75ZT Community

I was talking to Wesley this morning and he told me that there is some argument about the diesel running better without the MAF (Mass Air Flow Sensor) sensor.

Does anybody have any knowledge, anecdotal or otherwise please?

I thought that fuel consumption would be adversely effected?


Cheers

Mike

Thanks Mike. Anybody else have any views please?

I can't offer any facts, but I suggest neither can those saying 'it runs better'. However I'd go back to this. If it was better without, why would Rover and BMW specify something that costs money to include, and makes something work less well into the bargain?

Duncan wrote:If it was better without, why would Rover and BMW specify something that costs money to include, and makes something work less well into the bargain?

The same might be said of the catalytic converter Duncan. It is suggested that political pressure to enforce emissions control might be the reason.

Yes, but then again no. There are emissions requirements which must be met yes. However these requirements in general can be met without catalytic converters using so called lean-burn technology, but someone somewhere decided that they would be mandated anyway. At least that is what I was told some years ago. And its certainly not political pressure, but actual legal requirements to meet emissions standards.

The same is not true of air flow sensors. You need to know how much air is being drawn in on each stroke to put in the correct amount of fuel whether to give maximum power, maximum economy, or meet particular emissions requirements (and these are often mutually exclusive). You can make an engine run, using mapping only (like when you disconnect the MAF), or if you have a throttle plate (like on a petrol) you can map quite accurately and do away with the flow meter. But to calibrate for best performance / economy / emissions you need a more accurate measurement even though one won't necessarily go hand in hand with another. Hence my suggestion that running without one wouldn't simply worsen the emissions but improve everything else, so they are there for reasons other than just emissions.

Its also worth bearing in mind what we mean by emissions. There are a number of things that come out of the engine / exhaust: Carbon monoxide (from the engine itself), Nitrous oxide (largely formed in the exhaust itself), and unburnt fuel (hydrocarbons), plus particulates (on petrol as well as diesel). As a rule,improving one worsens another whilst again influencing performance and economy. Cats deal with some of these, for example converting CO to CO2.

Super post Duncan. Thanks

When I bought my CDTi, it felt pretty “flat”, as if the turbo wasn’t coming on properly. I discovered the MAF had been disconnected, so of course connected it – didn’t make a vast amount of difference to be honest.

After much discussion on the other forum, I bought a new sensor and fitted it to the MAF – it made a big difference, brought the car to life. I don’t want to get into the argument about whether they’re necessary or not – I really wouldn’t know – all I can do is tell you what happened with me.

PS subsequent to that, there was more argument on the other forum as to whether the sensors which were available separately (ie rather than buying the whole MAF) were the correct one for the Rover. Marinabrian, for whom I have the utmost respect, said definitely not, and it would overfuel by a few percent – yet, when PhilT4 checked it with his T4 (Testbook version 4.Computer Diagnostic System), he said the readings were perfect.

So make of that what you will! At the end of the day, my car doesn’t run well without it. That’s all I can say for sure.