vibrating_Cake Posted June 8, 2009 Report Posted June 8, 2009 im thinking of making an inlet plenum for my twin 45's.... meaning a single box around all 4 carbies running to one single pipe which goes to a remote cone air filter in front of the rad (mmm cold air!) going all girly to reduce the induction roar a little, have a place to put two breater pipes so i dont have to use a catch tank or breather filters which stink! and... hopefully gain advantage of the cold air AND the "ram" effect of having a single inlet tube.. thing is, how do i work out what diameter inlet tube i need, obviousley bigger the better is the failsafe, but having something thats big enough to not be restricting, but not too big, will create a higher speed of air coming into the "airbox" which helps "ram" air into it, more air more power man! ive searched as hard as i can and the only options to buy are like 150quid or something stupid!!! so, i have a plan on how im going to produce this so i can run pretty tall trumpets while still having a filter. anyone got any tips on this kind of thing? like how to work out all the stuff i need, and anyone done this before with previous examples. i MAY be interested in tapering the plenum so the last carbie gains equal pressure to the rest i think i can get away with that. also... are weber carbies suitable for a little "oil mist" to be passed through them from the oil breathers without any adverse effects? ^-^ i think things too much.
vibrating_Cake Posted June 8, 2009 Author Report Posted June 8, 2009 i knocked up a couple of 3d models to show what i mean, all made out of sheet ally basically cut a net up out of cardboard, copy it into alu, then bend and rivit it all together. the lid will be on a hinge so you can open it up to balance the carbies etc and secured on a lip of some sort with sealant (aint got that far yet haha) both plenums do taper, the smaller one has a 15mm gap (half an inch) above the last trumpet if using 50mm trumpets which tbh i dont think is enough?? any views on this bit. the bigger one i have a 30mm gap (1.1 inch) when using 50mm (2inch ish) trumpets. they all go to a 3inch outlet (76mm ish) to go to standard 3" flexi ducting in front of rad for cold aiiiir! thoughts?? ** with trumpets =)**
escort21 Posted June 8, 2009 Report Posted June 8, 2009 I use that, its a relatively simple 3d drawing package
Admin Vista Posted June 8, 2009 Admin Report Posted June 8, 2009 It may be the way it's drawn but it looks to me as if that one inlet hole isn't big enough, I'd say it needs to be at least as big as the combined CSA of the four trumpet inlets or it'll be restrictive
Supercharged Nat Posted June 8, 2009 Report Posted June 8, 2009 agree with last comment. also the 15mm gap between plate and trumpet isnt going to be enough. 30mm is probably getting close to the limits too. id have thought the more space the better. also think about your inlet tubing/ piping. std flexy pipe has ridges which will upset air flow, the smoother the better! if your going to the effort of ram effect and all that, you need to think about smooth flexy pipe.
Fiesta Steve Posted June 8, 2009 Report Posted June 8, 2009 I've seen these kind of things before and they usually hurt power. I'd personall save your time/effort/money and spend it on something worthwhile
V8ian Posted June 8, 2009 Report Posted June 8, 2009 It may be the way it's drawn but it looks to me as if that one inlet hole isn't big enough, I'd say it needs to be at least as big as the combined CSA of the four trumpet inlets or it'll be restrictive No, in theory the CSA does not need to be any more than the dia of 1 choke on a 4 cylinder car as 1 cylinder is only charging at one time, obviously, bigger than that would be better, just to avoid any radius obstructions, well thats the way I see it unless the engine is a 2 stroke
Admin Vista Posted June 8, 2009 Admin Report Posted June 8, 2009 It may be the way it's drawn but it looks to me as if that one inlet hole isn't big enough, I'd say it needs to be at least as big as the combined CSA of the four trumpet inlets or it'll be restrictive No, in theory the CSA does not need to be any more than the dia of 1 choke on a 4 cylinder car as 1 cylinder is only charging at one time, obviously, bigger than that would be better, just to avoid any radius obstructions, well thats the way I see it unless the engine is a 2 stroke That's a good point Ian, I hadn't considered that.
mr squidian Posted June 8, 2009 Report Posted June 8, 2009 were did you get that from? is the program free got a link to a download?
