Performance difference between 2 1/2" and 3" tailpipes
#2099393
06/27/16 04:36 PM
06/27/16 04:36 PM
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Joined: Jan 2003
Posts: 180 Confusion
Dodger440
OP
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OP
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Joined: Jan 2003
Posts: 180
Confusion
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So, I must be getting old, because driving around in my car that has turndowns right after the mufflers is starting to be less enjoyable. I am ready to put tailpipes on the car, and I wanted to know if anyone had any real world test results comparing 2 1/2" and 3" tailpipes? The head pipes and mufflers on the car now are 3", and they will be staying the same. I remember reading somewhere that once the exhaust gasses have cooled down, the exhaust pipe size can decrease without any horsepower loss. I would love to use 2 1/2" tailpipes, because they will be much easier to fit on the car, but I don't want to give up anything performance wise. The car is a 67 B-body with around 600 flywheel horsepower. I have a electric fuel pump, fuel filter, and braided lines coming from the gas tank sump all taking up room under the back of the car, so space is at a premium back there. Any input would be greatly appreciated!
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099443
06/27/16 05:53 PM
06/27/16 05:53 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Posts: 52,972
Romeo MI
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Depending on the muffs there isnt that much of a HP drop.. just a few HP... I did testing at work checking the difference.. but on those engines it was 6 hp difference... in the end your muffs can and will make a bigger difference.... there was a article on a Pontiac that showed what little difference there was in ET just in changing the tail pipes... then they went back and did the same tests with different muffs... and with certain muffs and the 2 1/2 pipes... the same muffs and the 3" gained less than .02.... I want to say they were Dynomax muffs... but part of the test was noise also.... I cant remember all the data on it but it was a good article... it was all at the track EDIT and your right the temp is less so the volume/area is less... the longer the car the cooler it is
Last edited by MR_P_BODY; 06/27/16 05:57 PM.
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099463
06/27/16 06:43 PM
06/27/16 06:43 PM
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Joined: Jan 2003
Posts: 4,334 Morrow, OH
markz528
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Morrow, OH
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All I can say is 2 1/2 tailpipes are very tight but doable on a 67 B Body in a stock location. I had a set on my 67 Coronet from Don's Custom Exhaust.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: markz528]
#2099465
06/27/16 06:52 PM
06/27/16 06:52 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Romeo MI
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All I can say is 2 1/2 tailpipes are very tight but doable on a 67 B Body in a stock location. I had a set on my 67 Coronet from Don's Custom Exhaust. Were they press bends like any muff shop or mandrel... I'm talking all mandrel bent exhaust... press bend you lose 15% per bend... thats why MOST all production exhaust is mandrel bend... aftermarket... different world
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099467
06/27/16 06:52 PM
06/27/16 06:52 PM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
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Puyallup, WA
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This episode of Engine Masters may not look at tailpipes only, but it gives a good idea of 3" vs 2-1/2". I have 2-1/4" tailpipes on my 67. I'm not so worried about street performance though, since I don't street race. I uncork with 3" cutouts at the track. https://www.youtube.com/watch?v=_PVXvHkr-Vs
Last edited by StealthWedge67; 06/27/16 06:55 PM.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: StealthWedge67]
#2099478
06/27/16 07:18 PM
06/27/16 07:18 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Romeo MI
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This episode of Engine Masters may not look at tailpipes only, but it gives a good idea of 3" vs 2-1/2". I have 2-1/4" tailpipes on my 67. I'm not so worried about street performance though, since I don't street race. I uncork with 3" cutouts at the track. https://www.youtube.com/watch?v=_PVXvHkr-Vs Thats a great vid.. BUT.. he has the 3" all the way out of the muffs... not changing from a 2.5 out the back... he wants to change the tail pipe... and the muff difference is a major part... so its not apples to apples
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: MR_P_BODY]
#2099496
06/27/16 07:36 PM
06/27/16 07:36 PM
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Joined: Oct 2003
Posts: 11,702 W. Kentucky
justinp61
I Live Here
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I Live Here
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Depending on the muffs there isnt that much of a HP drop.. just a few HP... I did testing at work checking the difference.. but on those engines it was 6 hp difference... in the end your muffs can and will make a bigger difference.... there was a article on a Pontiac that showed what little difference there was in ET just in changing the tail pipes... then they went back and did the same tests with different muffs... and with certain muffs and the 2 1/2 pipes... the same muffs and the 3" gained less than .02.... I want to say they were Dynomax muffs... but part of the test was noise also.... I cant remember all the data on it but it was a good article... it was all at the track EDIT and your right the temp is less so the volume/area is less... the longer the car the cooler it is Mike was your testing on 600+ hp engines?
