Thoughts on eCVT temperatures

[Automate]

My thoughts on eCVT temperatures.

 

First the facts:

• Conventional manual transmissions don't need coolers because they have minimal friction surfaces / clutches inside the transmission, they use gears that generate very little heat
• Conventional automatic transmissions do need fluid coolers because they use friction surfaces / clutches that generate heat every time they change gears
• Automatic transmissions also use a torque converter which generates heat whenever it is slipping. The fluid in the torque converter is shared with the fluid in the automatic transmission.
• eCVT have less gears than even a manual transmission and do not have clutches or torque converters like an automatic transmission
• The FFH motor and generator are inside the eCVT and integral to the transmission shafts.
• Scan gauges consistently show the eCVT motor and generator are at a higher temperature than the transmission fluid temperature
• Motors/Generators, wiring and electronics all have higher electrical losses at higher temperatures because the resistance is higher at higher temperatures.
• Transmission components (seals, bearings, motors) generally last longer at lower temperatures
• The lower the transmission fluid temperature the higher the viscosity or resistance to movement.

 

Based upon the above facts here are my conclusions / recommendations:

• The primary purpose of the FFH transmission fluid cooler is to remove the heat generated by the motor and generator
• Although high viscosity of the transmission fluid at lower temperature effects fuel economy (FE), the higher temperature of the motor / generator has a bigger effect on FE.
• At very low temperature (maybe less than freezing) a transmission heater may help FE but at normal operating temperatures a cooler eCVT will result in better FE.
• Once up to operating temperatures the eCVT should be kept as cool as possible for better FE and motor/generator/transmission life

 

Interested in your comments.

Edited May 30, 2015 by Automate

[ptjones]

I generally agree with Automate's conclusions having just had my Trans replaced.

Automate said "Once up to operating temperatures the eCVT should be kept as cool as possible for better FE and motor/generator/transmission life."

 

 

The problem here is that FORD doesn't have a operating temp range for the TFT and I have gotten up to 192F with new trans on the FWY, I hit 199F with old Trans, it had 98K mi. on it. It would seem to me that it would be better if it stayed below 170F. ;)
Paul

Edited May 30, 2015 by ptjones

[Automate]

Without all the data Ford has on the eCVT we won't know for sure. If you graphed it, the motor/generator losses is a line with a positive slope with increasing temperature. The transmission viscosity losses would have a negative slope with increasing temperature. The point at which these two lines intersect would have the highest fuel efficiency. My guess is this intersection would be somewhere between 32 and 50 F. So anytime you are above 50 F you are better cooling the transmission. So back to your question. Getting eCVT temperature down to 150 F would be better than 170 F and getting it down to 100 F would be even better. But since it is cooled by ambient air, getting it any lower during the summer is not going to be possible.

[GrySql]

The transmission viscosity losses would have a negative slope with increasing temperature. The point at which these two lines intersect would have the highest fuel efficiency. My guess is this intersection would be somewhere between 32 and 50 F.

For info on Motorcraft® MERCON® LV Automatic Transmission Fluid XT-10-QLVC used in the HF35 transmission and how temperature affects the viscosity, take a look at this:

 

Product Data Sheet MERCON LV.pdf

 

 

 

 

[Texasota]

Using grill blocking to achieve slightly higher MPG is not worth the risk to the eCVT and all the other power train components. This seems obsessive. I think it is likely that Ford Engineers would not endorse the use of grill blocking and it would seem reasonable to me for Ford to deny warranty claims on power train components of any FFH that was subjected to grill blocking. Obviously, this is only my opinion and I understand others will differ.

Edited May 30, 2015 by Texasota

[ptjones]

Using grill blocking to achieve slightly higher MPG is not worth the risk to the eCVT and all the other power train components. This is obsessive behavior to the max. I think it is likely that Ford Engineers would not endorse the use of grill blocking and it would seem reasonable to me for Ford to deny warranty claims on power train components of any FFH that was subjected to grill blocking. Obviously, this is only my opinion and I understand others will differ.

The facts don't support your conclusion. FORD did replace my Trans at 98Kmi. under warranty and I have had Grill Covers on since about 5kmi. No one else that have had Trans replaced used grill covers and I had at least 25kmi. more than anyone else that has had a Trans replaced. I have taken the lower Grill Cover off when TFT got up to 170*F, but the TFT kept going higher because the WT couldn't get to 215*F to cause shutters to open to allow air through Trans Cooler to lower TFT. Kind of a catch 22 situation. ;)

 

Paul

[Griswald]

Do you really know that fluid heat caused the tranny failure or are you just guessing? Could a pure mechanical failure (porousity, bad machining, crack in metal, etc) have happened?

 

Really, synthetic fluids can handle lots of heat without degrading.

[ptjones]

Do you really know that fluid heat caused the tranny failure or are you just guessing? Could a pure mechanical failure (porousity, bad machining, crack in metal, etc) have happened?

