Philip

Having very low octane unleaded fuel in Johannesburg South Africa means that the car's performance is disappointing to say the least - so much so that I've decided not to buy one. Higher octane leaded fuel is available. What are the problems associated with using leaded fuel?

Philip

abetts

The answer really depends on how much you care about the environment and whether they have emissions testing in SA. If the car you buy has a catalyst then using leaded petrol will trash it. If you have no emissions testing or relatively lax testing in South Africa and you couldn't give a hoot about the environment then you can replace the cat with a straight through section of pipe. Many of the Imprezas I have seen in Japan have had the cat removed in exactly that manner (presumably to improve performance) although over there they would have to re-fit the cat every so often to get through Government emissions tests.

Philip

Yes I do care about the environment - I recycle all I can and I don't smoke :-) Seriously though 85% of cars in SA use leaded fuel and no - cats are not compulsory.

Nick

Leaded fuel will destroy a catalytic converter.

mikep

you can't just rip out the cat and replace it with a striaght bit of pipe. This is because there is a lambda sensor in the exhaust, which feeds back to the engine management system.

Ripping out the cat may cause some strange performance without also changing the engine managament. Perhaps you can get hold of a replacement chip that 'ignores' the lambda sensor?

Mike...

abetts

If the Lambda sensor is in the Cat Section couldn't you could just re-position it?

Stevebyng

I have replaced cats on previous cars with cat replacement pipes.
Om my 306 XSI the lambda sensor was in the cat section and the replacement pipe had a flange that the lambda sensor simply screwed into.
On my 106 GTI the lambda sensor was in the downpipe and the cat replacement pipe was literally a straight through pipe - albeit with the correct shape and flanges.
On both cars there was a noticeable increase in performance (matched with better fuel consumption!) without the cat. Of course, come MOT time you have to replace the cat to pass the emissions test. I havent bothered to investigate replacing the cat pipe on my WRX yet ( I still seem to have plenty of performance to be getting on with!!) but you should be able to find a supplier who will provide a pipe with the necessary flange to plug the lambda sensor into.
The only other consideration is that the cat does provide some back pressure in the exhaust system that enigne designers rely on when tuning the engine performance - and hence the software in the ECU.
With the next round of emission legislation it will become harder to remove cats as future cars will actually be fitted with twin lambda probes. One will be fitted before the cat (as now) and the other will be fitted after the cat. The second probe will be measuring the performance of the cat and will be like having your vehicle permanently connected to a gas analyser. The ECU monitors the 2nd lambda probe and if the emissions are not within tolerances these incidents are stored in the fault memory. This memory will be able to be read by roadside "authorities" using handhels testers known as "Scan tools". This new legislation comes under the heading of EOBD=European Onboard Diagnostics - real "Big Brother" stuff. EOBD equipped cars will start to be sold in the UK this year.