Exhaust pipe size

[WayneT]

I've been thinking about what size pipes to run behind my 415 SB stroker. I'm planning on TTI step headers. I want to have the T/A AAR side tailpipes and I can get Dynomax mufflers that are 2-1/2" in & out on the front. So I have 2 questions.
1. Would there be any performance advantages by running 3" pipes from headers to the mufflers and reducing them to 2-1/2" at the mufflers and have 2-1/2" tailpipes vs running 2-1/2" from the headers back?

2. Anyone know who makes 2-1/2" T/A style tailpipes? LOL.

I have a set of 2-1/4" tailpipes and thought of having someone mandrel bend some in 2-1/2" for me. That may be hard to find locally.

[dwc43]

Unless your making over 500 hp you want need 3" pipes. All that will do is kill your bottom end.You'ld be better off with 2 1/2 andan X pipe. I'd pass on side exit exhaust too. With windows open it will easily pull fumes into the car.

[WayneT]

Thanks for the input.
I'm not too worried about fumes. I've had the T/A tips (2-1/4") for 5 years and the only time I smell the exhaust is when I start it in the garage. I could understand this being a problem if I drove around in reverse all the time

So I have one vote for all 2-1/2". Any more?

[dust]

Originally Posted by WayneT

Thanks for the input.
I'm not too worried about fumes. I've had the T/A tips (2-1/4") for 5 years and the only time I smell the exhaust is when I start it in the garage. I could understand this being a problem if I drove around in reverse all the time

So I have one vote for all 2-1/2". Any more?

I had no problem with side exhaust. Had it for years and plan on installing new side exhaust system on my Duster after the 408 transplant. Seems that the ones that say that side exhaust is 'bad' are those first hand experiance with side exhaust on a street car...

For my street 400hp 408, I went with 3" but am thinking that 2.5 *may * have been better. As for killing my bottom end, I'd like to see some proof... 'kill' seems like too strong of a word for this situation.

[Dodge_Dean]

If the inlet to the muffler is 2.5, go with 2.5 pipes, if you reduce a 3 inch pipe it forces more exhause back up the pipe and will blow your mufflers faster believe it or not. If the headers are long tube 2.5 will sound stronger too. As for the tailpipes, use 2.75 pipes (not very common) and reduce it at the front and the hydraulic bend won't hurt the flow, then reduce it for the tips

[wayne123]

don,t do that if u use 3' and then redus u will have back presure
that will cause hp loss stay with 2.5 all the way

[rumblefish360]

don,t do that if u use 3' and then redus u will have back presure
that will cause hp loss stay with 2.5 all the way

Can you explain "redus?"

[BDS 871 Cuda]

You said this one other time. Dwc, Tell me how in the hell do you
get fumes inside the car from side exaust. I think you are the only person
on this earth that can fall asleep from side exaust. ENOUGH SAID!


Wayne T.
The biggest difference from 2 1/2 to 3 inch pipe is cost. 3 inch sounds
good on the street and a crossover pipe will help a little bit. Most cars
at the track pull the exaust and run open headers. It's not really that
big of a deal. Pipes out the side work fine also. If you fall asleep, it's
probably from the crack pipe.

[WayneT]

Thanks for the input guys. I think I'll do the 2-1/2" all the way.
As for falling asleep....I don't do crack, I don't drive around in reverse, I don't sit in the garage with the car running, and I don't hang around with DWC, so I should have no problems.

BTW I found a company, www.weldtechstainless.com that makes large tube T/A style tips. The look nice.

[ehostler]

The only time that you'll get in trouble is if you terminate the pipes under the car. Then the fumes will get in at any hole they can find.

A proper dump out the sides should be no problem.

[dwc43]

Originally Posted by BDS 871 Cuda

You said this one other time. Dwc, Tell me how in the hell do you get fumes inside the car from side exaust. I think you are the not only person
on this earth that can fall asleep from side exaust.


Wayne T.
It's really that
big of a deal. Pipes out the side work fine also. If you fall asleep, it's
.

It's simply areodynamics. Matter of fact rear windows,hatches and sometimes roof vents (like on the RamCharger) will pull in exhuast fumes. MAtter of fact most hatch back cars and RanChargers have warning decals on them and it was a problem with the one year they put them on the T/A too. NOt to mention I've run a few race cars with side exits and they pull fumes inside.

[dwc43]

[QUOTE=WayneT]Thanks for the input guys. I think I'll do the 2-1/2" all the way.
As for falling asleep....I don't do crack, I don't drive around in reverse, I don't sit in the garage with the car running, and I don't hang around with DWC, so I should have no problems.
QUOTE]

Most of that is fact, but you can very well pull in exhaust with side exits and falling asleep is the least of your problems in that case, matter of fact it can be pretty deadly.

