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May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 1:17 pm
by LegacyofDan
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Can you explain in detail what the purpose of the intake piping being so large and then reduced when coming into the throttle body and intake manifold.

Thank you.

Re: May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 3:59 pm
by 2_Liter_Turbo
Well, if the intake truly does expand like that on the inside, it will slow the air flow down (velocity) and increase the air pressure in the expanded part. When it necks back down, the velocity will increase and the pressure will go down. I do not think this is the case however, as the expansion and contraction are too abrupt with sharp edges. If it were the case, and the design was better, it could increase the volumetric efficiency of the engine due to the high pressure zone wanting to equalize with the lower pressure in the intake manifold, thus forcing more air in the engine.

What I'm guessing is that the inside diameter is the same, and there is just an added "cylinder" of metal welded around the pipe. With either vacuum or special gasses (Argon I think... but I may be wrong), this will act like a calorimeter. This will prevent heat transfer from the surrounding air and the intake charge. So if the turbo manifolds are blazing hot, it will have little effect on the temperature in the intake tube.

Re: May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 4:30 pm
by LegacyofDan
ahhh i see...well thank you very much for the detailed explanation, i feel enlightened! :)
thank you again man!

Re: May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 4:41 pm
by klue
Look at the manifold plenum... There basically isnt one.
That big tube is acting like the manifolds plenum, just on the wrong side of the TB.

Re: May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 5:14 pm
by 2_Liter_Turbo
klue wrote:Look at the manifold plenum... There basically isnt one.
That big tube is acting like the manifolds plenum, just on the wrong side of the TB.


If that's the case I sure hope the inside is nice and smooth, unlike the outside! That follows the theory in the first scenario I posted about, ha ha. I've seen people run the cosworth manifold without an over sized intake pipe though.

Re: May 1 of the many brillant people explain this to me please

PostPosted: Mon Sep 20, 2010 5:14 pm
by 2_Liter_Turbo
LegacyofDan wrote:ahhh i see...well thank you very much for the detailed explanation, i feel enlightened! :)
thank you again man!


No problem, I didn't got to engineering school for nothing! Ha ha

Re: May 1 of the many brillant people explain this to me please

PostPosted: Thu Sep 23, 2010 12:46 pm
by Mafix
hmmm. i wonder if that has any real application. i.e. way cheaper and easier than actually having a manifold made