The Power of 2.5- vs. 3-Inch Exhaust - Engine Masters

[ctrlraven]

https://www.youtube.com/watch?v=_PVXvHkr-Vs
_PVXvHkr-Vs

[Lowndex]

Great video to help newbies like me better understand the effects an exhaust system has on rwhp and torque.

Big myth busted: your engine needs some back pressure, so stay with 2.5" exhaust over 3.0".

[MOTOWN]

I watched it last night, interesting.

[CWright]

Makes me glad I went with 3".........:D

[RubberCtyRauder]

Makes me glad I went with 3".........:D

Gimme 100 of your ponies and you can stay at 2.5 and so can I. : D

[Mr. Man]

Two questions come to immediately to mind. They used no H or X pipe. So what about this harmonic exhaust pulse I keep hearing about? Second they made no mention of the size of the exhaust vs.the power the engine is producing. I'm not convinced a 3" exhaust system would benefit a stock Marauder.

[CWright]

Gimme 100 of your ponies and you can stay at 2.5 and so can I. : D

Come and get em! :P

[CWright]

Two questions come to immediately to mind. They used no H or X pipe. So what about this harmonic exhaust pulse I keep hearing about? Second they made no mention of the size of the exhaust vs.the power the engine is producing. I'm not convinced a 3" exhaust system would benefit a stock Marauder.

Bryan Jones said the rule of thumb was 1" per 100HP.

[RubberCtyRauder]

I have heard dual 2.5 should be good to around 600 hp

[FordNut]

I have 2-1/2 inch exhaust. And factory tips.

And cats.

[ctrlraven]

I have 2-1/2 inch exhaust. And factory tips.

And cats.
So what you are trying to say is that you could be making more power. :lol:

[Fastbob]

Interesting, but the video could have been edited to about 1 minute. Editing of course would have left out the Amsoil and Magnaflow commercials. Good information and about as expected. Including an X-pipe or H-pipe would have been interesting.

[Turbov6Bryan]

That engine is twice the size of ours, so it's moving a bunch more air!

I would have liked to see the exhaust less than 20 feet in length lol

[FordNut]

I have 2-1/2 inch exhaust. And factory tips.

And cats.


So what you are trying to say is that you could be making more power. :lol:

Maybe I could, but I'm really saying 2.5 is ok for way higher than this V V V

I have heard dual 2.5 should be good to around 600 hp

[MOTOWN]

2.5" exhaust is fine for the majority of applications , but it has it's limitations as with anything else, my car had the 2.5" stainless works exhaust system when it was on the dyno , it now has a full 3" Vband Stainless Steel Exhaust, and runs much better , next dyno will tell how well.

[lifespeed]

Bryan Jones said the rule of thumb was 1" per 100HP.

That makes no sense, cross section of a pipe increases as the square of the radius. A 3" pipe flows 44% more than a 2.5" pipe.

[cer0413]

2.5" exhaust is fine for the majority of applications , but it has it's limitations as with anything else, my car had the 2.5" stainless works exhaust system when it was on the dyno , it now has a full 3" Vband Stainless Steel Exhaust, and runs much better , next dyno will tell how well.
Wait, so the 761rwhp listed in your signature is from the 2.5"? I see you have more to offer lol.

[MOTOWN]

Wait, so the 761rwhp listed in your signature is from the 2.5"? I see you have more to offer lol.

Yes sir! I'll make 800+ before I tear it apart , and go twin turbos! :banana:

[cer0413]

Yes sir! I'll make 800+ before I tear it apart , and go twin turbos! :banana:
MADNESS I tell you!!!!!!

[MOTOWN]

MADNESS I tell you!!!!!!

Exactly playa!:banana2:

[CWright]

That makes no sense, cross section of a pipe increases as the square of the radius. A 3" pipe flows 44% more than a 2.5" pipe.


I'm just passing info along the info shared with me brother. I can tell you it works for me!