 

Really, synthetic fluids can handle lots of heat without degrading.

RICH FORD has put in a request for why the Trans failed. What we do know is that the fluid was darker than normal and it smelled burn when they took the Trans out. I drive 83% HWY driving and I have observed that the faster your speed the higher your TFT is going to be which makes sense. A number of CMAX owners commented that they were seeing TFT around 150*F as an average. ;)

 

Paul

[Texasota]

The facts don't support your conclusion. FORD did replace my Trans at 98Kmi. under warranty and I have had Grill Covers on since about 5kmi. No one else that have had Trans replaced used grill covers and I had at least 25kmi. more than anyone else that has had a Trans replaced. I have taken the lower Grill Cover off when TFT got up to 170*F, but the TFT kept going higher because the WT couldn't get to 215*F to cause shutters to open to allow air through Trans Cooler to lower TFT. Kind of a catch 22 situation. ;)

 

Paul

 

In this post (http://fordfusionhybridforum.com/topic/9839-high-transmission-temperature/?p=96802) you stated that you removed the grill covers when you brought your car in for the transmission problem and the service department did not notice them. Did you tell them that you had been using grill covers since 5K miles during this visit to service department?

 

It would seem Ford would be on solid legal ground to deny your repair under warranty based on these excerpts from the FFH Warranty Guide:

 

 

Damage Caused by Alteration or Modification

The New Vehicle Limited Warranty does not cover any damage caused by:

• alterations or modifications of the vehicle, including the body, chassis, or components, after the vehicle leaves the control of Ford Motor Company

• tampering with the vehicle, tampering with the emissions systems or with the other parts that affect these systems (for example, but not limited to exhaust and intake systems)

• the installation or use of a non-Ford Motor Company part (other than a certified emissions part) or any part (Ford or non-Ford) designed for off-road use only installed after the vehicle leaves the control of Ford Motor Company, if the installed part fails or causes a Ford part to fail. Examples include, but are not limited to lift kits, oversized tires, roll bars, cellular phones, alarm systems, automatic starting systems and performance-enhancing powertrain components or software and performance ‘‘chips’’

 

Owner’s Warranty Responsibilities

As the vehicle owner, you are responsible for the performance of the required maintenance listed in your owner’s manual. Ford Motor Company recommends that you retain all receipts covering maintenance on your vehicle, but Ford cannot deny warranty coverage solely for the lack of receipts or for your failure to ensure the performance of all scheduled maintenance.

You are responsible for presenting your vehicle to a Ford Motor Company dealer as soon as a problem exists. The warranty repairs should be completed in a reasonable amount of time, not to exceed 30 days.

 

As the vehicle owner, you should also be aware that Ford Motor Company may deny you warranty coverage if your vehicle or a part has failed due to abuse, neglect, improper maintenance, or unapproved modifications.

Edited May 30, 2015 by Texasota

[lolder]

The problem may be grill covers and the shutters. When they upped the max EV speed, they are producing more heat in the transmission without producing it in the engine. The shutters then open less and the transmission is hotter and there is no transmission fluid circulated to the cooler when the ICE isn't running. This may have put the whole system out of balance when they upped the EV speed. "No good intention goes unpunished." This sounds like the Thiokol engineers arguing against the shuttle launch in cold weather and being over-ridden by management ( reprogram the EV speed ). Until we know more, my advice remains the same; don't encourage EV and if you're in EV for more than a few minutes, goose it so the ICE runs 10 or 20 seconds.

We've talked a lot about how these cars are very carefully designed compromises. The 2010-12s don't have these problems because they didn't try to get as much "blood out of the stone" in mpg as the 2013+s. They got caught with their pants down with the 47/47/47 and things have been going downhill since. It's sad.

Edited May 31, 2015 by lolder

[GrySql]

RICH FORD has put in a request for why the Trans failed. What we do know is that the fluid was darker than normal and it smelled burn when they took the Trans out.

 

SSM 22553 explains how the Mercon LV fluid changes it's color/appearance.

Edited May 31, 2015 by GrySql

[billford]

I also could not find anything that states what transmission operating temperatures should be, but I did find some typical reference values based on speed from the Ford Powertrain manual.

 

Note that on page 5, values can change 20% under different conditions. And on page 10, TFT is referred to TOT.

 

I remember reading somewhere that if the trans gets too hot, it will set a code, but I don't recall what the temp would be, I'll do some more digging...

Ref Values.pdf

Edited May 31, 2015 by billford

[Texasota]

The problem may be grill covers and the shutters. When they upped the max EV speed, they are producing more heat in the transmission without producing it in the engine. The shutters then open less and the transmission is hotter and there is no transmission fluid circulated to the cooler when the ICE isn't running. This may have put the whole system out of balance when they upped the EV speed. "No good intention goes unpunished." This sounds like the Thiokol engineers arguing against the shuttle launch in cold weather and being over-ridden by management ( reprogram the EV speed ). Until we know more, my advice remains the same; don't encourage EV and if you're in EV for more than a few minutes, goose it so the ICE runs 10 or 20 seconds.

