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Catalytic converter for a R4?

AdamWilkes

AdamWilkes

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Am thinking about fitting a catalytic converter to my R4 F6, after my partner reported obvious noxious smelliness when following me in her car. Just a thought, but has anyone else tried this?

Jetex sell a Classic Car Converter (available on ebay for about £240), which looks like a solution, but am thinking that a pre-lambda-sensor-era Cat of about a tenth of the price which is new old stock for a 1990's Fiat Panda or little Rover could be pressed into service...... Fitting it close enough to the engine may be an engaging puzzle. Maybe the cat in place of the wheel-arch silencer & use an under-body silencer instead?

All ideas would be welcome! Also may relieve me of any ironic guilt at driving a non-politically-correct but happily non-obsolescent vehicle.
 
It's a nice idea, but not quite as simple as it sounds. The catalytic converter works in conjunction with the engine management system, which in turn receives messages from numerous sensors throughout the engine, including the fuel supply, the exhaust gases and air flow, amongst others. In doing so the computer adjusts the air to fuel ratio (usually referred to as the Lamba ratio) so that it burns at a ratio of 14.7 parts of air to one part of fuel, which is the optimal rate of burn. If this ratio is not met the excessive fuel going through the exhaust system will prevent the catalyst from functioning properly. Modern fuel injection systems measure fuel very accurately and this, coupled with the computer systems, keep the levels where they should be. With one notable exception *, no car company have ever managed to produce a normally aspirated (carburettor) engine that works with a catalytic converter and your Renault 4 will not buck the trend.

Drive your Renault 4 with a smug grin, as you realise that the car's at least 35 years old and you have not replaced it every 3 years, so that's TEN new cars NOT made, NOT using the earth's resources, NOT having to be delivered half-way around the world and NOT needing 9 other cars you would have bought being destroyed!

*=Lada built their Riva cars with carburettors and they DID work, but were extremely complicated and a nightmare to set up-I know, I've had to do it on quite a few occasions!
 
I shall drive with a smug grin then !

However, I found this via Jetex's website - purportedly from a Swedish magazine ‘Klassiker': https://www.jetex.co.uk/files/downloads/Classic-Car-Converter-Article-Klassiker Magazine.pdf

In the report there are exhaust emissions test results before and after using a non-Lambda cat on a Volvo P1800s and a Rover 3500 V8 (both carburettor-fed), which suggest that the cat was working fairly well at least during the tests.

I wonder how long the catalytic converters lasted.
 
It's a very interesting article and thanks for posting it. Yes, I can see that a non-managed catalyst would reduce the emission levels, although not by as much as a managed engine would. I'd be very interested in any progress you make with this idea and, in particular, any measurements made BEFORE the catalyst is fitted. I goodly amount of emission reduction can be obtained by ensuring the car's tuning & timing are correctly set, before going down the catalyst route.

I await further reports with interest......
 
I do get the idea of good tuning to reduce smells & increase efficiency, and perhaps I should look at that again, though I can't recall many 1980's cars running odour-free even when new. It passed the MOT summer 2017 with good readings (0.12% CO; 111ppm HC) but I have no readings for this year's MOT - though it passed emissions without comment. It doesn't visibly smoke or use any oil between changes that I notice. I have a Gunson Gastester which is cheap but tricky to get a consistent exhaust emissions reading from - whether that is the car or the tester (or me!), I know not. The engine is 109,000 miles old and has probably never been rebuilt.

The idea of fitting a modern device (Catalytic Converter) to an old car is interesting - and valid, I think, to probably reduce pollution to a lower level than when new. It of course involves welding fabrication and much head-scratching, but for me that makes it more appealing!
 
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Gunson Gastester: can be very useful in at least a rough setup for the MOT - immediately after an MOT I have tested the car with the Gunson to 'calibrate' it to the far more accurate MOT centre results! Maybe my carb is not right as I find the mixture very difficult to change, but kind Mr MOT has tweaked it for me a couple of times during the test. I have had good results on other cars using the Gastester, though patience and a calm day is needed to allow the Gastester to remain settled. Ten minutes to allow the thing to warm up in fresh air, then set the start point using a knob (set it to 2% CO I think). Insert tube into exhaust and leave for a minute to settle down - adjust idle mixture needle bit-by-bit to the CO reading needed. Allow 30 mins all in. Don't allow any fluid to settle in the tubing. Never seemed to be totally accurate - but can provide a decent ball-park figure and it is worth getting the Gunson, considering the enormous expense of the next-step-up of exhaust gas tester.
 
I have an 845cc TL 1985 model, which on a run, in the 60-65 mph area does 65 mpg. There may be something in the fact that as is does more MPG than almost all cars, that any pollution is divided by the miles covered to give a lower pollute per mile figure. My car went through a UK MOT and the French control Techniques, and had no problems and was well within the limits set on both tests. So whilst per gallon, the car may or not not meet some of the best current standards, when you divide it by the diluting effect of so many more miles covered, per gallon, it must be less bad than most cars, and could be up there with the best. Just a thought from a wine addled R4 driver.
 
