DS BVH Transmission, How do you drive them??
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Thread: DS BVH Transmission, How do you drive them??

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    Default DS BVH Transmission, How do you drive them??

    Having never driven a BVH before, I'd like to know about the intricacies of driving them-

    Do they run a torque converter? Do they stall out in any gear when at a standstill?

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    Thanks in advance.
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    Quote Originally Posted by OnSafari View Post
    Having never driven a BVH before, I'd like to know about the intricacies of driving them-

    Do they run a torque converter? Do they stall out in any gear when at a standstill?

    Thanks in advance.
    The BVH is a conventional 4 speed manual gearbox but with a hydraulic control instead of linkages. It uses a single dry plate clutch. The hydraulic system is basically a master and slave set up. The driver selects the gear via the "wand" and moves it accordingly. This works as the "master" the hydraulic system operates pistons in the gearbox top to engage and disengage the cogs. The system has devices that lower idle speed when the brake is applied ( comparable to "creep" in a torque converter auto )and a speed sensitive device engages or disengages the conventional clutch which also has a hydraulic slave cylinder. The system is delightful but requires some learning and timing as the driver still has to control revs for the up and down changes. It is a servo assisted manual not a real automatic. All leg work is done for the driver. The gearstick also functions as the starter button.
    It is a complex system that requires sequential adjustments however some latitude re change speed is possible...sporting quick or slothful slow.
    No doubt others will contribute.
    Compared with a pure manual D the clutch pedal in a BVH becomes a foot operated parking brake.
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    Very good, succinct, explanation. In terms of "anti-stall", when braking or at standstill, the engine revs drop to a point below that which engages the clutch.
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    In my limited experience, with a very great deal of pleasure. What a superb system the BVH is. To think of it is pretty good. To actually build working prototypes is remarkable. To put it into successful production engineering is absolutely beyond belief.

    I'm in awe of those engineers and dreamers who made it all happen.
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    In practice it is somewhat difficult to stall a BVH car provided it is set up properly. You can slam on the brakes in 4th gear to a dead stop and the system will automatically disengage the clutch to keep the engine running. I wouldnít recommend doing that regularly (once was enough for me) though. Conceptually you shift up and down the gears exactly as if driving a regular manual.
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    Driving a well sorted BVH is blissful. Driving an HML equipped 5sp BVH is "next level".

    The one catch with a BVH, and the cause of its demise in the Australian market, is that when parked the gearbox by default is in neutral and therefore is not a secondary park brake. Combine that with the tendency for front park brake pads to slightly lose grip as the front discs cool can trap young players.
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    Technically, the gearbox will stay in whichever gear is selected as long as there is hydraulic pressure (and even then it can get stuck in gear). As such it is possible to leave the car parked in gear however upon starting it up again it can lunch forward until either you press the brake or there is sufficient pressure in the system to throw out the clutch. I have had cars leap 2 or so meters with the handbrake on pretty hard. Depressing the brake button while starting may prevent this happeneing but it relies on having pressure in the brake circuit.
    Last edited by faulksy; 4th April 2019 at 08:02 PM.
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    They are easy to drive and relatively forgiving.

    There are several ways to answer your question. Before I try, please tell us why you ask.

    Also, there were three slightly different versions of BVH: late 50s, early 60s, and late 60s onwards. The driveability of the different versions was relatively similar but the implementation and the feedback to the driver differed and some of the things to be aware of (and things to NOT DO) differed. So could you also please tell us whether you are thinking of a particular version.

    Thanks,
    Roger
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    For smooth changes just ease the accelerator pedal when changing up;no need to do so on downshifts;hope this helps,Andy.
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    Quote Originally Posted by Budge View Post
    Very good, succinct, explanation. In terms of "anti-stall", when braking or at standstill, the engine revs drop to a point below that which engages the clutch.
    Wow !! Thanks for the literary compliment.

    I did forget to mention ( as has UFO below added ) that there was a legislative problem for us and probably the USA as well. Which I suspect may have been an impetus in adding the Borg Warner automatics to the D range.
    There is no PARK facility. ... and when the stored pressure drops the vehicle will gently put itself out of gear and roll away. Repeated trips to load and unload the car ( which results in stored accumulator pressure being depleted from repeated self levelling ) will speed up the roll away situation. Hence the necessity for a good well adjusted parking brake.
    Poorly adjusted CXs also have the same "hide and seek" quirk I am told.

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    Quote Originally Posted by fritzelhund View Post
    Wow !! Thanks for the literary compliment.

