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mudguard
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  #1173164 11-Nov-2014 22:11
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The brakes did their job. But yeah in a manual you could coast down Coronet and almost not brake at all. But in a big heavy SUV then you'll have to engine brake or simply drive slower down the hill. Brake firmly, release, brake firmly, release.

Talkiet
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  #1173174 11-Nov-2014 22:22
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Jase2985: engine braking is not going to damage your transmission, look at race cars who are using standard treansmissions they engine brake all the time (in addition to the brakes)

throw it into second, take your foot off the accelerator and let it settle on a speed (normally about 30-40) and away you go, need to go faster throw it into 3rd need to go slower, brake. the car will normally settle on a natural speed for the motor and transmission combination.

if you overheat your brakes once generally it will do it again much more easily (warping) in the future.

TBH it shouldn't have to say it in a manual, but im pretty sure most cars ive owned suggest you change into L or 3 etc when going down a hill or when towing, why would you not apply this?

Plus i thought it was common sense?



Um WOT??

No, race cars driven properly don't use engine braking, plus engine braking at racing speeds would be hell on a standard transmission but that would be the least of your worries because you would crash.

Engine braking in manual transmissions on the road is normally fine however

Cheers - N

[edit - regenerative hybrid systems aside - but that's a totally different thing]





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Please note all comments are the product of my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.


 
 
 
 


Batman

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  #1173177 11-Nov-2014 22:26
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Talkiet:
Jase2985: engine braking is not going to damage your transmission, look at race cars who are using standard treansmissions they engine brake all the time (in addition to the brakes)

throw it into second, take your foot off the accelerator and let it settle on a speed (normally about 30-40) and away you go, need to go faster throw it into 3rd need to go slower, brake. the car will normally settle on a natural speed for the motor and transmission combination.

if you overheat your brakes once generally it will do it again much more easily (warping) in the future.

TBH it shouldn't have to say it in a manual, but im pretty sure most cars ive owned suggest you change into L or 3 etc when going down a hill or when towing, why would you not apply this?

Plus i thought it was common sense?



Um WOT??

No, race cars driven properly don't use engine braking, plus engine braking at racing speeds would be hell on a standard transmission but that would be the least of your worries because you would crash.

Engine braking in manual transmissions on the road is normally fine however

Cheers - N



+1

lol race cars use standard transmission would rip it up upon launching :)
they use dog box

or does jason mean boyracing ;p





Involuntary autocorrect in operation on mobile device. Apologies in advance.


Jase2985
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  #1173265 12-Nov-2014 05:47
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Ive been in and driven a few race cars, all running standard transmissions and the only modifications have been uprated clutches, and all have been fine with engine braking on the track. There has been no damage to the transmission. and they have lasted many a season.

Some drivers like it some dont, those who do claim it gives them an extra little bit when braking.

it all comes down to personal preference, but thats a different topic, as you have said its fine in a road going car and its fine in an auto/cvt

as for the OP, i just think you are doing it all wrong, and im really surprised they fixed the issue under warranty considering it was caused by your actions

Batman

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  #1173267 12-Nov-2014 06:02
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It doesn't matter whether they fix it or not, I'm getting rid of it and getting a non suv. But my better half disagrees, so she might get to keep it. Glad to know engine braking doesn't wreck the transmission.

What I am surprised though is that a race car would use a non upgraded transmission. If you call those things that people use in fun races on tv3 Sunday afternoons I think our definitions of race car is different. If you mean wrx sti or evo or 911 gt3 /rs or gtr or z06 ummm ... they are performance cars with upgraded transmission to be able to handle the torque without ripping to bits.

Anyway, on thinking about it the stress with engine braking is the opposite of acceleration forces are at most similar if not less, but in the opposite direction and shouldn't wreck anything.




Involuntary autocorrect in operation on mobile device. Apologies in advance.


MikeB4
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  #1173269 12-Nov-2014 06:13
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Get a vehicle with descent control, give the brake pedal a rest, and relax or use the vehicle transmission as designed, reduce speed, increase engine revs.

