Lets talk science, Stillen Gen3 Intake

Mandingo

Oh I like sciencey threads. This old physics relation shows what many of us already know from experience or intuition:



Resistance (R) is directly proportional to the length (L) of the tube and viscosity of the fluid (a constant in this case obviously). R is inversely proportional to the radius to the 4th power.

So as length increases, resistance increases (we know this already). What isn't as obvious is that as radius of the tube increases, resistance decreases dramatically.

Of course we need more complicated math (computer models) to see how turbulence is created by bends in the tube and how that affects resistance. The flow through the filters could even be explained by the above relation in a sense, but it would require calculus and lots of data we can't get.

Basically, the large area of the K&N filters used on the Gen3 overcomes the negative effect of having longer tubes (I think their radius is a little larger than stock as well? correct me if I'm wrong). The lower IAT due to the filter location is not what gives the noticeable power increase. The difference in temperature between the stock draw location and the Gen3 location is too small to affect air density enough. Perhaps the computer is responding to the lower temperature readings and making adjustments that translate to more power?

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synolimit

Someone measured for me when I was making my intakes and said the pipe is same as OEM. 2.5" OD or 2.34" ID where it counts.

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luigi90210

iirc the stillen uses 90 degree mandrel bends and that reduced flow by 30% which is the equivalent to trying to flow air through 3ft of additional piping(at least this is what i know for intercoolers on turbo cars, it might be worse for N/A cars)

the reason stillen intakes make more power over stock is it is tricking the ECU by mechanically leaning it out(like all intakes except for AEM) so the computer will only read X amount of air when there is really X+Y air(Y being the additional air not accounted for), and that combined with the cold air and better flow account for the rest of the gains

no the stillens are slightly bigger than OEM(OEM is 2.34 i believe stillen is 2.38)
if someone were to modify a stock airbox to fit on a SRI and completely seal it off from the engine bay, in theory it should outperform the long tube intake at speed because it is getting similar temps as the LTI and there is less restriction and in some cases(like fujita intakes), the short rams are physically larger than the long tubes are

EDIT these videos are pretty interesting

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Mandingo

I remember reading about this a while back. Wouldn't the leaning-out effect be negated by a tune? The folks that posted before/after dynos showed gains from the G3 intake even after the A/F was corrected with Uprev if I remember correctly.

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Rusty

I got to laugh at some of the posts on here. Good entetainment.

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