VASasha

iTrader: (5)

I have been looking at various exhausts and one thing keeps jumping out at me. Most of these exhausts start out as a 2.5-3" tube and then turn into a dual 2-2.5". What doesn't make sense to me is if they are only displacing (may not be the right word here) 3" of air to start, why do they need 5" (2x2.5) towards the end? Wouldn't dual 1.5" be sufficient? I understand that the rotary doesn't have backpressure issues but, besides the audial/visual factors, are there any other things that would require the reverse bottleneck?

Thanks in advance,

Sasha

Keef

hot is dense

cold is not

VASasha

iTrader: (5)

isn't it the other way around? which is why a CAI works (in theory) since it pulls more cold air which is denser?

BigRed

you are right

VASasha

iTrader: (5)

heh, which brings us back to our original question

shaunv74

3" exhaust=14.13 square inches of x section
2.5" exhaust= 9.8 square inches of xsection
1.5" exhaust=3.5 square inches of xsection

If you split into pipes smaller than 2.5" then you start reducing your total xsectional area and ability to flow.

grinn253

debating whether this should be my new signature

VASasha

iTrader: (5)

Thanks Shaun.
I am assuming that "xsection" is what I was referring to as "displacement"? How is it calculated? Just looking at the #'s it seems to be a curve.....and it seems that a 2" exhaust would be somewhere around 6.5-7?

VASasha

iTrader: (5)

Water was the thing that was throwing me off, because I always thought that ice expanded.

Keef

hahaha, oops

LabDad

You don't know how to calculate the area of a circle?

BigRed

it would be the area of tons of connected cylinders. pie(radius)squared times height. here it would be length. i guess if you knew how long it would be in addition to the pipes getting smaller or larger you could figure out the flow. I dont know much about this, but I am assuming equations that would make mucho sense. FYI, if you think hot air is better for the engine, dont put oil in your car, take the fan off, and put a heater in front of the engine. lol

VASasha

iTrader: (5)

I guess I keep missing the obvious. Now that you said that it makes more sense. This is the kind of stuff I never thought I'd ever use again in high school.

LabDad

Nope, just talking about cross sectional area here. No need to get too complicated unless you like going through a full Navier-Stokes equation. I don't ever want to do those calculations again.