automatic brake assists

[gcd55@hotmail.com]

This is probably a dumb question but I'll ask it anyway because I believe that it would improve gas mileage but other then feathering the gas pedal with your foot is there a way to turn off the brake assist? I truly believe that allowing the vehicle to coast it would improve gas mileage and trying to feather the gas pedal is annoying. Anybody else feel this way?

 

[svzuki]

What are you talking about?

Brake assist is a software feature which will build brake pressure when the vacuum booster is not getting enough vacuum from the engine. The ABS unit will run its motor to build brake pressure to ensure the driver doesn't have to stomp on the brake pedal to get the same output under lower vacuum. This only occurs when you have your foot on the brake. The vehicle doesn't automatically apply the brakes without you asking it to....:blankface:

 

[nocoolnames]

Shot in the dark but some people with auto tranny have complained about what feels like engine braking when the car is slowing down. If this is what your asking about the car isn't actually braking just shifting, there is a thread on this on here if ya search. If I'm completely off topic from what your question is actually asking please ignore.

 

[Maddmatts]

I agree that it sounds like engine-braking too since I haven't heard anything about automatic brakes beyond the hill hold feature on manuals. It's inherent to all automatic transmissions to some degree or another depending on gear ratios and what gear it's in at what speed while decellerating.

While engine-braking, the engine uses no/next to no fuel. Certainly less than it would be while idling.

 

[Bogus]

I agree that it sounds like engine-braking too since I haven't heard anything about automatic brakes beyond the hill hold feature on manuals.

Hill hold is on autos too.

 

[Swordsmith]

I really don't drive auto, but if this is similar to the difference between coasting with the clutch in and the clutch out, I'd still want to avoid it; if you're trying to just coast but the tranny insists on downshifting to "help out" that would be pretty annoying. And while the engine slowing might indeed not use much gas... speeding back up to the speed you were trying to maintain would.

You could try shifting into neutral. Or maybe (and again I'm just speculating here) switching to manual shift mode, would that prevent it from trying to be clever for you?

 

[key1cc]

I really don't drive auto, but if this is similar to the difference between coasting with the clutch in and the clutch out, I'd still want to avoid it; if you're trying to just coast but the tranny insists on downshifting to "help out" that would be pretty annoying. And while the engine slowing might indeed not use much gas... speeding back up to the speed you were trying to maintain would.

You could try shifting into neutral. Or maybe (and again I'm just speculating here) switching to manual shift mode, would that prevent it from trying to be clever for you?

Switching to neutral solves the issue. I have the auto tranny and there is about a .8 mile grade I drive down everyday coming from work. If I leave the car in "drive" I actually slow down a little or maintain speed through the auto downshifting (which I can understand why the OP thought it felt like braking). When I shift the car to neutral I continue to accellerate all the way down until I reach the bottom of the hill.
Key1.

 

[gcd55@hotmail.com]

This is probably a dumb question but I'll ask it anyway because I believe that it would improve gas mileage but other then feathering the gas pedal with your foot is there a way to turn off the brake assist? I truly believe that allowing the vehicle to coast it would improve gas mileage and trying to feather the gas pedal is annoying. Anybody else feel this way?

I should say its a 1.8 with automatic and it feels like a Jake brake on my 18 Wheeler when you take your foot off the gas pedal when you have the Jake switch on. So in other words its engine braking i believe and most noticeable under 35 mph. If you feather the pedal it does not happen. Its annoying. Having a switch to turn it off would b good.

 

[Bogus]

Is it like a slight jerking kind motion? Like the tranny is kicking into another gear? I've never experienced a jake brake.

 

[gcd55@hotmail.com]

jake brake

A Jake brake on a diesel. There are several kinds but basically the engine. Closes the intake valves and does allow the free flow of exhaust to exit the cylinder and causes the engine to slow the vehicle. Its a great way to slow down without useing your brakes. It helps to keep you brakes cool. As brakes get hot they become less efficient at stopping. There is a switch to turn them off when not needed, electronic controlled. I have noticed on the sonic the feeling of this when you remove you foot off the gas pedal under 35 MPH and I'm shure the transmission also is gearing down too. So I guess what I'm trying to say is when I want to coast so to speak it. Feels like the engine is slowing the vehicle down rather then coasting to a slow speed like a Jake brake is on. If you just feather the gas pedal the feeling of slowing is not there.

 

[Bogus]

Hmm, I have noticed that it maintains speed when coasting downhill. But I never tried feathering the gas pedal. Hopefully someone experienced on this topic will see your question.

