Towing
Created March 18, 2008, at 1:46 pm by GaryG
Many people including myself have wondered why the tow capacity is only 1,000 pounds for the '05 - '08 FEH/MMH. Ford doesn't give a reason why the regular 2.3L gas Escape is rated for 1,500 pounds which is more than FEH/MMH, but now I think it all comes down to engine torque, the eCVT transaxle and the HV battery.
The Scangauge ( http://scangauge.com/ ) has clearly identified that engine LOAD goes to 99% and requires electric motor assist with any kind of torque demand at low RPM's. This occurs without towing any weight, so we must conclude it is very hard to tow any additional weight without constantly calling on electric motor assist. Now that I've had time to study my '05 FEH, I can see this constant assist if not controlled by the driver or driving in the mountains, could overheat the electric motors, electric components and the HV battery. The systems have built in safety measures to shut these components down when they get to hot, but your left with a gas engine with very little torque at low RPM's.
The electrical assist will allow the HV battery State of Charge (SoC) to drop below the normal lower limits on acceleration demands and provide needed temporary electric motor torque. However, there is a point the electronic control module can't allow the battery SoC to drop to a point the gas engine does not have enough battery Soc to restart the engine. This would put electric motor assist at a point where it is no longer available and all acceleration would be at a dangerous level with the low RPM torque of the Atkinson Cycle gas engine in our FEH/MMH. There would be no way for the engine to get to the higher RPM and higher torque range quick enough for fast acceleration if needed. Remember, the electric torque allows the Atkinson engine to increase RPM's to a point it has the torque to no longer need electric motor assist.
I'm sure Ford designed the FEH/MMH to handle 1,000 pounds for towing, but when these limits are way over exceeded, I can see possible operational problems with the present design.
Any thoughts?
GaryG
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I just want to add a few comments to this post:
A poster in Greenhybrid.com did state (2007 year) he towed a 14 foot Shasta trailer (1400lbs?) from Kansas City to Washington DC area. This included a trip thru the "Mountains" of West Virginia. I believe this poster stating his FEH producing RPMs in the 4500-5000 driving in West Virginia and was only getting(?) 12-14mph. Someone on this same site also mentioned to this response "just because you can, it doesn't mean you should tow like this". My gut feeling is you can exceed the limit safely for short distances in "sane" environmental conditions. The new engine in the 2009 model could be a significant improvement in this area if the torque curve is improved with the variable valve timinig engine. How heavy is your boat and how long of a drive is it to the lake/ocean?
Power for reverse is only generated from the generator and hybrid battery. Thus, there is limited horsepower for reverse.
As for dropping the hybrid state of charge--I acutally dropped my below 29% last fall opening and closing the doors, on and off with the radio during a six speaker replacement modification I performed. My vehicle started right up and had a 26% hybrid battery SOC immediately after starting.
On demand, like in powerful acceleration, Electric motor assist (as I understand it) can provide 10 HP for 40 seconds or 40 HP for 10 seconds. During highway driving, electric assist occurs naturally once the hybrid battery SOC exceeds 53%.
Hi Billy
I agree with everything you said and in most cases the driver that know these things can tow much heavier loads if they monitor for problems. I would have no problem towing my 3,000 pound boat a few miles to the closest boat ramp, because I know as you that you don't drive it like you would with my V8 Explorer. I would not tow my boat over 50mph or at highway speeds for any long distances for a number of reasons. As far as reverse, I would not allow myself in a place it would take a lot of torque to back-up like uphill or in mud or sand. For these reasons I didn't put a hitch on my FEH.
Most likely my Explorer gets better MPG pulling my boat and running the A/C than the FEH just pulling the boat. Even if the '09 FEH increases tow capacity, it will most likely not be enough for me to go to places with my boat like the FL Keys. It is possible I may install a hitch on the '09 for towing my boat because of an evacuation because of Hurricanes here. If I have a new Prius and a new FEH, the Explorer stays and the new ones go with me and my wife. My boat has a 63 gallon gas tank I could tap if needed. I keep it full during Hurricane season to supply my generator and cars if needed.
BTW, I've been searching for any news of any increase in tow capacity in the '09 2.5L gas Escape or the FEH/MMH. Any help would be nice.
GaryG
I am waiting for the 2009 models, But does anyone have a comment on towing a 400 lb tractor? This would be your average lawn tractor and some gardening tools and maybe a lawn mower.
I can't imagine these tools and the trailer weight more than 1000lbs.
Should I be worried?
Thanks
-paul
A 1,000 pound trailer is no problem with the '05 -'08 models, so the '09 should certainly not be a problem with the bigger engine.
GaryG
Gary, Does the Escape have the bolting holes already in the frame, or will they need to be drilled?
Thanks
-paul
Paul, people that have installed the hitch themselfs have stated they used existing holes in the frame. Not positive, but I think the '09 FEH/MMH will not have a HV battery A/C and lines , so this should make for an easier installation of a hitch.