    I did forget to mention ( as has UFO below added ) that there was a legislative problem for us and probably the USA as well. Which I suspect may have been an impetus in adding the Borg Warner automatics to the D range.
    There is no PARK facility. ... and when the stored pressure drops the vehicle will gently put itself out of gear and roll away. Repeated trips to load and unload the car ( which results in stored accumulator pressure being depleted from repeated self levelling ) will speed up the roll away situation. Hence the necessity for a good well adjusted parking brake.
    Poorly adjusted CXs also have the same "hide and seek" quirk I am told.
    That'd be C-Matic CXs I suppose.
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    Quote Originally Posted by UFO View Post
    That'd be C-Matic CXs I suppose.
    I cannot recall if CX Cmatics had a park pawl. The problem I am aware of is that to properly adjust CX parking brakes requires some adjustment of eccentrics that maintain the pad to disc clearance on the actuating levers. After some years the eccentrics become rusted and difficult to rotate, so those who don't know, just adjust the cable length....the result being a pad that ends up with minimal and non parallel contact with the disc .. and the cooling and wearing disc means inadequate pressure is maintained.
    That is my understanding...no doubt others will add more.
    I cannot even remember if my GS Convertisseur had a park position.
    All ancient history now.
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    It was the clutch engagement at low engine RPM's that I was missing in my minds eye. Thanks.
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    Quote Originally Posted by Roger Wilkinson View Post
    They are easy to drive and relatively forgiving.

    There are several ways to answer your question. Before I try, please tell us why you ask.

    Also, there were three slightly different versions of BVH: late 50s, early 60s, and late 60s onwards. The driveability of the different versions was relatively similar but the implementation and the feedback to the driver differed and some of the things to be aware of (and things to NOT DO) differed. So could you also please tell us whether you are thinking of a particular version.

    Thanks,
    Roger
    Roger, my question arises from my desire to finally go and buy a DS. Given the that there are a couple of 70 / 71 BVH's on the market in addition to conventional manuals, I wouldn't discount going straight to the top of the pile! Need another Citroen after selling my Traction.

    Thanks
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    Quote Originally Posted by fritzelhund View Post
    I cannot recall if CX Cmatics had a park pawl. The problem I am aware of is that to properly adjust CX parking brakes requires some adjustment of eccentrics that maintain the pad to disc clearance on the actuating levers. After some years the eccentrics become rusted and difficult to rotate, so those who don't know, just adjust the cable length....the result being a pad that ends up with minimal and non parallel contact with the disc .. and the cooling and wearing disc means inadequate pressure is maintained.
    That is my understanding...no doubt others will add more.
    I cannot even remember if my GS Convertisseur had a park position.
    All ancient history now.
    CX C-Matics have a parking pawl However it is often broken by people engaging 'Park' before the car has stopped moving. The dog tooth on the pawl just snaps straight off. This necessitates a gearbox strip down and the pawl being either replaced or welded up and ground to shape. I opted for the latter.
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    Cheers Gerry

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    Quote Originally Posted by gerrypro View Post
    CX C-Matics have a parking pawl However it is often broken by people engaging 'Park' before the car has stopped moving. The dog tooth on the pawl just snaps straight off. This necessitates a gearbox strip down and the pawl being either replaced or welded up and ground to shape. I opted for the latter.
    Yes, treat the CX park pawl with care. Mine is fine.

    If anyone wants an "all care but no responsibility" mug's guide to CX handbrake adjustment, PM me with an email address. It is an extension and upgrade of words on the forum from Shane and others, written by me after doing it twice and with photographs. What a system! The handbrake works well when adjusted but it is critical to use it as a stationary parking brake as the tiny pads will wear quickly if applied to a rotating rotor.

    Cheers
    JohnW

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    Quote Originally Posted by OnSafari View Post
    Roger, my question arises from my desire to finally go and buy a DS. Given the that there are a couple of 70 / 71 BVH's on the market in addition to conventional manuals, I wouldn't discount going straight to the top of the pile! Need another Citroen after selling my Traction.

    Thanks
    This is how a well adjusted BVH is driven (sound on so you can hear engine speed)
    https://www.youtube.com/watch?v=N_thSNmdHE4

    And one from Harry Martens Limmen who is present on this forum:
    https://www.youtube.com/watch?v=VB4TMtSU8P8
    Last edited by harrisson_citroen; 5th April 2019 at 04:34 PM.
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    Quote Originally Posted by OnSafari View Post
    Roger, my question arises from my desire to finally go and buy a DS. Given the that there are a couple of 70 / 71 BVH's on the market in addition to conventional manuals, I wouldn't discount going straight to the top of the pile! Need another Citroen after selling my Traction.

    Thanks
    Hello On (or should I call you Mr Safari?),

    The short answer is BVH DSes are indeed the top of the pile, going straight to the top of the pile without the intermediate step of a DSpecial is a perfectly sensible idea, and if you have navigated ownership of a Traction you can handle a BVH DS.

    The long answer goes something like this. BVH is how the DS was originally designed. It was not an add-on to make the DS more complex. In the beginning there was only the DS19 with hydraulic power everything. The ID19 with manual steering, manual clutch, manual gear change and manual brakes was the simplified version for people who could not cope with the complexity. So if you want to experience the original DS, the first flush of the designers' vision, the way it was supposed to be, go BVH.

    The point of all these hydraulic powered controls is to make the driving as smooth and easy as possible. Apparently Citroen wanted to use an automatic transmission but nothing was suitable. So they invented BVH.

