How bout magnaflow cat back and GMPP manifold

 

to expensive for now.
Magnaflow is 700$
Gmpp exhaust (450)and manifold (350)is 800$ That is canadian dollars!

I dont want to void warranty if that any conselation, i mean i can swap the pulley in 10 mins, so the rest is good, u know!? so what would u do?

 

Like with my setup, would the gmpp be restrictave?? I know 2.5 for my setup would be perfect, but would 2.25 be that bad??

 

id stay away from the 2.25, save up and do it right, thats why i dont have some ghetto fabbed **** on mine by now

 

(Y) thanx boss! so like get a manifold and magnaflow catback?? or is there any other 2.5 catback??

 

You have to understand that no matter if you have a 2.2" pulley, you're only pushing out as much exhaust as your:

1. Camshafts allow to leave in one cycle
2. The size of your exhaust ports

The fact of the matter is that you're supercharged, yes but you're not reliant on your exhaust system like a turbocharged application would be. A bigger exhaust system helps on a turbocharged system cause of the lack of backpressure helping the turbine spin faster and easier.

That's my take on the matter.

 

So njhk, would you go for the gmpp manifold and gmpp exhaust?? or get just the magnaflow catback for the same price?? In canada the gmpp duo or magnaflow catback are the same price. SO what would be my best bet for hp/$ value...

 

I'd get an actual "header" design rather than a honed stock manifold. Check out Pacesetter.

As far as the cat-back, I'd look for something 2.5" max.

 

sweet, but like if this is the final upgrade i want to do the car after i get my 2.9" pulley, is it still a good upgrade worth while for the price u pay and the fact that gmpp cant harass you because its their parts?? except the pulley, i would take that off

 

Well GMPP wouldn't harrass anyone lol

If you mean GM as far as your warranty...your exhaust system won't void your motor warranty, no matter if you get it from GMPP or if it's custom.

Now, what will void your warranty is that Non-GM Stage Pulley you're going to put on (2.9"). You do some engine damage...bye bye warranty. Also, you'd need some type of tuning cause you're changing the amount of air being seen in your motor and the air pressure.

Now if you don't care about the warranty and going 2.9" pulley, I'd start looking into aftercooling upgrades. Your IATs are going to get higher the smaller pulley you go, which is not a good thing. Bad things could start to happen, parts will wear and problems will start happening if you're not careful.

Also, invest in monitoring devices to see whats going on with your car.

Sorry for going off the "exhaust topic" but you posted you're going 2.9" pulley, just looking out for you. If you want to read more into what your options are for cooling your IATs, read this:

http://www.ecotecforum.com/forums/showthread.php?t=1469

Good luck.

 

No way, sorry bro but if your running 12 psi into the cylinders, your not going to be moving as much air as you would if you were running 18-19 psi. You have more pressurized gas in the cylinders therefore more gasses needing to be moved out of the cylender. If you fill an air tank up to 12 psi and release the valve you will a get a blast of air. If you fill the same take with 18 or 19 psi the blast of air will be considerably larger and more powerful.

 

That is true.

But, my statement was mostly referring the need to go bigger with an exhaust system. Now, you're right as far as air tanks situation but there are other factors when it comes to an engine, this is why I pointed out the profile of camshafts (on the exhaust side) and the size of your ports. It's about velocity but as well as volume.

 

I think ptpaker is running a dynomax muffler on the stock exhaust PM him

I think a 2.5 inch setup is plenty.

If your head only flows 227 CFM then it only flows 227 CFM no matter what, putting a 500 CFM exhaust isn't gonna change much.

 

No no man, i want your opinion!! U must know alot more than me about this ****!! Well would you then just get the magnaflow for 800 and wait later on to get a header for another 800 then?? Because i can get the manifold and gmpp for 800 aswell. Thats my delima right now!! Its all in canadian funds obviously!! what would u do in my shoes

 

What size is the magnaflow setup (diameter)?

