CVT tester

[mac]

Nice and quiet today on the board - everyone off to the BKV no doubt.

I am just putting feelers out at present.
I strikes me that one area that gives problems is the diagnosis of faults with the operation of the vacuum control system and 4 way vac.valve on CVT cars.
To amuse myself in my dotage I am developing a test unit (based on the Volvo unit that dealers didn't always use). The idea is to monitor engine and CVT vacuum under various operating conditions, to detect leaks, to check the operation of the various control switches and 4way valve etc. etc. Should also be able to test the clutch disengage servo valve.

Finished article should look something like this,

My reason for posting is to ask if there would be any call amongst members for the use of it (I have the idea of loaning it for the cost of postage, to established members. (We should have a tool hire/loan scheme like the VOC but without the huge deposits)).

If members would think it a good idea I will go ahead and develop a test proceedure and instruction set for it (if it would never get used I probably wouldn't bother - but who knows - diagnosis clinics at meets perhaps ?).

This won't appear overnight (I still need to find a CVT car to proof it on) but over the next month or so I'll get on with it. (and yes Aymat I am still getting to import my CVT article into a form for posting).

Still, post your comments or ideas and give me an idea if there is call for such a device.

[petefarrell360]

Interesting stuff Mac! Well, my CVT was all working well when I tested it last, but things may have changed. I need to get it up and running again soon. So should you need a car to test your device on, it might be possible to use mine, if it's MOT'd etc by then. It should be a useful bit of kit, though sadly there aren't many CVT's on V3M, or some have disappeared recently.
Pete

[foggyjames]

Ooh, you have an original CVT vacuum gauge too. I thought I was special having one of those

There are quite a few CVT cars lurking out there, but none are owned by people who have expressed much interest in maintainance topics - at least not consistantly. Perhaps it is a bit of a chicken and egg situation?

cheers

James

[mac]

Don't worry foggy - I'm sure you are special (to someone).

Seriously though - the vac gauge (and the tap) came fron an old main stealer CVT tester (which had been driven over). I've had the bits kicking around for years and thought I should do something with them.

I had a vague idea of 'diagnosis clinics' at meets but it seems there's a CVT wasteland out there!! I appreciate that the average CVT owner probably isn't into diy - but how many garages (even modern stealers) know anything about the system any more??.

I will probably go ahead and finish the rig and test proceedure anyway (I infuriate the wife by living in the w/shop as it is), so if anyone ever need to borrow it ??.

Mac

[Chris_C]

I reckon its a great idea Mac, we already have a sort of similar thing, loads of us help out on others cars at meets, it's part of the fun!

I reckon it is a chicken and egg type thing, whenever over the few years I've been here someone has asked about CVT stuff, not many of us know enough to help, there are a couple of guys on here who are quite hot on it, just never at the time needed it seems!!!

[SteveP]

Yeah spot on there Chris, and it'd definitely be a valuable resource mac!

[shimon340]

I'm very interested in this! Im just beginning to learn CVT for my cars!

[Serg_V340]

Hi!
Please help me to find malfunction in СVT

What vacuum in highways of management between the vacuum valve and СМЕ in different modes and on different speeds of movement of size should be?
I connected vacuum indicator in a highway up to the valve and after it, results have surprised me.
Up to the valve idling the indicator shows approximately 0,7 kg/sm
After the valve I disconnect a tube with CVT and connect indicator, it shows: the-thick tube, this part works by pressing a pedal of a brake 0,7 kg / sm
-thin tube which forces the motor to work on smaller turns- 0,4 kg / sm

I made gaugings on different turns of the motor, and in a mode of idling, and at great values, operating the valve submitting on it a pressure wires from the accumulator
I wished to ask those who has the information, tell to me, such situation is normal? Or it speaks about outflow in the valve? I can submit 0,7 kg / sm
on a thin tube simply having connected them, but I am afraid to damage membranes in CVT

Excuse me on bad knowledge of English and possible discrepancies, I use the program the translator

[mac]

Hello there Serg,

Firstly do not worry about your English - Как бы плох оно будет им будет очень более лучше чем мой русский! (which should read something like " however bad it is it will be better than my Russian).

Firstly if you look on this site in the technical resources section under "how to guides" you will find an article about the CVT which should give you some basic ideas.

If I understand you correctly you are measuring the vacuum in the pipe between the engine and the 4way valve and reading 0,7 (exact value is not critical). This is of course the vacuum generated by the engine (in this case at idle).
You are then fitting the gauge to the CVT side of the 'brake' solenoid of the 4way valve and operating it by the high pressure brake switch (solenoid should also operate when you engage the low ratio hold switch, or when you FULLY depress the throttle pedal). You are reading the same vacuum value - this would be expected and is correct.
You then connect the gauge to the other side of the 4way valve (the 'overdrive' solenoid) but only read 0,4 ??. At idle speed there should be no reading on this side of the valve - the solenoid should only operate when the Tachometric relay switches it (Above 1750-1850rpm). Then you should read the same as before the valve - in this case 0,7.

I assume at this point that the readings you are taking are directly from the 4way valve and that your vac.gauge is not in series.

The 4way valve simply directs vacuum to the inner or outer halves of the outer pulleys of the primary unit (the chambers separated by the diaphrams (your 'membranes')). If you read vacuum on the o/d side of the valve at idle it indicates a leakage within the valve itself.

