Ram Y pipe..shop says bad idea

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Dubstep Shep

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You actually WANT some CSA reduction the further from the motor you get.

That's because the exhaust gasses cool and become more dense. They also slow down because of this. If you maintain the cross section the whole way, you'll actually have more back pressure.

Ideally, you wouldn't lose any of the exhaust heat, and that's one reason why ceramic coating and wrapping are used.
 

MANual_puller

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You actually WANT some CSA reduction the further from the motor you get.

That's because the exhaust gasses cool and become more dense. They also slow down because of this. If you maintain the cross section the whole way, you'll actually have more back pressure.

Ideally, you wouldn't lose any of the exhaust heat, and that's one reason why ceramic coating and wrapping are used.

This is why a lot of guys axle dump too. Shorter exhaust cools less :happy107:
 

joepizuro

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ANyone think running 2.5" pipe from headers to a Dual in Single 3" out is the same as a Y pipe? The magnaflow is a straight thru..
 

MANual_puller

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ANyone think running 2.5" pipe from headers to a Dual in Single 3" out is the same as a Y pipe? The magnaflow is a straight thru..

Like stock manifold or aftermarket headers? Most headers have 3" collectors so you may run into a problem there getting it to match up. I had thought about doing that with my old truck just cutting the factory y off and putting a dual in single out muffler forward in place of the factory y. I don't see any reason why it won't work.
 

Rustycowl69

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somebody said they were 2.25" Dia pipes merging into a single 3" y-pipe. Now I don't know if that is true, but it looks & sounds about right. Flow is proportional to cross sectional area. So the total area of two 2.25" pipes is 7.948 Sq in. One 3" pipe has a x-sectional area of 7. 065 Sq in. Which is approx a 12% reduction in x-sectional area. Now that seems like a fairly small reduction in area to me, considering the exhaust has probably cooled and become more dense. What say the rest of you?
 

Dubstep Shep

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somebody said they were 2.25" Dia pipes merging into a single 3" y-pipe. Now I don't know if that is true, but it looks & sounds about right. Flow is proportional to cross sectional area. So the total area of two 2.25" pipes is 7.948 Sq in. One 3" pipe has a x-sectional area of 7. 065 Sq in. Which is approx a 12% reduction in x-sectional area. Now that seems like a fairly small reduction in area to me, considering the exhaust has probably cooled and become more dense. What say the rest of you?

That's not entirely true...

Flow is proportional to flow resistance. Many people think that cross sectional area is the ultimate measurement of flow resistance, and that's not true either.

Cross sectional area, surface area of the flow, and length of the flow path all factor into flow resistance.

For instance, two pipes with same cross sectional area as a single pipe will flow less than that single pipe, all other things being equal.
 

joepizuro

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I love this thread so much. Helps me make my exhaust without running true dual x pipe for good performance.
 

Rustycowl69

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That's not entirely true...

Flow is proportional to flow resistance. Many people think that cross sectional area is the ultimate measurement of flow resistance, and that's not true either.

Cross sectional area, surface area of the flow, and length of the flow path all factor into flow resistance.

For instance, two pipes with same cross sectional area as a single pipe will flow less than that single pipe, all other things being equal.

I don't disagree. And in fact, I said the difference in cross sectional area seemed negligible to me.
 

MANual_puller

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somebody said they were 2.25" Dia pipes merging into a single 3" y-pipe. Now I don't know if that is true, but it looks & sounds about right. Flow is proportional to cross sectional area. So the total area of two 2.25" pipes is 7.948 Sq in. One 3" pipe has a x-sectional area of 7. 065 Sq in. Which is approx a 12% reduction in x-sectional area. Now that seems like a fairly small reduction in area to me, considering the exhaust has probably cooled and become more dense. What say the rest of you?

Also just adding to the conversation that this assumes that the 2.25" pipes are still round. They are crushed going into the factory y-pipe and thus have less cross section area than the 3" pipe after it. Also there are 2 layers of pipe wall down the middle taking up some area. An open y-pipe like the magnaflow piece the op mentioned wouldn't have any restriction at all and is definitely an upgrade over stock.
 

Rupert

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I keep forgetting to measure my stock pipes. I believe its 2.5" going into a 3" going out, but I need to measure to be sure.

I agree the "cobra mess" / Y pipe is a restriction not just in diameter but with all the turbulent flow caused by the bends and the way the two pipes are crammed into one.
As I stated earlier, I eliminated the Y pipe, and ran two pipes back to a accelerator 2 in 2 out muffler.
combing this with my other mods, a Vararam intake, 180 stat and Hemifever tune, the truck is pretty impressive. sounds good at idle, not to loud at cruising and when I go WOT it plenty loud and aggressive.
 

Rupert

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stock pipes are 2.25", which provides a area of 3.98 sq."s each= 7.96 or 8 inches
the 3" pipe that they are crammed into at the factory Y pipe provides 7.07 sq."s.

So, in addition to the bends and crimping causing lots of turbulent flow at the factory Y, there is a 1 sq" reduction, or 12.5% less. This all occurs within about 6" of linear pipe.
That's why I eliminated the Y totally and had 2 separate 2.25" pipes brought back to the Xcelerator aftermarket muffler.
 

U&A

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SPOILSPORT!!

I bet you're the kind of guy who blows out a child's birthday cake candles and act like you sneezed too.

I CANT STOP LAUGHING. THAT WAS TOO GOOD!!:roflsquared:
 

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