At what point do you think a 3 inch exhaust is actually warranted?

[Ghoste]

Firefighter's recent dyno results with his headers on his big wedge stroker were making me wonder just how much air the engine has to actually be pumping through it before a 3 inch exhaust is really needed?  I know there are a bunch of guys running them and I know there have been some dyno runs by folks comparing them to the more common 2.5 systems but I wonder how many people starting going over to the bigger one right away and maybe didn't need to?

[Cooter]

IMO, I have run 3" exhaust not primarily for the performance, but for the sound of 3"....

Length of pipe, Diameter of pipe, and I.D. of pipe ALL play key roles in how a certain car/truck sounds...

I have 2 1/2" Full exhaust on Christine with 40 series, 2 chamber Flows on her and at WOT, it sounds EXACTLY Like Glasspacks because of those 6 ft. Tail pipes....

Now, if Say I coulda got 3" tucked over the crossmember like these cars exhaust systems run? I wonder how it would sound....

One more thing to remember is that with typical exhaust shop benders that are NOT MANDREL benders, the area where the bend is on a 3" pipe, is only about 2 1/2", cause the bender "Crushes" the pipe in the bends...

I know running "Dumps" on a street car makes Flowmasters sound GOOD!
BUT! Here in Va., it is illeagal to do so as the exhaust HAS TO exit the body of the car...
I reallize that magazine articles are NOT the best way to get a point across, but lets face it, NONE of us have as easy access to Chassis/engine dyno's like they seem to have..NONE of us can afford to build Forty different engines just to see what happens...
SO, with that said, Mopar Muscle did an article on 440 C.I. engines and the power potential of them...
They also did a few on SB and BB Stroker combo's and the power of those..

What they termed as a street cammed 440 That could be driven on the street was making over 700 H.P.....On PUMP GAS..

Their Stroker wedges at 500 C.I. were making the same amount, maybe a little more like around 750 H.P.

ANY of these engines would IMO, NEED a minimum of a 3" exhaust...

[firefighter3931]

Anything more than 525hp at the crank will benefit from a 3in exhaust, inmo.  


Ron

[dstryr]

Ok, same question with respect to headers.  I picked 2" Doug's for my build and will have a full 3" exhaust.  

Do you have(or suggest) ballpark HP #s for 1-3/4 v. 1-7/8 v. 2" headers?

Thanks,
FS

[471_Magnum]

The thing to remember is that exhaust gases cool and condense as they travel through the exhaust. To maintain velocity, and improve scavenging, and exhaust needs to be properly sized. The further downstream you get, the less critical the pipe size. Header sizing -> very critical. Tailpipe sizing -> not so important.

As Firefighter stated, 3" is probably necessary for 525 hp and up, but only at the front end. Pipe size can be dropped after the mufflers with no ill effect on performance and will quiet the car.

Most OEM exhaust decrease in diameter after the mufflers.

[Ghoste]

Although the cool factor of having a big 3 inch pair of tips poking out under your bumper cannot be denied.  Six inch ricer fart cans are another matter.

[69rtse4spd]

Wander what it would sound like.

[BigBlackDodge]

This guy must be pushing 5,000 hp or so..........




BBD

[Ghoste]

I once had a pair on my car, you CANNOT believe how fast I was that day.  The best part was, I got mine for free just by purchasing Maxwell House coffee!

[firefighter3931]

Ok, same question with respect to headers.  I picked 2" Doug's for my build and will have a full 3" exhaust.  

Do you have(or suggest) ballpark HP #s for 1-3/4 v. 1-7/8 v. 2" headers?

Thanks,
FS

Frank, you have a healthy cam and ported heads....no question that 2in is the right size for your application. Your dyno results prove it....+38hp & +22ftlbs. The dyno don't lie 

Smaller tubes tend to limit the powerband somewhat and bring peak power in sooner. In a sense you could essentially tune your engine to a specific range by limiting the primary tube diameter...a crude and somewhat inaccurate way to do things but effective none the less. The best way of course is to match the heads/cam/intake/carb & headers so that they all funcion in the same RPM range....

On my own dyno results comparing the 1 7/8 vs 2 inch headers this was apparent. The smaller 1 7/8 header had the horsepower peaking @ 5900 (535hp) while the 2in header had peak hp @ 6100 (528hp). The interesting thing to note is that despite the higher peak (2in header) it made less power than as compared to the 17/8 tube that peaked 200 rpm sooner. 