vibrating_Cake Posted June 8, 2009 Author Report Posted June 8, 2009 It may be the way it's drawn but it looks to me as if that one inlet hole isn't big enough, I'd say it needs to be at least as big as the combined CSA of the four trumpet inlets or it'll be restrictive well i have 36mm chokes in the carbies, so thats 36xpie squared. times 4 =) 355.3x4= 1421.2mm squared 76.2xpie squared is 752 which is near enough half of the entire inlet. the idea is to get a "flow" into the plenum increasing air velocity increases the base inertia of the air, meaning it "wants" to carry on flowing into the plenum even when throttle is closed/you're changing gear, increases throttle response. the idea is not to gain power, its to loose some of the induction roar, for a daily driver its a bit of a pain, and whenever you get to the slightest gradient and you have to use the engine to "pull" the volume of it increases quite a lot, so when having a conversation in the car you gotta shut up for hills, cause they are loooud =). as said after, only one cylinder "sucks" air in so in theory with a perfect inlet tract a 36mm inlet diameter's cross sectional area would be enough to not restrict flow at all... but its not a perfect world, and to get the piping to the cold theres gonna be a few bends! and yeah the flexi piping has lots of ridges in it, which is another reason why the CSA is doubled so this doesnt really matter as much, if it all works and im happy with the results ill get some tubing made up (guttering near enough 3" ) could be used.... also, i have lots of spare time and its not gonna cost a lot to be fair! anything else really? just playing with card now see if i can get a propper net made up
vibrating_Cake Posted June 8, 2009 Author Report Posted June 8, 2009 were did you get that from? is the program free got a link to a download? ilegally it is lol. its a few grand if not.... i got it from university student edition!
Admin Vista Posted June 8, 2009 Admin Report Posted June 8, 2009 well i have 36mm chokes in the carbies, so thats 36xpie squared.times 4 =) 355.3x4= 1421.2mm squared 76.2xpie squared is 752 which is near enough half of the entire inlet. the idea is to get a "flow" into the plenum increasing air velocity increases the base inertia of the air, meaning it "wants" to carry on flowing into the plenum even when throttle is closed/you're changing gear, increases throttle response. I'm not following your maths, what are you trying to calculate? The CSA of each trumpet inlet? It should be Pi x r Squared so each trumpet will be 1018.88 mm squared, x 4 = 4071.5mm sq
emu Posted June 8, 2009 Report Posted June 8, 2009 Bit of square section guttering because its easier to fit to the carbs, a round/square guttering adaptor to fit your cone filter to and away you go even better, it'll only cost you £15 and you can get it in brown
vibrating_Cake Posted June 8, 2009 Author Report Posted June 8, 2009 well i have 36mm chokes in the carbies, so thats 36xpie squared.times 4 =) 355.3x4= 1421.2mm squared 76.2xpie squared is 752 which is near enough half of the entire inlet. the idea is to get a "flow" into the plenum increasing air velocity increases the base inertia of the air, meaning it "wants" to carry on flowing into the plenum even when throttle is closed/you're changing gear, increases throttle response. I'm not following your maths, what are you trying to calculate? The CSA of each trumpet inlet? It should be Pi x r Squared so each trumpet will be 1018.88 mm squared, x 4 = 4071.5mm sq ooops i used diameter
w p e Posted June 8, 2009 Report Posted June 8, 2009 pie=chips and i just had mine cheers. ps been there done that and lost 11hp. carbs dont like dense still air thats the reason they have ram pipes to move the air faster take your ram pipes of and see for your self.
Johnson Posted June 10, 2009 Report Posted June 10, 2009 vibrating_Cake you need my DCOE's i drew up on solid works a while ago....
Retromotorsport Posted June 10, 2009 Report Posted June 10, 2009 ^^^^^ flash bugger .. Only joking Johnson
Johnson Posted June 10, 2009 Report Posted June 10, 2009 haha well i needed to draw them up for my engine
antz Posted June 10, 2009 Report Posted June 10, 2009 Bit of square section guttering because its easier to fit to the carbs, a round/square guttering adaptor to fit your cone filter to and away you go even better, it'll only cost you £15 and you can get it in brown budget tuning at its finest
vibrating_Cake Posted June 10, 2009 Author Report Posted June 10, 2009 vibrating_Cake you need my DCOE's i drew up on solid works a while ago.... hahaha yes, flash bugger, do assemblies cross over from solidworks to solid-edge tho? we have had troubles with assemblies crossing from solid edge to solidworks, it forgets all the relationships
Supercharged Nat Posted June 10, 2009 Report Posted June 10, 2009 haha well i needed to draw them up for my engine oooooh! is that supercharged? do you have a project thread or anything?
Johnson Posted June 11, 2009 Report Posted June 11, 2009 i have never tried importing from solidworks to solid-edge i usually save things as STL files and they tend to import into 3DS max ok. Nat na i drew up a 3d crossflow engine a while ago, and i needed some webers for it as for webe plenums, ive seen a company in australia that does some for the down draft beetle boys.# ive also seen acouple on ebay for old lotus espris i think
mk2rudkin Posted June 12, 2009 Report Posted June 12, 2009 anychance of the pics the 3d cross flow engine ..... that would be ace to see
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