Right now im runnin the GMPP Extrude Honed Manifold and the GMPP Sport Cat Back and im thinkin about gettin a catless downpipe from ZZP but im worried it mind sound raspy... Is anybody else runnin this setup or a similar one and if so how does it sound and was it worth the extra rasp for more power?

 

being that both your manifold and cat-back are pretty restrictive, i wouldn't worry about the extra power you'll get from no cat. just play it safe and get the cat. not having a cat on your setup is probably worth about 1 whp or so, and it's not worth the extra noise.

 

man i dont know what to believe i know that the gmpp manifold isnt the greatest for flowing and efficiency or whatever but i always see people writing stuff like that for a supercharger setup you shouldnt have as big of an exhaust (like a 3") as for a turbo because the turbo needs more volume flow and the supercharger needs a higher speed of exhaust flow or something like that. I am sure i am stating it wrong so somebody help me out here... what are the diameters of the gmpp primaries and collector anyways?

I couldnt really resist buying the gmpp manifold and sport cat back anway because while i was stationed in norfolk i found this guy selling the header, the cat back, the tip for the cat back (like 50 bucks from gm) and the aem intake all BRAND NEW never intalled for 500 bucks so i had to get it.

 

you're right, 3" for many members on this site is too big. 2 1/2 is perfect for most ss/sc owners on this site. the gmpp is 2 1/4.

 

cool thanks, so what would be the best bang for my buck as far as a d/p with a cat?? zzp or what? i really want to buy a new d/p and header combo but i dont wanna go through the pita of installin another header since i dont have access to a lift anymore...

 

i've never heard the zzp downpipe by itself, but i have the header/downpipe combo and think it sounds great.

you can do the install with jackstands if you have them, i've done many local members on them.

 

nice i think im gonna buy the vibrant header and dp combo from helltime.... what is the diameter of your magnaflow exhaust?

 

2.5". the vibrant setup is a little raspier than the zzp, but it's not terrible with the magnaflow. a full vibrant exhaust sounds like a chainsaw in my opinion.

 

do you think the resonator and muffler on the gmpp will quiet it down enough to still sound good? because i love the way it sounds now i just know my stock d/p is really restrictive and i want to get a new one before i get it tuned next month.... if i do get just the d/p what brands will fit in the stock location?? does the zzp still have the problem with the flex pipe poppin off?

 

not sure how it sounds with the gmpp to be honest. i'm a videographer, and i know how innacurate online videos can be in terms of sound, so i only go by what i've heard in person.

 

I wish we had more before and after catback only dyno's . Everyone says the GMPP is too small but yet this sites owner did a before and after dyno good for 12whp. I'm not say 2.5'' isnt better , i just wish we knew how much better it is . Stick with the cat thou, most catless cars sound raspy imho.

 

that's one car, otherwise stock, on one dyno, along time ago. and dyno gains prove nothing. you can dyno the same car on the same dyno 10 times, and get 10 different #'s. put a new exhaust on, dyno it again, and get 10 new numbers, again all different.

moral of the story is that dyno's are great for tuning, and bragging rights. but as accurate measurements of horsepower, not so much.

 

If the same car on the same dyno reads as unaccurate as you say, they wouldn't be a very useful tool. He did his baseline at the same dyno , then his exhaust pull. I'm not saying that its a garanteed 12 whp , but it does show gains.

 

i said it's useful for tuning. in other words, sitting in a shop running your car to redline in 4th gear while logging data through a tuning program is a little safer than doing it on your local backroads. as far as hp #'s, it's not accurate at all. if they were accurate, you would get the same # if you did 3 pulls in a row. you can get differences of up to 10 hp from the same car, same dyno, same day. when you're looking at the power gained form bolt ons, which is less than the margin of error, i think it's safe to say that they're worthless.

 

If you plan on going cat-less for the downpipe hooked up to GMPP exhaust parts, there's no doubt in my mind that it will be raspy. The GMPP exhaust tends to be a little raspy to begin with so going cat-less will definitely increase the raspiness. GMPP exhausts are a little too restrictive for me.

 

well i think im goin with the zzp d/p and header combo to bolt up to my gmpp sport cat back is anybody runnin that set up??

 

i recently helped a member put this setup on his car, and it sounded pretty sweet. it was a 2.2, but it was a pretty mean sounding car.

what i like about the zzp is it's not super loud at cruising speeds, but you know it's not stock. and it gets nice and mean when you step on the gas.

 

are you runnin the 1.5 inch primaries or 1.75 cuz the one im thinking of buying is 1.5 primaries... will i be losin out on a lot of performance with the 1.5 vs 1.75s?

 

get the 1.75. 1.5 is too small.

 

so if i go with larger primaries will i lose low end tq but gain high end hp and speed basically? how much of an improvement is the zzp 1.5 inch primaries and 2.5 inch d/p over the gmpp extruded header and stock d/p?

 

getting the 1.5" is a waste of money. the whole point is to get rid of the restriction. by going with teh 1.5" you're intentionally CREATING restriction, instead of getting rid of it. especially running it through an exhaust that's too small as is.

 

damn bustin my *****...tryin to do the best i can with what i got man... im about to just say **** it and buy a new zzp downpipe that should get rid of what restriction i have now with the stock d/p and maybe in the future if i can round up another grand i will upgrade to a bigger exhaust setup...

 

not bustin *****, just bein honest : and tryin to help

with my first cobalt, i was impatient, and just got parts instead of waiting and getting what i really wanted. and it just costs morein the long run. with the 2.0 i didn't cheap out, got exactly what i wanted, and it's just so much more worth it.

 

i gotcha i appreciate the honesty my new d/p will be here tomorrow i think that should get rid of a lot of restriction in my exhaust for now especially that damn crimped section in the stock dp where the o2 sensor is... in the future i think im gonna go with either the hahn setup or maybe the magnaflow...

 

well i put the zzp downpipe in last night with the highflow cat and man it sounds and flows so ****** sweet. Power comes on much smoother and the engine doesnt feel as restricted now it really screams at wot. awesome product i highly recommend it.