    Of the various versions, the later one (1967 onwards) is the best sorted and easiest to handle. Think of is as having a centrifugal clutch like some motor bikes but with several refinements.

    You start it with the gear lever "wand" so you cannot start it in gear. With your foot on the brake mushroom you shift the wand into first gear. Release the mushroom and press the accelerator pedal and the clutch will take up smoothly and off you go. Accelerate until you want to change into second, release the accelerator pedal and flick the wand into second, then hit the throttle again. And so on. Changing down is just as easy, you don't even have to let go of the throttle. The higher the engine revs, the quicker the clutch re-engages. As you brake to a stop the clutch releases, guided by the centrifugal regulator which detects both the slowing engine revs and the fact you have pressed the brake mushroom.

    In the later versions such as you mention, there are refinements that allow you to engage first gear on the move if you are moving fairly slowly. (This is an absolute NO-NO in earlier versions as there is no synchromesh on first in early DSs and you can break the gearbox.) Another refinement prevents the engine from over-revving during gear changes.

    Another nifty feature in all BVH DSs is the accelerated idle. This speeds the engine up a little when you take your foot off the brake mushroom, which allows the clutch to engage just enough that the car will creep slowly in first or reverse. This means you can manoeuvre in a car park without touching the accelerator.

    Do not be concerned that BVM (manual gearbox) DSs often have 5 speed gearboxes but BVH cars have 4 speed. Fourth in a BVH is almost as high geared as 5th in a BVM. You won't miss the extra gear.

    Roger
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    Quote Originally Posted by Roger Wilkinson View Post
    Hello On (or should I call you Mr Safari?),

    The short answer is BVH DSes are indeed the top of the pile, going straight to the top of the pile without the intermediate step of a DSpecial is a perfectly sensible idea, and if you have navigated ownership of a Traction you can handle a BVH DS.

    The long answer goes something like this. BVH is how the DS was originally designed. It was not an add-on to make the DS more complex. In the beginning there was only the DS19 with hydraulic power everything. The ID19 with manual steering, manual clutch, manual gear change and manual brakes was the simplified version for people who could not cope with the complexity. So if you want to experience the original DS, the first flush of the designers' vision, the way it was supposed to be, go BVH.

    The point of all these hydraulic powered controls is to make the driving as smooth and easy as possible. Apparently Citroen wanted to use an automatic transmission but nothing was suitable. So they invented BVH.

    Of the various versions, the later one (1967 onwards) is the best sorted and easiest to handle. Think of is as having a centrifugal clutch like some motor bikes but with several refinements.

    You start it with the gear lever "wand" so you cannot start it in gear. With your foot on the brake mushroom you shift the wand into first gear. Release the mushroom and press the accelerator pedal and the clutch will take up smoothly and off you go. Accelerate until you want to change into second, release the accelerator pedal and flick the wand into second, then hit the throttle again. And so on. Changing down is just as easy, you don't even have to let go of the throttle. The higher the engine revs, the quicker the clutch re-engages. As you brake to a stop the clutch releases, guided by the centrifugal regulator which detects both the slowing engine revs and the fact you have pressed the brake mushroom.

    In the later versions such as you mention, there are refinements that allow you to engage first gear on the move if you are moving fairly slowly. (This is an absolute NO-NO in earlier versions as there is no synchromesh on first in early DSs and you can break the gearbox.) Another refinement prevents the engine from over-revving during gear changes.

    Another nifty feature in all BVH DSs is the accelerated idle. This speeds the engine up a little when you take your foot off the brake mushroom, which allows the clutch to engage just enough that the car will creep slowly in first or reverse. This means you can manoeuvre in a car park without touching the accelerator.

    Do not be concerned that BVM (manual gearbox) DSs often have 5 speed gearboxes but BVH cars have 4 speed. Fourth in a BVH is almost as high geared as 5th in a BVM. You won't miss the extra gear.

    Roger
    Lovely explanation. I want another one!
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    Quote Originally Posted by Budge View Post
    Lovely explanation. I want another one!
    Thanks. Is it another BVH you want or another explanation? I could write more explanations but I cannot get you another BVH. If you do buy another BVH, I would recommend you go for one as different from yours as possible. Ideally a first or second nose DS19, but a DS23ie would do at a pinch, or maybe a BVH Safari. I once bought a DS23ie BVM because it was as different from my DS19 as it could be, while still being a DS. That's the benefit of a 20-year model run with a variety of changes along the way, while maintaining the same basic body shape, suspension and handling, and vibe. There are several different models but they are all Dees.

    Roger

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    Well, I've had a green fluid ID19, and now have a bvh - but it's off the road. If i did have the luxury of a second bvh, I'd want a mid period safari. Never thought I'd say that!
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    Quote Originally Posted by Budge View Post
    Well, I've had a green fluid ID19, and now have a bvh - but it's off the road. If i did have the luxury of a second bvh, I'd want a mid period safari. Never thought I'd say that!
    If I remember correctly ( and there is no guarantee of that ) a BVH Safari will be a rare beast .. very limited production period.

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