allows you about 1.3 miles of EV mode.
The biggest reason I was able to exceed 60mpg for first place at the MPG Challenge in a '05 FWD FEH was EV mode. My engine restarted at 40% SoC and charged the battery to 42% where the FEH/MMH can return to the EV mode. This is a EV operating mode with only 2% SoC (40%-42%) between the engine shutdown for EV and restart to recharge the battery. The problem is compounded when the generator uses more SoC to start the engine. The SoC will drop past the 40% to as low as 39.3% sometimes, so now your engine will run much longer to get back to the 42% where you can go EV again. If you could eliminate this large loss of battery SoC from a restart, you could build the SoC from 40% to 42% much faster in a shorter distance. This could increase your EV time and distance up to 30% and shorten your engine running time and distance.
Well, Carl found the technique to eliminate or reduce the amount of SoC wasted on a restart. It works by letting off the accelerator in "D" a second and then do a quick light blip on the accelerator to trigger a restart. Keep you foot off the accelerator till you have a complete restart where you can now accelerate with the engine running and recharging the battery. The blip must be fast and short and not hard acceleration for it to work. What I think is causing this effect is regenerative braking from the traction motor. Instead of using the battery SoC to start the engine, the generator/starter motor uses regen energy from the traction motor which doesn't have conversion losses like the battery. It might take some practice to get this technique down pat, but I'm getting almost 100% effective at it now. Already my tank MPG average has increased to almost 50mpg in my '09 FEH.
For the folks that have the '09 FEH/MMH, I discovered we have a bonus technique that does not require the SGII too know it's working. Unlike prior models, our '09 restarts from EV anytime you shift to "L". If you shift to "L" with your foot off the accelerator in EV, the engine will start the same as above not using any battery SoC. Again, regen from the traction motor provide the energy for the generator/starter to start the engine. This was my find and I have verified the results 100% of the time with my SGII SoC gauge. The other benefit of shifting to "L" in decel in the '09 is you get 100% fuel-cut (DFSO) till you press on the accelerator. This is a good technique to use while slowing down for a stop or stoplight.
11-15-2009 12:16 AM #2
- Join Date
- Oct 2006
In addition to the
In addition to the accelerator blip to restart the engine from EV, I've found another modification in the '09 FEH P&G (Pulse & Glide) technique. The newer 2.5L Atkinson engine in the '09 has a higher efficient way of acceleration than the prior 2.3L Atkinson engine. This allows you to Pulse (accelerate) faster and higher to a target speed. The problem I have with my '05 FWD FEH is I can't Pulse as hard with the 2.3L without using the battery for electric motor assist. With the '09 2.5L engine, I can Pulse up to my target speed faster without using electric motor Assist and also still charge the battery.
So now I know I can accelerate faster in my '09 and go EV much sooner for the Glide (neutral coasting) and save more gas than my '05 FEH. During my everyday commute, shopping and errands I went 785 miles on 13.6 gallons of gas (E10) and averaged 57.742mpg on that tank of gas. The Nav Sys had a 60.8mpg reading for that tank. My 2nd tank using this technique was 751.2 miles and burning 13.712 gallons which was 54.748mpg. The Nav Sys had a 48.9mpg reading on the second tank.
One other thing I changed was not letting the Battery SoC fall below 42.5% so I could always go EV if I needed to stop. I Glide as soon as I can after the Pulse when traffic permits. This allows the battery SoC to slowly increase with each P&G till the battery is ready for a long EV steady state speed with the cruise control On.
Good Luck and ask for more details if you need too.