wouldn;t mind hearing the high pitch lawn mower as long as its boosted but not NA thank you!..lol

 

i have a straight pipe exhaust, full 3in, cold start its loud but driving its quiet not loud .. i like it, the low end is sick but top end feels like it lost acouple of whp, ill try to get some vids of it soon

oh and it doesnt sound like a srt4 either

 

"what do u think the pressure inside the exhuast pipe right before the exhuast valve pens up? won;t be at the same level as the autmosphere? that's where i got the kpa # from. "

Because the pulsations of exhaust, it goes from pressure to vacuum. I mean, the exhaust pulse is pressure (obviously), but the void behind the pulse is a vacuum, which pulls air/exaust from a non companion cylinder. Once the car shuts off atmoshperic pressure rushes into the pipe to equalize.

"i agree with u that the pressure drop would help speed up the flow out of the cylinder, but don't u think if u don;t have any restrictions then u will have a greater pressure delta?"
Definitely on a boosted car. A lot has to do with valve work, rpm valve events (cams) etc.
"A friend of mine is an exhaust engineer and iam hoping he will get back to me with his opinion as well which i will post on here.
Thanks,"

Cool. I'd think like everything from port work to valve angle info would make a considerable difference. Plus, turbo cars are totally different. I mean we have a big *** restriction--the turbo.

 

Post vids, Id like to hear it! Have you had it tuned for a straight pipe?

 

not tuned yet, i have to get it tuned soon

 

ya pls post some vids would liek to hear and see it.

 

Ok, time to get this cleaned up for the benefit of everyone.

First of all, the notion that a lack of backpressure reduces power in a NA engine is pure myth. Understanding NA exhaust system design reveals that backpressure never does anything but reduce power and torque 100% of the time. The end.

Now that we have that out of the way, an NA engine depends upon a negative pressure wave to enhance scavenging and increase VE (volumetric efficiency). If we have a correctly designed system, but the pipes are too large, this reduces torque (VE) because it reduces exhaust gas velocity. Backpressure has nothing to do with it, and arises from the opposite problem (pipes too small). Sizing and tuning pipes with an NA engine requires a balancing act between maximizing exhaust gas velocity while keeping exhaust backpressure in check. Too far in either direction reduces power. It's tricky to get it right, and it is rarely done to perfection with off-the-shelf performance parts.

A turbo motor does not depend upon exhaust scavenging to the extent that a NA motor does, and the turbo makes up for a multitude of exhaust inefficiencies. The most critical exhaust parts in a turbo engine are the manifold and the turbine housing. In a turbo motor, once the exhaust gas has 'spun the wheel', its job is done. It can do nothing else at this point but get in the way. This is why one can stick a 10" diameter downpipe on the back end of the turbo and it will lose no power. In our case, it probably won't make any more power than a 3" downpipe, but it won't cost power.

 

makes sense. thanks!

 

a catless tbe with a muffler and no resinators is what i run. quiet enough for dd and allows for the most power

 

which tbe do u have ?

 

Mandrel bends are important. Meaning at each turn of the pipe, the inside diameter of the pipe remains the same.

 

btw is mandrel the company of the company that makes them or type of bend?

 

Mandrel is the style of bending used on the exhaust where the tubes inner diameter is unchanged at the bends. Crush bend is what most OEM exhausts have and maybe some aftermarkets, where at the bend the inner diamter changes (gets smaller) due to the process they use for bending the pipes in shape.

 

Just do a downpipe, testpipe/cutout.... Save you alot of money and when you get sick of the noise you can close it manually for super cheap(free labor =-p) or buy a race ready cutout ( this brand because of a lifetime warranty that they actually back up... failure of unit or speed bump... they cover everything)

Cheers!

 

Think of the scavenging effect like drafting behind a car at 200mph in NASCAR... is it less 'work' for a car to draft behind another car or to be the head car?

Get the Megan O2, AMS Downpipe and turndown if this is track only. If you want a full-back straight pipe get the downpipe and have a local shop do the rest for cheap or look into the buschur unit that is similar.

I think there is also a RRE/Works/some company that has a straight pipe that replaces the factory muffler if you are interested in keeping the rest of the factory exhaust.