[moparmussel]

falling asleep while driving or sitting in a muscle car sounds like a CHEBBIE thing!when my MOPARS are running,the thunder and rocking of cam and flowmasters has my heart pounding!

[rusty duster]

I think that most of us believe anything that a magazine article tells us to believe.If I was writing a story about mufflers and performance and a major muffler company was a big advertiser of the magazine;and I wrote that a muffler hurt power output thru-out the whole rpm range,how long would I be working for that magazine?
For all the years that I 've been around cars,never saw a car yet slow down when the exhaust was dropped! And after a fatter jet change even bigger gains.That includes the bottom end too! To me the fact that back pressure helps in an exhaust system is a huge myth.Why is it so that people making mufflers do everything they can to reduce back-pressure if back-pressure is a good thing for performance?
Most of us car guys read all the car rags that are out there;but should we believe everything that a writer writes about a muffler company that he is working for?
Put the biggest pipes you can get under that car and a muffler that flows the most and if you can't live with the noise just add some back-pressure.

[dwc43]

Originally Posted by rusty duster

I think that most of us believe anything that a magazine article tells us to believe.If I was writing a story about mufflers and performance and a major muffler company was a big advertiser of the magazine;and I wrote that a muffler hurt power output thru-out the whole rpm range,how long would I be working for that magazine?
For all the years that I 've been around cars,never saw a car yet slow down when the exhaust was dropped! And after a fatter jet change even bigger gains.That includes the bottom end too! To me the fact that back pressure helps in an exhaust system is a huge myth.Why is it so that people making mufflers do everything they can to reduce back-pressure if back-pressure is a good thing for performance?
Most of us car guys read all the car rags that are out there;but should we believe everything that a writer writes about a muffler company that he is working for?
Put the biggest pipes you can get under that car and a muffler that flows the most and if you can't live with the noise just add some back-pressure.

You need to play with a dyno and you will see that your idea does not hold up. Header tube size,length,collector size,pipe size and lenght,muffler types will make major differences in how an engine runs, how wide it's torque range is and where it comes in at.

[rusty duster]

Dwc, Headers are a whole different story,I was talking about an exhaust system after the headers.

[dwc43]

So was I. For instance on a real race car,unless it's rules related, you wont find an H pipe anymore. IF the H pipe is not properly designed it can reduce hp and tq, leave it the same, or increase on or the other. MOst pros will use an X pipe that shows a gain in both hp and tq everytime from a small gain to a pretty large gain. HAs to do with reversion and back pressure. Also boom tubes really help. As for one class that we run in the rules says we must run a muffler and max 3" pipes into a single 3" exit no H or X pipes. Here's how we got around that. Two mufflers at the end of each header with 2 1/2" pipes to a boom tube (acts like an X pipe) and that was the single 3" exit even though it's a flat not round outlet. Do some reading at www.drgas.com in there tech sections. Exhuast pipes make a big diff.

[rusty duster]

I never saw a race car with an exhaust system yet unless they make up some kind of a rule which by the way just happens to support the company that is a sponser of the sanctioning body.Like mufflres on a race car at n.h.r.a.
As for dyno experence all I know is that every car that I have seen that has removed the exhaust system and run open headers the gains were big.
Why do you think that nascar runs pipes out the side instead of out the rear and risking the fumes coming inside the car?
Just think of running open headers for 4 hours right under you're feet,not to mention the fumes coming in the car.

[pishta]

I believe the HP loss of a tuned exhaust over a open header in a racing environment is more than made up for the gains in torque made by the tuned exhaust. Im not talking tailpipes under the bumper here, but the NASCAR boom tubes, H/X pipes and even Vizards unique "expansion chambers" for lack of what he actually called them. Pontiac had a Rear mounted transmission drag car based on a 421(?) block in a Tempest and you could clearly see an opened header exhaust, but there were 12 inch pipes coming off the header and right in the middle was a long crossover tube attaching the 2 headers. There is a certain amount of design that goes into todays motor combinations, engineered as a collection of components designed to work with each other. Motor, exhaust, etc. Straight headers may generate the most HP, but Dyno runs dont win races, its the torque that accompanies the readings that gets the car groovin.