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: lewtot184]
#2099524
06/27/16 08:35 PM
06/27/16 08:35 PM
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Joined: Dec 2004
Posts: 10,611 Rittman Ohio
fourgearsavoy
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I Live Here
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Rittman Ohio
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I have the Flowmaster pipes and they don't seem like they were even made for my Savoy. Ron 383man has the TTi's on his 63 and they look real nice maybe I will just sell the Flowmaster pipes and pick up some tti's. Thanks Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099547
06/27/16 09:19 PM
06/27/16 09:19 PM
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Joined: Jan 2003
Posts: 17,928 Akron, Ohio
ProSport
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I Live Here
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Akron, Ohio
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I very badly want tailpipes for my Duster, I have a 3" H-pipe system so I'm debating on getting TTI's 3" tailpipes or just getting the 2.5" tailpipes for ease of installation...?
1970 Challenger, all aluminum 528 Hemi, HDK suspension, Tremec 5 speed manual
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: justinp61]
#2099555
06/27/16 09:28 PM
06/27/16 09:28 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
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Posts: 52,972
Romeo MI
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Depending on the muffs there isnt that much of a HP drop.. just a few HP... I did testing at work checking the difference.. but on those engines it was 6 hp difference... in the end your muffs can and will make a bigger difference.... there was a article on a Pontiac that showed what little difference there was in ET just in changing the tail pipes... then they went back and did the same tests with different muffs... and with certain muffs and the 2 1/2 pipes... the same muffs and the 3" gained less than .02.... I want to say they were Dynomax muffs... but part of the test was noise also.... I cant remember all the data on it but it was a good article... it was all at the track EDIT and your right the temp is less so the volume/area is less... the longer the car the cooler it is Mike was your testing on 600+ hp engines? No.. about 400-450hp so the percentage will change but they were changing the complete exhaust from 2 1/2 to 3 and their muffs were straight through... if you have a 3" muff(if its truely 3".. a lot are 2 1/2 to 3") the data would have changed... guarantee it EDIT Everyone that buys what they did love what they bought.. its always the best.... try using stuff thats given to you to test and do it on the dyno or the track... then say whats best... all the stuff was given to use to test for production... it meant MILLIONS to the companies
Last edited by MR_P_BODY; 06/27/16 09:34 PM.
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099574
06/27/16 09:47 PM
06/27/16 09:47 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Google "Jim Hand exhaust system testing" and see if his results are still available online.
That's the guy that did a bunch of muffler & pipe diameter comparisons on his bb Pontiac street/strip wagon.
Last edited by BradH; 06/27/16 09:53 PM.
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099661
06/27/16 11:28 PM
06/27/16 11:28 PM
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Joined: Aug 2003
Posts: 43,741 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,741
Bend,OR USA
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I had a complete three inch sytem on my old Duster, that car had coil overs on it so the exhaust shop ran the 3 inch tailpipes under and around the rear end housing and mounted the three inch by 14 inch long oval Magnaflows between the rear end and the rear bumper outside 1/4 panel and the rear subframes behind the rear end. It had a stock Gas tank also. I'm puttng a 1966 Coronet Deluxe two door sedan together right now,440 4 speed car now I bought the Summit three inch B body exhaust system for it but I haven't taken that system out of the shipping box yet . I did buy a set of 3 inch Ultra flows for the car and plan on mounting them back behind the rear end like my Duster had, I had the rear leaf springs move into the rear subframes and moved the rear end forward two inches I'm using a new stock gas tank also so it might be lots of fun routing the exhaust back there
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: MR_P_BODY]
#2099662
06/27/16 11:28 PM
06/27/16 11:28 PM
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Joined: Jan 2003
Posts: 4,334 Morrow, OH
markz528
master
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master
Joined: Jan 2003
Posts: 4,334
Morrow, OH
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All I can say is 2 1/2 tailpipes are very tight but doable on a 67 B Body in a stock location. I had a set on my 67 Coronet from Don's Custom Exhaust. Were they press bends like any muff shop or mandrel... I'm talking all mandrel bent exhaust... press bend you lose 15% per bend... thats why MOST all production exhaust is mandrel bend... aftermarket... different world They were not mandrel bent. I went 13.30 at 101.75 mph with a full 2 1/2 exhaust with 1 3/4 inch headers with a lot of tuning left. Lousy 60 foot because converter was bad so only made one decent run with the combo. Lost a second the next run because of the bad converter. It would of been a solid 12 second car with a working converter and some tuning. 4000 lb car, 3.55 gears, small tire, light converter, home ported 906 heads, 9.1:1 compression and a .550 lift hyd roller cam that floated the valves on the one decent run. I was pretty happy with the combo for a cruising street car.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Performance difference between 2 1/2" and 3" tailpipes
[Re: Dodger440]
#2099743
06/28/16 01:18 AM
06/28/16 01:18 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Romeo MI
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You should have all of it mandrel bent... specially the front where the temp is.. thats where you need the area and the bend reduction hurts it
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