Engine revving when applying brakes

D

D_mazda_5

Member
Hello

I have the 2014 - CX-5 GT for the last 6 months.

I noticed when the brakes are applied when the car is at decent speed(normally noticed when 50 or higher), engine starts revving and the RPM goes to 4K or above.

Is this a normal behavior? anyone have experienced the same??

Please advise

Thanks
DN
 
Nope. That's strange. Does it seem to be revving as if it were in neutral, or is the car still fighting against you as if you still had your foot on the accelerator?
 
Check for vac leaks. Perhaps the brake booster is affecting the rpm.
 
This car is programmed to do Rev matched downshifts when braking. It simulates what most good drivers would do during heel toe downshifts in a manual trans.

I love it, but come from a performance driving background. I could see where some find it weird.
 
kekek said:
This car is programmed to do Rev matched downshifts when braking. It simulates what most good drivers would do during heel toe downshifts in a manual trans.

I love it, but come from a performance driving background. I could see where some find it weird.
Click to expand...


Thanks for the reply, I have definitely experienced same/similar when driving manual transmission cars, so you are saying this is working as designed and nothing to worry ? :)

I googled the term 'Rev matched downshifts' and got some hits too
http://www.leftlanenews.com/new-car-buying/mazda/cx-5/
http://www.edmunds.com/mazda/cx-5/2...t/2014-mazda-cx-5-smart-shifts.html.html.html
 
Last edited:
kekek said:
This car is programmed to do Rev matched downshifts when braking. It simulates what most good drivers would do during heel toe downshifts in a manual trans.

I love it, but come from a performance driving background. I could see where some find it weird.
Click to expand...

What he said, its normal. The computer uses engine braking to help slow the car down and also puts the transmission in the ideal gear when you get back on the throttle. The engine braking also allows the computer to cut the fuel and save gas.
 
This transmission keeps the torque converter locked to the engine so as to provide speedy response when you accelerate (no more 'slush box' as autos used to be known as). This also means when on the highway and you let off the gas, the tranny drops gear which increases engine revs.

I don't think its necessarily trying to emulate a manual's rev match, the goal is really just to improve fuel economy and pedal response. The mazda tranny is a little unusual compared to past autos in that it tries to keep it locked as much as possible.
 
I gotta say, ive never experienced what the op described. On the hiway im at about 2k rpms or so and if i brake it does not shoot to 4k. Maybe i have the problem then. Lol
 
Don't know if this is the same as the OP, but I've had several occurrences where I would be accelerating kinda hard (thus high revs) and had to immediately break, and the RPMs didn't come down like I expected. I don't think this is like downshifting. Seems more like a very delayed reaction to no longer wanting to accelerate and needing to drop the RPMs. I doubt this is normal, and I've only experienced it a few times.
 
robertmazda said:
Don't know if this is the same as the OP, but I've had several occurrences where I would be accelerating kinda hard (thus high revs) and had to immediately break, and the RPMs didn't come down like I expected. I don't think this is like downshifting. Seems more like a very delayed reaction to no longer wanting to accelerate and needing to drop the RPMs. I doubt this is normal, and I've only experienced it a few times.
Click to expand...

This happens to me almost every time I had to brake suddenly on a highway speed
 
If I do heavy braking in the city (so not going very fast, maybe 60km/h) I notice it downshifts a bit earlier than if you were coasting to a stop. Comes up to the 2000rpm mark (normally it hits 1500rpm if coasting) so I can see how in some situations it would downshift even earlier and make higher rpms. I actually like that it does this, and is exactly how I would drive a standard (well, not as aggressive, but the idea is the same).
 
robertmazda said:
Don't know if this is the same as the OP, but I've had several occurrences where I would be accelerating kinda hard (thus high revs) and had to immediately break, and the RPMs didn't come down like I expected. I don't think this is like downshifting. Seems more like a very delayed reaction to no longer wanting to accelerate and needing to drop the RPMs. I doubt this is normal, and I've only experienced it a few times.
Click to expand...

That is normal, if it stays in the higher RPMs your car will slow down faster. The computer recognizes that you are braking hard and is assisting you.
 
I wouldn't say you can slow down faster by using engine breaking, but it certainly takes some load off the braking system. And in a panic situation, it may provide a bit more braking that you may expect, which is normally a good thing since most people don't slam on it as hard as they should.
 
phoned said:
I wouldn't say you can slow down faster by using engine breaking, but it certainly takes some load off the braking system. And in a panic situation, it may provide a bit more braking that you may expect, which is normally a good thing since most people don't slam on it as hard as they should.
Click to expand...

Woah there contradict yourself.
 
No, not really. Using your brakes you can already hit ABS/very close to lockup no problem (lets call that 100% braking force). Using engine braking at the same time isn't going to slow the car down any quicker. What it can do, is if you are at like 30% braking force, you may only need to use 20% braking force to achieve the same amount of deceleration when we add engine braking in to the mix.
 
ABS is only if the tires capability is overcome. If I get nice tires I can easily overwhelm the brakes and then ABS is useless. Engine braking helps absorb some of that energy.

Engine braking also makes sure you are in the proper gear in case you need to accelerate quickly to maneuver as well.
 
The service manual indicates that if you quickly take your foot off of the gas it will hold the gear for a short time. This is to see if you are braking to add engine braking or if you are going to quickly accelerate again like following close to pass on a two lane you will want to keep the lower gear for passing performance. Normally upshifting occurs as you slowly decrease the gas pedal rather than quickly removing your foot which holds the gear. I find that the slope of the road also affects the shift pattern which increases engine braking going down a steeper hill.
 
kekek said:
This car is programmed to do Rev matched downshifts when braking. It simulates what most good drivers would do during heel toe downshifts in a manual trans.

I love it, but come from a performance driving background. I could see where some find it weird.
Click to expand...

I can honestly say that this feature has helped me avoid an accident already. Having power readily available like that can make a world of difference. Truly amazing.
 
There is a fancy term for this feature that Mazda has used (dynamic driving mode or some such). I forget what it is at the moment. When you are aggressive with the throttle or the brakes, it will hold gears longer or downshift to keep you in the power band. Its a great feature and one that makes owning an Auto, when i really wanted a manual, a bit more tolerable. You may also notice if you drive in the mountains that if you drag the brakes for a while downhill, the transmission will downshift more aggressively to provide engine breaking. I also notice that if I quickly apply the accelerator to say 50% throttle, the transmission will downshift. If i slowly apply to 50%, it will hold the current gear. The TCU unit is obviously very smart and well thought out.
 
Also cool is that on the 3, it'll hold a lower gear when on twisty roads so you can power out of a turn.

Finally they're getting smart enough to be able to deal with vs a manual.
 
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