Hey guys! I know there are a ton of exhaust threads but none of them actually seem to answer my question... I know most people buy a catback, usually first, but many people buy them for the sound and looks. I just purchased a Clear Image Automotive 4-1 Header with 1.75" primaries, velocity cone and 3" collector. I also got a 3" downpipe with cat (PA emissions). Right now the downpipe is setup with a slip fit 3" to 2.5" flange so I can hook it to my stock catback. Their header/dp dyno'ed 15whp...

This is the header/dp I just got. It's nice!



Now my question is, would I actually see more power increase with purchasing a catback exhaust with this combo? Or would I be better off leaving the stock catback and putting the money elsewhere. Clear Image is doing a 3" Stainless GP now also and I was going to buy that. However if I am going to be pissing away $500 on sound and little or no performance gain, I am not going to do it. My mods are in my sig and VB Garage...

Can anyone please give me their opinions of finishing off the exhaust fully with a catback after they have already put on a header/dp? Factual info such as dyno or 1/4 miles numbers would be helpful. I would greatly appreciate it....

 

The stock exhaust with its 2.25in crush bend at the axle , and restrictive muffler is probably holding some power back, considering the new header and DP. I'd hate to speculate how much thou,maybe 10hp-15hp? Just a guess.

 

Whatever you get make sure you get a big resonator. I went with magnaflow and my exhaust dosen't drone at all. I have a ZZP midlength with a high flow 3 to 2.75. My exhaust is a Dezod 2.75" and before I put my resonator it was obnoxiously loud and droned really bad.

 

Thanks for the responses. However I am more concerned with the question of whether or not the catback exhaust will give performance gains if a header and downpipe are already present. 15whp was suggested (which seems high). Is that 15whp for header/dp + 15whp for catback to equal 30whp for the full exhaust? That seems like a lot for the mods. I'm sure that may be possible with other supporting mods. Anyone with some exhaust experience?

 

The header and downpipe are going to be your biggest gains...the catback isn't going to give you as much. Didn't they do any tested back to back wtih stock exhaust and their exhaust?

 

As far as Clear Image is concerned they have not released any dyno numbers from just their exhaust. They did dyno the header/dp and it netted 15whp. The exhaust however was still in R&D and they have not fully completed it yet. Thank you for reassuring what I had thought. I figured the gains from the catback would not be that significant. Can anyone provide some more evidence of this? Gains with a 3" exhaust on a high flowing header/dp combo?

 

the gains from a catback would help with your mods. you are flowing a decent amount of air but you header and midpipe have done most of the work already. you may get 15 to 20 hp from the full exhaust setup.

 

Soo all in all is it really work it to get a catback? 15 to 20whp gains don't seem to dramatic. Clear Image dyno'ed it with just the header and downpipe on the stock catback and made like 15whp and 15wt... Spending another ~$500 to not get anything more than sound and a very slight gain is unreasonable to me...

 

well. i may be able to help you out. my engine is stock right now (mods in my sig), and i have been talking with dan and beth and i will be doing a before and after dyno with their head/dp/exhaust so we can see some real numbers. and i'll be posting them up once its done. hopefully by the end of august.

 

Sounds good man, I will def be interested. I got their header and dp in the mail yesterday and I will be installing it tomorrow night. I'll update on that.

I still am curious as to what other people with exhausts have to say about this..?

 

get the catbcak, it will ultimately open up the entire exhaust more. I have the 3 inch vibrant and love it. I was told it had proven gains of 7-10 hp, but i dont know for sure yet. All in all, it cant hurt, the stock system is fairly restrictive.

 

Thanks for the input, I know the the catback will "ultimately open up the entire exhaust more" however, would the additonal performance numbers be worth it? For about $500 the exhaust would cost, I could get HP Tuners or other mods that would make better performance or reliability such as Meth, Tune, etc. Any suggestions? Is the FULL exhaust worth it? Or does the header and downpipe remove most all the restriction?

 

My thinking is that you still have a 2.25inch restriction in the stock exhaust where it goes over the rear axle. So are you going to see the gains that you should out of the header and DP when that restriction is still there ?

