09-17-2011, 09:04 AM | #1 |
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Does X3 has Hillstart assist?
I was driving in a rather steep incline and a car was in the way, so i braked. I was going to pass the car but the space is rather tight, so I ease off the brake pedal to creep up slowly. The car didn't move forward nor roll backward, and when I press back the brake pedal, it was stiff as if the Auto-H is active. I press the gas pedal and the car move forward. The thing is, I didn't activate the Auto hold function nor I see the symbol on the instrument panel.
Is there a feature i don't know about (hillstart assist?) or is it a malfunction? (hope not) |
09-17-2011, 10:04 AM | #2 |
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My guess is physics was at work and the grade was just high enough that the idle power of the car kept the car in one place. The brake pedal thing could have been psychological? I've never experienced the car depressing the brake pedal by itself except when auto-hold was activated. There have been many occasions in my car that with the foot off the brake the car isn't creeping forward (hills) but on the flats the car creeps forward normally. Having said that, I didn't read the manual before posting this so I could be 100% incorrect!
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09-17-2011, 12:43 PM | #3 |
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There is a hill hold function...it is the button on the front (I think) of the shifter..in front of the parking brake.
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09-17-2011, 01:54 PM | #4 |
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Hill start assist is standard on 3.0D
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09-17-2011, 02:08 PM | #5 | |
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"Hill holders" typically keep the brakes applied on manual transmission vehicles when you take your foot off the brake pedal and allow you to move to the accelerator pedal without the car rolling backwards. Last edited by Lotus7; 09-17-2011 at 02:14 PM.. |
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09-17-2011, 04:06 PM | #7 |
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This is what I thought too. I'm going to try again next time I find a steep incline with no vehicle behind me, just out of curiosity.
I normally don't use Auto-H feature in daily driving since I have a habit to put the transmission to N in red light. I noticed if i used Auto-H, the brake pedal becomes stiff, and I need to press the brake pedal to put the transmission back to D, it's just feels weird trying to press a stiff pedal. I did use it once when I was caught in a really bad traffic jam on mountain road with lots of uphills and downhills (so bad that it shows about 4km/liter (about 10 MPG) in the computer.. and i have the 2.0 diesel ), and it really helped a lot |
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09-17-2011, 05:15 PM | #8 |
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Haven't got my X3 yet but according to the video you should only need to press the accelerator / gas pedal to release the brake and move off, but I guess you would need to stay in Drive.
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09-17-2011, 05:31 PM | #9 | |
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There's really no reason to put the ZF 8-speed transmission in "Neutral" when stopping, it removes a very light load from the engine but does not reduce fuel consumption significantly. Plus, you have the slight delay once you put it back in "Drive" and the slight added drive line shock loading when that happens. |
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09-17-2011, 05:49 PM | #10 | |
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09-17-2011, 06:05 PM | #11 |
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Got it on my 3.0D.. standard option
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09-17-2011, 06:36 PM | #12 |
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The ZF 8-speed uses a torque converter and (3) planetary friction clutches to change gears. at idle in "Drive" the torque converter is absorbing all the slippage and the first gear clutch is fully engaged (not slipping). There is no mechanical wear. There is a tiny bit of energy being deposited as heat in the transmission fluid. but it's designed for that. When you shift from Neutral to Drive, the lowest gear planetary clutch engages (the other (2) are already on) which actually does cause wear, even though the load is very low. Shifting in and out of Drive will actually increase internal wear rather than reducing it, but the amount is insignificant.
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09-17-2011, 11:34 PM | #13 |
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09-18-2011, 12:01 AM | #14 | |
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Interesting, can't wait to test this feature out again |
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09-18-2011, 01:33 AM | #15 | |
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09-18-2011, 02:06 AM | #16 | |
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The last published BMW description of the "Hill Start Assist" describes it's operation as: "The feature ONLY activates if all the following are true: a) You are at a complete stop b) The clutch is pressed c) The brakes are engaged d) The car is in first gear" Sure sounds like it applies to manual transmissions only. BUT: Curiously, although the NA spec cars (28i and 35i) do not list "Hill Start Assist" as a feature, the NA spec does mention something called "Start-off Assistant" which sounds like it may be the same thing. However, there is no mention of this feature in the Owner's Manual. NA cars also have something called "Brake Assistant" but that actually refers to a system that boosts braking force under emergency-stop conditions. On NA cars there is no control to disable that feature. I've driven my 35i (automatic) up 15 degree service ramps, and if you don't keep the revs up a little the car will certainly roll backwards while in Drive, so there does not seem to be any system to hold it on hills without using the engine even though the spec sheet mentions "Start-off Assistant. The common complaint against using HSA in manual transmission cars is when trying to parallel park while the car is pointing uphill. Depressing the clutch and letting the car roll backwards into a parking space is blocked. You have to shift into reverse instead of just letting the car roll as you depress the clutch. |
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09-18-2011, 10:12 AM | #17 |
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I found an incline today in a hotel parking lot, so I decided to try this out.
Without Auto-H active, if you drive up an incline and braked to a stop, the car will automatically hold it for you, and the brake pedal will be stiff (even the Auto-H is off and no indicator of Auto-H the instrument cluster) and when you "level off" the car doesn't hold anymore after you braked to a stop. So I guess it is confirmed that mine has that hill-start assist or start-off assistant feature, really neat feature |
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