[Comin' in Hot]

I don't know about horsepower yet, but I went from about 13 lbs of boost to 8 lbs. switching to a full 3 inch exhaust. I know people will argue my next statement.... lbs of boost just shows inefficiency in air flow. The bigger exhaust allows air to exit the engine easier, allowing air to enter easier.

http://i22.photobucket.com/albums/b335/Witman40/33B822DB-F17D-4E97-A86E-FC972EDD45F3_zpsngzj3wxi.jpg (http://s22.photobucket.com/user/Witman40/media/33B822DB-F17D-4E97-A86E-FC972EDD45F3_zpsngzj3wxi.jpg.h tml)

[lifespeed]

I'm just passing info along the info shared with me brother. I can tell you it works for me!

Not arguing with the results of larger exhaust, just that screwy "rule". So 500HP needs 5" exhaust pipes :)

[lifespeed]

I don't know about horsepower yet, but I went from about 13 lbs of boost to 8 lbs. switching to a full 3 inch exhaust. I know people will argue my next statement.... lbs of boost just shows inefficiency in air flow. The bigger exhaust allows air to exit the engine easier, allowing air to enter easier.

Sounds like you opened up a restriction. Boost pressure decreasing and horsepower staying the same or increasing shows an improvement in airflow.

[CWright]

Not arguing with the results of larger exhaust, just that screwy "rule". So 500HP needs 5" exhaust pipes :)

Oh I know, it's cool. If you were at 500 then 2.5" would be perfect. That totals 5" together.

[lji372]

Interesting,

I'm still good with 2 1/2 on taxi car :2thumbs:

[MOTOWN]

Interesting,

I'm still good with 2 1/2 on taxi car :2thumbs:

Hell when is the last time it had a arse in the drivers seat :P

[lji372]

Hell when is the last time it had a arse in the drivers seat :P

I believe it was October :lol:

May have been early November :dunno:

[Bad_S55]

I believe it was October :lol:

May have been early November :dunno:

Just go check the ticket date :beatnik:

[lji372]

Just go check the ticket date :beatnik:

Go to bed!! :fishslap:

[CWright]

Hell when is the last time it had a arse in the drivers seat :P


I believe it was October :lol:

May have been early November :dunno:


Just go check the ticket date :beatnik:


Go to bed!! :fishslap:



LMAO!!:lol::lol:

[MOTOWN]

Just go check the ticket date :beatnik:

Lmao! I remember his face in the picture , priceless!:D

[RubberCtyRauder]

Go to bed!! :fishslap:

Lmao.......

[babbage]

Mandrel bending is important.

A 2.5" exhaust pipe that has crush bend in it is equal to 2.25"

If you take a 3.0" inch pipe and bend it 1 degree or 90 degrees you will loose 1/2" of pipe size.

http://www.bobsmuffler.com/images/mandre1.gif Press Bent
http://www.bobsmuffler.com/images/mandre2.gif Mandrel Bent


I have 2.25" mandrel bent pipes..

[ctrlraven]

Mandrel bending is important.

A 2.5" exhaust pipe that has crush bend in it is equal to 2.25"

If you take a 3.0" inch pipe and bend it 1 degree or 90 degrees you will loose 1/2" of pipe size.

http://www.bobsmuffler.com/images/mandre1.gif Press Bent
http://www.bobsmuffler.com/images/mandre2.gif Mandrel Bent


I have 2.25" mandrel bent pipes..
Mandrel bent ss is better, carries the ID throughout the bend.

I have 2.5" mandrel bent stainless from stock manifolds to tips.

[Serge]

Is mandrel really better though? In one of the other videos that they did they took a hammer to the headers and kinked the **** out of them which is basically same as crush bends. It made no difference. If you have an exhaust pipe that is crush bent, and allows for enough air flow, crush bends won't have any effect.

[babbage]

Is mandrel really better though? In one of the other videos that they did they took a hammer to the headers and kinked the **** out of them which is basically same as crush bends. It made no difference. If you have an exhaust pipe that is crush bent, and allows for enough air flow, crush bends won't have any effect.

yes.

http://www.bobsmuffler.com/images/dyno.h1.gif

[MOTOWN]

Crush bend , and Mandrel bend is no comparison in flow or qaulity, Mandrel is superior.