If you see reduced vacuum with the gauge in series with the CVT it indicates a leakage from the pipework or across one of the diaphrams (membranes).

Do not worry about applying full engine vacuum to the 'small pipe' you won't damage the membranes - when you operate the 'brake' side of the valve the 0,7 you were seeing is applied to the other side of the same membranes. The CVT vacuum system is designed to operate with whatever vacuum the engine can generate.

What is the problem that you have with the car ??

I hope you can make a little sense of all this - do get back if you need more info - and let us know how you get on.

Mac.

[Serg_V340]

Thanks for the answer, I did not expect that Ва will answer so quickly.

I have found section on this site with detailed description СVT

http://www.volvo300mania.com/forum-uk/v ... php?t=3803

I have disassembled the 4-way valve and have found out a surprise in its design. That its part which becomes more active by pressing a pedal of a brake, incorporates to a thick tube directly, and pressure in a thick tube at operation of the valve will be same, as in an entrance highway.
Other part of the 4way valve which forces the engine to work on smaller turns, has the built in terminator which does not allow to give out in CVT vacuum more strongly 0,4 kg / sm !!!
Probably the valve on my car is serviceable, and the problem consists not in it.
Now I for experiment have changed places operating wires and vacuum tubes on the valve, force of vacuum in a thick tube now is limited, and in thin the vacuum without restrictions moves. But essential changes in work of the car has not occured, and now a situation such:
60km/h - 2300-2400rpm
80km/h - 3200-3300rpm
100km/h - 3700+ rpm
As you see, up to a set of 60 km/h CVT works superb, and at the further set of speed there are problems - very high turns of the engine.

Before occurrence of malfunction was on another:
60km/h - 2400-2500 rpm
80km/h - 2700-2800 rpm !!!
100-110km/h - 3300-3500 rpm !!!!

Now I am assured, that the vacuum system has no outflow, the electric part too works truly, the 4way valve is serviceable, the problem in a mechanical part means, I suspect that conducted pulleys badly work. I think one of them rests at attempt to be moved apart and I shall try to check up my guess as soon as possible.

I assume to make it as is specified in this figure





Or you can recommend something another?

[mac]

Hi Serg,

From your speed/rpm figures it looks like the mechanical (centrifugal) operation of the primary unit pulleys is operating ok but for some reason the vacuum assistance to 'change up' is being lost. Or there is a mechanical reason why the primary pulley halves cannot be fully moved together to produce an 'overdrive' ratio. It is unlikely that the problem lies in the secondary pulleys (which simply respond to the action of the primary unit).

One possibility is a leak across one of the primary unit 'membranes'. If you leave the o/d side of the 4way valve connected and fit your vac.gauge to the pipe from the primary unit to the brake side (not to the valve) - operate the o/d solenoid and see if a vacuum appears. If it does then vacuum applied to the outer chamber of the pulley is leaking across a membrane and appoearing on the other side.

Another possibility is that for some reason the drive belt tension has changed. If the belts have become slack drive could be lost through belt slip, and even though the primary unit pulleys might be fully moving together slack belts would not allow the secondary pulley halves to move enough apart to give the highest gear ratio.

Thank you, by the way, for reminding me about the vacuum restrictor (the little spring loaded regulating valve in the o/d solenoid side of the 4way vac.valve. It's many years since I had one in pieces and had quite forgotten about it. It's not there to prevent damage to the membranes (which in any event receive full vacuum on their other side from the 'brake' solenoid) but to prevent full vacuum causing the transmission to change up ratios too quickly in 'normal' acceleration.

Good luck - Mac.

[pettaw]

just a quick couple of ideas although Mac has given lots of thoughts already

Is the tachometric relay switching on correctly? They are apparently - because of their design - quite prone to cracked and dry solder joints. Also the vacuum lines could have come off the primary units causing a vacuum leak. Another possibility although remote is that the change up mechanism has perished completely meaning it no longer operates properly.

[antiekeradio]

the 'high ratio' side of the valve not only has a regulator valve, but also a non-return valve.

if you wire up the 'low ratio' side of the valve, the vacuum on the transmission drops together with the engine vacuum on higher throttle. this leads to higher revs at higher throttle.

normally the non-return valve prevents this and keeps the vacuum in the transmission at the last attained value, as long as the electric part of the valve remains engaged.


on a good airtight system you can observe this if you are in high ratio at moderate speed (around 30 mph). at these conditions, the transmission vacuum is at the regulated level of about 0.4 to 0.45. engine vacuum is higher.
from these conditions, apply ca. 80% throttle. engine vacuum plummets,
transmission vacuum will rise!! (belts are forced in lower ratio, causing the diaphragms to suck more vacuum)
once observed the vacuum rising clearly above 0.5. at first i thought the regulator valve was defective.

Greetings Wouter

[mac]

Mornin'

4way vac valve - I've knocked up these simple diagrams which, if I remember correctly, is how the valve works.

Wouter - if I've got it wrong please come back and correct me! (it's many years since I had one apart)



Mac.

[pettaw]

Not an expert Mac, and quite happy to be proved wrong, but IIRC at full throttle, both solenoids remain shut so the system changes up under the centrifugal mechanism rather than actively holding the primary units at 'low gear' The diagrams look 100% correct though, good work.