Asphalt Assault

I am going with GMPP header honed, custom 3" downpipe, 3" inlet and outlet magnaflow catalytic converter, 3" to 2/5" reducer and 2.5" magna flow catback. the ultimate exhaust for 300 to 400 HP. my target is 300 hp as a minimum but may go bigger.

Manny13

I previously posted info that I received straight from Tim Richards of GM Performance who worked on the time attack Cobalt. He told me that the key to success with our car’s exhaust was to be less restrictive early in the pipes with a 3” setup. He also told me to pick a muffler that created some restriction for applications under 300 HP. If you go over 300 HP between 300-385 HP use less restriction or free flow design. I told him I would stay within the 300-385 HP range so he suggested going from 3” pipe into a slightly smaller inlet in the muffler to created necessary back pressure. I chose the Tenzo R Carbon muffler with a 2.75” inlet and 4” exit tip. I have had this set-up since May 05 and have loved the sound and performance ever since. Furthermore, as we add more mods the car’s low end torque will improve regardless. At one point too much low end torque in combination with a extremely quick first gear will make our car very difficult to launch.

Asphalt Assault

your setup sounds like a venturi setup which is the same principle many carbs and throttle body's use to create more flow. meaning it would create more flow than a straight three in exhaust. you are running 3" reduce to 2.75" and then to 4" causing a venturi effect. again this sounds like to me your system has a venturi effect.

R33P3R007

our Downpipe connects the manifold to the catback. it is still called the downpipe

Manny13

Venturi effect is exactly what it is! I'm an Air Dynamics Engineer at Seton Hall University. I wasn't sure if it was going to be worth explaining when I made the post so i didn't. However, it is true venturi effect is a scientific explenation for achieving higher airflow or in more extreme cases vacuum effects (wich too much of would be bad for our exhaust) through certain amounts of air restraint. So by slightly bottlenecking the exhaust into 2 3/4 inch it creates enough back Pressure to not loose any or much low end torque (1200 RPM-2800 RPM) yet immediately after the air can rocket out of there at a faster speed than it was traveling previously. This increase in air speed or free flow at the end would in most cases defeat the purpose of the restriction right before it but there only is couple of inches left in the muffler so it works to be a perfet combination of restriction to air flow.

06black

so if i was to stick with my 3in pipe and put a 2.5in muffler on the end that might help bring backsome of that bottom end? than slap the 3in back on once i'm makeing the power i want.

is that the rite idea?

zinner

Ok What should I call the pipe that connects to the header and to the cat back ?

I called it a downpipe cause it routes the exhaust down.

Brian MP5T

Downpipe is a term usually only used to describe a part on a Turbo System.


The part you are talking about is called a "Head Pipe"


It's a silly terminology thing.

"Original equipment exhaust systems usually have stainless steel head pipes (the pipe between the exhaust manifold and catalytic converter)"

Manny13

that part that connects the header two the exhaust is called the flex tube by GM performance

Nocturn

Learn something everyday...

06black

so ummmm guys hows about an answer???????...this whole flex pipe/down pipe/head pipe is all fun and good but not what i'm lookin for....

i'll ask agen....if i keep my 3in pipe and swap a 2.5in muffler on it will that help bring the back pressure back and give me back my bottom end?

max_boost

****, you were there. I didn't even realize it

06black

hows the 3.1 runin?

max_boost

I love it. I'm going to order a 2.9 as soon as Doug gets the billet tensioners ready.

3fo893013L

yah, had my girl there. We were with Jason mostly outside for a good 1/2 hr bullshitting with the Neon owner. he showed me his neat butterfly valve.

06black

dangit mike shut up!!!!

i want my dam answer here!!!











love ya bud

06black

your gonna waite?????

i showed you the tensioner garry and myself are runing...go that route and get the power NOW then make the tensioner pretty when Doug gets them out.

the 2.9 will rock your world

djt81185

SERIOUSLY...I want one too...dammit doug lol...

djt81185

The 2.7 is like a Chuck Norris roundhouse kick to the face!!!!!

max_boost

Yea I'm waiting. I'm real close to ripping my blower off and sending it to Stiegemeier so I want to see Rice's results before I do anything else.

06black

i'm with you on that one....from what rice was sayin his resaults from porting the blower/intake were DAM good

06black

2.7=good with out stg 1

BUT

2.7=bad with stg 1...WAYY to many blower rpm....



just a lil FYI

djt81185

FYI back at ya gen V eaton blower maximum sustained rpm under constant load = 16k rpm ...guess what gen of eaton blower we have If you guessed gen V you'd be correct.

Therefore 2.7 + stage 1 or whatever is still fine also...they run 2.6" pulleys on M90 on the gtp and they redline at 14k with no ill effects

06black

from what LSJ enginers have told me runing that small of a pully (2.7) with the stage 1 rpm bump(7100k) the blower would be above its limit to offten...that leads to roter swell and the teflon coating with come off voer time....in the end causeing mayjor heat, friction problums

Asphalt Assault

I would agree with that.