 

[gcd55@hotmail.com]

conclusion to my comment about brake assist

After several days of really paying attention it is the transmission shifting down that I'm experienced not the engine as I thought was the cause of the braking feeling I was opcorn:experiencing although I'm shure some engine compression is also the feeling of brake assistance. I'm certain the salesman was trying to describe the hill hold feature and not brake assists he was apparently confused because he did tell me brake assist.

 

[River_Rat]

I'm pretty sure the Sonic does have a "feature" called brake assist (aka panic brake assist), but it's quite a bit different from what you are describing. In my understanding, it is designed to compensate for a tendency of drivers to not press the brake pedal hard enough during emergency (panic) situations. When the computer senses that the brake pedal has been pressed quickly, but not firmly, it will apply extra braking force.

 

[Bogus]

I'm pretty sure the Sonic does have a "feature" called brake assist (aka panic brake assist), but it's quite a bit different from what you are describing. In my understanding, it is designed to compensate for a tendency of drivers to not press the brake pedal hard enough during emergency (panic) situations. When the computer senses that the brake pedal has been pressed quickly, but not firmly, it will apply extra braking force.

You know what, I think I've experienced this. When not paying attention and I look up and have to stop kinda quick, not in a panic but I hit the pedal kind of quick and it totally nose dives. lol

 

[sx sonic]

Not sure if the "panic brake assist" has changed at all since the last time I was wrenching, but as of 08 whenever the gas pedal was immediately lifted the ABS system would tighten up the clearence between the pad and rotor an anticipation of an immediate panic stop.

Although haveing the ABS boost brake pressure is logical and plausible but there would have to be some sequence to "prime the system" such as quickly releasing the sytem followed by the brake being depressed. Elsewise the brakes would always be obnoxiously touchy but that would be a relatively easy programming change... I'll have to look into that, its a great idea

 

[BOOMSONICBOOM]

Thank you! I was looking for this type of issue! This is annoying with our sonic! We just returned a sedan loaner didn't do this. Good firm beefy brakes and pedal, no surging or lunging forward when slowing down and braking just before a stop light. The RPM's on our sonic go up to like 2,000 then drops to under 1,000 when you apply the brake's it grabs car hard, quick, kinda jerky....then lets loose a bit, then pedal goes closer to floorboard and then you come to a stop.... After much to do about this. I think we have an issue with brake calipers or pressure? Ugh I don't know what to do it's annoying! G

P.s. This only happens under 35mph, slowing down foot off of brake coasting to a stop or foot on brake slowing vehicle down to a stop and the speed drops below 35! It's like your holdin down brake pedal but, feels like your pumping the pedal....sorry you guys hard to explain!

 

[SonicBoy24]

If you use manual mode you will prevent this.
My automatic used to do this, but after 3,000 miles or so it learned how I drive and doesn't do this in "drive" or "manual" mode.

I would suggest using manual mode if you want your car to learn not to do this more quickly. It will stop eventually.

The reason the loaner car didn't do this is, and I'm speculating, is because it had a lot of miles on it and had already learned not to do this.

 

[BOOMSONICBOOM]

Sonic boy24- thanks for the re-assurance! I pray you are right then! Makes sense. Im going to do tht! I noticed tht in manual mode it did work alot better! thx g would you sugest letting it auto shift down in manual mode or for me to do it? Thc g

 

[Bogus]

Yeah these cars have a learning curve. I try not to let my car auto downshift in M mode only because it feels and sounds like the tranny doesn't like it. I downshift each gear when the RPM's get below 2000 for the smoothest shift.

 

[SonicBoy24]

Yeah these cars have a learning curve. I try not to let my car auto downshift in M mode only because it feels and sounds like the tranny doesn't like it. I downshift each gear when the RPM's get below 2000 for the smoothest shift.

I've never had an issue downshifting in manual mode, so I'm not sure about your car. Maybe it'll learn not to do that, but that seems different.

Sonic boy24- thanks for the re-assurance! I pray you are right then! Makes sense. Im going to do tht! I noticed tht in manual mode it did work alot better! thx g would you sugest letting it auto shift down in manual mode or for me to do it? Thc g

Personally, I usually let it downshift by itself, because it will downshift around 1200-1400 rpms and I don't even notice it usually when I'm slowing down for a light.
If I want to be a little sporty or I'm trying to slow down without the brakes, I'll downshift myself for the better response to keep the rpms higher for when I get back on the gas.
Personal preference really. I hate having an automatic car, so I use the manual mode 95% of the time until I can get a car with a standard tranny.
Good luck.