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Discussion Starter · #1 ·
Gents,
Having read a bit about some of you removing snorkels, are we talking about the inverted U-shaped thingy above the filter casing?

Having removed this, do you just leave the aperture at the top of the casing open to the elements? And some of you have drilled some holes into the end of the casing to improve flow - how many?

Nagging question: Does any of this substantially increase the chances of water ingress? Because the filter unit is relatively low-slung in the engine bay/wheelarch. Tell if if I'm just being paranoid! It's just that I used to have a Renault 25 which had a very low air intake, and it became a casualty of the Easter 1998 floods...

Simon (9K 2.3 CSE '96)
 

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Yes, we're talking about the curved "thingy" that comes out of the rear of the airbox and points forward. I left mine open, but added a bell-mouth to the stub to help airflow a bit.

I haven't drilled extra holes.

Originally posted by Saab-jager:
[qb]Nagging question: Does any of this substantially increase the chances of water ingress?[/qb][/b]
The difference in height of the intake before and after removal is only a few inches. The standard intake is pretty low, so I'd have thought it is almost as likely to suck in water as it is without the snorkel. Drilling extra holes near the bottom will increase the chance a little bit more.

If there is a downside, I'd say that it is much increased noise. The restriction in the snorkel is there to reduce noise and with the snorkel in place, the intake faces away from the passenger compartment. Without the snorkel, the intake faces rearwards, towards the left-hand footwell and the noise is quite pronounced. You will hear all manner of strange noises and from inside the car, the standard dump-valve will sound almost like an atmospheric one. It'll probably be a bit louder than normal even from outside.
 

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I took mine off too but I got the old b+d out and a 24mm flap drill and went bananas on the top of the filter ..(to preserve the wading characteristics...)
I have not seen the increase in noise that bill is describing however I do run an atmospheric dump valve so that might drown the induction noise out !!
 

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I've done the same as Bill- and used a cheap loudspeaker reflex port with a nice flared bell to help smooth the flow of air in. The bell is quite important for this.

If anything I would say it should reduce the chance of water intake as the open part is now a few inches higher.

Originally posted by BillJ:
[qb]You will hear all manner of strange noises [/qb][/b]
I thought that was the chillie


I'll get me coat
 

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I fitted the bellmouth after reading an "Autospeed" article where they measured the pressure drop across the end of a straight-cut pipe and compared it with that across the end of a flared (bell-mouthed) pipe. The flared end gave a significantly lower pressure drop, i.e. gave less resistance to flow.

Unfortunately, I can't find that article now (I suspect it's now subscription-only), but this one explains why a bell-mouth is important. This may actually be the article I read, but the test results are only available to subscribers.
 

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Discussion Starter · #8 ·
Thanks everybody, very interesting reading. I like the idea of the bellmouth, so I will go that route. Now I think about it, one of the ports from my old B&W speakers might fit very well (sacrilege to B&W I know, but it's all in the name of er, development )

I'm on a little campaign for free HP at the moment, concentrating on the induction side. Will do the filter, snorkel and the heatplate (yes, I've got one of them [email protected]'=ers) next weekend. Will let you know how it went. BTW, if heatplate removal hasn't been photo'd step-by-step yet, I'm happy to take some pics, if anyone's interested?...
 

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I know you're talking 9000's, but my c900 16v (non-turbo -sadly) has a really small diameter 'trumpet' intake. This goes from about 65mm down to about 40mm dia and back to 65 again.
I couldn't tell if it went any better without it, but the noise was like an old mini with no air filter.
It was entertaining for about 10 minutes, but my other half didn't like the noise.
My old turbo had a 'periscope' type of intake which drew from the top of the wing - is there any benefit in putting one of these on my injection?
 

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SJ, I think NA cars rely on some restriction in the air intake to help increase intake velocity and increase low end torque at the expense of top end power- or something like that

The reason the periscope arrangement is used on the turbos is to help keep the inlet air as cool as possible by taking it from outside the engine compartment.
 

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Since BillJ mentioned it... I know about the flaring theory from work on speaker design. Basically by having a radiused edge, you help the tube to draw air in uniformly from a hemispherical pattern- ie equal radius, thus equal velocity and so less turbulence/resistance.

It will also be quieter as a result
 

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I only have a couple of photos, and none of the whole thing. The airbox is in the wing (on all but the earliest 9000s), where the air filter goes. This is the bit I modified:



The snorkel came from where I've fitted a bellmouth. This is my snorkel alongside that of the 9000 CD that the airbox came from, showing the difference in restriction between the two. Perhaps the CD was normally-aspirated?
 

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You need to remove two screws securing the snorkel, but I seem to remember I was able to do it without taking the airbox out. If you wanted to add a bellmouth, though, you'd probably need to take the box out[/b]
Whatever I do I presume it involves removing the N/S wheel arch liner. I've never had that one off that's why I've never spotted the snorkel.
My bike has (had) a similar arrangement and despite arguments to the contrary they do nothing for performance but are simply there to minimise induction noise. The ones on the bike were a smaller diameter than the carbs so what ever they did they couldn't pass as much air. From the pictures, those on the Saab look like they're similarly restrictive.
 

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Originally posted by Derek:
[qb]Whatever I do I presume it involves removing the N/S wheel arch liner.  [/qb][/b]
No, you can get to it if you take the front undertray sections off, which is slightly less hassle. Same tip applies for access to the washer bottle BTW.
 

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Bellmouths on motorbikes do have a benefit as usually bikes have a separate carb for each cylinder and the length of the inlet tract i.e distance between the inlet valve seat and the inlet of the bellmouth is of great importance to getting max power or torque. Everytime the inlet valve closes there is a reverse pulse and if the inlet tract is a certain length this pulse can be used to get a larger charge of air/petrol mixture into the cylinder just before the valve fully closes. There is a formula around for this, it works better on high reving engined. I think the japanese manufacturers have already designed a system that shortens and lengthens the inlet manifold to make use of this.
The fact that the bellmouths on the bikes are usually of a smaller diameter is to keep the velocity of the incoming air high to add atomisation of the petrol, this aids throttle response at low revs.
 

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OK - I thought I may as well add this question to the existing topic... At the weekend, I took the headlight off and reached in 'calfing style' and got the two scews out that hold the snorkel onto the airbox. Then I thought excellent - the snorkel should just pull off - but of course not!

There is something at the back - feels like a disc at the bottom of the snorkel. Is there a third screw pointing toward the passenger footwell that is still holding the snorkel on? Or is do I need a technique to get it off? I was sure there are only 2 screws. Try harder?

(If I do notice a difference (when I finally get it off) I plan to attach a nice flared port facing forwards - which means I'll need to remove the wing liner anyway)
 

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The "3rd screw" is one of those plastic rivet things that pushes in and expands 3 prongs that hold it in. You should be able to get it out but maybe with some difficulty because of the restricted access.
 
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