Testing 2CV crank case vacuum with a manometer

28th August 2016 13:25

The 2CV’s two cylinder boxer engine configuration means the crank case volume changes with each revolution of the crank, reducing as the two pistons come towards each other on the inlet/power stroke and away from each other on the exhaust/compression stroke.

If the crank case was a sealed system this change in volume would cause resistance to the running of the engine.  To prevent this the crank case has a breather that vents through the oil filler and out to the air box.

The breather is fitted with one-way valves that allow the air out of the crank case but not back in thus maintaining a negative pressure.  This negative pressure has the advantage that the oil has a tendency to be drawn back into the engine rather than leak out.

2CV egine breather schematic

To ensure these one-way valves are functioning the crank case vacuum should be tested with a manometer – the pressure differential here is quite low (~0.1 psi) so a normal vacuum gauge typically won’t be sensitive enough to show a reading.  Per the Citroën workshop manual, this vacuum should not drop below 5cm even at high revs.  (At high revs there is less time for the air to be pushed out of the crank case as the pistons move towards each other before they move out again.)

There are various options for a manometer – from the simplest being a loop of tubing up to one made to the same specifications as the original Citroën workshop tool (MR. 630-56/9a) that is available from Burton.  I went with a generic plumber’s manometer from an on-line retailer.

I also added a liquid trap to the engine side of the manometer to prevent water being sucked into the crank case but another option is to use LHM fluid as this won’t contaminate the oil if it does get into the engine.

Manometer used to test 2CV crankcase vacuum

(The water level doesn’t show up too well in these photos so I’ve highlighted it, a bit of dye would mean the level is more obvious but, when you’re actually stood in front of it, seeing the water level isn’t a problem.)

With one end of the manometer open to the atmosphere the other is connected to the inside of the crank case via the dipstick opening.  The 6mm (inside diameter) PVC tubing I’m using wasn’t large enough to seal so some insulating tape wrapped round the end did the job.

2CV manometer dipstick end 'gasket'

Make sure the engine is nicely warmed up then take out the dipstick and connect the manometer to the crank case via the dipstick tube.

Manometer inserted into 2CV crankcase via dipstick aperture

With the engine idling, gently rev it a couple of times to stabilise the fluid level in the manometer.  We’re now ready to take a reading.

At idle, the water level on the engine side should be at least 5cm higher than the side open to the atmosphere – indicating the pressure in the crank case is lower.

Keeping an eye on the water levels, rev the engine all the way up to full throttle – we’re expecting the water level to fall but it should never get low enough to be level with the side open to the atmosphere.

A vacuum of less than 5cm at idle or dropping to zero at high revs indicates that the one-way valve in the breather has failed and needs to be replaced.

Manometer in 2CV engine showing vacuum

I was pleasantly surprised to see that Judith was showing a vacuum of over 30cm , especially as the breather hasn’t been replaced recently – if ever.

2CV engine heat map

12:37

Playing around with an infra-red camera and took a couple of pictures of Judith’s engine when it was running.  The effect of the cooling ducts moving the heat away from the cylinder headers is clear.

FLIR picture of a 2CV engine

From underneath the sump, which is part of the engine block, is the main heat source.

FLIR picture of a 2CV engine sump

Lego Gee Bee fuselage rebuild

27th August 2016 14:48

Spent some time today re-working the fuselage of the stock Aviation Adventures kit to make it look more like a Gee Bee Model R.

At this point I’m working entirely with the parts that came with the kit, I’ve not delved into my bits box, so whilst some of the colours aren’t ideal I’m happy with the overall shape I’ve achieved.

Lego Gee Bee
Lego Gee Bee

It’s now recognisable as having the characteristic shape of a Gee Bee racer but the wings are much too big – tackling them will be the next task on this build.

2CV hybrid race car

14:30

At the 24 hour 2CV race on Anglesey TomB engineering and I got a chance to look at a Belgian 2CV hybrid race car being worked on in the pits.

There’s very little of an original A series left here: chassis, suspension and gearbox being the main components.  The engine is a BMW 1100.

Engine of a 2CV hybrid racer
Engine of a 2CV hybrid racer

The bodywork barely resembled an A series but the door was from a Dyane and the gear lever was distinctly familiar.

