Anyone done the swirl flap delete? NC 2.0

I currently have no issues with my swirl flaps but seems to be something to look out for in the future or just delete now and save hassle down the line.

Anyone done it? Did you notice anything negative effects? I heard it can mess up the emissions and mpg a little bit but guessing not enough to cause an MOT failure.

Also later models apparently were revised and don’t tend to have the issue, mines a December 2007 car.

Looks quite straight forward to do.

Well you got me on this one… what is a Swirl Flap?

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On the intake manifold I believe?

I had these on the Chrysler 300c which were prone to failure.
They are somewhere in the inlet manifold and change position to invoke a swirl into the airflow.
Which in effect affects performance and efficiency (apparently).

I wasn’t aware the NC had them, that’s a first one for me, and I’ve not heard of any failures.

Never heard of a swirl flap !

It can help with improving the mixture of fuel and air. See the Wiki. However, the NC does not have swirl flaps, as such. (I am wrong here. see my post further down)

Instead it has a variable intake air shutter valve to adjust the length of the inlet tract and introduce some tumble. It uses vacuum to open it, and the vacuum flow to the valve is controlled by a solenoid. Either of these can have a problem when the shutter itself is perfectly OK.

The length of the duct can thus be tuned for optimum performance at different rev ranges.

If you combine this with VVT and ECU mapping then it can all work quite well.

I would try and keep it working as standard.

And no, I don’t know how to fix it, but the INTAKE AIR.pdf is probably a good place to start.
See also for an alternative search starting point

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BMW diesels have swirl flaps, in fact, they like to swallow them and then the pistons like to kiss them. :rofl: :joy:

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That’s good news then, one less job to do!

In the Fords the 2.0 MZR (I think mx5 is the LF-VE version) engine has swirl flaps/tumble flaps. They break apart and kill the engine so I assumed the MX5 with the same engine had the same issues but the inlet must be that bit different.

I was going to be disappointed in Mazda if they allowed such a design but seems it was implemented by Ford.

This is the ford inlet for the same 2.0 4cylinder engine that is in the MX5 NC.

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I’ve been digging a bit deeper for a reality check.

The implication from the various manuals I have access to is that the Variable Tumble shutter (Swirl Flap) was only fitted on the cars with Automatic Transmission (The two letters AT are added next to the relevant items on the drawings). It lives in the short straight bit of cast manifold between the plastic variable plenum length airbox system and the cylinder head. This variable flap is in addition to the variable plenum length flap.

So I had a look at my car (2008 Manual 2.0 NC). A borecam was needed to see down the back end of the manifold, and sure enough it has the solenoid and the actuator arm. It has the Swirl Flaps.

So don’t always believe the books or what one sees on the web. Always check on reality.

Here are some pictures I took just now.




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I looked at a few inlets for sale form breakers.
They still have the actuator arm on the manifold body but the inlets are free of swirl flaps.

From the diagrams I saw the VIS system was much further down and not right at the end of the manifold like the swirl flaps on the ford version.

This pic I found seems to show the V.I.S system so our engines should be free of any problems related to swirl flaps like the fords.

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The short manifold fits between what your pictures show - the air system - and the cylinder head.
The pictures I took were of the end of the cast metal manifold, not the plastic snail shell.
Alas, it looks like we have the dreaded swirl flaps.

I think we’re okay.

We have these plates, they look like good quality construction.

The problematic swirlflaps are found inside the plastic snail inlet, we don’t have those.
The issue is said to be the “bearings” that they used, they wear out after around 30,000 Miles/50,000km. The whole system starts to rattle and if not investigated results in the main shaft of the system snapping and falling into the engine. The flaps that are problem are also plastic, so for some reason Ford added their own flap system but seem to have done it on a budget.

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A while ago I posted on here about a DTC I had logged; is it related to the item under discussion here?

I have not had a recurrence of the DTC, so just curious.