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-   -   Hard braking in CVT!!! (https://www.team-bhp.com/forum/technical-stuff/34968-hard-braking-cvt.html)

funkydevil 1st February 2008 08:53

Hard braking in CVT!!!
 
The other day i was on the highway at about 120+ in the fast lane, the whole highway was nearly empty as it was about 6 in the morning. There was a civic in the middle lane on my left n he was also doing about the same speed. when out of no where i happened to see an indigo cool cabbie going cooly at maybe 40 in the same lane as i was. I mean why? the whole damn highway was empty. I couldnt swerve left as the civic was next to me nose to nose. i braked hard but my car didnt slow down as expected. i mean it took quite a while.. i realised that, only when the revs got lower did the car start slowing down properly, i swerved to the left once the civic got past in order to avoid hitting the cabbie. the wheels didnt get locked. I was in sport mode at the time, the civic meanwhile had to take a right turn at the signal ahead and just zipped ahead and braked, he was almost at the same speed as me n he stopped amazingly fast in order to take that turn.

Now since that incident i wanted to ask if in case of emergency braking in cvt. how to go about it as there is absolutly no way of downshifting. Would shifting the gear to neutral and then braking be better or would just pressing the brake hard enough and hoping the wheels dont get locked be good enough. I have before noticed the same thing in 'D' mode before too. Is there a problem with my car?? Plz help please:

dadu 1st February 2008 10:53

Do you have ABS ???

If not, this answers most of the questions you have.

snaronikar 1st February 2008 11:04

These white termites (taxis) are everywhere and they will give enough trouble to all the people driving the vehicles be it driving on highways or on city roads. Our people does not have even commonsense to move to left side if they are driving slowly. This is true for all type of vehicles in highways and city roads.

ABS is the ideal solution in these type of cases. But while you are doing high speeds, do not ever think of shifting to neutral and braking. The car will justnot obey your command and it will certainly swiver to left/right. But shifting from top gear to lower gear is certainly advisable which will certainly slow down the rpm. Also, you cannot use the hand brake at that time. The hand brake will not get engaged also at that speeds.

bblost 1st February 2008 11:51

most highways have a speed limit set at 80 kmph.

you were going 40 kms over it.
the other car 40 kms under it.

Think about it.

Akshay1234 1st February 2008 11:59

the s isnt for sport mode. its something else. i remember reading the manual.

ram_hyundai 1st February 2008 12:53

if its not for sports then maybe sedate.jokes apart if you dint have abs your tyres would lock and the rpm would come down and then just release the brakes for a sec and then brake again.this would be the procedure for braking in a non abs cvt.at this point you would get the assistance from the gear braking also.if in a non abs version your tyres dint lock means your engine braking was happening and that mostly wont support locking of wheels unless something slippery or mud is present in most of the cases.
ram

Akshay1234 1st February 2008 12:59

turns out i was wrong. s is sports mode. but i am quite sure i remember reading something different in my friends cvt manual.

trrk 1st February 2008 13:10

Hi,

S is sports mode. It shifts to upper gears at a higher RPM than in D mode.

I have so far not encountered a situation where I had to brake hard in my CVT.

From observations, it yields better results when the pressure is gentler on the brake pedal.

If you are in D, shifting to S while braking may get better results as the lower gearing will help engine braking. Shifting into L should help, but I am not sure if it is good for the gearbox, though!

Food for thought, being a CVT owner myself.

Shifting to neutral and braking at high speeds is the most dangerous option.

Sahil 1st February 2008 13:27

I have found similar problems on my CVT too but this is common on all non-ABS cars, i often find the wheels locking up and emergency braking is a nightmare. All my other cars are equipped with ABS and its hard to adapt to a non-ABS car once your so used to confidence ABS gives you.

Shift to S and L would provide some engine braking but where does one have the time to do all that in an emergency situation.

archerdyal 1st February 2008 13:52

hey dude one thing is.....CR-V is so good on brakes...i mean u prees it ful the wheels never lock r u usin the stock tire coz they slip aa lil bit

trrk 1st February 2008 14:17

Hi,

> Shift to S and L would provide some engine braking but where does one have > the time to do all that in an emergency situation.

The best would be to be defensive and not getting into an emergency scenario.

It is easier to go down or up in an auto gearbox than in a manual as there is no clutch to press.

Torque-ative 1st February 2008 14:57

Quote:

Originally Posted by akshay1234 (Post 707732)
the s isnt for sport mode. its something else. i remember reading the manual.


"S" kepts the City CVT in third gear !! This is similar to O/D Off mode in cars like the corolla auto. This is not a gear meant to be doing 120 in. You are going to keep the revvs too high and strain the engine. Not going give you the best top speed either.

You flip to S only when you need to over take and need the extra power under 80-100 kmph ~ !

extreme_torque 1st February 2008 15:00

@guys... his problem is not locking up the wheels, but the brakes started responding reasonably only after revs came down. I case of manual transmission, we can press the clutch and brake hard but what happens in case of a CVT car.

Torque-ative 1st February 2008 15:16

Having driven both the CVT & the MT very reguarly at highway speeds. Here are my observations.

In the CVT you need to learn to modulate the throttle more often than the MT, as the CVT responds to even the tiniest input and shifts cogs. Hence easy driving is what it excels at. However in the hands of the skilled driver you can drive at higher speeds at lower engine revs in the CVT ;-example in the MT @ 120kmph I am at 3500 rpm~, in the CVT if cruising with a light foot you can manage the same speeds even at 2500 rpm~.
I refrain from pushing the CVT above 100 on roads where I would be doing 120 on the MT. The extra confidence does come with the gear braking possibilities on the MT.
The CVT will on the other hand take a couple of "nano-seconds" more to down shift, but engine braking will still provide assistanace in lowering speeds,..but not as agressively as the MT can be put to use (and in turn RISK ruining the tranny/mill if used with overzeal) .
Also its a lot on the mind of the driver. In the MT when you hard brake you are busy down shifting and makes you belive a whole lot is happeneing within those few seconds, however with the CVT all you are doing is let go of the throttle and braking hard. I dont know if there is a real difference is stoppage time & distance I guess only telemetry would tell. I have a old edition of Overdrive lying at home will look to see if there was any braking difference cited between these versions.

OK,.. EVENTUALLY MADE MY 100TH POST !!!!

Bomi 1st February 2008 15:19

I have experienced this in my previously owned Honda City Automatic. Managed to rear-end a car while coming down a bridge. Emergency braking in that car always made me uncomfortable after that. In American cars of yore (Ford Fairlane to be specific), I once had an opportunity to see the engine bay of a manual and an auto. I noticed that the brake master cylinder of the auto was almost 50% larger than the manual one. Perhaps that is for more stopping-power required in an auto? I had mentioned this to the service manager of South End Honda after my accident. Ofcourse, his response was the brakes in the automatic were adequate for the job and a smaller master cylinder would exert more hydraulic pressure on the brakes.


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