jackb_ms Posted December 8, 2011 Share Posted December 8, 2011 Air can go trough a 50mm ID hose and would it be enough for my engine? That is the question I am currently asking myself and I cannot answer it. The engine is a 1.8VVC on roller barrels Can blatchat help to answer that question? Jack Link to comment Share on other sites More sharing options...
Rich N Posted December 8, 2011 Share Posted December 8, 2011 jack... what? Link to comment Share on other sites More sharing options...
charlie_pank Posted December 8, 2011 Share Posted December 8, 2011 OK as a rule of thumb, in a normal IL4 only one cylinder sucks at a time, so the hose diameter has to be as big or bigger than one inlet trumpet. More detail for fun... Every 1/2 revolution one of the cylinders is filling Volume of 1 cylinder is 1.8L/4 = .450L .450L = 450cc = .00045m^3 This means that every revolution you need to be able to suck 0.0009m^3 of air & fuel. At an optimal AFR of 14.7:1, you'll need 14.7/15.7*0.0009m^3 of air = 0.0008426m^3/revolution At 3500rpm (probably around about where your peak torque is), you'll be running at 3500/60 rps = 58.3333 rps At this engine speed you'll need 58.333 * 0.0008426m^3 / s of air = .04915 m^3/s Diameter of hose = .050m Cross-sectional area = .05m^2*Pi = .00785m^2 Length of column of air required / second at that diameter = .04915m^3/.00785m^2 = 6.211m Therefore you'd require the air to be moving at 6.211m/s to feed your engine at that diameter. I can't tell you about friction because I don't know how long the hose is, or what the coefficient of friction is between the hose lining and air. Edited to correct misplaced decimal! Edited by - charlie_pank on 8 Dec 2011 16:41:11 Link to comment Share on other sites More sharing options...
jackb_ms Posted December 8, 2011 Author Share Posted December 8, 2011 Rich, I need something at night to wind me down and stop thinking about gates 😬 I'm working on my cold air induction thingy! Thank you Charlie Not sure if I understand everything... So the air inside would need to travel at close to 139mph. Next question, if the air travel at 139mph in a 50mm ID tube, what speed does the car needs to be doing Jack Edited by - jackb_ms on 8 Dec 2011 16:19:22 Link to comment Share on other sites More sharing options...
charlie_pank Posted December 8, 2011 Share Posted December 8, 2011 My mistake, that'll be 13.9 MPH. You don't need to ram the air in there by driving at 13.9MPH, the engine will suck it at that speed. Link to comment Share on other sites More sharing options...
Dickie Normuss Posted December 8, 2011 Share Posted December 8, 2011 Jack I have no scientific answer but if you look at some of the commercially available airboxes with a cold air inlet they're more like 100-150mm. Link to comment Share on other sites More sharing options...
virden Posted December 9, 2011 Share Posted December 9, 2011 Just to add a couple of small complications. The suction from the piston is subject to lag and so effectively you will be lucky you get more than 80% of the swept volume in any cylinder. (hence the advantages of super/turbo charging). Given that the air movement is subject to lag, it means that the air will be accelerating into the cylinder rather than flowing at a constant rate. Oh yes, and when the inlet valve shuts, the inflowing air rebounds and sets up a reverse shockwave Link to comment Share on other sites More sharing options...
Mavic82 Posted December 9, 2011 Share Posted December 9, 2011 ..and don't ram the air in, use a still air box. Link to comment Share on other sites More sharing options...
jackb_ms Posted December 9, 2011 Author Share Posted December 9, 2011 ..and don't ram the air in, use a still air box. Why? I was thinking of using an in line air filter something like that with this air box What I want to achieve is to recreate the air intake system from the 21 GTO here on a budget Jack PS: does someone has an unused Auto-teknix i could borrow to check it it fits in a 21? Link to comment Share on other sites More sharing options...
EFA Posted December 10, 2011 Share Posted December 10, 2011 Right, so the question here is not dissimilar to the question I posed here regarding using the intakes in the doors of my P4 replica to feed an F355 engine. The F355 engine is 3496cc (so roughly 2 x 1.8k) and gives about 1.8x the power in standard form of an SLR 1.8k. The tube (37 in this drawing http://www.eurospares.co.uk/userImages/003/Large/003_012.gif ) through which both banks of cylinders draw air through the AFM has an internal diameter of 82mm. 82mm dia is a CSA of 52cm² So half that is 26cm² A 50mm ID tube (going back to the OP) has a CSA of 19.63cm2, so you should be OK. Link to comment Share on other sites More sharing options...
Molecular--Bob Posted December 10, 2011 Share Posted December 10, 2011 or you could buy this here or here Edited by - Molecular--Bob on 10 Dec 2011 13:27:51 Link to comment Share on other sites More sharing options...
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