Dyane door and dash items on a 2CV hybrid racer

BEHIND THE OLYMPIC CURTAIN

14th August 2016 23:41

Original source

I wrote this essay after the Olympic opening ceremonies in Rio, struck by the way the Olympic experience repeats itself. Sadly, that insight might better have been sold as prediction, rather than analysis, as it proved to be a self-fulfilling prophecy in which no one was interested, since they had been seduced and distracted by the games…..

The Olympic Games in Rio are underway, and like a battleship’s slowly turning cannon, the media’s focus has finally been shifted away from crime, or pollution, or shoddy construction, or corruption, or even an unexpected change of elected government, and over to the competitions themselves (and the attendant questions of which athletes and federations are ‘clean’ of performance enhancing products). With swimming one of the early foci of attention, the federation quietly reinstated a twice-banned Russian swimmer, apparently deciding that if the water in the pool did not bubble or steam when she entered the water she must indeed be drug-free.

This is the eleventh Olympics at which I have worked, eight in the summer and three in the winter. The first was in my then-hometown of Montreal in 1976, and it set the pattern for virtually every games that has followed. The month’s run-up to the games produces stories about ineptitude and delays in preparation, about potential accommodation and transport disasters, and in some cases about the government corruption, mis-apprehension of funds, or political unsuitability for staging the world’s biggest sporting event. Then the games begin, and the curtain draws shut around the wonderful wizard of Olympic Oz.

Montreal was a veritable showcase of disaster, putting huge financial burdens on both the city and the province of Quebec which took decades to crawl out from under. The stadium remained unfinished because of design flaws and a constant stream of strikes by workers who wound up almost-finishing things with months of golden overtime. French Canadians were furious when it was learned the royal yacht Britannia deposited its royal wastes untreated into the St Lawrence River; a boat was dispatched each day to collect and deposit them instead into the Montreal sewer system, whence they were returned to the river, untreated, because the money for sewage treatment had been spent instead on a magnificent fountain outside the Olympic stadium.

After the financial disaster of Montreal, no one wanted the Games. Moscow already had 1980/ the IOC traditionally admiring authoritarian governments who could allocate resources without voiced complaints. I was at the Olympic Congress at Baden-Baden in 1981 when Los Angeles were ‘awarded’ the 1984 games, with no other bidders. Peter Uberroth’s committee, citing the potential huge losses, cut deals to get services donated, drew on huge numbers of unpaid volunteers, and sought sponsorship for the games. After it was over, far from the expected financial disaster, the Los Angeles Organising committee announced a series of steadily increasing profits, and bonuses for its bosses. The race, as they say, was on.

The IOC moved swiftly to appropriate sponsorship for itself rather than leave it to the organising committees. Tied to the potential bonanza of advertising revenue from American television, the IOC created a profit centre which benefited from both a worldwide audience and an assembly of competitors who did not require payment. The Olympics became a brand cities fought to stage on the IOC`s behalf, with the committee`s VIP treatment extracted from those cities. It was a  largesse which only occasionally was revealed to the public when the bribery became too obvious.

Rio de Janeiro is in many ways a poster child for the Olympics. The government was overturned shortly before the games, the kind of timing that is commonplace in Brazil, where bad news is usually run through Parliament just before Carnival begins and thus is ignored for the next weeks and forgotten before the hangover has worn off. The weeks before the games found a steady stream of disaster stories: unfinished or shoddy buildings, including the athletes’ village, the collapsed cycle path, the polluted water, the mosquitoes carrying the Zika virus, capybaras roaming the new Olympic golf course, described as `giant rodents`, which is technically true but conjured up visions of huge plague-carrying rats, rather than cuddly pig-sized hamsters.

Then came the opening ceremony: a Tonga disguised as a WWF wrestler entered the arena coated in olive oil and everyone forgot their problems. It was Vendredi Gras, and it reminded me that London 2012 was not that much different. Who in Britain tracked the property deals that saw virtually all spectators at the Olympic Park routed through a shopping mall. Who has followed the awarding of the Olympic stadium to West Ham? Who remembers the promises to Britain’s youth as luxury flats go up where once sporting arenas stood in East London? In London’s opening ceremony James Bond, The Queen, Mr Bean, and (blessedly) Ray Davies were presented to the world as the happy face of Britain. The £12 billion that came from nowhere in a country whose budget cannot be stretched to pay doctors or nurses is now forgotten. Curiously, the cost in Brazil has been estimated at $12 billion, in a city whose separation between the rich, who live vertically in gated high rises, and the poor, who live horizontally in favellas, seems like a model for a London of the future.

