Andrew Dunk Shaw Posted April 3, 2003 Share Posted April 3, 2003 Right guys, can i have your thoughts on this please. Can you have too much air pressure or volume of air in the airbox ? Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 3, 2003 Share Posted April 3, 2003 Let get this started, however this may be BS. I would have thought it would be possible to have a theoretical level of air pressure that was too great for the system , but that level would not be possible to achieve with any ram air effect reliant on the forward motion of the car. Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 4, 2003 Share Posted April 4, 2003 As terminator says, it must be theoretically possible, but I reckon the airbox would blow apart before you damaged the engine. I would expect it to be drawing a vacuum downstream of the filter element. Are you planning a super huge pressurized airbox conversion or something? Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 4, 2003 Author Share Posted April 4, 2003 Ive made my own fabricated airbox which is a sealed unit, at the moment it has one 3" diameter inlet which comes in through the inner wing and routed up to the front bumper with flexi hose, i was considering having a second inlet just like the stock one which comes in under the headlight. Just to add, ive done away with the stock top inlet above the radiator. My problem is will i get enough air in through just the 3" inlet or do you think i should go for a second in through under the headlamp. If i worked out the surface area of both the stock inlets do you think as long as i get a similar surface area with my inlets it'll be ok. Quote Link to comment Share on other sites More sharing options...
Ian C Posted April 4, 2003 Share Posted April 4, 2003 You can have too much air going in, usually caused by a turbo too big for the engine (yes, it can happen). This is, I think, called compressor surge and it's nasty on your turbo but not necessarily on the engine. So a ram air box won't come anywhere near this level of overpressurisation. -Ian Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 4, 2003 Share Posted April 4, 2003 I would guess that as along as your alternative intake/s are equal to or exceed the cross-sectional area of the narrowest part of the stock induction system you will be OK. I thought Nathan posted about some prototype induction box with a big intake at TDI. He may have some thought on intake aperture issues. Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 4, 2003 Author Share Posted April 4, 2003 Thanks for the input guys. Roughly speaking the stock inlets are 7500 square mm for the 2. and my 3" or 76 mm dia pipe is 4300 square mm so looks like i'll need to keep the top intake on till i figure where to route a second intake or i could just go bigger diameter with the 1 inlet. If im working it out rite ( pye x r x r = area of a circle ) Which would need 4" or 100 mm diameter pipe which would give me 7835 square mm. Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 4, 2003 Author Share Posted April 4, 2003 Well i took the car out for a test drive but nice and sensible, just kept going a touch harder each time, up the local airstrip ofcourse . Seemed to be fine, pulled the same as usual, until i did a sort of 35ish rolling start and floored it, didn't seem to like that, it hesitated big time, started to go fine then just lost power so i backed off, so im thinking i'll try with lid on tomorrow and do the same test and see what diff there is, im not giving it hell but could i be doing any damage ? Did it with the lid off as pictured, theres about a 1" gap approx, between the box and the underside of the bonnet when shut. Put the stock top intake on as well, not useing the intake under hdlamp yet, just the 3" feed from underneath through wing and as pictured underneath indicator. Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 4, 2003 Author Share Posted April 4, 2003 bumper shot Quote Link to comment Share on other sites More sharing options...
dude Posted April 5, 2003 Share Posted April 5, 2003 I once talked to a guy about a ram-air conversion on a m.bike and the prob was getting a big enough airbox that the intake wouldnt 'suck' dry , this was a 750cc bike and the airbox would have been bigger than the one you are trying to use for a 3000cc engine , i think that box is far too small , would it not be better to put the filter down in that bottom scoop where it should be in the nice cool air . John:flame Dev Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 5, 2003 Author Share Posted April 5, 2003 Originally posted by dudersvr I once talked to a guy about a ram-air conversion on a m.bike and the prob was getting a big enough airbox that the intake wouldnt 'suck' dry , this was a 750cc bike and the airbox would have been bigger than the one you are trying to use for a 3000cc engine , i think that box is far too small , would it not be better to put the filter down in that bottom scoop where it should be in the nice cool air . John:flame Dev I see what your saying, but the stock airbox isnt really that big either and that wrks fine, my box measures approx the same volume as the stock one, so guess i'll have to do some more testing. Quote Link to comment Share on other sites More sharing options...
Steve Cargill Posted April 5, 2003 Share Posted April 5, 2003 Andrew, I'd say the intake and air box is WAY too small. Have a look at the link below, where my fag-packet maths shows at 6KRPM and 1bar you need 300 litres of air per second. http://www.mkivsupra.net/vbb/showthread.php?s=&threadid=7326&perpage=15&pagenumber=2 Quote Link to comment Share on other sites More sharing options...
dude Posted April 5, 2003 Share Posted April 5, 2003 Andrew the difference is that the stock airbox is not sealed (this was the same problem on the bike ) as soon as you use a sealed airbox (the only way to achieve ram air AFAIK) it has to be huge and hold more air than the system can suck . John:flame Dev Quote Link to comment Share on other sites More sharing options...
Andrew Dunk Shaw Posted April 5, 2003 Author Share Posted April 5, 2003 Looks like its back to the old drawing board then. 300 litres of air per second, how the hell do you measure that, damn those clever jap techies Quote Link to comment Share on other sites More sharing options...
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