04-16-2005, 11:22 PM
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Join Date: Apr 2005
Posts: 3
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airbox questions?
has anybody tried fabricating an air box set up rather than just pushing those horrible foam filters on top of their trumpets? from what i understand these cancel any flow benifits you get from the trumpets. i tried building a pair of stainless boxes to bolt up on top but now im not sure if they are big enough. any ideas would be great
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04-17-2005, 02:02 AM
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Join Date: Oct 2003
Location: In the Australian Outback.
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I modified the stock airbox for my twincarb 33 - basicly a cold-air type setup. Wasn't easy to build as it still had to clear the bonnet, all the emmissions stuff, alternator & aircon...
Not the prettiest prototype, but any pics are better than nothing
Car now has induction noise in between stock & leaving the airbox lid open, definitely made a difference on the S.O.T.P. dyno 
(probably just sounds faster though  )
Last edited by evilgidget; 04-17-2005 at 02:13 AM.
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04-17-2005, 02:17 AM
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Join Date: Oct 2003
Location: In the Australian Outback.
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I too didn't like the thought of using pods, but there's little room to play under the hood of my little 33
As you can probably see, I did keep the stock inlet to the airbox in addition to the new one.
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04-17-2005, 02:24 AM
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Join Date: Oct 2003
Location: In the Australian Outback.
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Incidently, the ideal size for an airbox is 4x engine displacement, for plenum chambers, it's 2x engine displacement
So on a 1.5 boxer, you would ideally like a pair of 1.5 litre capacity plenum chambers, fed from a 3 litre capacity airbox
Good luck fitting it under the bonnet though.
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04-17-2005, 02:26 AM
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Join Date: Aug 2004
Location: Adelaide, Australia
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the air box runs from the bottom half up - the air passing from underneath, through the filter and then into the elbow joints. i have thought many times that reversing this and combining it with a small bonnet scoop would be an excellent method of feeding cold air in.... another option ive seen is removing the two inner lights and running tubing from these to your filter box..
have u tried using a high flow panel filter like a k&n? these can flow considerably more and as the factory box is quite well designed may be your best bet....
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04-20-2005, 04:38 AM
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Join Date: Apr 2005
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 Quote:
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Originally Posted by evilgidget
Incidently, the ideal size for an airbox is 4x engine displacement, for plenum chambers, it's 2x engine displacement
So on a 1.5 boxer, you would ideally like a pair of 1.5 litre capacity plenum chambers, fed from a 3 litre capacity airbox
Good luck fitting it under the bonnet though.
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my engine builder supplied me with trumpets and told me to make boxes for them and not use the original box, maybe the size of my larger 45 carbs is why? good idea with the front cut inlet on your air box, il probably do that to my road car with smaller carbs. thanks for the photos
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04-20-2005, 05:08 AM
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Join Date: May 2003
Location: Sydney Australia
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My engine builder used to make airboxes but then they found out that in most cases you restrict the air flow ... maybe due to not being able to make a big enough box as evilgidget states.
Thus they now find they get the best result with air filter setup like Max's GTA Replica. See pictures area, or here , below:.
I guess the whole under bonnet area thus becomes the airbox  ... atleast it might be the right size
So I'd forget the airbox myself ... and if you want to feed cold air to the carbs just run a pipe to the area.
Pete
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'71 1750 Series 2 GTV: http://www.alfabb.com/bb/forums/showthread.php?p=208078
Last edited by PSk; 04-20-2005 at 05:10 AM.
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04-21-2005, 02:36 AM
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Join Date: Mar 2005
Location: Adelaide, South Australia
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Quote:
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Originally Posted by evilgidget
Incidently, the ideal size for an airbox is 4x engine displacement, for plenum chambers, it's 2x engine displacement
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It also really depends (from what I've been told...then again it may be wrong!) on what induction system your motor is running.....With the new inlet manifold I'm building for the 33, I'm trying to keep the internal volume as small as possible without restricting the poor thing.....
As for airboxes, I'm just useing a VL/VN Commodore airbox, mounted where the charcoal canister (replaced by a MUCH smaller Nissan one, mounted out the way) sits normally, then running some ducting down to the front bar.....
BTW if your after 3 inch pod adapters, use VN Commodore Airbox adapters. They are exactly the same thing as they sell in the shops, and are made of aluminum instead of plastic (not to mention you pick them up for next to nothing) If you have a 16v motor, they bolt strait onto the AFM......hrm 
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04-23-2005, 02:09 AM
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Join Date: Mar 2005
Location: Melbourne, Aus
Posts: 139
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wow pete, that car is hot.. twin carb, twin spark... pics?
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