# Air intake resonator - is it needed ?



## bas (Oct 12, 2005)

I am unable to fit a CAI due to spending a lot of time off-road and don't want to suffer the dreaded hydrolock. Although the current factory intake is ok, I am unsure of the purpose/need of the lower resonator (which sits in the wheel well). 

In my view, this would cause the air to divert into this box, swirl around and then come back out, causing further disturbance for the air travelling along the air intake. So my dilemna is... can I remove it and will this cause any problems. I understand it is also designed to keep the noise down - how much ??? 

Once removed, any ideas how to cap the end so I don't suck any water in.


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## LEONGSTER (Apr 9, 2006)

Hi Bas, 

Thanks for the PM on engine timing.

Thought I'd pipe in with my thoughts on the resonator before someone else comes along.

The helmholtz resonators are really there to reduce drive-by noise levels. The air in them doesn't really swirl around, but acts more like a pneumatic shock absorber of sorts.

Sometime ago I conducted a series of crude tests to see if blocking off the resonators would have an effect on vibration, noise or performance. I filled each one (there are three altogether) progressively with polyurethane foam; dry, and saturated with water.

The difference in noise and performance was not noticeable to me, apart from a mild vibration that turned up in the lower rev band (1500-2500rpm), although I couldn't be certain without proper test gear what was causing this. Eventually I abandoned the idea of 'tuning' the existing air intake system.

I have also contemplated fitting a CAI. But I do not like the idea of the airfilter being exposed to all that crud in the wheel well - it would only mean more maintenence with no guarantee of better performance, and worse - the fear of hydrolock which would be ever present since it's been flooding a lot nowadays in Asia.

If you decide to remove the lower (and largest) resonator, you'll need to still find a way to route fresh, cool, outside air to the airflter box. Otherwise you'd end up with poorer performance, since you're feeding the engine hot air which when you should be doing the opposite.

The rule of thumb in gaining better performance (up to a point)

1) Warm fuel is better
2) Cool air is better

There are other ways to get better performance. Not all of them expensive. Good lubrication is one of them.


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## bas (Oct 12, 2005)

Thanks for the very informative read. I have removed the larger lower resonator and attached some 3" flexy pipe to it. I have run this back into the engine bay and sealed it closed. Doesn't the original air intake above the radiator give adequate fresh air.


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## LEONGSTER (Apr 9, 2006)

Personally I do think the original intake above the radiator does its job well enough.

While on that note, I used to wonder if the X had sufficient air filteration as the total pleated surface area of the air filter is about half that of one of my other vehicles - which has a NA 2-litre petrol engine.

I have found recently that the X's intake system is sensitive enough such that any slight alteration to airflow has a noticeable effect on performance/fuel economy.

In one instance, by running a partly restricted air filter (using a baffle over the original element) I was able to see an improvement in FE of almost 10%, with a slight drop in power.

Conversely, when I retrofitted the original paper element with a stainless steel mesh air filter, the top-end power appeared to improve, but fuel consumption jumped almost 15 percent.


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