Dodge Challenger Forum banner

1 - 16 of 16 Posts

·
Premium Member
Joined
·
618 Posts
Discussion Starter #1
I am wondering what the pros/cons of 2.5" & 3" catback exhausts installed on an RT?

Some of the exhaust companies make 2.5" and 3" exhaust pipes for the RT.

I am not sure if I want to install headers or not.

3" seems big for a stock 345 c.i. motor. I would also think there would be slightly different sound with a bigger exhaust. Maybe a lower rumble sound from the bigger exhaust.

Performance wise, I think the 2.5" would dyno the same as the 3" with a stock motor.

Anybody have experience with this?
 

·
Registered
Joined
·
540 Posts
Go with the dual 2.5. 3" will be too big and you'll lose torque from the lack of back pressure at certain RPMs.
 

·
Registered
Joined
·
413 Posts
Go with the dual 2.5. 3" will be too big and you'll lose torque from the lack of back pressure at certain RPMs.
While this is technically accurate I disagree with it lol. At a recent dyno day with the West Coast Challengers my car with 3" put down 2 more HP than the other cars with 2.5" but also put down 4 ft lbs less so truly insignificant numbers between 2.5 and 3 just my experience 3" sounds better


i did 3" cat back with single chamber spintech mufflers and re used factory tips

here is a link to how it sounds
http://youtu.be/2aE0GWpyILc
 

·
Registered
Joined
·
329 Posts
I just put a 3"Mbrp catback on my RT a feel now negative affects...love the sound and actually feels a bit peppier. I think the type of system makes the biggest difference, 3" of straight pipes would definitely cause more loss than a system with 2 mufflers and 2 resonator's. The mbrp is 3" kept the back pressure that RT needs to feel beastly in the lower rpm range.

Sent from AutoGuide.com Free App
 
Joined
·
1,931 Posts
2.5" is more than enough...My 426 stroker has a Corsa Extreme with 2.75" pipes. I had an air flow analysis done on a dyno. This checks the how the whole system (throttle body to exhaust) is working to move air thru. My engine scored way above average. In fact, the tuner said my engine may have been the best score he had seen. The right size pipes will actually flow faster...too big and air speed slows. That is why the torque drops and you need that torque for a heavy car..
 

·
Premium Member
Joined
·
618 Posts
Discussion Starter #8
Thanks to all for your posts.

I'm getting old, but I remember my 68 Camaro had 2" dual exhaust with headers. I thought 2" was the norm 20-30 years ago. Not that everything was perfect back then and the norm changes. 2" was probably too small.

I think TNCHARGER is right. It should come down to cubic inches and rpm. For a 345 c.i. engine, 2.5" should be good. If I had the motor heavily modded and was running it at 7,000+ rpm, I might could justify a 3" catback.

You want the exhaust to be free flowing, but some back pressure is needed to keep things optimal. Finding the optimal parts and settings for our cars are why we are on this forum!

Happy motoring!
 

·
Registered
Joined
·
2,463 Posts
Before you drop big money on cat-backs know exactly what your future plans are. If you ARE going to replace your manifold/mids with 392 takeoffs as many do, get the 3" cat-back system FOR the 392 and you can have a muffler shop adapt the 2.5" mids to work with the 2.75" hookup for the cat-back. If (my personal case) you intend to go Long Tube headers eventually, get a 2.5" (stock R/T) cat back and when time comes to add the Long Tubes, it will just bolt on/tune and go! :D
(Added; Im an old coot too, trying to keep up/current but some things we just love no matter the logic, headers is one!)
 

·
Registered
2010 Challenger R/T Classic
Joined
·
19 Posts
Well if you don't change the cats you will maintain the back pressure as the stock cats are a bottle neck like the stock R/T exhaust manifolds. Personally mine has 2.75in cat back SRT exhaust with the anti drone tech and it sounds bad ass. Not sure how it would be with headers and high flow cats.
 

·
Registered
Joined
·
81 Posts
Hi there just came across your post, I have a 2010 rt auto, I have MDS turned off, a 91 cai tune, a mopar cai and a 180 t stat installed, I just bought a 2013 srt8 6 speed exhaust for only $50 . I am going to adapt this to fit my car and I am wondering if drone will be an issue with MDS off? Also will I lose any low end power? I hope it will alittle throatier with this setup. Thanks for any help Ron
 

·
Administrator
2009 Challenger R/T
Joined
·
8,918 Posts
Hi there just came across your post, I have a 2010 rt auto, I have MDS turned off, a 91 cai tune, a mopar cai and a 180 t stat installed, I just bought a 2013 srt8 6 speed exhaust for only $50 . I am going to adapt this to fit my car and I am wondering if drone will be an issue with MDS off? Also will I lose any low end power? I hope it will alittle throatier with this setup. Thanks for any help Ron
I would suggest getting the srt manifolds and mid pipes or a set of jba shorties, as far as drone you won't get any the stock exhaust isn't very loud so drone won't be an issue, you shouldn't have much loss in torque either and your going to reduce weight by getting rid of the suitcase muffler. You can find everything you need from our Vendors BTW or check the for sale threads.
 

·
Administrator
2009 Challenger R/T
Joined
·
8,918 Posts
Before I started modding my car I started with the MBRP 3" Cat Back loved the sound, if your looking to go with forced induction, headers ect... in the future go with the 3" I am currently using the Stainless Works 3" with Turbo S Mufflers and love the sound it's loud just the way a muscle car should be... :saythat:
 

·
Registered
Joined
·
1,312 Posts
If you not going to install headers or go wild with engine mods, the stock pipes and mufflers flow great. But the resonators suck. I installed the Magnaflow axle back kit, and it sounds great. Plus with the savings from not purchasing a full cat kit, I got a tuner, catch can, and front strut tower brace.
 

·
Registered
Joined
·
50 Posts
hi all,
about a month ago I went from FlowMaster S-10's & 2-1/4" cat cat back to their Flow-Fx 2-1/2"...MPG has gone from 17-19 to 12-15mpg...anyone else 'suffered' this? Didn't buy it for MPG, but actually thought it would be the opposite....??!? BTW all else is exactly the same drive time, speed, miles, etc. Thanks,
Jess
 

·
Registered
Joined
·
80 Posts
hi all,
about a month ago I went from FlowMaster S-10's & 2-1/4" cat cat back to their Flow-Fx 2-1/2"...MPG has gone from 17-19 to 12-15mpg...anyone else 'suffered' this? Didn't buy it for MPG, but actually thought it would be the opposite....??!? BTW all else is exactly the same drive time, speed, miles, etc. Thanks,
Jess
Looks like an old thread got revived here........no worries, my own '12 R/T w/M6 trans/5.7 hemi returned me an average of right at 25 mpg on my last road trip over the summer. I run a full SRT exhaust from shorty "headers", factory mid pipes and a Flowmaster American Thunder 3" cat back exhaust with very successful results. My driveability is unchanged off the bottom and has picked up a noticeable mid and top end power increase from these mods, not to mention it passes emissions tests easier this way(none required where I live in AZ).
Everyone's car will run differently........
 
1 - 16 of 16 Posts
Top