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Cold air feed pipe diameter


Sherv

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I'm having to reroute my air feed to my airbox,due to the lack of space in my engine compartment on one side ;it means i cant route a pipe that well to the inner wing on the gen4 where the intake box hides.

I want to keep the standard airbox,not go the cone route,so im blanking off the original large diameter feed hole on one side of the base of the airbox,and planning on making a new hole on the opposite side and run a a cold air feed pipe through to the front of the car.Question is,the largest diameter hole i can make in the airbox base is about 40-43mm,(I'm restricted due to the design of the box)so will a 40mm diameter cold feed pipe be of adequate size to get enough air in there?Bearing in mind the original 'hole' for the box is twice that size.The air itself will be much cooler with no heatsoak from the engine bay,im just wondering if its a large enough diameter before i start cutting the box..

Original hole

airbox039_zps24de98ad.jpg

Idea of new size hole under the base of box

airbox041_zps94ae8b8d.jpg

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What diameter is the rest of the intake plumbing ? I wouldn't go smaller than that..

As a suggestion, how about going through the inner wing into the area above the wheel arch liner. I believe this has air accessable from the area outside the fog light.

Edited by _Chris_
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The actual feed through to the throttle body from the top of the airbox is pretty big,its the diameter of the body itself.

Strutbrace002_zps9f4bd7b8.jpg

In theory i could go the short route maybe from the original hole through to the inner wing of the gen4,it has a resonator box (thats what i call it) ,i dont know where the air would come in,but theres a hole in the inner wing already there;all i could do is feed the cold air pipe from the airbox through there into the depths of the box as far as it would go.I preferred the idea of a feed through to the front of the car as a ram air system though.I've already made a plastic template to cover over the large hole in the airbox that side though,its just waiting for a hole to be drilled into it to incorporate the feed pipe if i decide to go from that otiginal side.Could probably go to a 60mm or so pipe that way though

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Can see the box that is inside the wing,never really checked it out closely though,but if i go that route,the cold air pipe would be sitting inside that box ,the reason i havent just fed it through there in the first place is the fact i have the gen6 relay box that sits right next to the airbox on the passenger inner wing, which makes it a PITA to get access direct to the feed to that inner wing box.Though it would mean a larger diameter pipe feed to the air box if i can get it in there.Any links to decent quality flexible feed pipe of around 60mm would be handy as well ta

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This is the thing,that box may feed right from the bottom.If i go the other route,the feed will be around radiator height.I could also swivel it to avoid any driving rain as well and it would be high enough to avoid that.The car doesnt go out in shit weather having said that,its not a daily.Mind you I wouldnt have to feed the cold air pipe right down inside to the bottom,id have to be driving into a lake like Ady did to risk Hydrolock ?As long as im not getting any heatsoak from engine bay is the main aim,as at peak power the car drops off a bit (on a dyno) and runs rich as its not getting enough air,or enough cold air anyway.Thats why im concerned about the diameter of my original pipe idea.

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I done away with that lot on the gt4 mate and used a 3" flexi feed up through the wing where the original would normally be.

If you wont it unseen go from behind where the fog light would be or above the black lower valance, But you do need to be careful though as you are doing a direct feed in to you air box so the higher you can take the feed from the better,

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Cheers Shaun,yeah I want to keep it as high as possible,the only thing that the Beams conversion has done is made it awkward to do a feed properly.Im going to have another look at the box to see of i can get a bigger diameter pipe in somewhere

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Im currently looking at this stuff on ebay for brake ducts, its had some good reviews so il chance it!

http://www.ebay.co.uk/itm/190885412270?_trksid=p2055119.m1438.l2649&var=490175561672&ssPageName=STRK%3AMEBIDX%3AIT

The ali ducting you can get from places like Wickes/Homebase is also good stuff but I think its only available in 4" diameter

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Hi Paul,Yeah i have just looked at that stuff,its a 1 ply stuff from ASH, they do also do a wire wrapped 2 ply kit too though

http://www.autosiliconehoses.com/silicone-hose-shop/air-ductings/black-silicone-2-ply-air-ducting.html

If we're working on the theory that more,cool air is whats required for a better expansion upon ignition= better power delivery,providing the ECU supplies the correct fuelling,then theoretically i could negate my 'size' issue with my original idea by making a twin intake rather than struggling to fit in a single larger one to the airbox.

