I will soon be fabricating an air box for the aprilia engine but will have to re position the box to clear the bonnet this means a bit of handy work on the inlet trumpets! My questions are:
• Does anyone know what the two slits in the inlet trumpets do (don’t know if jap 4’s have them)?
• Would I get away with blocking them up?
• what sort of effect would lengthening the inlet trumpets have, I may need to feed air into the throttle bodies via a 90° bend is this going to have any adverse affects!

I know that in an ideal world I shouldn’t be playing with air boxes as they have been designed for a purpose! At this stage I would like to stick with an air box instead of a sock filter.

All ideas and opinions gratefully received

Thom
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when the air box plates up to the throttle bodies can you see any holes that line up with the holes in the trumpets,if not block them up if thats what you want to do,they might just be there to give a little flex in the trumpets so that they can be pushed into the air box,apart from that i havnt a clue

Lengthening trumpets will make a difference to how the engine runs, whether it will be noticable or not is hard to say. If I recall correctly, longer trumpets give slightly stronger mid range but at the detriment of top end power (could be the other way round tho ), so I wouldnt change them too much from what you have if you want to guarantee it performs as expected.

no they don't line up with anything, shall block them up and see what happens! thanks chaps