I read and have been reading alot of you with your 2.5" cat-back exhaust feel like your cars hasn't imporved that much in the performance department except that the noise level has changed? I am running 2.25" and i can tell you it was a night and day diffrence from stock to a performance cat-back.

Unlike my Injen intake , when added i felt a huge torque loss from take off compared to stock.But a small noticable diffrence after 80 mph +. But when i got my custom 2.25 custom cat back exhaust, i gained my torqe back and then some. Before i had my new exhaust put on the guy that was doing the work (awesome guy , been doing performance exhaust for 20 years now) asked me wether i wanted top end or all around performance? Not knowing to much about exhaust for N/A application ,i blurted i wanted a 2.75" exhaust system. He laughed at me and said i would have no low end or mid end punch if i go that big. I then said i wanted something that will give me good all around performance and he agreed as well. He suggested a 2.25" from the cat back with a high flow muffler. I agreed!

My performance from stock was a great improvement. Regained torque on the low end, and i gained a significant amount of mid to top end pull as well across the power band. I think mated with the Injen, it made the response a tad bit more effective, high end pulls feel alot better than just with the Injen intake by itself.

Do you guys think maybe 2.5" is just a bit to open for a 3.0 or 3.5 VQ?Stock the car comes with 1.85 diameter from the exhaust manifold back.
.25" isn't much of a decrease form .50" but it could be enough to lose power across the band and make your car just a top end car.

 

I thought stock OD was 2" piping not 1.85? Correcet me if i am wrong...

anyway, I have 2.5 cattman catback...I love it...feel no low end lose at all....actually feels like I gained all through the RPM band

 

I thought stock was 2.25"... haha... talk about some serious misinformation in this thread... hope its not me...

Anyways... I have a 2.5" Frankencar cat-back and my old GReddy EVO was 2.5" diameter too... I haven't seen dynos of either, but I can't feel any difference on the low end... maybe some improve at high ends, but could be all in my head...

 

[QUOTE=Puppetmaster]I thought stock was 2.25"... haha... talk about some serious misinformation in this thread... hope its not me...

I hope its not me either.....

I definitely felt a difference with my cattman....only on the high end side tho....I remember when I was stock....I had trouble reaching 100mph on the on-ramp....with the GAB (ghetto airbox) and cattman catback put on....I could reach that speed noticeably quicker....

 

[QUOTE=steven88]
You guys are right , its 2".

From the sound of it it sounds like you guys are satisfied with your 2.5 " cat back exhaust. I guess its the guys who don't have the complete cat back system. I know a cat back doesn't give you gains say like a FI mod, but i do believe it definitely helps out. I want to dyno mine so bad just to see the comparisons of 2.25 vs 2.5 application. Even though every maxima in here is diffent wether stock or modded , babied or abused but at least to see the gains or loss on the dyno would be cool to see and discuss.

 

I just went out and measured the internal diameter of my stock y-pipe and its pretty much between 2.2-2.25".... I think I'll safely assume that the rest of the exhaust piping is the same... if ya have an OEM cat-back lying around... measure it and see...

And yeah, I'm very happy with my FC cat-back...

 

it could also have to do with design. There is this one 240sx with an sr20det motor who had a 3 inch exhaust and went down to a 2.5 magnaflow titanium exhaust (some type of magnaflow). He gained 6 hp over the 3 inch exhaust. The owner is Niel Tijn, editor of HCI magazine, has an orange s14 with strawberryface and carbon fiber hood and top...

 

See on V6 turbo cars 3" is great to have , on four cyclinder turbo cars i think it might be over kill as such. Plus it depends on your setup to....
For N/A cars a good enough system that alows your engine to beath and flow yet retain a good amount of back pressure to gain hp is such a feat.
And like you mentioned too, design materials , etc all play into the equation.

 

how much did you pay for your cattback Daily Driver? I was set on getting the Cattman cattback and y-pipe, however now you have me second guessing...

you should really get it on a dyno so we can see the graph, this could make all the Cattman and Franken owners very sad

 

No dynos? .

 

I payed 210 for mine,the guy who did my custom job knew his stuff and had the proper tools to do mandrell piping plus he had reasonable knowledge of getting the best performance when creating my cat-back system for me.(Shade Tree Performance ,You guys are the bomb!!!)He wasn't you typical muffler shop , he just didn't throw some POS pipes on my car and stick a muffler on there,even my muffler is performance oriented, i have a 7lbs Rayactive stainless steel high flow muffler, its one of the lightest mufflers on the market today. Hell the muffler cost more than the fabrication and labor of the pipes, but he suggested that muffler beacsue of its light weight and high flow design. I was going to get a Greddy EVO II but i couldn't justify the price of paying 450+for a name plus having that huge coffee can muffler.

I think you will be happy with your Cattman as many here are.There craftsman ship and design build is superb ,one of the best out there.The Cattman Y-pipe is my next mod either next month or April. The gains are resonably noticiable with cattman bolt on products then i have seen or read from many other manufactures claims.So don't beat yourself up to much, you made a wise choice.

I know i made a terrible mistake when i had my GLI Jetta 89' when i gutted my cat and ran a 2.75" from the cat back. The car had no low or mid range punch , but boy after a 80 mph she sure would scream and fly. Too open for a 4 cylinder.

I keep making a schedule at Titan motorsports here in Orlando, but they keep canceling my dyno appointments ,there Dyno keeps breaking testing out these 600+ HP Supras and other extreme high Hp cars there .