3" Exhaust Upgrade?

[ImportSlayer347]

I have been considering changing out my exhaust setup for better flow and a meaner sound.

My current setup...
BBK Longtube Headers 1 3/4" Tubes with 2.5" Collectors
BBK Off Road H-Pipe
Flowmaster 2.5" American Thunder System - Series 40 Mufflers

I would like to go with a 3" system with a louder/deeper sound. Is it worth it? Has anyone done it? I have read some people actually experienced a LOSS in power. Seems impossible to me.

 

[skunk21]

you will loose torque.

 

[ImportSlayer347]

Please explain.

 

[90lxcoupe]

Please explain.

we cant tell you if the car will loose power if you dont tell us what the engine combo is...

Generally a 3'' exhaust is only good for cars making 500 hp, thats the genereric number where people start stepping up to a full 3" system. You loose backpressure and loose low end tq with the bigger exhaust but if the motor breathes hard enough it will make more power up top. It basically just shifts the powerband up.

If your switching to 3" just to make it sound cooler, than its definitly not the right reason to do it... just buy a set of race mufflers if thats the case

 

[ImportSlayer347]

Sound is only a small part of it.

347 ci Stroker
Compression - 10.8:1
Naturally Aspirated
426.6 HP
408.6 TQ

I also plan on putting a 75 shot of nitrous on it. I can answer just about anything you need to know about setup. It is a long list though. What else do you guys need to know to answer my question? I appreciate the help.

 

[ttopstang]

the more an engine can breath the better. that back pressure myth is still going around but just ignore it. only 2 strokes require backpressure and i dont think you 347 is a 2 stroke.

 

[ImportSlayer347]

It is actually a 347 dirtbike motor...so it is a 2-stroke.

J/K. I never knew that. Why is it only 2 stroke motors need backpressure?

 

[ttopstang]

that should be one fast motor!!

i dont know about ALL 2 strokes but i know they have power valves that opene and close with the backpressure pulse of the exhaust, if you run no exhaust, they can get stuck open. 2 strokes really dont have any valves except those 2 exhaust. im not too familiar with them, i just know that the back pressure on a 4 stroke is a myth. y dont we all just run 8 catalytic converters and 6 mufflers and get the most back pressure we can get? lol.

 

[purpl_stang]

Sounds like a good combo you got there but my buddy has a 331 with the 3 inch flowmaster kit and it doesnt sound all good it you want to sound better then i would go wh the SPINTECH SUPER PRO STREET mufflers i have heard those on a biut 5.o and they sound awesome thats my next move for sure.

 

[skunk21]

you loose lower rpm exhaust velocity with a larger dia pipe this reduces scavenging. Think of scavenging like a siphoning effect, keping the exhaust gases flowing and clearing the cylinders. The problem with too large of a dia. for the particular application is you are now pushing the gases instead of pulling. you will make gains like stated in the higher rpm range but kill your lower off the line power. ttopstang backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect like I stated. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. This all gets tossed out the window for turbo cars, but we aren't talking about one. it's all about finding the happy meduim.