turbo_fb Posted June 13, 2006 Share Posted June 13, 2006 I am planning to fab my own intake manifoil for my rb25det in the Z. This way I can get a cheaper manyfoil that fits well. So far I have read quite alot about making them so I wanted to know if u guys sits on any more information, which I know you do Atleast 9" runners with "trumpet" ends inside the plenum. Atleast same liters plenum as engine. 2.5L (not quite sure about this) My plan is to make a wooden block and hammer a thin alu sheet around it to make the shape I want. Then weld it on to a plate where the runners go trough. Then either weld the runners onto the original cutoff manifoil or fit them with sillicone hoses. Since I am running 3" piping from turbo-IC-Throttle I could use a 80mm throttle since it's almost same size, but maybe 90mm to be on the safe side. Guess it doesnt realy matter aslong is not to large/small. Quote Link to comment Share on other sites More sharing options...
cheftrd Posted June 14, 2006 Share Posted June 14, 2006 Want to properly build an intake manifold? Buy "Design Techniques for Engine Manifolds/Wave Action Methods for IC Engines". Better know math... Lots of it. That said, here are some verry, verry, verry, basics: 1. Thin sheet metal you can bend easily around a piece of wood will balloon at 20psi. Think more around .125" 5052 H34 for easy forming and welding do-it-yourself. 2. 88,000 devided by peak torque will get you in the neighborhood for runner length as measured from the intake valve. This is very general, but you're going to find that it's not much different than the stock runner length. 3. On single throttle applications, 70% of engine displacement for high response, circuit engines; 125% of engine displacement for drag motors. This is very basic and doesn't cover anything about how pressure waves from one cylinder affect the others due to the shape, etc. If you are running stock cams and head, you can not beat the stock manifold for best across-the-rpm-band power. Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted June 14, 2006 Share Posted June 14, 2006 Helmholtz Resonator Quote Link to comment Share on other sites More sharing options...
turbo_fb Posted June 14, 2006 Author Share Posted June 14, 2006 Thx. Gonna get me that book asap. As for the runners I was calculating the length but the length is dependent on what rpm area I want it to be most effective in. I did some searching on intake valve open time on rb25det.org. It was said to be open for 20 degres. Sounds a bit low? Stock cams though. Idea would be to get best flow just before turbo starts boosting. Gonna get me some tomei cams and might port head. Must check wallet Problem with stock manifoil in my Datsun is the piping on wrong side. Could hook it up this season just to get the car up and running. http://auto.howstuffworks.com/question517.htm This link also gave some good info. Helmholtz Resonator Did look into that. Also described in the howstuffworks link. http://en.wikipedia.org/wiki/Helmholtz_Resonator Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted June 14, 2006 Share Posted June 14, 2006 This is the design that I am building mine to. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted June 15, 2006 Share Posted June 15, 2006 This is the design that I am building mine too. You've always got something up your sleeve!!! Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 15, 2006 Share Posted June 15, 2006 I am planning to fab my own intake manifoil for my rb25det in the Z.This way I can get a cheaper manyfoil that fits well. So far I have read quite alot about making them so I wanted to know if u guys sits on any more information' date=' which I know you do Atleast 9" runners with "trumpet" ends inside the plenum. Atleast same liters plenum as engine. 2.5L (not quite sure about this) My plan is to make a wooden block and hammer a thin alu sheet around it to make the shape I want. Then weld it on to a plate where the runners go trough. Then either weld the runners onto the original cutoff manifoil or fit them with sillicone hoses. Since I am running 3" piping from turbo-IC-Throttle I could use a 80mm throttle since it's almost same size, but maybe 90mm to be on the safe side. Guess it doesnt realy matter aslong is not to large/small.[/quote'] Have a look at the pic's of my manifold that i had professionally built by a RB30DET expert engine builder in NZ. It has bell mouths on the inside, and i run a billet 80mm TB. Quote Link to comment Share on other sites More sharing options...
turbo_fb Posted June 15, 2006 Author Share Posted June 15, 2006 That intake looks very nice, so does the exhaust manifoil in the back there I bet it wasnt cheap. Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 15, 2006 Share Posted June 15, 2006 No it wasnt, but its a nice solution. The exhaust manifold isnt mine, but the same chap makes those as well, very nice parts. If you wanna know who it is, R.I.P.S Rotorua Import Pro Shop in New Zealand. He has posted on here before - search for posts by R.I.P.S Cheers, Clint T Quote Link to comment Share on other sites More sharing options...
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