[lifespeed]

Mandrel bend is better than press bend, fixed calipers are better than floating, float axles are better than c-clip. Some of this stuff is just obvious, although as always the better stuff comes at a price.

Sometimes cost compromises must be made, but the reality remains the same.

[Mr. Man]

How about a 3" crush bend vs. a 2 1/2" mandrel bend? Same car

[babbage]

How about a 3" crush bend vs. a 2 1/2" mandrel bend? Same car

A 3" crush bent exhaust = 2.5" inches at the bends. So you might have a 3" straight pipe, then it goes down to 2.5" then back to 3" - turbulence will slow down the gasses and loose velocity (torque)

A 2.5" mandrel bent exhaust will outperform a 3" crush bent exhaust.

[Serge]

How about a 3" crush bend vs. a 2 1/2" mandrel bend? Same car

That's what I am saying. If you put a 3 inch crush bent exhaust on there that flows as good a 2.5 inch mandrel and 2.5" pipe is enough for the motor there would be no difference.

[crownvic97]

I always thought the difference between crush bends and mandrel was slightly overstated. If you are making 600HP and need every bit of flow possible then sure, but for most cars?

[MOTOWN]

No one in their right mind is going to go through the trouble of getting a 3" exhaust system only to have it crush bent , not to mention most exhaust shops don't have equipment to bend 3" tubing .

[lifespeed]

Press bends are for replacing the rotted tailpipe in your grandmother's '98 Camry.

[babbage]

That's what I am saying. If you put a 3 inch crush bent exhaust on there that flows as good a 2.5 inch mandrel and 2.5" pipe is enough for the motor there would be no difference.

No, the turbulence created from going from a 3" pipe to a crush bend at 2.5" will slow the exhaust down and loose torque. Even though 2.5" is the smallest part of the exhaust, not as good as all mandrel 2.5"


For proper and efficient exhaust flow, it is important to keep a consistent pipe diameter for the entire length of the exhaust system. Narrow places and widened places cause turbulence in the exhaust flow and reduction in the speed of the exhaust flow. Each compression or crush bend in an exhaust system represents a bottle neck in the flow of exhaust through that exhaust system, and each bottleneck causes an increase in back pressure and a reduction of both efficiency and engine power output. How much of a reduction in power? A 2 1/2 inch compression or crush bent exhaust system will dyno only one half to two thirds the performance gain of even a 2 1/4 inch mandrel bent exhaust system, or one third to half the performance improvement of a 2 1/2 inch mandrel bent exhaust system.

Mufflerman in London Ontairo does great work - and It's mandrel stainless. Too far for you?

[Serge]

No, the turbulence created from going from a 3" pipe to a crush bend at 2.5" will slow the exhaust down and loose torque. Even though 2.5" is the smallest part of the exhaust, not as good as all mandrel 2.5"



Mufflerman in London Ontairo does great work - and It's mandrel stainless. Too far for you?



I have mandrel on mine and no need to drive to London, had it done much closer to home. I didn't say I would put crush bends on my car, just trying to see if mandrel is snake oil.

Those guys proved that bashing headers makes no difference in exhaust flow. Wouldn't the same theory apply to crush bends?

[babbage]

If you slightly kink a Mcdonalds straw can you drink as easily?

[Serge]

If you slightly kink a Mcdonalds straw can you drink as easily?

Depends on the diameter of the straw.

[lji372]

Depends on the diameter of the straw.

and the suction of the sucker.

to some it would be a walk in the park while others would never attempt it......... :beatnik:

[ctrlraven]

I have mandrel on mine and no need to drive to London, had it done much closer to home. I didn't say I would put crush bends on my car, just trying to see if mandrel is snake oil.

Those guys proved that bashing headers makes no difference in exhaust flow. Wouldn't the same theory apply to crush bends?
They did that with basically an open exhaust. It would of been interesting to see if the banged up header tube/s made any difference with a complete exhaust system.

[RubberCtyRauder]

At Header Has Alot more velocity than downstream, tail pipe. I can see it slowing it down with kinks, crushed areas