It's safe to say that most 440's are fine with a 1 3/4 or 1 7/8 header. Strokers are a different animal and it depends on the cam profile and head flow. 


Ron

[Ghoste]

In a sense you could essentially tune your engine to a specific range by limiting the primary tube diameter...a crude and somewhat inaccurate way to do things but effective none the less.
Ron

Exactly what Chrysler was doing in the early 60's with their different length intake runners for their various ram tuned packages.

[TylerCharger69]

IMHO.....I think...for a basic build...2 1/2 inch pipes are enough....that's what I will be running after Thorley headers into a 2 1/2 inch collector...and then series 40 Flowmasters with 2 1/2 inch tail pipes out the rear..

[John_Kunkel]

I'm not a particularly big fan of 3" exhaust systems but when I went to replace the system on my old '62 Dart Max Wedge I went with the TTI 3" system simply because I liked the quality of their product over some of the smaller replacement systems available at the time.

Doing nothing but replacing the factory exhaust from the manifolds back, the engine idled 200 rpm faster than before and the throttle response was noticeably better....no before/after dyno or ET numbers, just a seat-of-the-pants evaluation. I loved how it ran but hated the noise from the Dynomax mufflers.

[69chargerR/T]

I'm not a particularly big fan of 3" exhaust systems but when I went to replace the system on my old '62 Dart Max Wedge I went with the TTI 3" system simply because I liked the quality of their product over some of the smaller replacement systems available at the time.

Doing nothing but replacing the factory exhaust from the manifolds back, the engine idled 200 rpm faster than before and the throttle response was noticeably better....no before/after dyno or ET numbers, just a seat-of-the-pants evaluation. I loved how it ran but hated the noise from the Dynomax mufflers.

Did you get the X-pipe or the H-pipe system ??

[471_Magnum]

the engine idled 200 rpm faster than before and the throttle response was noticeably better....no before/after dyno or ET numbers, just a seat-of-the-pants evaluation.

What this means is the motor was probably too rich before. The improved exhaust flow leaned out the motor causing your idle speed to increase.

I remember when I switched mufflers on my 318-2V Satellite and had the same thing happen. The improved exhaust flow actually made it very hard to tune with the limited range of the stock Carter BBD.

[Rolling_Thunder]

My Road Runner will have 4" exhaust...     I know what ya'll are thinking - but here is my logic....

the 4" exhaust is off my friend's Truck...    with about 100 miles on it...     He can not off load it for even $150.00...     so he says "why don't we just throw this on your 69...     that way I can get rid of it" -

So - I wonder what it'll sound like...   

[Ghoste]

However it sounds, you have to promise us that you will go to at least one ricer hangout and point out to those clowns that even though they have a big tip, the rest of their exhaust is tiny and restrictive.  Unlike your car which HAS to have the massive 4 inch system all the way back (on account of the unGodly amount of nozz you are blowing through it all the time).

[John_Kunkel]

Did you get the X-pipe or the H-pipe system ??

H-pipe, just like the original.

[69chargerR/T]

Did you get the X-pipe or the H-pipe system ??

H-pipe, just like the original.

Very nice

[Tom Q]

Until some one straps a car to the dyno and does some testing we will never know if 3 inch exhaust is required or it is just for being a manly man.  I don't think too many of us are driving cars that require big pipes. A friend of mine who is a manly mopar man tried to tell it's worth at least 10 hp....where might this 10 hp appear I asked....I dunno, probably at the top end he says...are we racing pro stock where 10 hp might make or break who wins I ask...no he says ...then why do you need 3 inch exhaust tell me tell me???...because it looks cool!!!

I give up

[flyinlow]

I have 3 inch on my mild build 446 . Magnaflows , hooker comps. Put Jegs bullet mufflers in the tailpipes and an H pipe to mellow it out.  2.5 inch with mandrel bends would probably have work well too.

[Cooter]

Until some one straps a car to the dyno and does some testing we will never know if 3 inch exhaust is required or it is just for being a manly man.  I don't think too many of us are driving cars that require big pipes. A friend of mine who is a manly mopar man tried to tell it's worth at least 10 hp....where might this 10 hp appear I asked....I dunno, probably at the top end he says...are we racing pro stock where 10 hp might make or break who wins I ask...no he says ...then why do you need 3 inch exhaust tell me tell me???...because it looks cool!!!

I give up

Nitrous engines benefit from being able to get the exhaust out quickly and this is why I run 3" on my Dart, but for the "pig" 440 in the GL, I run 2 1/2"
Bigger pipes don't just help on "the upper end"...