pinto
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| posted on 30/7/07 at 07:21 PM |
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air filter grill
Hi all can any body recomend a metal grill i can use to filter air
have tried making air box with induction type filter but cant get engine to run well
seems to choke engine wont go above 4000 rpm when fitted
so looking at using airbox and fitting grills to it
trying not to poke filter out of bonnet
(2000 pinto with bike carbs ) 
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DarrenW
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| posted on 30/7/07 at 07:24 PM |
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Have a look at Jacko's archive.
Can you not mod a k+n element?
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BenB
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| posted on 31/7/07 at 12:09 PM |
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I'd use a K+N type filter. At the very least they don't kill power.
Wire mesh type filters (like the mesh covers you can get for Webers and Dollortos) actually often result in power loss and don't actually filter
that well anyway.... They still let sand and grit it which'll do a hell of a lot of damage....
If it chokes @ 4000rpm it might well be the jetting, if not then the induction filter is likely to be too small a cross section for the big boy Pinto
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BenB
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| posted on 31/7/07 at 12:16 PM |
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How much space have you got between the top of the carbs and the top of the airbox on your current setup? I've heard 2/3 choke width is the bare
minimum (as a very rough rule of thumb). Less than that and you'll cause a local bottleneck (strangling flow) regardless of what super-duper
filter you've got upstream....
If you attach some nipples to various points on the induction system and hook them up to manometers made from some tubing and coloured water you can
run the engine and see what relative vacuums you're getting and where any restrictions are occuring.... (obviously make sure when you make the
manometer U big enough to prevent water being sucked into the engine....)... You could do it properly with a vaccum meter (like a Carbtune) but some
clear tubing and food dye is more Locost...
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pinto
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| posted on 31/7/07 at 04:27 PM |
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hi ben sorry did not reply sooner
ive got about 32mm from carb to air box face but the box is about 100mm tall
the induction filter is big its got a 75mm outlet (took trumpets of to fit air box dont no if this is not helping)
thanks for all the other info i will give it a go this weekend
ps the car runs great with out filters
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BenB
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| posted on 31/7/07 at 05:29 PM |
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The problem with taking trumpets off is that it will prevent the airflow from being laminar within the airbox. So although it creates space, it also
creates turbulence. When the airflow is turbulent you're going to need a greater space between the throat on the carbs and the airbox for a
given amount of CFM airflow. You may well find that fitting cut-down trumpets (if their design allows) would improve power and flow even though it
will reduce the already quite small gap....
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DIY Si
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| posted on 31/7/07 at 05:41 PM |
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I wouldn't ever use metal filter elements, as they don't really work as filters. The mesh things Ben mentions are poo. They filter out
rocks and stones, but not a lot else. They also limit flow, and can cost power over a proper filter. A big enough airbox with a large enough space
between it and the trumpets (I'd suggest a minimum of at least the diameter of the trumpets at their open end) and then as big a filter as you
can get. I have one on my mini that's rated at 450 BHP! Mainly, though, as the 48 IDA only has huge filters available!
If it won't rev above 4k rpm when the filter and what have you is fitted, they aren't flowing enough air. They are strangling the carbs of
air in some way.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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DarrenW
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| posted on 1/8/07 at 09:00 AM |
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Im using a 100mm K&N challenger air box filter as it allows plenty of space for the stock Kawasaki trumpets and loads of filtered air. It i shuge
though and i dont know what it will look like when fitted yet (awaiting manifold from Boggs). If it i stoo big i know i can get a 75mm element and
clips from Vision plus which is still big. Apparently the 100mm unit flows enough air to feed a 500bhp motor.
Without the trumpets i could take it down to 25 or 50mm which is still good for air flow but im not tempted to junk the trumpets for the reasons
outlined above.
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iank
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| posted on 1/8/07 at 09:34 AM |
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See this thread http://www.locostbuilders.co.uk/viewthread.php?tid=46508 which goes into some detail about trumpet design - stub stacks look a good
idea in your case, a plain opening is awful and will create all kinds of problems for the reasons given by BenB.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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DIY Si
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| posted on 1/8/07 at 03:01 PM |
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I was looking for that thread my self recently!
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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