 

Go custom. There is a website that does mandrel bent exhaust pipe for a lot of cars and its got the cobalt ss/sc. I know the 2.5 in was 120 bucks shipped to my door. Im going to order the 3in pipe I think it was 150 shipped. Im not sure of the name but I think its mandrelbentexhaust.com or mandrelexhaust.com you might have to search since im not so sure on the name. But id def go that route and pick a muffler that is 3in inlet to have a complete 3in exhaust

There's no point spending 500 for a catback when you can make your own for 250 tops. And its a true mandrel bent 3in

Okay website is called mandrelexhaustsystems.com its actually 195 for 3 inch. 120 for 2.5. I still think this is a better idea then paying 500

 

Thanks for the info. The only problem with that mandrelexhaustsystems.com stuff is that it is aluminized steel and not stainless like the Clear Image Exhaust....

What is everyone's thoughts on 2.5" or 3"... I have a 2.8" pulley and might run a 2.7" in the future. Do you think I would benefit from the 3"?

 

Bump, anyone want to comment on when a 3" exhaust is beneficial over a 2.5" system for a Supercharged SS..?

 

If u have the 3in dp no point in going smaller than 3in exhaust otherwise ur just waisting it. Imo that is. Why bottleneck to a smaller size? You want the most flow possible right?

 

Well I want the most flow that will build power and not sacrifice low end torque and make the car worse. I want performance out of the catback or else it is not worth the money spent...

I just want some confirmation that a 3" exhaust is or is not too big for a 2.7", 60's, tunes, etc... Or would a 2.5" be more beneficial..?

 

But your header is steel and your downpipe is aluminized, so whats the problem?

 

Well for the whole catback system, if I can get a good deal on the stainless setup then why not? The Clear Image exhaust is rather cheap for a stainless setup. The regular aluminized only saves like $50. So to me it's worth it to go stainless. As far as my "cheaper" header and downpipe, I correctly painted them with high temp paint and it has held up so far for about 800 miles and looks brand new. That includes street tuning with lots of WOT passes and lots of heat.

So what about the 2.5" over 3" sizing???

 

go with corsa sport
or if u want 3" than hahn

 

So 500 dollars is cheap for a catback? Considering you can get full 3in pipe for 195 plus muffler at 100 bucks TOP and install maybe 50. So your saying by going with the alumin saving 90 bucks? So 340 is only 90 bucks cheaper than 500 ? Lol. Idk about you but id go custom setup. Its going to save you money. Plus I will never buy a catback for 500. Its a waste

Ahh you must be talking about the clear image exhaust is 50 bucks more for stainless. But still not worth the 500 bucks

 

Yes, the Clear Image setup in 3" stainless is like $490 shipped to my door.

Yes, the custom would be fine... However I HATE LOUD RICEY SOUNDING 4 BANGERS! So, I would have to do something about that like getting a nice quiet resonator and muffler that still makes good power. Plus I'd have to pay someone money to weld up the system.

Soo $200 piping + $100 muffler + $50 resonator + $100 labor = $450. Now that is possibly overshooting it a little bit, but I'm not sure what shipping would be. The CI setup is $490 shipped and it's stainless and already welded and ready to go. It only needs 1 band clamp which is like $15 and I can live with that... Soo that leaves me pretty indecisive as to what to do...

When it comes to it, I don't even know if I need to have an catback exhaust with the setup I'm running... The 3" piping will likely shift my powerband, and take away more low end torque. The 2.5" wont be that huge of an increase over stock...

 

I didn't realize there is an interest for just hte mandrel bent tubing only. We can offer just the bends too. Same price as the link above.

 

As far as horsepower, $500 cat-back is not what you're looking for. But dude, if you get the right Cat-Back system.. The sound itself is worth it. Also, it seems like you're planning on modding your car and getting good performance gains from it. In the end you will definitely want a Cat-Back. There's a reason why everyone goes for that first- It's simple, and sounds nice. Also allows for better air flow. No need to constrict the air going through your after market downpipe. Just go for it and get one. I'd say Magnaflow is the best bang for your buck to be honest. Close behind is GMPP. (Magnaflow allows for better air flow). Trust me man. Cat-Back is the thing I've LEAST regretted in my lifetime haha. You will fall in love with your car more than you thought possible