Catbacks and Horsepower

[2003blustang]

I am getting ready to buy a catback. I'm lookiing at Magnaflow, flowmaster, and spintech. Is it true that straight-through systems like the Magnaflow make more horsepower than the Flowmaster and Spintech systems because of less back-pressure? Flowmaster claims to flow better and make more horsepower due to "scavenging". I don't know who to believe. I was hoping that someone has tried both on a dyno and is willing to share their results. My 2003 GT is stock and I will be adding a Magnaflow or Doctor Gas X-pipe in the near future. In short, which catback system will make more horsepower with the off-road X-pipe? Thanks in advance,

Matt

 

[TonyG]

Based on my experience, I don't think you'll see any significant gains with either catback. I have a blower, and got zero gain after a Magnaflow catback. The X-pipe is a diifferent story -it netted me about 25 rwhp. To me, a catback is a "sound mod", not a performance mod.

 

[1tirefire]

To me, a catback is a "sound mod", not a performance mod.

 

[2003blustang]

so, if there is no horsepower benefit in adding an aftermarket catback, should I just buy the new X-pipe and keep the stock catback? My primary goal is more horsepower. If the aftermarket catback doesn't help in reaching that goal, I will spend that money on a 75mm throttle body and plenum combo. I read in another post that the stock mufflers are not the bottleneck in the exhaust system.

Matt

 

[2003blustang]

Bump

 

[Josh97GT]

Catback is much more of a sound mod like they said. So I would just buy the mid-pipe you wanted and then maybe change the mufflers to get some nice sound, but I think it's a waste to change the whole cat-back.

 

[WickedDropTop]

No doubt, go with the mid pipe first, you will notice a sound change, I did, and you will probobly not be disapointed with a plenum and TB if your looking for some HP

 

[TonyG]

If HP is your goal, then there are definitely better ways to spend your money than a catback. Factory cats (all six of them) are the biggest bottleneck in the exhaust. But if you think you'll be getting headers in the future, you may want to hold off on the X-pipe as well, since that would have to be replaced again.

Another idea to kick around besides TB/Plenum, headers and X-pipe is 4.10 gears. No HP gain, but great bang for the buck.

 

[Red03Mustang]

If HP is your goal, then there are definitely better ways to spend your money than a catback. Factory cats (all six of them) are the biggest bottleneck in the exhaust. But if you think you'll be getting headers in the future, you may want to hold off on the X-pipe as well, since that would have to be replaced again.

Another idea to kick around besides TB/Plenum, headers and X-pipe is 4.10 gears. No HP gain, but great bang for the buck.

What is the stock throttle body size? I'd like to know everything else that has to change to accomodate the upgrade in mm size, if there is anything.

I'm looking at a 70mm one right now for $199. Is 70 stock, or no?

BTW, go Magnaflow!

 

[03gtmustang]

I THINK the stock t/b is 65mm, I might be wrong though. I say Magnapacks, they look 10x better then the others you listed, 100% stainless steel, and they are straight through. I have a clip of my set up on my site, check out the link in my sig.

 

[3.8L_of_Pain]

The 2.5" Dynomax cat-back with Ultra Flo (flow through) mufflers dyno tested + 4.2 rwhp on a 2000 GT. So a cat-back will give you a little more flow, performance, and better sound. As people mentioned, the biggest gains are in the mid-pipe with a catted X-Pipe. If not for emission laws in California, I would be all over a catted X-Pipe.

 

[turboscrew]

I agree that the midpipe will give you more power gains than a catback. Seems to me that the cats would be the biggest restriction in the exhaust. You may get a little power gain if you go from a chambered muffler to one thats straight thru but the gains will be so minimal that you wont really be able to tell. Midpipe w/o cats makes the power, catback sets the tone you like.

 

[decoy562]

Just get whatever sounds good to you for the catback, and get a midpipe for power

 

[Linz]

In the new MM&FF they did full Bassani, from the headers back,and gained something like 17 hp and torque on a totally stock mustang. (Excuse my guess, I don't have the mag. right here with me) But Bassani is expensive. Thier catback still sounds the best to me though!