Conference terri::cars_uk

    What does the T stand for?
    

>>    What does the T stand for?
    
    Transmission ?

re .1

�Constant Velocity What?

I hope it's not constant velocity! Not much acceleration there!

I thought it was "continuously variable"?

Steve.

    I'd have CVT *right now*, if the cars I like had it.  I think Citro�n
    are seriously letting down a lot of faithful techno-freaks by not
    getting on the bandwagon.  A 90bhp limit lets in a lot of 1600cc
    engined vehicles.  Another option would be to put two CVT boxes on a
    4WD car - big silly engine and getting it down very accurately. 8*)
    
    Why should supermini people have all the fun?
    
    Richard
    
    

    Not just the mini's either!
    
    - Fiat Uno and Tipo 1.5, called Selecta
    - Ford Fiesta
    - Volvo 440/460 1.8i (90bhp)
    
    Btw Subaru actualy offers it on the 1.3 4WD Justy!
    
    I liked this tranny so much that I took the Volvo in the deal.
    Six weeks in a 1.5 Uno Selecta got me hooked and a month in an Astra
    had me appreciate the 440. 
    Given the fact that it's transport I wanted, I have the wife's Fiero 
    and two motorbikes for fun, the choice has realy paid off. The 
    thoroughly practical and roomy 5-door 440 with it's smooth 1.8 injected 
    Renault engine matched to the incompaireble CVT makes me actualy relax 
    when commuting! Even trafic jams are taken in it's stride.  
    Do yourself a favour and try the CVT concept in a Fiesta, Uno or 
    whatever even if just for the fun of it.
     
    Peter

    Oh, I forgot.....I regularly pull a trailer with the two motorbikes or
    a caravan and usually have 350 lbs of live dog meat in the back when
    travelling this way. The CVT excells! Smooth and completely hassle
    free. Since it comes with a standard oil-cooler the extra load doesn't
    get it(the 440) sweating either.
      
    Peter

    	Didn't Top Gear do a piece of it not too long ago, where they took
    a number of members of the public and had them test drive a few small
    cars fitted with CVT, without first telling the that it wasn't a
    standard auto transmission?
    
    	IIRC, they were all inpressed with it and a couple were very keen
    to ensure that their next cars had it...

    Yep. And these were 35-45 hp cars with the previous generation CVT!
    Even the ones not keen on automatics decided this was the way to go.
    
    Peter

	Is it actually limited by the maximum Horse Power, is is limited by the
Torque?

	I'm thinking in terms of Diesel where the HP is usually lowish, but the
Torque is often VERY high for the engine size, eg. Citr�en BX TZD Turbo (1769cc)
which has only 90 HP but 134 lbs foot (more than the 1.9 litre 16 valve) of 
Torque.
				Malcolm.

    Malcolm,
    
    Taking the principle in view I think it is actually HP since the torque
    is determained by the gearing of the input shaft. As Hp devided by rpm
    results in torque the diesels give the same loading on the CVT.
    The variation of the pulleys is the same for a given hp, no matter what
    the revs and thus torque. It's the differential- and input-shaft
    gearing that determain the highest and lowest ratio. The CVT takes care
    of a constant variation between these.
    
    Peter

    re .3
    
    Yep, silly me ! I was thinking of those universal joint things that go
    to the steerable wheels of a FWD car.
    
    (Although isn't the idea of CVT that the engine does a constant speed?)
    
    Anbody know a technical description of how CVT works?

    CVT basicly works like this:
    
    
    The principle:
    A band of a fixed length runs over two axles, transmitting drive from
    the one to the other and vice versa. Variation of the drive ratio is
    created by enlarging the diameter of the one axles exactly as much as
    simultanuously decreasing the diameter of the other and thus keeping
    band length constant.
    The max. possible variation in ratio is limited by the constructional
    limits on the min. and max. diameter of the axles.
    
    The construction:
    A high-tech chain built from space tech. metal rings forms a flexible
    but VERY stretch resistant band.
    This band runs within two drums. The band/drum construction is such
    that drive can be applied in two directions.
    The whole mechanism runs in oil and is hydraulicly operated.
    
    The governing:
    The governing mechanisme uses, engine revs, road speed, inlet vacuum,
    throttle position and several related functions as input to determain
    the optimum revs/gearing ratio.
    
    Result: 
    Engine speed remains constant under light loads. Differing loads ask
    for differing engine speeds and thus the speed settles again.
    
    Peter 
    
    

    I never quite understood how a metal band running on the smooth faces
    of metal cones could actually transmit any power at all.  I could cope
    with the old rubber band having enough grip, but the current glorified
    expanding watch bracelet has me foxed - has it got rubber facings or
    the like?
    
    Richard
    

    No rubber. Just high-tech, in fact nuclear reactor tube, material.
    Precision engineering and manufacturing with incredible tolerances
    enables a very close "conical fit". You know, the type that made the
    fly-wheel of your moped stick to the crankshaft.
    A very trick shackle shape takes care of the rest.
    
    Meanwhile I'v doen 5K miles and are even more enthusiastic. On a trip
    to the Yorkshire moors with two motorbikes on a trailer I realy got to
    appreciate the optimum availebillity of torque. Hairpins,
    unexpected stops, pull-oofs, starts and whatever on 1:5 climbs were
    taken in the stride. Just aim and squeeze!
    
    Peter

    Nuclear reactor tube material?  You mean maraging (sp?) steels?  Oh.
    8*)
    
    You mean it wrings and un-wrings whatever many times a second?  Wow!
    Techy!
    
    I didn't have a moped, it was a BSA 197cc in a 350 RE frame.  And no
    force in the universe could induce the flywheel to stick to the crank
    in anything other than the most casual fashion... I became an expert in
    field re-times - haul out the plug/screwdriver in to detect TDC/line up
    the Tippex (sorry Snopake in those days) marks....  I have faith in
    Science, but only belief in engineering.....
    
    Logic compels me to buy another BX:  I only wish I could get one with
    CVT.
    
    Richard