Transmission surge when turning

[Spitinuri]

Over the last 5K miles or so I have noted a particular event when turning the car onto a street from a moving position.

 

As I approach a street say at 20-30 mph I put on the brake and quickly turn (left or right) and notice during the turn a surging (amost like the engine races) sensation is felt almost like someone pushed on the accelerator during the turn for a moment and it is gone..

 

Has anyone else noticed this event?  Is it possible it is related to a recept system update?  Or,.. is this a transmission issue?  I am currently at 96K miles.

 

Thanks

[fbov]

Yes, I get this on a regular-but-rare basis.

 

I would describe it as more of a reduction in braking than a surge (increase in speed). Reminds me of dropping the clutch to downshift going into a turn. When the clutch opens, you lose engine braking, so the car feels like it's surged into the turn, but it didn't surge.

 

Listen to the drivetrain. My sense is there's no sound associated. Extending the clutch analogy, it's as if the traction motor stops braking once you start turning. Now that I think about it, it's about the opposite of the braking surge in wet weather, if you've ever noticed that one.

 

Note that if you've ever gotten into RSC, this is positively subtle by comparison. When RSC intervenes, there's no question, no subtlety, you're just a passenger in the drivers' seat. This one's more of a "shiver - hey, what was that?"

Have fun,

Frank

[Bugblndr]

I had this happen for the first time today. I figured the CVT tranny just got confused about what I was doing.

[stevedebi]

Yes, I get this on a regular-but-rare basis.

 

I would describe it as more of a reduction in braking than a surge (increase in speed). Reminds me of dropping the clutch to downshift going into a turn. When the clutch opens, you lose engine braking, so the car feels like it's surged into the turn, but it didn't surge.

 

Listen to the drivetrain. My sense is there's no sound associated. Extending the clutch analogy, it's as if the traction motor stops braking once you start turning. Now that I think about it, it's about the opposite of the braking surge in wet weather, if you've ever noticed that one.

 

Note that if you've ever gotten into RSC, this is positively subtle by comparison. When RSC intervenes, there's no question, no subtlety, you're just a passenger in the drivers' seat. This one's more of a "shiver - hey, what was that?"

Have fun,

Frank

That sounds more like traction control, which invokes the antilocking braking to resolve temporary loss of traction.

[fbov]

I've activated traction control, and this is decidedly different. I would never call traction control subtle.

 

Plus, you're going too slow to break traction....

 

Have fun,

Frank

[stevedebi]

I've activated traction control, and this is decidedly different. I would never call traction control subtle.

 

Plus, you're going too slow to break traction....

 

Have fun,

Frank

Activated TC? I thought it was always on? I'm not saying that is what is happening, or that TC should be engaging, but it uses the ABS system to stop the wheel from turning. It could be engaging due to an error.

 

TC is generally disabled above a certain speed (20 MPH in my past vehicles, but I haven't checked this one_. You may be thinking of the stability control, which is used at speed.

[fbov]

The car has traction control in three directions:

- when braking, we call it ABS

- when accelerating, we call it traction control

- when turning, Ford call is RSC.

 

All three use the same sensors and control logic, because all three are just modulating the brakes based in sensor input. I know they're connected because I lost my RCM module shortly after Ford issued safety recall 13S04 (RCM). When the RCM is disabled, you lose all three aspects of traction control, and gain a much brighter dash as a result of all the MILs.

 

More to the point, have you observed this behavior? It happens on a regular basis, now that I'm sensitized.

 

Have fun,

Frank

[stevedebi]

The car has traction control in three directions:

- when braking, we call it ABS

- when accelerating, we call it traction control

- when turning, Ford call is RSC.

 

All three use the same sensors and control logic, because all three are just modulating the brakes based in sensor input. I know they're connected because I lost my RCM module shortly after Ford issued safety recall 13S04 (RCM). When the RCM is disabled, you lose all three aspects of traction control, and gain a much brighter dash as a result of all the MILs.

 

More to the point, have you observed this behavior? It happens on a regular basis, now that I'm sensitized.

 

Have fun,

Frank

No, I haven't seen it.

 

I was aware that it was the same sensor and brakes, just used differently, but thanks for posting that - always good to have extra information!