If you look at air ducting products,they all start at around a 3 inch diameter,like Shaun has,which tells you that under that for a single intake system is probably not enough,especially for FI engines,though being N/A i dont see that having plenty of colder air available can be a disadvantage.I can run a smaller feed from the right hand side into the inner wing easy enough from the right hand side of the airbox,making sure the pipe isnt too long so its say a 1/3rd of the way inside the inner wing box.Its far enough away from the engine bay and nowhere near the bottom of the car.

I could then run another smaller feed from the other side of the airbox from my original idea,theory being that theres the same amount of air getting in as you would from a single bigger feed.Slightly over engineering the problem,but at least it means im getting enough cold air in which i cant really do from one feed as im restricted by pipe diameter both sides.But with two intakes i can get the same result .

280px-Prfrink_zpsbddeb3c8.jpg

Bwahey! it could work!Or,i could balls it up and be looking for a new airbox next week LOL. I shall use the Sonic way of thinking on this one.(without the setting myself on fire part)

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If the top of that resonator box already connects with the airbox, then just cut it off and leave the top piece poking through. I would presume the whole inner wing area would be fed with cold air from the front of the car so no need to run extra ducting down to the bottom, and it would save the risk of sucking in water.

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Derren may be a stupid idea but why not take the air box out then have a feed running on the inside of the bay over the top of the gear box and up that way could stick a direct in then as it should have enough angle with a filter in line should be enough to stop any chance of water getting up there

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just remember that 2 30mm diameter pipes do not equal the same as one 60mm pipe.

you should be looking at the size of the throttle body pipe and not be less than that in surface area or your flow will be down and no amount of cold air will make up for that.

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just remember that 2 30mm diameter pipes do not equal the same as one 60mm pipe.

you should be looking at the size of the throttle body pipe and not be less than that in surface area or your flow will be down and no amount of cold air will make up for that.

Id be more concerned if was half and half like your example Coops, but ive measured the exit hole from the top part of the airbox that connects to the throttle body pipework, and its exactly 65mm diameter.

.i can run a 65mm wide feed in from the original side of the airbox base which isnt much smaller than the area of the odd shaped original hole thats in the base unit from factory. ...so theoretically there should be more than enough volume of available air inside the airbox once its sealed up available for the car to suck in, also taking into account it has to go through a filter first?

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well the area of a 65mm circle is 13273.2 mm2

to equal this with 2 holes you need 46mm diameter = 13295.22 mm2

the choke point of any inlet should always be the throttle disc. if it is any smaller any were else in the system then you will never reach you top end peak performance.

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Okey dokey, so bearing in mind everything from the throttle body to the airbox remains factory, the maximum aperture that the engine can take in air is the 65mm inlet at the entry to the airbox, throttle body pipe end.

So the key is the volume of air that is available inside that airbox , which has to be constant and enough to supply the throttle body with enough air .I can supply the box with air from two feeds both with internal diameters into the box of 57mm each; the standard 'hole' in the box only has an area slightly less than the diameter of the throttle body inlet, so I am looking along the lines of two 57mm feeds supplying more than enough air for the engine to breathe in, compared to the original.I hope that makes sense, my low grade O level in maths has its limits lol (Google is my friend).Toyota obviously know exactly what they were doing which is why im not touching anything to do with the rest of the kit, just ensuring there's enough (cool) air inside the box for the engine to take as it goes through to peak revs.Does that make sense

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Derren may be a stupid idea but why not take the air box out then have a feed running on the inside of the bay over the top of the gear box and up that way could stick a direct in then as it should have enough angle with a filter in line should be enough to stop any chance of water getting up there

Thats an option if i think i know what you're getting at,though i think i can avoid the water issue with what ive got in mind,i just need to make sure ive got enough air feed into the box,if i can be sure.Only way to find out is to try i suppose,taking what Coops has said if the car runs sweet enough after the mods to the box,then ill get the exhaust downpipe replaced with a custom one when ive got the money and run it back down to Surrey RR and see what the AFR is compared to before.If it decides to run rubbish for any reason then i can reasonably easily go back to how it was and then rethink.

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sounds good as long as you are over the total area of 13273.2 then you should be fine. you can also adjust the hole sizes if you want and have them different as long as you end up with the same or more surface area. :)

Hopefully it should be ok mate,will have two cold feeds from either side with 57mm diameter each going into the box,hopefully it can suck on that and be happy :lol:

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