3" or 2.5" exhaust (pics)

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mullinax95

mullinax95

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First off what I have is

.030 over 360 10.7 compression
Holley HP 750 with mechanical secondaries
Eddy Performer intake
474/474 Mopar cam
Accel 300+ ignition
TTI headers
4-speed transmission

I am trying to decide what size exhaust I really need. I was going to go with 3" and bought the 3" collectors when I bought the headers. Then I read on a website that any motor making under 450 HP dose not need 3" exhaust. I don't believe my set up will make over 450 HP maybe 400 at the most. Which ever exhaust size I get I am going with a X-pipe and Flow mufflers. I just don't want to lose low end torque but find out later for some reason I should have went with the 3" I already have 2.5 Flowmaster mufflers that I can use if I go the 2.5 route.

What do you think I should run?

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I think with your combo Mullinax, 3" would be overkill. Ya got good headers and with good flowing mufflers 2 1/2" will probably be fine. I've always used 500HP as the margin between 3" and 2 1/2", that's why I stuck with 2 1/2" on the 383, it's just shy of 500 HP. My bottleneck are the Schmachers but it doesn't see much track time. It's like Clint says "ya gotto know your limitations".

Terry
 
you wouldent see much improvement between the two...just a clearance issue with the floor..
 
I ran TTI 2.5" on my Six Pack Challenger with Walker Dynomax Super Hemi Turbos and ran 12.800@110.6. Motor was built to pass the Certified Stock teardown (and did). Ran that @ 3960lbs and on repro PolyGlas tires. 3" wouldn't have made any difference on that car except to drop back pressure and make it sound like farting in the tub.
 
well what if you just have a X pipe then the mufflers right after?
 
would he lose torque if he goes 3? jw because if he goes three can he try to choke it a little by putting smaller exhaust tips or turndowns?
 
74Burntorange said:
would he lose torque if he goes 3? jw because if he goes three can he try to choke it a little by putting smaller exhaust tips or turndowns?
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I copied and pasted this off of Pypes Performance Exhaust.


Q: It seems as though 3" exhaust is the popular choice these days. Is there any disadvantages?
A: Yes! A stock horsepower car with 3" exhaust can lose noticeable low end torque and affect performance. Also, 3" pipe usually requires increased installation precision because of limited clearance issues. As a general rule, cars with less then 450hp should use 2.5" exhaust. Cars in the 450hp range could potentially benefit by a 3" crossover and still keeping 2.5" tails. Cars with 500hp + should utilize 3" or even larger tube size.
 
74Burntorange said:
would he lose torque if he goes 3? jw because if he goes three can he try to choke it a little by putting smaller exhaust tips or turndowns?
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Well, maybe. But if you look at the stock exhaust on a lot of Mopars you'll see the pipes are smaller after the mufflers. This is because they (Ma Mopar) knew that the exhaust had cooled enough by that point that they had to reduce pipe diameter in order to keep the velocity up.

Darn cleaver those Mopar engineers
 
68sedan, I was just about to mention that.

IMO, a 2-1/2 at this point is fine though out the system.
IF you used a 3 inch pipe, I'd stop it about 1-1/2 feet after the collector and neck it down from there into a 2-1/2 inch pipe. (As it goes into a X pipe if posible.
 
kind of liek what ill be running. 3in x pipe and everything else is 2.50
 
rumblefish360 said:
68sedan, I was just about to mention that.

IMO, a 2-1/2 at this point is fine though out the system.
IF you used a 3 inch pipe, I'd stop it about 1-1/2 feet after the collector and neck it down from there into a 2-1/2 inch pipe. (As it goes into a X pipe if posible.
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I guess that is what I will do since I have the 3" collectors and still have the 2.5" mufflers.
 
Dr Gas sells a nice X pipe that is 3" in to the X and 2.5" out. I think 2.5" from the headers back is fine though.
 
AdamR said:
Dr Gas sells a nice X pipe that is 3" in to the X and 2.5" out. I think 2.5" from the headers back is fine though.
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Adam,

First thing I like to say is "Thank God you changed your avator!" I hated that dang monkey! :toothy10:

Dr Gas huh? I'll try to Goggle that up .... thanks!
 
Good idea on Dr.gas there Adam. Like the distrib. for the avatar as well.
 
AdamR said:
Dr Gas sells a nice X pipe that is 3" in to the X and 2.5" out. I think 2.5" from the headers back is fine though.
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Adam,

The only X-pipe I found that is by Dr Gas that goes from 3 to 2.5 is $249.00.

Am I looking in the right area? Man that's high!
 
Thats the one. DR gas isnt cheap. Summit sells an X pipe kit for $100 2.5" in and out though.
 
mullinax95 said:
Adam,

First thing I like to say is "Thank God you changed your avator!" I hated that dang monkey! :toothy10:
Click to expand...


The monkey was here to send off eveil want to be members. He needed a vacation though, He'll be back.
 
I used this flow tech kit in 3" and then after the X I necked it down to 2.5" that way i have 3" cut outs still- I know its a little over kill right now but I don't want to spend the money later when/if I go with a bigger engine. That kit from Jegs is 142.99- not to bad

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ahhh i run 3" with an X-pipe on my dart. (about 350 hp at the wheels). seemed to run damn good to me. and it sure had no problems down low i can assure you of that.. :) . sounded good to me and everyone that heard it. it sure didn't sound like farting in a tub or bubble on decel. don't know where you guys are getting that stuff from.

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Looks to me like your "X" is to far back. Ever used a grease pencil on your pipes?
 
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