"It passed the MOT summer 2017 with good readings (0.12% CO; 111ppm HC)"
These figures are at idle (and the CO is too low). Above idle, the jetting in the carb will determine the mixture and emission/smell level.
 
Good point retrospecpats - I have wondered about that particular CO reading - previous MOT was over 1% - with MOT pass limit 4.5% (possibly! and limit for HC at 1200ppm). I wonder if the test probe was really in the exhaust pipe!
 
I'm with Adam Wilkes on the prolonged set up process for the Gunson but another plus for the Gunson is at a flick of the switch it gives a lovely big clear rpm readout and as it sits firmly on its own four feet in plain view I use it frequently for other fettling exercises. Mine came with enormously long leads, necessarily so that in exhaust test mode one can be connected to the coil and battery forrard while the probe is up the chuff.

As has been said the reading does wander about quite a bit, to two, possibly spurious decimal places but as a matter of (mild) interest we've always ended up with a Gunson reading of 1.9% to 2.2% each year from the first recorded reading back in July 2011. Car is a 1977 TL with the 782cc engine. Carbs (the one on the car and the spare) are both off 845cc vehicles and jetted as such and we do seem to run rich but our journeys are mostly pretty short and hilly so I couldn't guess at an mpg figure beyond a top up every two to three weeks....
David
(bright sunshine in the Pyrenees)
 
Catalytic converter - seems that Renault used an Oxygen sensor in the exhaust (before the catalytic converter), water temp sensor strapped to the heater hose plus tweaking of the mixture richness using electronically-controlled air bleeding into the carb, rev-measurement from the coil and a sort of ECU to juggle it all.

See: https://www.franzose.de/flexxtrader/data/pdf/82400-Einbauanleitung.pdf - it's in German, but the pictures tell quite a lot. The Cat seems to be wrapped in steel, spaced away from the cat sides to protect the cat from thermal (water) shock under the wheelarch, where it sits in place of the silencer (where the silencer is in my van anyway). If anyone knows of an English translation, that would be fun!
 
Hi guys the best co2 readings i have set up have been with the colour tune, very old fashioned but at least you can see the mixture results
 
Hi Prospector - I have used Colour Tune quite a bit in the past but I found it difficult to see what was going on sometimes - with constantly varying flame colours etc. Perhaps I was running the engine too slowly at the time - does the engine speed need to be faster than tickover ?
 
Not necessary, but if you get rapid colour variation between blue and orange you know you have too lean idle mixture, air leaks or poor combustion due to e.g. bad ignition.
 
I just watched an old 'Wheeler Dealers' program on TV, where Ed China forces an old but newly-completed Cobra replica through an SVA test (UK new vehicle compliance test), partly using just catalytic converters (it was a V8, so one cat per bank of cylinders) to halve CO and HC emissions. There were no added electronics or feedback wiring, and it appeared to work well.
Food for thought !
 
I wouldn't do it. You need to take care of your catalyst ideally using some sort of monitoring and feedback system to control what goes into it and a bit of experience about how to prevent it from overheating/ clogging up/ making horrible smells. Anything else is decoration.
Of course you can bolt something on to get through a test but it won't work for long. Did Ed trailer the car there by any chance?

The basics of getting an engine running correctly have been almost forgotten in the modern world, but that ought to be the first thing to fix before looking at palliatives like cats. If your car is stinky it isn't running right and a cat won't fix it.
 
malcolm said:
I wouldn't do it. You need to take care of your catalyst ideally using some sort of monitoring and feedback system to control what goes into it. Anything else is decoration.
Of course you can bolt something on to get through a test but it won't work for long. Did Ed trailer the car there by any chance?

The basics of getting an engine running correctly have been almost forgotten in the modern world, but that ought to be the first thing to fix before looking at palliatives like cats. If your car is stinky it isn't running right.
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+1 on this! A catalytic converter works by speeding up the chemical reaction but not actually taking part in it. The precious metals used in converters are designed to work within very precise parameters and running an engine outside these parameters for even a few seconds can irreparably damage them, which is why the fuel, air, temperature and other factors are precisely measured by car engine management systems. As an example of this, cars with catalytic converters should NEVER be bump-started, as the shot of neat petrol pushed through the catalytic converter will destroy it. I've removed a converter from a car that's been repeatedly bump-started and it looked like a fist had been pushed through the delicate honey-comb structure of it. I feel that fitting a catalytic converter to a car without an engine management system will eventually have the same outcome. Careful tuning, accurate adjustment of valve clearances, carburettor mixture settings and plug gaps would, I feel, achieve much more in the way of cleaning up the emissions. Fitting electronic ignition would prevent the system driving out of tune, too, so it would continue to burn the fuel more efficiently for longer.
 
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