Yet listening to the speeches, watching the happy athletes of the world, seeing Kip Keino honoured for working with children in Kenya, seemed to make it all worthwhile, even to the most cynical of us. When IOC president Thomas Bach said we were all equal in “Òlympism”‘ I almost believed him enough to have my taxi driver try the lane reserved for IOC VIP vehicles next time we got caught in a traffic jam. Then experience, the little Toto of the mind, pulled back the curtain to reveal Frank Morgan pulling levers and playing Wizard of Oz. For the people of Brazil, the one-off Carnival has brought Oz to Rio. The circuses eclipse the bread for the next two weeks. Then, like London, the memories will be happy ones and the questions that linger will remain largely unasked, much less answered. Like Dorothy, Brazil will wake up, thinking `there`s no place like home`.

Gearboxes in Citroën flat air-cooled engines

12th August 2016 21:09

The Citroën flat air-cooled engines all seem to have gearboxes that can be mated to an A series engine. This means it’s theoretically practical to interchange gearboxes. However, before attempting this it’s worth knowing what ratios are in the different boxes.

* So I’ve read – I’ve not tried it.

This is a summary of the information I’ve been able to find about the different gearboxes and their ratios from a variety of sources. Where it’s been available to me I’ve take the information from Citroën workshop manuals, the rest is from various corners of the internet (mostly French Wikipedia 1,2,3) so…

CAVEAT LECTOR

This information is provided as-is with no guarantee of accuracy. Your mileage may vary, the value of investments may go up as well as down, the only certain things in life are death and taxes.

Table of contents

  1. A series engines
  2. M series engines
    1. 2CV 6
    2. Dyane 6
    3. LN
  3. V series engines
    1. Visa
    2. LNA
  4. G series engines
    1. GS 4 speed
    2. GS 5 speed
    3. Axel 11R
    4. Axel 12TRS

A series engines

This is the engine that debuted with the 2CV in 1949 and powered the 2CV 4. I’ve not included details of the gearbox on these but there are quite a few listed in the workshop manual.

M series engines

This is the base model, two cylinder, 602cc, engine that first appeared in 1961 in the 2CV 6. It is an evolution of the A series engine.

There seem to have been a variety of gearboxes for the different models produced (Mehari, vans, &c.) so to simplify things I’ve stuck with the post 1970 2CV 6 and Dyane 6 as they’re the most common.

2CV 6 (from 1970)

Engine: M28/1, 602cc flat 2, 8.5:1 compression ratio.

Tyres: 125 R 15 X, 1.8000m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 5.202 4.125 21.458 5.033 3.145
2nd 2.656 4.125 10.956 9.857 6.160
3rd 1.785 4.125 7.363 14.667 9.166
4th 1.315 4.125 5.424 19.911 12.444
Rev 5.202 4.125 21.458 5.033 3.145

Speedometer drive ratio: 4/16

Dyane 6

(& Ami 8?)

Engine: M28, 602cc flat 2, 9:1 compression ratio.

Tyres: 125 R 15 X, 1.8000m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 5.748 3.875 22.275 4.848 3.03
2nd 2.934 3.875 11.372 9.497 5.935
3rd 1.923 3.875 7.451 14.816 9.26
4th 1.350 3.875 5.231 20.646 12.903
Rev 5.748 3.875 22.275 4.848 3.03

Speedometer drive ratio: 4/16

LN

Engine: R06/627 (re-badged M28), 602cc flat 2, 9:1 compression ratio.

Tyres: 135 SR 13 XZX, 1.670m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 4.55 4.375 19.91 5.2 3.2
2nd 2.5 4.375 10.94 9.5 5.9
3rd 1.81 4.375 7.92 13.1 8.1
4th 1.15 4.375 5.03 20.7 12.9
Rev 4.18 4.375 18.29 ??? ???

V series engines

Normally referred to as the Visa engine, this is an evolution of the M28 A series engine with changes to the major components (crank case, crank, cylinders, heads, ignition).

Visa

Engine: V06/630, 652cc flat two, 9.1:1 compression ratio.

