muzchap
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| posted on 13/7/06 at 12:55 PM |
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Calling all experts - What size Airbox?
Hi guys,
Ok - car is running sweet - but as usual, I want that little bit extra out of the engine, so need a cold air fed airbox.
I'm hoping to take 2 feeds from under the nosecone and channel these into an airbox where the Bike TB's are.
Now - does anybody know how big the airbox should be, is there a 'known' calculation?
Eng: Stock 2.0L SilverTop Zetec
Inlet: Gixer 750 TB's
Inject: Gixer Keihin ones
Zorst: 4-2-1 Mac#1 special
Currently produces just under 160hp - will rev to 7000 (after short run-in period)
I'm looking to make the airbox out of fibreglass - and don't really want to cut a hole in the bonnet.
Any ideas?
Cheers,
Murray
[Edited on 13/7/06 by muzchap]
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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Stu16v
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| posted on 13/7/06 at 09:34 PM |
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Quite simple really, as big as you can possibly get it...
Dont just build it.....make it!
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ned
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| posted on 14/7/06 at 07:50 AM |
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look at single seaters and sports cars, a lot of them run stretched rugby ball shaped airboxes, though usually with a restrictor in. Some of the lower
series would be nearer your power but do run a restrictor in most cases afaik.
also look up westfield and caterhams, flukemotorsport, sbd sell them iirc which may give a guide.
Ned.
beware, I've got yellow skin
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Syd Bridge
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| posted on 14/7/06 at 08:32 AM |
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Those external airboxes are that shape for aero reasons.
If making an internal air 'plenum', with feed at one end try as follows...
Cross section area at far, 'unfed' end may be about 1.5~2 times single choke area.
Cross section at 'fed' end 1.5~ total choke area.
Try and keep the distance from the throttle plates to the external wall of the plenum the same on all of the cylinders.
I'll try and find a drawing when I'm back at the cad station.
Cheers,
Syd.
Those dims are all minimums.
Now wait for all the experts to start on about pulse waves and reflected pulses and so on......  Just don't go there, therrrrre be
drrrragons!
[Edited on 14/7/06 by Syd Bridge]
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TangoMan
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| posted on 14/7/06 at 05:45 PM |
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I have a photo of mine in my archive.
I went for a size that allows sufficient static air around the pipercross.
The bit I was unsure of was how big for the feed pipes. I thought about trying to size the ipes to keep a constant steady flow of air to minimise
pulses. In the end I just decided on 3 inch bore so as not to restrict the inlet.
I am not sure if it has helped the power but it certainly isn't any slower since fitting it.
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ned
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| posted on 14/7/06 at 07:51 PM |
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quote:
Originally posted by TangoMan
I have a photo of mine in my archive.
Sorry, I can't see it, can you point me in the right direction or a link?
Ned.
beware, I've got yellow skin
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RichyMkIndy
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| posted on 19/7/06 at 11:44 PM |
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the long rugby ball shaped ones may have a diffuser inside them to try and recover the pressure drop accross the resrictor that the formula runs.
on the formula student car we ran a plenum which was sized at 3.1 litres on a 600cc engine. this was to ensure that when the restrictor size of 20mm
was choked there was enough surplus air in the plenum to enable the engine to rev past the point where the throttle was choked. The nature of the
circuit meant you would only be chokiung the throttle for a short time so a large plenum wasnt needed and having a smaller plenum means a lower air
intertia for quick reviing engines.
Does anyone know the point of having an airbox on an unrestricted car other than ensuring the cold air is being fed into the engine?
Maybe you could have a small intake on the front of the car and use a diffuser to create cold atmospheric pressure in your air box..
Can someone clarify this.. im not an expert as i dont have experience just going on what ive learnt at uni
RIch
[Edited on 19/7/06 by RichyMkIndy]
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Stu16v
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| posted on 20/7/06 at 09:12 PM |
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quote:
Does anyone know the point of having an airbox on an unrestricted car other than ensuring the cold air is being fed into the engine?
What other reason do you need? May also help with noise issues too...
Dont just build it.....make it!
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TangoMan
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| posted on 20/7/06 at 11:20 PM |
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quote:
Originally posted by ned
quote:
Originally posted by TangoMan
I have a photo of mine in my archive.
Sorry, I can't see it, can you point me in the right direction or a link?
Ned.
Not sure what happened to it, it was there. Try this one!!
Summer's here!!!!
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muzchap
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| posted on 25/7/06 at 05:33 PM |
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Cheers guys - I'll have a look at this and try to work something out
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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