[dwc43]

[QUOTE=rusty duster]
Why do you think that nascar runs pipes out the side instead of out the rear and risking the fumes coming inside the car?
QUOTE]

For one, there's no room to run them out the back. Running them out the back would actually be an advantage to them by using areo help with exhuast evac. And the fumes do come inside the car and they complain about it all the time. IT's not a major issue due to the fact that they use helmets with filtered cold air units just like what I use. And the carbon filters really help get rid of the fumes and keep you alive. Read Pishtas post below. He's on the right trac and use the link I sent you. You'll learn a lot on exhuast systems and how you can make them work to your advantage. To win, don't do what everone else does, do what works.

[rusty duster]

If there was an advanage to running pipes out the back in nascar somebody would have doon it by now.As far as winning goes,if I had the choice of driving two identical cars,one with the latest X,Y,Z,H pipes and one with open headers,I'll take the open headers every time.

[dwc43]

If you'll go back to the late '60's early '70's some did run pipes out the back. I have some pics of cars in the garage area and you can clearly see 3" rear exit exhaust pipes so it has been tried. BUt the way the cars are designed today they will not fit out the back. The battery is just in front of the LR wheel, there's a pump on the 9" rear and cooler lines and cooler that hangs under the car. There's shocks,truck arms, rear sway bars, and track bars all in the way, so there is no room for pipes. Besides that would take away from the great effect that the current boom tubes have on the engines performance.

Take your open headers, you'll get beat. Even pro stock guys don't run open headers. Look inside them at the baffling and venture collectors and adjustable collectors that they use. You'll just get beat.

[rusty duster]

Dwc,now your're talking headers again! Bring it on! I love you DWC

[humbulayed]

the first symptom of carbon monoxide poisoning is death

[pishta]

I would think you would get more scavenging out of the pipes by running then angled 45 degrees back by the slipstream than running them lopped off at the bumper anyway. Sure there is vacuum back there but no where close to where they are placed nowdays.

[dwc43]

Originally Posted by humbulayed

the first symptom of carbon monoxide poisoning is death

You pass out first then later you die. LOL.

[cageman]

Hmm, I have three inch all the way from my headers on my pickups, both 318, I like it.
I used to have My valaint dump in front of the axle, under the car, but I was pulled over and I had to put tail pipes on it. He told me when you are parked it will just rise into the vehicle, not really something you want to happen.

You get sleepy and your done, thats it, no second chances.

If the wind was right and you were idling with a side exit, it could happen real easy. Hate to see someone get sick, just trying to warn if I can.

[TK]

Hmmmmm................

Well...............

Rusty Duster? These guy are all right, there is a lot more science to exaust that open headers. (I dont agree with the side exit exaust thing, unless it was a four door and the pipes exit in front of the rear door)(there also is a vacuum behind a car, you know, it would help with HP at high speeds)
OK, backpressure, as I understand it, helps keep intake charge from exiting out of the exaust port, for one. Flames in your headers are no way to make HP. Another reason for running the right size pipes, is, just like the intake, the exaust has to have a certain amount of velocity, to keep the exaust moving when there is a pressure drop. (Hmmmmmm, low end torque maybe) Nahhhh.....................
Here is my experience with open headers...................
1971 D200, 318..............Had a 2 1/2" glasspack dual system, with no H or X, hey, it was homeade! I took it all off, to build a real system, and decided to take it to the store, just to be obnoxious........(it rad a real nice rolling 1000+ RPM slobbery idle) I didn't notice a real difference when stomped, but, even with the cheezy glasspack exaust, there was a great difference in how much throttle it took to get the thing to make power at lower RPM's.
Also, it was not as "snappy" like if you let off, and hit it again. The new 2 1/4flowmaster system was a big increase, from the open, and the glasspacks.
Open headers, from what I see at the strip, are a thing of the past, un less they are just totally sick. (alchohol burning supercharged................) Yeah, but, we are talking street cars, right? Right.
Rumblefish? opinion please? How did I do?
LOL

[rusty duster]

Once the exhaust gas leaves the header,the only way to speed it up is to put a restriction in its path.Like going from 3" pipe to 2" pipe.Sure the gas in the 2"pipe will move faster,but the gas in the 3" pipe will slow down.Thus back-pressure is created in the 3" pipe and overall flow is reduced.If you had to fill up a 5Ga. bucket with a garden hose,What would be the fastest way?Would you put your finger over the end or just leave the hose open?With your thumb over the end of the hose the water coming out would be faster than the open hose:but which way would fill up the bucket first?

[TK]

there is a bit more to it than that.

Wish my brain would connect to my fingers better..................

You need a certain amount of back pressure, and velocity, going to big, or too small, will hurt your performance.

I did my best to say what I meant in the last post......................