Intake pipe theory

[Jovan Ceklaj]

To put it very simple - yes large to small would compensate for air volume reduction due to cooling, but it also affects other factors like overall back-pressure, friction, sharpness of bends etc.
The LICP is also less length than the UICP - this affects resistance pre-and post IC

hey! that's what I was saying....just a lot more wordy and fragmented :laugh:

Jovan

[Marty van den Bosch]

Ya - but I don't do math  

[Kimyee Lai]

I think most of the points have already been made...except that inlet velocity to the head is ultimately determined by the intake and head.  It has pretty much nothing to do with the IC pipe at all.  So how do you size an IC pipe?  In this case, when we're talking about pipe ID, It's basically a balance of velocity flow losses and losses due to diameter changes.  Anything that disrupts flow, even a smooth transition from small to large pipe or vice versa, causes a flow loss.  

Why a round pipe?  Because it'll give you the smallest wall area / pipe volume, or smallest circumferential wall length/x-sectional area.  The wall is what slows the flow down.

[John Hartman]

I had a few thoughts about this very subject a few weeks ago.

My thoughts were the reverse of whats been said here tho.

I figure make the lower pipe smaller in diameter than the upper pipe.

This in theory would make the air expand while inside the I/C, thereby cooling itself just by expanding.  Compress something, it gets hotter, let it expand again, it cools, right?  Do that inside the I/C where that cooling can be more effective, and it might have a small positive effect.

I'm thinking 2inch inlet and 2.5" outlet pipes on the I/C itself with matching pipes.

Of course, this is just some thoughts, but I did run it by a freind of mine who is an engineer(for real, papered and all) and he said it had merit.

[Kimyee Lai]

You do realise that when you let something expand...it cools it and the pressure DROPS right?  Why spend all the effort using the turbo to compress the air, and dropping the expansion just to cool the air down?  Might as well not compress it as much to begin with.  Additionally, cooling via expansion doesn't really take heat away...the energy is still there, just spread thinly.  Now, the intercooler, on the other hand, actually rejects heat from the system.

[Mike Schmid]

Good point Kimyee, you actually have to pull heat energy out of the system to be doing any real good I think...

I guess it all depends on what makes more power eh?  Does boost pressure, intake velocity, intake temp or intake density make the most power? Which should be the paramount concern...?  Everyone's gonna have theories but the only real way to figure it out would be a well equipped fabrication shop, a dyno and time and money.

Which comes back to the real problem of hobby modification like we do vs what a race team does.  I mean, lots of people have run lots of parts but everyone's setup is different and no one doing hobby mods has the money to run different setups back to back on a dyno or properly setup flowbench, and do scientific experimentation like that, comparing one setup to another directly, changing one variable at a time.