Last weekend was the first time I've had the Mariner in the big mountains outside of winter, and I experienced some weird behavior on downhills at full SoC (which I saw at a highest point of 69.3%). Are these things normal?

• The ICE would not shut off in "L", but would shut off in "D" if I was below 40mph.
• At low speed, I could get the car to go into fuel cut in "L", but I never managed fuel cut at freeway speed (in L or D).
• At 45mph on Loveland Pass (steep) I was only getting 60mpg in "L" and couldn't do better than 100mpg in "D", even though I wasn't touching the gas.

I've experienced similar things before in the winter, but I chalked it up as the cold engine. However, temps were between 60 and 80 degrees on the way down and my coolant temp ranged between 150 and 190 degrees.

What is the best strategy for mountain driving once your SoC hits the ~64% range at freeway speed? I don't want to only get 60mpg in "L", nor do I want to ride my brakes in "D" and still only get 100mpg...

 

xx

 

This photo was from Feb. 2008 in Maryland at the bottom of a 1.5 mile downhill.

fordescapesoc686.jpg?t=1222907200

GPSman1 has answered this type of question in the past. He gets fuel cut at the top of the mountain by shifting into "L", when the tach "jumps", shift to "D" to cut fuel and glide down the mountain with full braking power. Once you hit the gas pedal, fuel cut is eliminated.

 

The 08s seem to work a little differently (or my Scan Gauge does). It will only go into fuel cut at lower speeds, and I can use the gas pedal to bring up electric drive mode without turning the fuel cut off. I've followed GPS's directions in the past to get fuel cut at higher speeds without success. Has anyone else driven in the mountains with an '08?

 

Kristian-

I HIGHLY suspect your HV battery was too warm with all that downhill charging... forcing the A/C to run for cooling, and hence, your ICE was on more than you'd like.

The FEH does not ever use gasoline to "burn off" excess battery charge... just to clarify that.

The car will use battery power to propel the car at it's first opportunity to lower the battery SOC to it's preferred state of 53%.

FYI the battery has many ohms of internal resistance, and gets hot much quicker than most people suspect.

Do you ever use the Tav xGauge to monitor battery temp?
It could be a real eye opener for most people.
The A/C comes on at 86'F and disables EV at 96'F.

P.S. When my HV battery gets full and/or hot, I switch to N on downhill coasts.
This cuts off regen, and you will use brake pads, but it will keep the engine off, more of the time.

P.P.S. I have never gotten my battery too full so it stops all regen. However, as the SOC climbs above 60%, the amount of regen allowed will gradually decline. Sometimes, if the battery is getting warm, all regen will stop for a few seconds, and then restart again... I presume, to reduce the production of heat and/or to give the HV battery a few seconds of "rest" on a long sustained downhill ( like I70 or Loveland Pass ). I have gotten my battery up to 78% SOC with downhill regen, but my car behaved just like yours. Yours sounds "normal" to me. My ICE would come on when the REGEN quit for a few second of battery "rest" on a long downhill like loveland pass.

-John

 

Just to make sure readers are aware...switching to N and preventing engine and or/regen braking and relying ONLY the friction brakes on long downhills has been a topic on this site many times... Some people say its perfectly safe, some do not. In the interest of presenting the other side.

http://www.cartalk.com/content/colum...tember/13.html

http://www.cartalk.com/content/colum...vember/11.html

Short little bursts of "N" just to let the battery cool a bit shouldn't be a problem I would think. But putting it in N and riding the brakes all the way down might not be safe... one should have all the information before trying it. I wouldn't even count on the above links as being definitive... they are the CarTalk guys after all! But its a starting point to learn about the issues involved and I happen to like listening to them anyway.

One should always learn before trying something new...Of course that goes for alot of advise one learns online and even in friendly conversation.

 

I was in the mountains a few weekends ago for the first time in about 20,000 miles. I let a friend drive through a particularly steep up and down section (lots of curves too). This was his first hybrid experience so there was nothing but D driving the whole time. There was a bit of brake smell at the end of a few long downhill sections where the battery indicator was completely full (all green on the hybrid display) and I could see that there was VERY little regen being allowed. So even in D there appears to be a chance for the friction breaks to get a good workout.

BTW, he pulled a solid 30MPG and was thoroughly impressed with the FEH all around (and let's don't kid ourselves the '05-'08 ICE appears to a 1st time driver to work really hard in the mountains). I kept telling him that the computer is in control and would manage the RPMs and keep the engine safe. It was his first CVT experience too.

 

By all means, use the brakes smartly.
I assume the readers in this case are traveling at slower speeds, since the effort is to keep the car in EV mode.

On a side bar... on Loveland Pass in fact, once, I was "riding the brakes" a little too much.. in Drive, and the car noticed this, and did an engine run-up ( compression brake ) while I was in Drive. ( this normally occurs only in Low ).

I don't know if there are brake temperature probes ( probably not ) or the car used predictive software ( probably so ) and figured.. hey... the brakes must be getting hot by now, so I'm switching to compression brake. It was long ago, and I don't remember if the car was in fuel cut or not, but it most likely was.

 

Thanks for taking that post as it was intended and not as a personal attack. It certainly wasn't meant as one.