 

However, I believe they are used differently, since the ABS is used when braking, whereas the RSC is used when cornering (generally during acceleration, but always at speed), and the TC is used when accelerating from a stop. Same sensors, different implementation. Note that RSC would use a different sensor, to detect tipping.

Edited June 11, 2015 by stevedebi

[openair]

Sounds like, in at beast fbov case, the same issue being discussed in this thread on the hybrid fusion forum.

 

http://fordfusionhybridforum.com/topic/9866-new-regen-braking-issue-got-to-love-this-one/

[fbov]

Actually, no.

 

This guy reports a loss of regen braking (post 7) to the point where he's missing turns, which is very different from what I reported.

 

Frank

[openair]

Yes, I get this on a regular-but-rare basis.

 

I would describe it as more of a reduction in braking than a surge (increase in speed). Reminds me of dropping the clutch to downshift going into a turn. When the clutch opens, you lose engine braking, so the car feels like it's surged into the turn, but it didn't surge.

Reduction in braking. Temporary loss of braking. Semantics?

 

Both you, the OP and the linked thread report an issue with controlling the vehicles speed during a turn. Specifically the regen braking.  At similar velocity. That the vehicle did not slow down as expected. What is the result of not slowing down due to a reduction or brief loss of braking? Surging forward.

 

A loss can be anything less than what was achieved. Or in other words a reduction. It seems far more likely that this is the same issue being described slightly differently than two separate issues that have very similar symptoms.

 

This guy reports a loss of regen braking (post 7) to the point where he's missing turns, which is very different from what I reported.

 

If you take a turn at a high enough speed, with the expectation that the vehicle will brake in the usual controlled manor, it is very possible that even a brief reduction of regen braking (such as a clutch), would cause you to "nearly miss" your turn.  He uses the words "nearly miss" in post 7.  'Almost' is not missing turns.

 

Unless you can be more specific?

Edited June 21, 2015 by openair

[fbov]

Reduction in braking. Temporary loss of braking. Semantics?...

It's rare I get to say "actually, no" twice in a row!

 

You should try reading the threads, here and FFH. This is not semantics. Have you ever lost your brakes"? ... it's not pleasant, and it's not what I'm saying, it's what acdii is saying on the FFH forum.

 

acdii feels his car is unsafe to drive. Mine's fine.  

 

acdii says his car is not slowing down. Mine slows just fine under regen braking, with scores in the 95+% range.

 

acdii is nearly missing turns because the car doesn't slow down. I'm already slowed down before this happens.

 

The last post in that thread is someone reporting something similar to my observation:

" I can reproduce it, but only at speeds of less then 10 mph in a turn with light pressure on the brake petal in regen mode when mechanical brakes are not active."

 

Spitinuri was concerned about something he noticed. I reported some similar observations. Now add Sleddog (above) over at the FFH forum with the same observations. None of us are reporting brake failure.

 

Frank

[openair]

It's rare I get to say "actually, no" twice in a row!

 

You should try reading the threads, here and FFH. This is not semantics. Have you ever lost your brakes"? ... it's not pleasant, and it's not what I'm saying, it's what acdii is saying on the FFH forum.

 

acdii says his car is not slowing down. Mine slows just fine under regen braking, with scores in the 95+% range.

 

acdii is nearly missing turns because the car doesn't slow down. I'm already slowed down before this happens.

 

The last post in that thread is someone reporting something similar to my observation:

" I can reproduce it, but only at speeds of less then 10 mph in a turn with light pressure on the brake petal in regen mode when mechanical brakes are not active."

 

Spitinuri was concerned about something he noticed. I reported some similar observations. Now add Sleddog (above) over at the FFH forum with the same observations. None of us are reporting brake failure.

 

Frank

 

lol.  And imo you should try reading them. Acdii  also reports still achieving regen scores of 98% during this issue.  That this issue can be the difference between 98% and 100%.  You and him both approach turns differently.  He drives the vehicle harder, slowing down as he turns.  You have "already slowed down."  Of course there is going to more and less difference in the turn itself with this different driving behavior.  

 

The last post in thread agree that their similar issue is the same issue as acdii, just slightly different, but you use this as evidence it is an entirely different issue???  Actually, no! Acdii is not reporting brake failure but a brief reduction in regen breaking.

Edited June 23, 2015 by openair

[fbov]

lol.  And imo you should try reading them.....