We've talked a lot about how these cars are very carefully designed compromises. The 2010-12s don't have these problems because they didn't try to get as much "blood out of the stone" in mpg as the 2013+s. They got caught with their pants down with the 47/47/47 and things have been going downhill since. It's sad.

It will be interesting to watch the Consumer Reports reliability data reported from FFH owners over the next couple of years. So far, the data for the 2013 & 2014 FFHs is showing top scores for both transmission categories (transmission major & transmission minor). While It is possible that a trend could be developing I don't think one can draw conclusions about a trend based on discussion/reports in this forum.

 

Assuming there is a trend developing and it is a heat problem as being speculated here, then that leaves me wondering if it is caused by the amount of continuous time (i.e. duration) spent in pure EV cycle or is it the amount of power demand on the EV components when traveling at highway speeds resulting from the software change that increased the maximum EV speed. My driving experience/observations consistently show that when I am in EV above 60 MPH it is for a relatively short periods of time (typically less than a minute) before the HVB SOC requires the ICE to start up again. On the other hand, when I am driving under ideal EV conditions (warm temps, 30-40 MPH speeds, and flat roads) like I experienced in SW Florida last winter I can nurse my FFH along in EV mode for much longer before the SOC requires the ICE to start up again. If it is length of time in a pure EV cycle that is causing a problem, then it would have little or nothing to do with the software change that increased the maximum EV speed.

 

PT's data/observations indicate that he is experiencing higher TFT at highway speeds but I don't think we can conclude his situation is typical since he has also stated that other C-MAX owners are reporting significantly lower TFT than he is. The software change that increased the maximum EV speed could be playing a role in transmission temps and contributing to a possible transmission failure trend but this is only interesting speculation at this point.

 

Ford has analyzed these failing transmissions and it is a given that Ford knows exactly what is causing the failures. It may be a manufacturing defect already addressed or it could be a heat/lubrication problem as being speculated here or some combination of factors that only Ford knows. But, if it was being caused by the software update that increased the maximum EV speed wouldn’t it seem plausible that Ford would have addressed that by now with another software update (TSB or recall) to prevent/avoid further failures and the associated warranty costs to Ford?

[hybridbear]

The eCVT temps are hotter after hours of continuous highway driving versus city driving. City driving doesn't raise the eCVT temp very fast. We've done lots of city driving in the Energi and the TFT barely reaches 100 F in city driving even after 20-30 miles of continuous driving. In freeway driving it reaches its peak after at least an hour of driving. Our peak has typically been around 170 F with all grille blocking removed in the summer. In the winter it stayed cooler even with full grille blocking. In the winter the eCVT temp struggled to reach 140-150 F.

 

The hottest TFT temps (and hottest motor/generator temps) were when descending down out of the mountains in EV mode for long stretches with lots of regen. Extended regen braking seems to generate the most heat of any type of driving.

 

The Energi can do much more EV driving and thus has an auxiliary TFT pump which runs when the ICE is off. Even with the TFT constantly circulating we saw the TFT go over 200 F when descending down out of the mountains and regenerating more than 3 kW into the HVB.

Edited May 31, 2015 by hybridbear

[Texasota]

The hottest TFT temps (and hottest motor/generator temps) were when descending down out of the mountains in EV mode for long stretches with lots of regen. Extended regen braking seems to generate the most heat of any type of driving.

I would assume the FFH would be doing much less regen descending out of the mountains compared to the the FFE because of the much smaller HVB capacity. When I descended our of the Smokey Mountains the HVB quickly reached full SOC and ICE compression braking took over. At that point it would seem the FFH should be generating no more heat in the transmission than would be generated with 4-down towing of the FFH?

[ptjones]

The Software speed change didn't effect TFT, the change in shutter opening did, before it would start at 190*F and fully open at 213*F, now it waits to open till 215*F. I made a trip 25 miles up and then back, I was only able to get WT up to 207*F on the way up, but TFT got to 175*F. Before returning I removed tape from 5x2" holes in the lower grill cover and then returned home down the I-85. the ICE had cooled down some so I had to run the ICE most of the time to get to 215*F for the shutters to open, by that time TFT was up to 179*F, but then dropped down to 175*F in ten miles with ICE running most of the time. The WT stayed in the 215-225*F so the shutters were open most of the time. My speed was 65-75mph for the most part and I averaged 52mpg. :)

 

Paul

[lolder]

I didn't realize they had raised the shutter opening temp also. That fits into the puzzle. Did that happen when the EV speed was raised?

[hybridbear]

I didn't realize they had raised the shutter opening temp also. That fits into the puzzle. Did that happen when the EV speed was raised?

Yes