发表于 4-3-2012 12:13 AM
本帖最后由 ntc2000 于 21-3-2012 10:37 AM 编辑 |
Bold CFE 引擎结构：
Proactive Magazine Page42 开始
以下是来只proton punch supplier对我们CVT的解答：
QUOTE (ntc2000 @ Mar 20 2012, 03:02 PM) *
hi Kristof bro,
I have several question regarding CVT for exora bold(CVT3) and saga flx (CVT2):
1) I notice that exora bold still roll back on even slight /gradual slope(not-too-steep slope). Normal auto gear vehicle only will roll back when the slope is too steep, if it is not steep enough, it's will lock at there. Is there anyway to make CVT lock it when reach slight/gradual slope? It is kinda dangerous esp for new driver.
You are correct. This is a know "issue", but is a design feature actually. Two things contribute to this:
First thing is what we call idle neutral, unlike all regular older AT's that have a constantly dragging torque converter or clutch, we open our clutch (a wet clutch, more pressure = more drag, even more pressure closes it) almost completely when you are pressing the brake and standing still. this way fuel is saved. If you release the brake a little time is needed to apply pressure to our clutch again. that is when you roll back a little, rollback only occurs on hills steeper than 10%.
secondly the engine cannot deliver a lot of power idling, when aircon is on, heavy car, on a hill, we can start closing the clutch in order not to roll back, but that will cause the engine to stall. When you apply trottle you will notice first the clutch opens a little bit so engine revs up, than we start closing the clutch, during revving up, you can encounter rollback.
What to do? use handbrake in stead of brake, this way we not shift to neutral (we only read regular brake signal not handbrake), use enough trottle, this way the engine produces engough power to close the clutch in one move.
2) A lot bashes arguing CVT from proton will end up like honda city CVT, after few year, this cvt gb will fail and it's will cost a bomb for us to replace the CVT GB. Can you describe a bit on punch CVT and it's reliability issue?
We are looking into this, we do know income in malaysia is not like europe meaning people will choose repaired or reconditioned gearboxes above new ones. Possibility is that Punch will open a local brand to recondition gearboxes and sell at prices comparable to normal AT ones. As you know our gearboxes are tested till 250000km.
3) A lot people(those basher) condemning on rubberband effect for proton CVT compare to those conti CVT(multitronic and etc). Rubberband effect quite obvious for punch CVT.
Rubberband effect is from CVT's that existed 30 years ago, we use a steel belt so not applicable.
4) Overheat issue on CVT2. There is rumours saying that Saga FLX always break down due to CVT2 overheat. Is there any solution already?
We use a wet clutch, when you would move uphill at very low speeds it would slip almost constantly. We cool this clutch with CVT oil, this is pumped trough the clutch by our CVT pump, this pump is directly connected to the engine. So yes, when not driving as you should with a CVT (and you cannot know this as this is new) you can overheat it. Please compare to manual, if you would keep it on a hill only using the clutch you would burn it.
What to do? avoid long slipping clutches by applying enough throttle when moving uphill, the engine will produce enough power for us to close fast without long slipping period. Shift to N when you can, this will have a cooling effect on the CVT, if possible in N apply little throttle till lets say 1500rpm, this will rev up the pump and increase cooling.
these tips are only for extreme conditions! all other condition drive as you want!
Our CVT's are tested under extreme temperatures! Worst case scenario clutch will open, resulting in no drive as we measure temperature and in order not to break the CVT we will open clutch. You will have to wait a few moments, key on and off and there you go again, this is no breakdown!
5) [Tourist bro question] I sat in a Bold and notice when moving away from stationary (not very aggressive driving), there are lots of dull humming or booming noise coming from the dashboard or gear lever area. It goes away when car is up to speed.
But I distantly remember sitting in another Bold before and don't recall hearing these noise in the other Bold. Are all Bold the same or some are simply quieter than the others?
It's different per Bold, it is dashboard assembly I am afraid. Primes seem to be even more sensitive than bold.
Actually engine is loaded at that time and as RPM is low it will vibrate, as a result the dashboard will vibrate and that is what you hear. This should be an easy fix for a dealer in my opinion.
QUOTE (yellowbox @ Mar 20 2012, 11:12 PM)
Questions related to Exora CFE:
1) You have mentioned that the clutch is almost completely open while standing still with D engaged, is this the prime reason of slight lagging when slowly pressing the gas to move?
yes, if you release the brake and immediately press the gas, this is the case. It is always better not to press the gas immediately unless you have to (uphill), you will notive less delay. That it isn't superagressive at launch (if you would mean this by lag) is calibration, it is to preserve both engine and CVT. it is called torque reduction, the engines power delivery is minimized, although full trottle.
2) Could you give some advices/tips in using CVT when going uphill (e.g. Genting Highland)? Also does it have engine-breaking effect when coming down?
yes it has an automatic engine braking, but only when trottle completly released. Even more engine braking can be applied by putting transmission in L mode. Also for uphill L mode comes in handy, lower ratio, more pulling power!Thanks.
QUOTE (ntc2000 @ Mar 20 2012, 11:14 PM)
Is there anyway to avoid CVT failure like honda city/jazz? Any special thing need to take care in order to longer the lifespan of punch CVT?
need your expertise how to take care on punch CVT GB.
Nothing really special, just drive and enjoy. If would have to say one thing it is to let it build up it's clutch pressure after releasing brake or putting in D before going on throttle, that will be better for clutch.
QUOTE (pgkia @ Mar 21 2012, 08:52 AM)
Need more specific info on the following:
1) Do we know when the cluth is fully open? is there an indication or behaviour that we can observe? i do not know what you mean, only open in N, almost open but small drag in D on brake, more drag (causing creep speed) in D off brake
2) as you said "when you would move uphill at very low speeds it would slip almost constantly", how slow is the slow (car speed and engine rev)? speeds under 10kph
3) The tips in the "what to do" is for extreme conditions. could you elaborate more on the conditions? Conditions where with manual car you would get in trouble, there is no real circumstances i can give you
4) When u said the CVT is tested under extreme temperature, how extreme is it? We do summer and wintertests, wintertests go up to -40degree, summer tests are extreme high temps and mountains.
5) If the car is in extreme condition, i believe the CVT oil might be degraded earlier than expected. Is there a way for us to check if the CVT oil is still at its functional condition to lub and cool the CVT? You cannot check but there is no need to. 60000km is fine as in service manual. (or 2 years)
I am currently driving a Honda City with CVT and it is working fine after 150k+ km. it has the idle neutral behaviour as you mentioned above. As we know, City CVT is not supplied by Punch. Thus, i want to make sure i drive like what Punch recommends in order to get the best out the CVT, yet with minimal wear and tear. i am getting my Exora soon in the next 2-3 weeks.
QUOTE (pgkia @ Mar 21 2012, 09:33 AM)
ok..i think i am getting clearer picture....
1) cluth fully open in N, minor drag when in D and accelerating, more drag when in D and brake applied (engine brake).
2) i think it is unlikely that we go uphill with the speed of <10kph
The CVT overheat issue, if i understand correctly from your replies, mainly touching on the cluth. In worst case, the cluth will open to avoid further damage. So, the CVT(belt, "gear") remains safe. Is that right?
Temperature build up in clutch is the problem, that is why it opens. Gears, belt, are not sensitive to these temperatures.
So, the cluth is a wear and tear stuff then? how frequent it needs to be replaced? It is designed to equal normal lifetime of a car.