Wednesday, 20 April 2011

Unintended Consequences

My favourite car I've ever owned - and have driven - is the Mark III Golf VR6 (pictured left).

It was a VW Golf fitted with a 6 cylinder 2.8 litre engine - the engine was specifically designed to fit on a standard Golf chassis with no further modifications needed, and it was the best engine that Volkswagen ever made.

I'd always wanted one but for obvious insurance reasons I didn't own one until I was 25. It was brilliant; the power output was so smooth I'm sure it ignored the petrol I put in to it and ran on double cream instead. And boy was it quick, without trying to incriminate myself on this blog I can confirm that never once did the engine get out of the; "tapping-its-fingers-impatiently-because-it-was-bored" mode. The engine far outperformed the car built around it.

Sadly, and inevitably, rust took its toll so I needed a replacement. The Golf R32 it was. In many ways the R32 was superior. It was quicker (a 3.2 litre engine), had more bells and whistles like air con, and was far more stable in corners at high(er) speeds. But the thrill was no longer there - the Mark IV Golf chassis had become too bloated and too heavy to have the same impact.

However there was a fundamental problem with the R32. There was a consistent issue that occurred in certain circumstances where, as the throttle was deployed, the car started to stall; in essence the pedal started to work in reverse - the more you pressed it the slower the car would go, and that is very unnerving to say the least. This was especially prevalent at roundabouts where you haven't quite stopped, have checked to the right that all is ok to enter the roundabout and then apply the throttle only to find that the car no longer responds. Effectively the car's problem left me stranded on a roundabout in danger of being 'T-boned' by another car that wasn't there seconds before.

Naturally I took the car back to VW many times, but despite 'expert' diagnosis by laptop the response I got was; "No Sir there's nothing wrong with it". I tried some independent garages too and received the same response. It wasn't until I went to a garage who specialised in sticking superchargers on VW V6 engines that I got a more honest response.

The R32, like many cars, had an engine management system which could constantly control the fuel mixture to prevent it being either too rich or too weak. This is great of course for maximum efficiency of the engine, but the management system had different priorities - EU car emissions legislation. In effect VW cheated. In order to get their larger engined cars to pass EU legislation they set up their management systems to prioritise emissions rather than performance or efficiency. So when the sensors in the tail pipe registered too much carbon monoxide it immediately weakened the mixture - effectively starving the engine of fuel. This is what lead to me 'stalling' at roundabouts causing a potential collision.

'Chipping' the ECU to prioritise performance solved the problem - at the cost of about £90, however as the car was more than 3 years old I had to have it changed back to factory default (i.e. emissions settings) every year to pass the MOT and then remapped again afterwards.

Bizarrely chipping the ECU actually improved the fuel consumption.

Can we leave yet?

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