Muffler pipe size

[Skitlz]

Hey, I just realized that the pipe actually attached to the muffler isn't 2 1/4 inches... it looks to be 2 inches but does anyone know the actual size? Kinda bogus that they did that. haha

[occasional demons]

They have been doing it for years. The exhaust necked down on my Shadow at the muffler connection also.

2 inches is basically what it is. But hey, the inlet on the cat is about 1.75" so that little bit at the axle is nothing. Besides the gasses have cooled a bit by the time they reach the rear, so there is less volume.

For normal driving, it is the better set up to have the piping get smaller the farther from the engine it gets. Better velocity keeps things moving along for better efficiency. That's pretty much what they marketed these cars for.

Even the SRT has the same pipe. The R/T is the only true 2.25 throughout, but IDK about the flex at the cat inlet.

That is one area that the 1gn cat inlet had a definite advantage. No internal reduction at the inlet.

[Donkeypuncher]

For normal driving, it is the better set up to have the piping get smaller the farther from the engine it gets. Better velocity keeps things moving along for better efficiency. That's pretty much what they marketed these cars for.

Interesting, now I don't feel so bad running the stock axle back pipe with the 2.5" piping up front.

[Skitlz]

Thanks for the input. Got it all set up, running great. While I was at it I fixed an exhaust leak, too, with this putty stuff I got for 4 bucks.

Normal driving means commuting, not racing, Donkey. For less back pressure you want to go bigger as you go, not smaller.

[occasional demons]

For less back pressure you want to go bigger as you go, not smaller.

Wrong.

Making the pipe bigger as you go increases the air mass the engine must push out of the pipe. The mass of air will create back pressure, along with the bigger opening giving atmospheric pressure more leverage.

Remember, atmospheric pressure is what pushes air into your IM, it is not sucked in. the same pressure is also pushing against the air coming out of the exhaust.

If you are racing, chances are you will have shortened the exhaust, to create less air mass, friction against the pipe walls, etc.

One single larger pipe will outflow two smaller pipes of the same cross section diameter of the single pipe, just due to friction against the pipe walls.

[UriahRR]

Even the SRT has the same pipe. The R/T is the only true 2.25 throughout

Wha? I swore SRT's had 2.5 inch piping stock.

[occasional demons]

Nope. Maybe at the down pipe. The SRT rear section is a direct fit on the SE/SXT.

[Skitlz]

For less back pressure you want to go bigger as you go, not smaller.

Wrong.

Making the pipe bigger as you go increases the air mass the engine must push out of the pipe. The mass of air will create back pressure, along with the bigger opening giving atmospheric pressure more leverage.

Remember, atmospheric pressure is what pushes air into your IM, it is not sucked in. the same pressure is also pushing against the air coming out of the exhaust.

If you are racing, chances are you will have shortened the exhaust, to create less air mass, friction against the pipe walls, etc.

One single larger pipe will outflow two smaller pipes of the same cross section diameter of the single pipe, just due to friction against the pipe walls.

But going smaller... wouldn't that be more back pressure than going bigger?

[Donkeypuncher]

Depends on the volume of air moving through the pipe, which in our case isn't a lot.

[occasional demons]

The stock piping handles up to fuel cut off quite well. The only exception is if you are running boost. Then you may need a larger pipe. More so on turbo to help it spool. Super chargers will shove it right out of the pipe. They don't require mother nature, and thermal expansion to function.

The gases cool as they travel down the pipe, becoming more dense, slowing down. thus the pipe needs to get a bit smaller to maintain velocity. Remember, it is all about velocity, not pressure.

Believe me, the manufacturers have designed the pipe size for optimum power for the engine. If the exhaust was really that restrictive, it would kill their CAFE. They wouldn't be able to sell high dollar pick ups and Vipers otherwise. They have far more at stake than intentionally restricting output via the exhaust.

[Skitlz]

I was going by what the guy at Autozone said. haha

Edit: Also, what is CAFE?

[occasional demons]

Corporate Average Fuel Economy.

All of the cars/trucks sold by X corporation have to meet a certain mpg, averaged between all of them. Too many gas hogs being sold will get their right to sell cars pulled by the EPA. (Read big fine, keep selling cars)

[Skitlz]

Well that's a shitty rule. Mandatory POSes to maintain an average MPG. Sounds like they're asking for less quality, making them follow arbitrary rules like that.

[occasional demons]

It's been a law since the late '70's? At least the early 80's


We would still be driving tanks that got 10 mpg at best if the automakers weren't pushed into it.

Or they would have been so far behind the eightball when gas prices truely did rise, there would be no american companies at this time. It was like pulling teeth to get them to make an economical car of their own through the 70's. About the only car that wasn't a rebadged one was the Pinto.

In all, the quality of cars has vastly improved, if you look back at what was mainstream in the late seventies/early eighties.

[Skitlz]

Well that's good, then. I'm going on one hour of sleep so my comments have been less than insightful.

[NickKo]

It's been a law since the late '70's? At least the early 80's


We would still be driving tanks that got 10 mpg at best if the automakers weren't pushed into it.

Or they would have been so far behind the eightball when gas prices truely did rise, there would be no american companies at this time. It was like pulling teeth to get them to make an economical car of their own through the 70's. About the only car that wasn't a rebadged one was the Pinto.

In all, the quality of cars has vastly improved, if you look back at what was mainstream in the late seventies/early eighties.

Bill is right !!!! He has a point.

Like this typical 'tank' from the 70's







Hell, Detroit would still be trying to build these today.... Not that anyone would necessarily buy them.

Who needs an underpowered Tank that gets -10MPG ??


- Nick

[illriginalized]

So if we re-pipe with 2.5" or at the very least 2.25" we would lose some power, at least at the bottom end?

Edit: I was planning to re-pipe a bit larger than stock once I got my hands on larger cams (Crane #10).

Also someone in another forum board said that after the 2002 models.. the Neons got 2.25" piping. But it's a fact that we only have 2"?

Good thing I came across this thread.. needed to know the stock piping beforehand.

[NickKo]

So if we re-pipe with 2.5" or at the very least 2.25" we would lose some power, at least at the bottom end?

Edit: I was planning to re-pipe a bit larger than stock once I got my hands on larger cams (Crane #10).

Also someone in another forum board said that after the 2002 models.. the Neons got 2.25" piping. But it's a fact that we only have 2"?

Good thing I came across this thread.. needed to know the stock piping beforehand.

Some of the confusion on pipe sizing is because..... Chrysler itself was confused.

I think what started the confusion, was the the 2000 model year. There were several different exhaust configurations and piping sizes.
I have heard that some early 2000's got 2 in. exhaust piping; most others got 2 1/4 in.

Also, there were different flex joints. Some had them at the headpipe; others had them underneath the car <-(the ones I have seen, looked rather restrictive and could be improved.)



- Nick

[occasional demons]

2000 and early 2001 had 2.0" pipe. My '01 had 2.0" pipe, a flex at the cat, and after. The one after is not really needed.

[illriginalized]

2000 and early 2001 had 2.0" pipe. My '01 had 2.0" pipe, a flex at the cat, and after. The one after is not really needed.

So after 2001 they made Dodge Neon with 2.25"?

[occasional demons]

2001 and up. But not guaranteed for '01.