Individual Throttle Body tech

[Spencer]

Yea for sure! the guy just used it as an example of a well designed 6cyl manifold, as the carbs would work shit if the had nasty un-even flow over them. It only started being a restriction at 20psi anyway

[Vintage Grumble]

Some interesting shit on here/pretty pictures: http://forum.e46fanatics.com/showthread.php?t=735897

[DJZ]

My "log" plenum works okay, I read that entire thread on Hybridz before I made it, cost has a lot to do with the way I made it if you look at the Audi copy manifold the guy ended up making on there it's pretty much perfect, he CNC machined it from two solid blocks of aluminium and it probably cost him several thousand US dollars, mine cost about $200.

Also I'm pretty sure the log in your first picture has a flat bottom where the runners exit the plenum (so it's a D shape), mine is a 3.5" round tube, I also left as much length before the first runner as would fit.

[Spencer]

^ yea not having a go man, and not saying you should CNC yourself something like his. I would just be concerned about even air flow thats all, it doesn't matter the shape or size of the tube your will still have some flow problems in cylinder one. All the decent after-market plenum's for a Rb or JZ's etc will move the throttle out to try compensate this, or manufacturers will run a centre entry plenum etc

[Testament]

Not disputing what you are saying all that taper etc. is definitely better - but one thing I still question a little is all these CFD flow calcs are always showing flow to all cylinders at the same time (or at least thats what it always looks at from what I have seen) BUT in reality only one valve is open at a time, at least on a 4cyl - so in reality there is no flow down all the other ports when one valve is open (or at least only transients due to air momentum) which means your not looking so much at one cylinder "not getting air" but rather the difference in pressure drop between the flow paths down the various ports affecting the volumetric efficiency of each cylinder - which is why I'm saying if you have a big log its not going to be too bad as the flow down the manifold is not restricted at all. And by big I'm thinking log dia. 3 or 4 times port dia. or something like that.

[Spencer]

^ yea I know what your saying, in reality you can get away with it allot of the time. With the speed the intake valves open and close the flow is not a 'stop, start' affair and the CFD definitely has its merits. Its well documented 6cly's with poor manifold designs havning issues with lean or rich cylinders. The aftermarket wouldn't bother making them like they do if there wasn't reason, they dont want come backs from their product being shit and wrecking engines

[westy]

if the log was a bit bigger it would probably be o-k, looks a little on the small side really. but yeah ideally a taper manifold or a central inlet with a gentle expansion would best.

also on those socks - what is that? an M3 6cyl engine? I woudl say the socks will lose you heaps over whatever smartey germans put with the factory setup which makes pretty much 100HP/Litre doesn't it?

They are E36 M3 ITBs on a E46 2.8 in an E30. The problem with the centre entry factory plenum is that it interferes with the retarded E30 remote brake booster.

I think it's still a work in progress but it pulled quite a nice graph.

[Spencer]

^ now build a plenum and try again with bikes on the dyno filter socks kill power every time vs a modded stock airbox. Sometimes it just what ever fits and is cheap though for sure

[westy]

Should mention they're not mine ha.

Some others

[kpr]

interesting links. slightly off topic, since single throttle, but while on the topic of plenums. for those that haven't seen it heres my attempt of a dual plenum. idea copied from various places. maybe of interest..

might get it setup with an egt prob for each cylinder at some stage, see what the cylinder variances are like

the downwards angle on the runners is more of a packaging thing, plus they have been cut down from a previous project. oh and each runner is made out of 13 pieces to create a taper throughout the runner. and merge to round at the bell mouth

[Roman]

Love your work KPR!

Here's a pic of the HKS dual plenum type manifold:

And some pics of a similar manifold that I never finished designing

http://www.gpforums.co.nz/thread/370679/?s=

and the airbox that I made, but had to scrap in the end because pipes were the wrong size

[Testament]

how is that top pipe attached to the plenum with the runners? I feel like im missing something obvious.

[Roman]

There's a slot that runs down the entire length between them, so that air is fed uniformly in along the whole side of the main plenum.

Throttle body gets attached to the top part, front of bottom part is just blocked off.

[kpr]

yup^ its just sitting there in that picture, slot yet to be cut.

roman, that was the one your for designing for old man glenn yeh? would have been good to see it in action

[Roman]

Yeah, for Glenn's car.

Had heaps of time off while unemployed at the time, but then got real busy all of the sudden, and he ended up selling his car eventually, so never got past the design stage.

I'm still keen to see something get machined that I've designed in solidworks! Just perhaps something a little less ambitious for starters.

I've got the same flowbench type software here as per some of the other pics in this thread, perhaps I should give my manifold a whizz through, and see how the air actually gets to the runners.

Stupid program crashes heaps though, I think my computer is too old and creaky haha.

[Abarth]

I got these 20V Silver top flanges cut out today by some guys out in Silverdale. Eight flanges for $80 in 8mm Alloy.

Excuse the shit cellphone pictures.

[Sisu]

Those are really cool.

Has anyone considered making the plenium/airbox out of a clear plastic instead?

Acrylic would seem the winner, generally has by far the best ballance of properties, unless you use very specialised, expensive, modified grades of polycarbonate. Standard polycarbonate, also has very poor resistance to some very common automotive fluids, ie the aromatic hydrocarbons found in virtually all modern fuels. Which you would get in an airbox.

If you use acrylic drape forming is the process of heating a sheet of plastic until it sags and then draping it over a form shaped like the finished article. You could make a mold of the alloy one you have made. Then use these 2 halfs to make an inner mold. so you have this sort of thing (0) You use a heat resistant material such as a Hobby plaster you get at craft shops and you need either a frame or clamp the edges of the acrylic sheet as it will shrink and then stick it in the sandwich while it is being heated to 215 initially to get out the bubbles then to the mold temp of around 180 deg C.

[mikuni]

Those are really cool.

Has anyone considered making the plenium/airbox out of a clear plastic instead?

Acrylic would seem the winner, generally has by far the best ballance of properties, unless you use very specialised, expensive, modified grades of polycarbonate. Standard polycarbonate, also has very poor resistance to some very common automotive fluids, ie the aromatic hydrocarbons found in virtually all modern fuels. Which you would get in an airbox.

If you use acrylic drape forming is the process of heating a sheet of plastic until it sags and then draping it over a form shaped like the finished article. You could make a mold of the alloy one you have made. Then use these 2 halfs to make an inner mold. so you have this sort of thing (0) You use a heat resistant material such as a Hobby plaster you get at craft shops and you need either a frame or clamp the edges of the acrylic sheet as it will shrink and then stick it in the sandwich while it is being heated to 215 initially to get out the bubbles then to the mold temp of around 180 deg C.

This stuff interests me. Not so much for airboxes, although it is a good idea, but for me more so for making parts for my racecar, such as headlights and other moulded components to save a lot of weight over glass or steel in some cases.

Would it be too much trouble to make a quick thread titled something relevant like "Plastic Moulding" or something similar and chuck up some information in there - plastic types, temps, maybe some photo examples of what you have done yourself?

[kpr]

used a heat gun and straight edge to make this one.

[westy]

This is also an interesting thread.

http://www.bimmersport.co.nz/forums/index.php?showtopic=28044&st=30&start=30