GaryG
I had a hitch installed on my 2005 FEH and no new holes had to be drilled. I can not speak for the 2008 model due to the changes from the 2005-07 version. There are photos and description of this process at greehybrid.com and escape-central.com. Good luck.
GaryG, I just pulled this off the Greenhybrid site. It is from Stanley who you have exchanged normal comments in the past. Here is Stanley's statements on towing:
It sounds to me as if you're probably okay. There is, however, another consideration with the Ford and Toyota hybrid systems that hasn't been mentioned so far, and that may in fact be the main reason for their towing limitations. (The Prius and Camry hybrids specify a zero towing limit.) These vehicles can't move forward or backward without electrical power flowing into or out of one or more of the motor/generators. Even when cruising on level ground, a goodly fraction of the power flow from the ICE to the wheels is through MG1 and MG2, without necessarily using the NiMH battery at all. This is because the planetary-gear set (the "Power Split" Device) can't transmit power from the ICE to the wheels without MG1 (the "generator") applying a load to the PSD, either positive or negative. Electrical power is continually flowing either from MG1 to MG2, or from MG2 to MG1 ("heretical mode"). I think the electrical power flow between MG1 and MG2 is likely the limiting factor. When towing, this would be further increased, and could overstress the MGs and/or the power electronics (inverters and dc-to-dc converters) thermally and/or electrically (i.e., over-current). Under prolonged high power conditions, this might be the real reason for concern on Ford's and Toyota's parts.
A different view for all of us to digest.
Hi Billy
Yea, I saw Stan's post and he's saying the same thing I concluded but worded differently. The 2.3L unlike the Toyota Highlander and Lexus V6 doesn't have the low end torque to tow 3,500 pounds like those are rated. The Prius and the Camry are not set-up like the Escape where MG1 does not provide energy to MG2 until the ICE exceeds over 99% LOAD. Stan is a sharp guy, but he doesn't own or drive the FEH/MMH. The Charge/ Assist gauge for the most part tells us when MG1 is assisting MG2. There is no question that much of the energy comes from MG1 to MG2 under assist to reduce conversion losses associated with the HV battery. It sounds like according to Stan, the Prius and Camry use electric motor assist more than the FEH/MMH.
My point was even the FEH/MMH could get into trouble under hard towing conditions and overheat the eCVT which includes MG1, MG2 and the converter. The thing I really like about the new '09 FEH/MMH is Ford is going to a Variable-Voltage Converter (VVC) which will drastically reduce conversion losses and heat. This is why Ford can down size the HV battery and eliminate the battery A/C system. Ford may leave the size of the present HV battery case as is and just increase the flow of outside air around fewer cells. Ford is really trying to reduce the cost of the HV battery from what I've read.
GaryG
I have installed a "Hidden Hitch" trailer hitch on my '08 MMH, it was a different type of installation, one hole on each side of the frame needed enlarged. And then a spring like wire is attached to the mounting bolts then you fish the wire through the frame, not too touch just requires a little patience.
Now for my question has anyone wired for the trailer lights, I have yet to find a kit to do this. My '98 Dakota had a kit with aaimple plug in adapter, no cutting of wires, slick and easy. Anyone know of a kit like that for the '08 FEH or MMH?
You hard wire the trailer wiring directly to 12V battery in the engine compartment. Do not wire into the tail lights. Try E-trailer.com as a source for your needs.
Does anyone know is a tranmission oil cooler comes with the Hybrid or not?
Thanks
- paul
PaulI--no. The hybrid uses an electronic CVT that is hosed internally. My 2005 Hybrid has three radiators! One for the ICE, One for the electronics and One for the Hybrid battery pack! Towing or not, you want to use a synethic oil. The transmission fluid is not to be replaced until one has something like 120,000 miles!
So what your telling me that there is no way even to add one?
You would/could void your warranty with this modification that I do not know how it could work since the eCVT is internally housed. Ford OEM parts for this type of work do not exist on the hybrid vehicle due to what I just mentioned. This vehicle is not really a long term or long distance tow vehicle.
Let me jump-in here, yes there is a transmission cooler so to speak that cools the components that need cooling in the transaxle. There is no torque converter to heat the transmission fluid, but there is electronics that are cooled by the electronics cooler. It does not cool the HV battery, the A/C compressor provides that with cooled air when needed.
The electronic coolant system has a motor that circulates coolant to the DC/DC converter and the eCVT (transmission) to keep things cool which is separate from the engine coolant system. So yes, there are three radiators so to speak like Billy said, one cool the engine, one is for the electronics and one for the A/C refrigerant for the cabin and HV battery to cool.
The bottom line is you can tow 1,000 pounds in the '05 - '08 model and you do have a transmission cooler for many electronic reasons.
Power for reverse is only generated from the generator and hybrid battery. Thus, there is limited horsepower for reverse.
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