Tyres: 135 SR 13 XZX, 1.670m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 4.545 4.125 18.749 5.344 3.321
2nd 2.500 4.125 10.312 9.716 6.038
3rd 1.642 4.125 6.776 14.784 11.674
4th 1.147 4.125 4.731 21.176 13.160
Rev 4.181 4.125 17.249 5.808 3.609

Speedometer drive ratio: 5 X 12

Engine: V06/630, 652cc flat two, 9.5:1 compression ratio.

Not got information on the gearbox, presumably the same as the LNA with this engine?

LNA

Engine: V06/630, 652cc flat 2, 9.1:1 compression ratio.

Tyres: 135 SR 13 XZX , 1.670m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 4.55 4.125 18.77 5.5 3.4
2nd 2.5 4.125 18.77 10.1 6.3
3rd 1.64 4.125 6.76 15.4 9.6
4th 1.15 4.125 4.74 21.9 13.6
Rev 4.18 4.125 17.24 ??? ???

Engine: V06/644, 652cc flat 2, 9.5:1 compression ratio.

Tyres: 135 SR 13 XZX , 1.670m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 4.55 3.889 17.70 5.5 3.4
2nd 2.5 3.889 9.72 10.1 6.3
3rd 1.64 3.889 6.38 15.4 9.6
4th 1.15 3.889 4.47 21.9 13.6
Rev 4.18 3.889 16.25 ??? ???

G series engines

This is the flat four engine that first appeared in the GS in 1970 and was the main engine in both the GS and Axel as well as powering the Ami Super.

I haven’t done all the cross-referencing required to match GS models to gearboxes but it looks like there were four and five speed gearboxes that came with either a 4.375 or a 4.125 final drive. (There was also a three speed automatic box but I’m not interested in that.)

The Axel was the final evolution of the Citroën flat air cooled engine and seems to have used the four and five speed boxes from the GS but with a final drive of 3.889 in both cases.

Ami Super

Engine: G10/612, 1015cc flat 4, 9:1 compression ratio.

Tyres: 135 SR 15 ZX, 1.821m rolling circumference under load. (?)

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 4.125 15.75 7.2 4.5
2nd 2.313 4.125 9.54 11.9 7.4
3rd 1.524 4.125 6.29 18.1 11.2
4th 1.12 4.125 4.62 24.6 15.3
Rev 4.182 4.125 17.25 ??? ???

GS 4 speed

Tyres: 145 SR 15 XZX, 1.873m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 4.375 16.7 7 4.4
2nd 2.313 4.375 10.12 11.5 7.1
3rd 1.524 4.375 6.67 17.5 10.9
4th 1.12 4.375 4.9 23.8 14.8
Rev 4.182 4.375 18.30 ??? ???
Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 4.125 15.75 7.4 4.6
2nd 2.294 4.125 9.46 12.3 7.6
3rd 1.5 4.125 6.19 18.9 11.7
4th 1.031 4.125 4.25 27.4 17

GS 5 speed

Tyres: 145 SR 15 XZX, 1.873m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 4.375 16.7 7 4.4
2nd 2.294 4.375 10.04 11.6 7.2
3rd 1.5 4.375 6.56 17.8 11.1
4th 1.133 4.375 6.56 23.5 14.6
5th 0.912 4.375 3.99 29.2 18.1
Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 4.125 15.75 7.4 4.6
2nd 2.294 4.125 9.46 12.3 7.6
3rd 1.5 4.125 6.19 18.9 11.7
4th 1.133 4.125 4.67 25 15.5
5th 0.912 4.125 3.76 31 19.3

Axel 11R

Engine: G11/631 engine, 1129cc flat four, 9:1 compression ratio.

Tyres: 145 SR 15 XZX, 1.873m rolling circumference under load.

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 3.889 14.85 7.2 4.5
2nd 2.294 3.889 8.92 12 7.5
3rd 1.5 3.889 5.83 18.4 11.4
4th 1.031 3.889 4.01 26.7 16.6

Axel 12TRS

Engine: T13/653, 1299cc flat four, 8.7:1 compression ratio.

Tyres: 160/65 R 340 TRX (???)

Gear Gearbox ratio Final drive Overall ratio Speed at 1000 rpm kph Speed at 1000 rpm mph
1st 3.818 3.889 14.85 7 4.4
2nd 2.294 3.889 8.92 11.6 7.2
3rd 1.5 3.889 5.83 17.7 11
4th 1.133 3.889 4.41 23.5 14.6
5th 0.912 3.889 3.55 29.1 18.1