David Jenkins
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| posted on 28/2/08 at 09:51 PM |
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Looks like I need to build an airbox...
Tried fitting the nose tonight - I don't think I'll be fitting a sausage filter... 
 
carb snug fit
I don't want to cut a hole in either the bonnet or the nose, so I'm going to have to make an airbox in the available space. I'd take a
pipe off the front to one of those tapered cylindrical filters.
Has anyone tried doing their own airbox?
One thought went through my mind - a rectangular box with a flat filter on the front. This would be a lot like the original airbox on the bike.
Though I don't know how long the filter would survive in that setup.
If anyone has any good photos of their home-made box they'd be welcome - I'm mulling over ideas at the moment.
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indykid
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| posted on 28/2/08 at 09:54 PM |
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you'd get a sausage filter in there
i suppose given you're up for the challenge though, you might as well make an airbox.
tom
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MkIndy7
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| posted on 28/2/08 at 10:02 PM |
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Or individual K&N style filters, we got some from the local Motorbike shop.. I think they were about £7 each.
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David Jenkins
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| posted on 28/2/08 at 10:03 PM |
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I thought I'd get a sausage in there (as the bishop said to the actress) but, when I measured up, one end of the baseplate will jam against the
nose, the other against the brake master cylinder, the top will hit the bonnet and the base will hit the chassis! This is using the measurements for
a Pipercross PX600 filter, which is the smallest that would cover the full length across the trumpets.
[Edited on 28/2/08 by David Jenkins]
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DIY Si
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| posted on 28/2/08 at 10:26 PM |
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I'm not sure you'd have space for a suitable air box in there. Smart51 had no end of trouble getting his right, and you need at least the
diameter of the open trumpet of free space in front of each carb to maintain a good flow of air. You may have space, it's difficult to tell from
the angle in the pic.
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David Jenkins
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| posted on 28/2/08 at 10:30 PM |
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There is a reasonable amount of space at the closest bit (at the front) - I should just make it. I would curve the box down parallel to the bonnet
line.
I know what you mean about leaving enough space though - at tick-over I could see a petrol-air haze zone hovering a centimetre or so in front of the
trumpet. I'd guess that I wouldn't want to interfere with that by putting something in the way.
[Edited on 28/2/08 by David Jenkins]
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locoboy
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| posted on 28/2/08 at 10:31 PM |
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Search for airbox by smart51
he made a timber one then IIRC used it as a plug to make a GRP one.
It worked out really well for him in terms of no loss of power (maybe a gain IIRC) and reduced induction noise on a carbed R1
ATB
Locoboy
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DIY Si
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| posted on 28/2/08 at 10:32 PM |
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Try revving it and then see how big that cloud, known as stand off, can get! I'd have a search for Smart51's thread about designing his
airbox, should give you plenty of tips and pointers.
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hobbsy
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| posted on 28/2/08 at 10:46 PM |
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I think I read somewhere that the individual sock filters are worse than a sausage.
Be wary of a squashed sausage (oo-er) there is supposed to be column of air above the intake trumpets for them to work as intended.
I could probably explain it better than that.
I'm sure someone else will post and explain it better than I have.
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hobbsy
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| posted on 28/2/08 at 10:48 PM |
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Seems in the time from when I read the thread to when I posted several other people have referred to the cloud / stand off is and that its a bad idea
to interfere with it etc.
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smart51
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| posted on 28/2/08 at 11:06 PM |
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I made my own and it works quite well. You need a clear height above your trumpets of at least 1 diameter of your throttle body to stop air
restruction, preferably 1.5x or more. Mine barely makes it but runs fine. You also need an inlet area about 3 times the area of one throttle body to
stop restriction. I found this out by trial and error.
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joneh
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| posted on 28/2/08 at 11:19 PM |
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Can you not just have the filter poking through the side of the bonnet? It would look cool. Or is that not SVA approved anymore?
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snapper
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| posted on 28/2/08 at 11:21 PM |
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Looks like a cardboard and origami weekend for you then
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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soggy 3
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| posted on 29/2/08 at 12:36 AM |
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I had the same problem after fitting my bike carbs but i decided to make a low air scoop to clear them (a last minute job 2 days before stonleigh) i
was plesently surprised how it came out as like you i didnt realy want to resort to cutting a hole in the bonnet.
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02GF74
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| posted on 29/2/08 at 08:00 AM |
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i like holes in the bonnet so am biased.
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MikeCapon
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| posted on 29/2/08 at 09:09 AM |
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These are our baseline specs for our bike motor airboxes. Bear in mind that these are for a 1000cc injected motor running to 13,100 rpm and producing
aroung 215hp at the crank.
We have had as little as 50 mm clearance between the trumpets and the opposite face without apparent ill effects.
The total volume of the airbox is important to help stabilise the air. The bigger the better.
The air pickup is important. I would avoid giving the motor hot air to breathe from under the bonnet. Try to use an air scoop or ideally a NACA duct.
I'm not sure how all this ties in with your installation and the space you have available. Equally, as stated, this experience is with a bike
motor and there may be subtle differences. One thing for sure is that a good airbox will be better than the sausage filter setup.
www.shock-factory.co.uk
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DarrenW
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| posted on 29/2/08 at 10:39 AM |
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Another bonus for using a Mac#1ZR - engine sits way back so bonnet cut out is in a nice position.
Cant tel from your pic but it looks like you might just get away with big filter. Get one with solid back plate that you cut out yoruself and you
might be able to fit it back a bit.
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David Jenkins
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| posted on 29/2/08 at 01:06 PM |
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On a different tack...
A bit of lateral thinking...
How about me building a rectangular box that fits over the front of the carbs, which goes out as far as the bonnet line.
Near the bonnet line would go a commercial rectangular flat filter. This could easily be at least 50mm from the carb mouth.
The bonnet would have a big hole covered in mesh to let the nice cold air in.
The box would have flanges at the bonnet line on which would go some some nice squidgy foam to make a tolerably good air seal with the bonnet.
If I can identify a suitable 'competition' air filter from someone like ITG then I would have reasonably good flow into the carbs.
Time to read the filter specs, and to buy some cardboard!
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paulf
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| posted on 29/2/08 at 01:17 PM |
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I had the same problem with the throttle bodys on my crossflow and made an airbox that fitted the space available.It wasnt a large volume but did seem
to work ok with no power lost.
Paul
 
Rescued attachment f4c4_1.jpg
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David Jenkins
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| posted on 29/2/08 at 01:30 PM |
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That looks neat...
Damn! Another alternative!
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rusty nuts
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| posted on 29/2/08 at 06:07 PM |
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Made my airbox although its not as neat as Pauls . Used some cardboard to get the shape then transfered to some ally sheet, bent and pop riveted.
Will get it welded up soon .Might be a good idea to get the filter first . I used a Fiat one but I can't remember which one possibly an Uno
Turbo. Local motor factors let me loose in the warehouse to find a suitable one . Seems to work OK although I did cut a hole in the side of the bonnet
everything is inside , the hole allows cool air in.
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