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Swirl Flaps


gassygassy

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I did search the forum before posting this and it didn't come up with any results.

 

Have you heard of swirl flaps? I hadn't till today when I was mooching around youtbe for videos on my diesel Volvo V70. Apparently swirl flaps open a second airway into the inlet manifold. They open gradually as the revs build or you accelerate firmly. Ford and Fiat are apparently keen on them, I don't know if the other usual suspects do. I think quite possibly all manufacturers do, it's to improve emisssion controls.

What's wrong with them? In essence, nothing, IF they were made properly. But they are not. They are made to wear and disintegrate. Ford and Fiat, at least, make them of plastic. Imagine the butterfly valve on a carburettor, They are like that. But not only are they made of plastic but the swivelling shaft they fix to is also made of plastic, and the manufacturers aren't too bothered about the quality of plastic they use. They wear out. When they wear it causes the wrong mixture to enter the combustion chamber and all sorts of things go wrong. In a diesel engine they can send unburnt diesel into the DPF and EGR valve clogging them up. If the condition persists, after the EGR and DPF have been cleaned, the swirl flaps can disintegrate and fly into the engine - which of course means an engine rebuild / new engine / scrap it. Which is what Ford wants, of course. Go and buy a new one, it's only £66,000.

If you think, or know that you have swirl flaps you can poke about your engine inlet manifold area and if there is play in the long shaft that runs across the whole engine inlet manifold you can feel it by wiggling the actuator end of the shaft. If it is worn the play will be obvious, you don't need a micrometer. Suffice to say if you feel significant play, the swirl flap mechanism needs to be replaced. My Volvo with this problem has only done 107,000 miles. I thought they were built to last but obviously not.

See this explanatory video

If you are interested

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There’s plenty of infomation on-line about ‘swirl flaps’ (example here)

 

https://en.wikipedia.org/wiki/Swirl_flap

 

There’s also plenty of discussion on forums about them and several companies offer advice about removing them (example here)

 

https://burchmotorworks.co.uk/performance-and-maintenance/bmw-intake-swirl-flap-removal/

 

Some of the Citroen, Fiat, Ford, Mercedes-Benz, Peugeot, Renault and VW powerplants that have been fitted to motorhomes will have these flaps and others will not. Some motors with swirl flaps have an external actuating mechaism (the "the long shaft that runs across the whole engine inlet manifold” you mentioned) and some do not.

 

A GOOGLE-search on “motorhome swirl flaps” produced nothing of significance results-wise.

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Thanks Derek. I had never heard of them - but then my previous diesel experience has been with old London Taxis FX3 and FX4, and Mercedes pre-1993. There is a video showing how to remove them and blank off the holes, but I don't know if it would then pass the MOT. As the car has only done 107k miles I will reconnect the linkage with this solution which I think is brilliant and how it should have been built in the first place:

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