Hi Abarthisti! 

The following message is brought to you by a late night rambling session on an old thread, "but for what reason?!" i hear you ask? Well I've got that one covered:

1.) I'm over tired and feeling philosophical towards air flow.
2.) I think it would be helpful to some users out there.
3.) I'm over tired and feeling philosophical towards air flow.
4.) It COULD increase noise, power and air flow to your beautiful engines.
5.) I'm over tired and feeling philosophical towards air flow.

For anyone unsure as to what this trumpet restrictivethingymadoob is, I'll post a picture at the end originally taken by another user.

Reasons For Removing Air Box Restrictor (Trumpet)

  BEWARE - small essay warning!     

To start with, it does nothing positive for the air flow at all, in fact, it only leaves less room in the bottom of the air box for air to gather before being forced up through the filter and sucked out into the turbo. As this trumpet is an extension to the external intake pipe, the space used up is actually bigger than just the surface area of the trumpet because it has air rushing through it. Either side of the trumpet is wasted space if you think about how the air is sucked through the bottom of the box, instantly being forced upwards through the filter, and not sideways into the available space either side of the trumpet, obviously meaning it's space which could otherwise be used productively for air flow to the engine as the entire volume of the box will be used instead of 'most' of the volume.

I wasn't sure how it worked at first but after thinking logically about it I concluded (IMHO of course) that it's taking up around 4-6 cubic inches of air space (including the space behind the trumpet which is blocked of by it being there) thus reducing air flow somewhat and, in turn, deadening the sound quite dramatically. So after speaking with Greg (Gb190), and removing the slide in trumpet I have noticed it's slightly louder and I also feel there's slightly more throttle response, this could of course just be placebo affect though, but it would make sense considering the increase in air flow.

I'll also be looking into removing the similar piece on the top of the air box (connected to the out-take for the turbo) as Greg (Gb190) has suggested as this does exactly the same as the bottom piece but worse still. As it doesn't allow the filter to have full effective airflow because of it's positioning (half way over the air filter), this will also deaden sound and reduce air flow. This is due to the air not having time and space to be pulled through the entire surface area of the filter, instead possibly only 3/5 or 2/3 of it.

Thirdly, the intake pipe will either be removed completely (as it's stupidly positioned right behind the radiator and also has no cold air feed to it whatsoever from what I can tell as it's positioned directly behind a piece of plastic with no air flow around it) or it may be replaced with a custom hose in a more suitable position for a sufficient cold/fresh air feed.

It's got me thinking what other modifications could be made to the air box and it's surroundings for better air flow and production/release of sound - So I'll be sure to post it somewhere if I come up with anything or if I find out anything else from other people.

Apologies for rambling on, but I hope people will agree with what I've discovered whilst thinking about how and why it increases sound and airflow, and also help anyone (like me) who has little understanding of things like this. If not at all useful or informative in any way, I at the very least hope it was an interesting read for my fellow forum members and guests with nothing better to do that read my ramblings.


Thanks for taking the time to read this, as I assume you have to get this far down the overly long page.

Your trusty thread hog, Olly.