Last time. Post 7 from acdii.

"When it is not acting correctly, that is I press on the brake, the car slows a little, regen circle is spinning, and the amps to the HVB are in the mid -50's, near -60, yet the car is not slowing down as it should, and I have to press harder on the brakes to slow it, engaging the pads instead before the car slows. There are times where I nearly miss my turn since the car is not slowing as expected, and at times I have to push really hard and it feels as if there is air in the brakes before the car slows down." (emphasis added)

 

This is not what I experience. I am not laughing.

 

Frank

[openair]

You should try reading more than just post 7. Like where he states the friction breaks work "100% perfect". Like the part where his wife says she only noticed what it was after he reproduced it for her. Or this being the difference between 98 and 100% break scores. Or the fact that the dealer at first said there was no problem they could reproduce. That only after showing two service mangers while driving the car himself did they agree there was a problem (at first). Or the fact that ford eventually told him this was normal behaviour they could not fix or improve.

 

Try reading post 41...

 

 

There is a software glitch in the car, somewhere. I discovered today that when the regen braking is lax, that if I shut the car off and restart it, the braking returned to normal. That explains why it is so hit and miss, when they work right, they usually work that way until I turn it off.  The surge while turning has to be some sensor that is cutting out the regen briefly.

Or are you suggesting ford would refuse to fix an issue where the breaks actually failed? Edited June 24, 2015 by openair

[fbov]

All I've "suggested" is that I didn't have the same problem acdii did. That Spitinuri need not be terribly concerned, comparing our symptoms.

 

What value have you brought to this thread?

 

Frank

 

PS we're discussing brakes, not breaks...

[openair]

All I've "suggested" is that I didn't have the same problem acdii did. That Spitinuri need not be terribly concerned, comparing our symptoms.

 

What value have you brought to this thread?

 

Frank

 

PS we're discussing brakes, not breaks...

Actually no, you've repeatedly stated acdii was reporting a brake failure. This statement combined with the information in that thread (that ford could not fix it) means you are suggesting that ford could not fix a failure of the brakes.

 

The only 'value' I'm attempting to bring to this thread is to show ppl experiencing this problem other ppl experiencing a very similar problem. The more ppl experiencing an issue the more likely ford is to find a solution.

 

Your attack on my path typing auto correction and clinging to one post while ignoring more clarified posts further on in that thread certainly adds a lot of value though.

[plus 3 golfer]

My 2 cents.

 

I've experienced what appears to be a reduction in braking in sharper turns when slowing down when I first started drving my C-Max.  I'm going to pay more attention to it as I'm used to the braking feel of my C-Max now and haven't paid attention to it anymore.  

 

Very early on I attributed this reduction in braking to use of ABS when turning to apply proportional friction braking to rear and perhaps front wheels when in regeneration.  I've posted this post about 2 years ago about control strategies using regenerative braking.  We don't know what strategies Ford uses but IMO it's likely that the traction motor and ABS are used together under certain conditions.   My theory is that at some point in the braking process when slowing down in curves ABS discontinues use of the friction brakes but regenerative braking continues.  One feels a slight surge (decelleration slows)  when use of friction braking ceases or perhaps a combination of friction / traction motor braking forces are changed.

 

For me this is has not been an issue.  Again in the papers the goal is to maximize regeneration efficiency but in a safe, controlled way to simulate friction braking.  There are likely slight anamolies under certain condtions when trying to integrate traction motor and friction braking.

 

 

 

 

 

[cheezy]

 

You should try reading more than just post 7. Like where he states the friction breaks work "100% perfect". Like the part where his wife says she only noticed what it was after he reproduced it for her. Or this being the difference between 98 and 100% break scores. Or the fact that the dealer at first said there was no problem they could reproduce. That only after showing two service mangers while driving the car himself did they agree there was a problem (at first). Or the fact that ford eventually told him this was normal behaviour they could not fix or improve.

 

Try reading post 41...

 

 

 

Or are you suggesting ford would refuse to fix an issue where the breaks actually failed?

 

 

Yeah, there appears to be A LOT of C-Max/Ford slamming in these Forums, using the tactics of "The Merchants of Doubt" to sway gawkers from buying these cars. There's A LOT of money at stake so I'm not surprised.