Intake tubes. Do size and shape count?

[baz]

Ok, what i noticed was the more direct throttle respons, the whale penis took a lot longer to get in the rpms, with the AEM it goes a lot smoother. But then agian the tube is a lot smaller so the air is faster compressed. Makes sences i think

[mynameisowen]

yes it does, good news

[saxophonias]

i think i get the jist of what your saying, yes porting your manifold could be good but its proabably best to just buy an aftermarket one. Porting and polishing the head is a must if your N/A though, so yeah.

If there are too many differences in diameter the air will loose velocity. When a fluid (gases are counted as a fluid from an engineering perspective) contacts a surface it will slow down. With the fluid in contact with the wall actually stopping for a short time this causes friction against the fluid "layer" next to it which will cause it to slow down aswell (you have to imagine the fluid flow through a pipe as loads of layers of fluid).

This is a normal striaght intake tube
The lenght of the lines is the airs relative speed compared to each other.
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This is one with smaller diameter

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As you can expect the air slows down at the junction but it also slows down all the air next to it, and that slows down the layer next to it etc. So yes you gain velocity for the uniterupted air in the middle but the air towards the edges gets slowed down dramatically. You might actually get less air flow so thats why i think you should match you inlet tubing to your manifold diameter, or try to make changes gradual so you dont get lots of interference. (this picture was done freehand, its not meant ot be accurate!!)

Very nice post!
Still my question is this. What is the biggest size we could have so as to have the max. air velocity?

[TassosNitrous]

what one really wants to have is the front tip of the pipe to be as wider as possible (think wisely) while
the other end of the pipe to be close to the width of the intake manifold. This is basic fluid mechanics. A more general treatment would require considering the effects of turbulence in this configuration however this is a far more complicated issue than we can address in this forum.

[mynameisowen]

i think its best to keep it all one diameter if possible, theres obviously going to be turbulence in the TB. But the air is turbulent throughout the whole piping anyway. Just stay away from sharp corners and large changes in diameter if possible.

Besides this is only one aspect of the engine, you could get the inlet perfect and the rest would drag it all down, best not to bother too much with the details, unless your designing race engines, or have lots of money/time on your hands!!!

[hondaNickx]

I had and tested most of the intake tubes.Short ram, Cold air , 60mm , 70mm and 76mm ,Big tube intake ,Blox velocity stack ,airbox ,Oem ek4 ...
Without a retune the difference is not that big.The Cold air intakes all gave me better bottem end power not so much top end.
Short ram gave me the best power on top.Also for diameters i would stick with a 2.5" 60mm tube.They are more then big enough ,and you need all the velocity you can get on a D14.One you should pay attention too is detail.Every connection from filter too TB has to be as smooth as possible.I don't even like commen rubber couplers as they tend to misaline the piping a little.Every little hump or bump (even 1mm ridges) disrupts airflow.Tb itself included .

[Dodo Bizar]

Finally someone not all-in-favor of the CAI. Yes I think 2 that short-rams give you high end power.

[hondaNickx]

The best experience was my short ram with a airbox ,and that's what i will be using next year.Even on the dyno i didn't even notice a power loss or a bad power graph.I think it even gave me a smoother and more straight torque curve that goes up to 6000rpm.
My new setup will be a smooth seemless short ram intake pipe with a velocity stack at the entry of the pipe and one at the throttle body.
Entry of the pipe sits inside an airbox where cold air is feeded from the bumper with a k&n filter .
Trying to eliminate as much water pick up as i can ,i'm going to seal the area where the filter sits (behind bumper/chassis) with plastic ,and installing some kind of air redirection pipe with baffles in them to slow the air down.That will cause water to drop down ,as water particuls are sucked in because of the velocity of the air.Even using the airbox as a chamber (where air velocity slows down again) will help to eliminate water particuls pick up.I might use a hydro shield over the velocity stack as an extra save guard when it's not hott summer time.
That is what i was thinking ,still need to work out some details though.

Another thing to look into is almost every Stock airbox ,and mugen airbox uses Velocity stacks everywhere possible.
Look inside the Oem D14 airbox under the filter panel,there's a rubber that sits around the TB with nice rounded shape ,that's a velocity stack.
At the end of the plastic air feeding pipe there's a flare ,that's a velocity stack. EK4 airbox has the same thing eg6 too , Mugen airbox uses a velocity stack inside the filter and a flare on the air feeding pipe.

There are only a few aftermarket companies that devellopped a cold air intake for the honda's.Mugen ,spoon ,J's racing ,ARC ,and others all use short ram intake's.

[DJ Left]

i'm going to make a new intake tube for my ej9. what material you believe it's best for the tube?? i have simota with heat shield. if i use a rubber tube used on d16 it will be ok???

[hondaNickx]

The best thing to do is to make a intake pipe that reflects heat or doesn't take up heat.In NASA they gold coate almost everything to reflect the heat up in space.Gold reflects about 80% of the radiant heat.So if you're fine with a gold intake i'd say get a general aluminium intake pipe and get it gold coated.In dutch the name is "Vergulden" don't know how that is called in english...I don't think the price would be that high to coate a short ram intake pipe.