Jase2985
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  #1173270 12-Nov-2014 06:15
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KiwiNZ: Get a vehicle with descent control, give the brake pedal a rest, and relax.


that normally only works on steep hills and limits the car to less than 10kph, the 2014 x-trail limits it to 7kph for example

 
 
 
 


MikeB4
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  #1173271 12-Nov-2014 06:20
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Jase2985:
KiwiNZ: Get a vehicle with descent control, give the brake pedal a rest, and relax.


that normally only works on steep hills and limits the car to less than 10kph, the 2014 x-trail limits it to 7kph for example


Hmmmm on mine its 35kmh, if the hill is steep enough to use it then 35k or less is appropriate. Make your speed match the conditions and road.

ilovemusic
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  #1173288 12-Nov-2014 07:48
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back in my car club days driving instructors would instill the following mantra;
gearbox for go, brakes for slow.
heel and toe downshifts to reduce mechanical stress.
nowadays with fancy dual clutch gearboxes a computer does it all for you.
faster but less involving.

insane
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  #1173298 12-Nov-2014 08:19
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joker97: yeah I guessed I've figured it out now.

went to google maps the coronet peak road was 3.2kms. the brakes over heated halfway down, so say 2km.

the thing with the manual mode on that cvt is
1) the ratios are horrendously geared for fuel efficiency not engine braking
2) takes around 1 second per downshift, so at 40ks it gives me 6th gear, to get to 2nd gear takes a while.

so I'm not very kind on my new car hmm


In-laws have a CVT in their Odyssey which I've had to drive many times..  the manual mode behaves exactly how you describe yours, it's horrible to drive! In Auto-mode the car always wants to go faster than you want it to too, meaning you either have you foot on the break or row the sudo manual CVT.

DSG gearbox in my VW on the other hand works exactly how you'd expect in manual mode, lightning fast changes too.

MikeB4
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  #1173301 12-Nov-2014 08:27
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CVT's you need to unlearn what you know, don't compare to manual or conventional automatics, they are completely different. The behave differently and are driven differently. Once you know how they are great and are very good on hills as they keep the engine Revs where they should be either ascending or descending.

Bung
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  #1173302 12-Nov-2014 08:29
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The issue is probably how the X-trail CVT handles overrun. Various Nissan saloons seem to have a variety of behaviours with some programmed to retard on overrun only if using cruise control.

Manual boxes and old school autos are simpler, using a lower gear does provide engine braking. In 3rd my auto won't go past 80 down Ngauranga Gorge.

MikeB4
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  #1173303 12-Nov-2014 08:34
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In our CVT's I use hold gears, allow the revs to match descent speed and the vehicle maintains controlled descent with minimal intervention.

kiwirock
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  #1173310 12-Nov-2014 09:01
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joker97: It doesn't matter whether they fix it or not, I'm getting rid of it and getting a non suv. But my better half disagrees, so she might get to keep it. Glad to know engine braking doesn't wreck the transmission.

What I am surprised though is that a race car would use a non upgraded transmission. If you call those things that people use in fun races on tv3 Sunday afternoons I think our definitions of race car is different. If you mean wrx sti or evo or 911 gt3 /rs or gtr or z06 ummm ... they are performance cars with upgraded transmission to be able to handle the torque without ripping to bits.

Anyway, on thinking about it the stress with engine braking is the opposite of acceleration forces are at most similar if not less, but in the opposite direction and shouldn't wreck anything.


There should be less forces at play using engine braking. In most modern vehicles, when your foot is off the gas and the RPM's are high, there's basically no fuel going to the engine. So the engine is is only forced to compress air which gives you your engine braking power. During accelleration not only does it have to compress air it has to take detonation of a radpily expanding combustion of fuel on top.

In older auto's (don't know about how the fuel management is programmed in a CVT), netural gear was angel gear... if you coasted it cost less than sitting in drive going down hill in fuel. Whereas in a modern vehicle, in drive, with the foot off the gas the computer doesn't have to use fuel at all to keep the engine running while it's RPM is up.

kiwirock
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  #1173324 12-Nov-2014 09:25
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mudguard: The brakes did their job. But yeah in a manual you could coast down Coronet and almost not brake at all. But in a big heavy SUV then you'll have to engine brake or simply drive slower down the hill. Brake firmly, release, brake firmly, release.


Yeah you're inclined to brake harder like that though, which can push the rotors to higher temperatures than say a constant 20% brake force with ventilated discs.

This is kind of why my next car will be a Subaru Forester. I looked at the X-Trail. But I don't like the idea of towing anything on a CVT which most of them are.

I prefer AWD, but the Forester's 5-speed dual range add's a pretend low range of 0.195:1 reduction in any gear that you can use on the pavement without firking the transfer box. Great for light-medium towing, overtaking or getting a little lower on the current gear on decents where a whole gear change maybe to much like going from 3rd down to 2nd.

It's a shame CVT's aren't usually designed to pull much. In principal they'd be the ultimate tow vehicle. Instead of a pretend manual mode, I'd rather a dial that let's you set the ratio anywhere you want it from the highest to lowest the transmission allows.

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