 

2.5"

 

Magnaflow is 2.5 inch, which i think is plenty for what iam running, I want to keep that bottom end. 3inch just turns me off, so its either gmpp or 2.5 magnaflow

 

go 2.5" whatever you decide to do.

 

So the 1/4 inch really makes a difference for a car lightly modded like mine?? I mean how much h/p would i loose??

 

No one could honestly answer how much HP you'd gain or lose.

 

I think some of you have heard of exhaust velocity and scavenging effects of a naturally aspirated engine and are confusing it with an engine which uses forced induction. A supercharged car like the Cobalt SS Supercharged will benefit from a larger exhaust, period. It may not "need" a larger exhaust, but too large of an exhaust doesn't have a negative effect like it does on a naturally aspirated engine.

The benefit of a "borderline" too-small exhaust system that builds a lot of velocity is the scavenging effect the negative pressure behind the exhaust pulse has on the cylinder. Naturally aspirated engines normally have a good amount of overlap between the time the exhaust valve closes and the intake valve opens. The scavenging of the cylinder helps to create a negative pressure which draws in more air/fuel before the exhaust valve closes. The rushing of the intake charge into the cylinder not only helps build cylinder pressure, it also helps fuel atomization by causing more swirl within the cylinder.

Supercharged engines don't benefit from the scavenging effect like naturally aspirated engines. Most cams for forced induction engines have very little, if any overlap at all. The overlap would literally draw some of the pressure built by the supercharger out the exhaust port if a lot of overlap was used. The high amount of cylinder pressure built by the supercharger is multiplied many times after the compression stroke. So high that most of the spent exhaust is forced out instantly after the exhaust valve is opened, reducing the need for any cylinder scavenging.

As someone mentioned (forgive me for forgetting your name at this moment), a 2.0L engine with 14+ psi of boost would theoretically expel the same amount of exhaust as a 4.0L naturally aspirated engine (Simple theory based on atmospheric pressure multiplied by 2.) So, basically, it would need the same size single exhaust a naturally aspirated 250 HP 4.0L engine would. Any restriction in the exhaust system from using a pipe that is too small will slow the exhaust flow and can cause some of the spent exhaust to linger in the cylinder, only to contaminate the intake charge once the intake valve opens.

I could go into much greater detail about this if time allowed, but if you're really that interested go to Barnes & Noble and look into it. It's really a very interesting topic. It simply boils down to supercharged/turbo charged engines need more exhaust flow than a naturally aspirated engine of the same size & hp output.

 

A couple, but just the though of the exhaust gasses flowing through such a tiny space!
2.25" has a circumfirence of about 3.98
2.5" has a circumfirence of about 4.91
3" has a circumfirence of about 7.07

 

I would imagine there might be a 2-3hp differance between a 2.25" and a 2.5" max. I am no expert, but i do not belive you could even feel the diferance. I have the GMPP sport and it sounds great, really deep and loud. I am sure the others sound good and add power, and you will be happy with whatever you get.

 

I actually fallow what he is saying about that and i does make sense. But the 64000$ question is then, What size should a 4.0l 250hp car exhaust should using, and would 2.25 be very restrictive considering its half the price of other 2.5 and 3.0 exhaust in canada.

 

I understand what you're saying actually but it still comes down to that yes, they need a bigger exhaust system but there is a such thing as too big of an exhaust system. If this wasn't true, people wouldn't be experiencing loss of power at one part of their powerband than the other when going with a very big exhaust system.

I'll give you an example...I have a 4g eclipse, 3.8L V6 SOHC w/MIVEC. Stock I come with a 2 1/2" exhaust system already. Know what most people change on the exhaust system? Just the muffler cause the exhaust is mendrel bent and 2.5"s, which is perfect for that size engine. Some people thought about going 3" and did it. What happened? Sounded nice but a good amount of power lost.

Now I know what you said, there is a difference but an N/A car and F/I car but you still used the theory of comparing a 2.0L S/C w/14 PSI to an 4.0L N/A engine.