Flat towing Hybrid Maverick why limited to 70mph?

[sseiler]

Who would drive any vehicle pulling a trailer over 70 mph?

… This guy.

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[TheGriffin1313]

Who would drive any vehicle pulling a trailer over 70 mph?

People who don’t understand the dynamics of mass distribution IE you can loose control of the vehicle. Add to that front wheel drive. Most of the mass is up front adding mass the end of the truck is messing with center of inertia. Now you have two points of mass the front and the trailer. Now the lightest point is in the middle. This makes an unstable linkage and will cause you fish tail and then flip the trailer and your truck too. This holds true in any case when you have two distinct masses are held by a pivot point (hitch)
When towing wisdom is paramount. Lady Luck is the other shoe that most experienced.

 

[MakinDoForNow]

Honestly, I've never towed anything at over 70 mph...so is that a thing people do? I can't personally imagine driving an rv at much over 70 mph, much less doing it while towing a truck.

Significant portions of interstate 10 between San Antonio and El Paso have 80 where it's wise to drive 75 so the 10mph over RV pulling flat tows don't blow your SUV into the bar ditch. It can be 10-20 miles between on/off ramps. I got pulled over once for only going 63 in an 80. He said watch it you're gonna get killed! I think it was because I was the only one he could catch!

 

[MakinDoForNow]

Actually I noticed this in the manual too, the procedure of having to run it every 6 hours. This is interesting to me because my understanding is we won’t be able to control when the 2.5L ICE actually comes on in the hybrid, and I thought the engine wasn’t even likely to turn on at first “start” unless it needed to for climate control or the battery was low.

Does this imply that the hybrid will have some sort of mode that‘ll allow us to turn on the 2.5L ICE?

My $0.02 = if I remember right the run time after 6 hours towing was very short and did not requiring any driving. So just something short and sweet -- so Hey it's still operational we can go 65 (if it starts). If not 35 to Ford house. The shifting requirement without driving (and presumably not enough pedal to do anything since still attached to RV). The only thing I see happening is maybe allowing the smaller motor/generator to turn in opposite direction to lube a shaft or bearing or something. As far as 70mph limit. I think they changed the size of the motor generators (less magnet size or number) but had to spin faster to keep power generation same. I am thinking the problem may be in the oil the oil pump is mechanical (most likely centrifugal) but when drive motor is turning (19,000rpm ??) At 70 mph or at what speed 82? Will the oil be "stacked" high enough on top of the motor/generators gears (also throwing oil etc) to the extent that the oil pump starts to suck air. God only knows how fast some of them puppies are turning.

 

[Redneck Garage]

You could even use your Ford App to start the truck every couple of hours LOL

 

[BDennis]

You could even use your Ford App to start the truck every couple of hours LOL

Yes I know you where kidding, but the engine has to start every six hours or less, but you must also run it through the gears with your foot on the brake. After running your engine, you must then place it back into tow neutral before resuming towing.

 

[Vongreg]

I “think” it is more related to heat. While flat towing there is no auxillary cooling in place. Can you go over 70 mph sure you can. Long term going over 70 mph for extended periods of time you will start to see degradation of components, bearing failures and thus early failure of your transmission.

The Kia Soul Turbo with DCT is also flat towable although I don’t think they have a speed limit on it. They do recommend not putting a rockguard on the front of the Soul to have maximum air flow through the components to aid in cooling.

Many other manufacturers have placed speed limits on their non-hybrid flat towable vehicles and others do not. No idea as to why they don’t but I can safely assume the speed limit is not hybrid related.

 

[shocontinental]

I’m planning to dolly tow my Maverick. This will let me tow at a top speed of 75mph(!!) that my RVs Ford F53 chassis is electronically limited to.

Also it can only hit that going downhill. . . at least it’s pretty.

 

[taralon]

There are two reasons why, AFAIK, for the 70 mph limit and the necessity to start every couple hours.

The speed limit is because I'm flat tow mode the high voltage battery, hvb, relay is not closed. This means that the only cooling the coils, stators, and transmission lube is getting is passive, as the coolant pump is powered by the hvb system. Even though no power is being fed from the system or to the system from the hvb, there is going to be heat generated by the induced current in the motor windings from the permanent magnet stator. The speed limit is to keep the system temp low enough you don't end up cooking the electrical motors, not overheat the transmission lube.

This fact that the hvb is not connected also means that the cars electrical system needs are fully supported by the 12 volt battery. Starting it every few hours and shifting from park to reverse to drive and then placing the vehicle back in neutral hold/ flat towing mode closes the hvb relay. During flat towing the (in the fusion hybrid and likely all other ford hybrids) the antilock brake system is active in order to avoid wheel lock, and there is some belief that the electrical brake booster is also active. This increases drain on the 12 volt battery and can result in deep discharge. In older Ford hybrids cycling the key off immediately opened the hvb relay, which in certain use conditions (especially tow flat) resulted in undercharging of the 12 volt battery. In newer models if there is a short 'drive' cycle the system keeps the hvb relay closed until the 12 volt battery is charged and the eCVT coolant temperature is nominal. Doing the start cycle when flat towing every few hours alleviates issues with 12 volt battery draining and and helps insure the eCVT doesn't get too hot.

A link that might be useful to some looking to flat tow their maverick is below.

https://community.fmca.com/topic/8917-tow-a-ford-fusion-hybrid/

 

[MakinDoForNow]

Actually I noticed this in the manual too, the procedure of having to run it every 6 hours. This is interesting to me because my understanding is we won’t be able to control when the 2.5L ICE actually comes on in the hybrid, and I thought the engine wasn’t even likely to turn on at first “start” unless it needed to for climate control or the battery was low.

Does this imply that the hybrid will have some sort of mode that‘ll allow us to turn on the 2.5L ICE?

I am guessing that at least in part that tow neutral mode may (or may not) will allow/require ice to start but the simple fact of the catalytic converter or engine coolant or battery not being at operating temp could trigger ice to start also when you turn vehicle on. By requiring procedure to only take "a few minutes" it apparently doesn't require any significant battery charging or they would have specified a specific minimum number of minutes so apparently the primary purpose is simply to circulate fluid in gear set. If so it may be solely accomplished by electric motors if HVB is adequately charged. (?)

 

[fbov]

... transmission lube is getting is passive, as the coolant pump is powered by the hvb system.

Reading through again, I missed lubrication. This video shows the internals, and he does a good job showing all the passive lubrication paths, and the circulation pump driven by ICE. It's really just pumping coolant over the stator coils, but it also hits a rotor bearing that's not in the passive splash pattern.

 

[BDennis]

Some

I’m planning to dolly tow my Maverick. This will let me tow at a top speed of 75mph(!!) that my RVs Ford F53 chassis is electronically limited to.

Also it can only hit that going downhill. . . at least it’s pretty.

Did buy the hybrid or Ecoboost? I am taking my hybrid to Roadmaster the end of this month to be their prototype for their baseplate. I am going to use a Ready Brute Elite II tow bar with a built in surge brake.

 

[shocontinental]

Did buy the hybrid or Ecoboost?

Hybrid, I know it’s flat towable, but I already have the dolly. I’m still months away from getting the Maverick, so I might rethink it at some point.

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