Exhaust

[Ryan from Ohio]

Well I bought me a fart cannon for the Buick.

Last night I cut off the stock exhaust.

This morning I mad a backet to attach to the factory one and I will have it welded on.

I have yet another bracket to make and design. I will get the muffler mounted up.

From there Im taking it to a muffler shop to have a connector pipe welded/fabed in because there not enough meat for couplers...

[GlassWolf]

is that muffler designed for your type of engine?
if the Buick is EFI, have you considered modifying teh onboard computer to account for changes in backpressure from the modded exhaust?

are you doing a catback or just the muffler or changing out the motor manifold(s) for header(s) too?

[Ryan from Ohio]

Just the muffler.

Its on now. I got all the pieces made I need made. The old muffler is cut off. Im kind of locked into this deal now.

Im not readjusting any computer or anything. lol

[Justin from Detroit1]

He's ricing out his Buick lol. He just wants to sound like a swarm of MADD BEEZ coming down the street lol. Screw real performance, right Ryan? lol j/k

[Ryan from Ohio]

I really dont think it will be that bad.

It has a cat convertor and some kind of a chamber right after it.

With no muffler it really isnt very loud...

I dont think this muffler change will make it sound to bad. Maybe just liven it up a tad...

Dunno...

I hope to have it on and done by Friday...

[Justin from Detroit1]

Well it's not a 4 cylinder so it won't sound as much like madd beez.

[Jonathan]

There aren't many factory mufflers out there that can choke a motor down worse than a catalytic converter, the performance gains will be minimal. As long as it's a 6 cylinder or more, it's ok :)

[Ryan from Ohio]

With the exhaust off theres not much power...lol

I hope this doesnt turn out to be a mistake.....

[Justin from Detroit1]

If it is, drive that bad boy up here and let my friends at PF&E give ya a full custom exhaust with stainless steel and mandrel bends for real cheap (under $300)

[GlassWolf]

Pipe flow doesn't behave like normal air flow... so there is more to be concerned with.

Turbulent flow actually results in a greater volumetric throughput than laminar flow even though it's coefficient of resistance from friction with the walls is higher. It has a greater "average" velocity profile. So in theory you can actually make an argument that mandrel bent exhaust pipes are bad. How so? Because mandrel bent piping is smooth enough that laminar flow can result. This will theoretically reduce your overall flow rate compared to the exhaust shop "crinkle" bend approach. So why do all companies make everything mandrel bent? Can we say marketing? Also, there are some cases when the unit is properly tuned with the right diameter and so forth that yes indeed mandrel bent is better.

more on the topic

"Contrary to common popular belief, a larger exhaust does not always result in better engine performance. There are situations where an engine could loose low-end torque from "too little" backpressure. I know it seems counter-intuitive to think that an engine actually needs a certain amount of backpressure but here's why. Most engines are set up from the factory for a certain level of backpressure. Changing the exhaust can create a situation where the cam has too much overlap for the RPM range it's being driven in. In that case, the incoming fuel/air will come in the intake valve, only to have part of it sucked straight out the exhaust valve without getting burned! Obviously, engine power will suffer if it doesn't get a full fuel charge to burn. Proper backpressure will prevent this. So will choosing a more appropriate cam for your RPM range, however.

There is another, more complex reason why 5" pipes on a normal sized naturally aspirated engine won't work. It isn't that the engine needs more backpressure, it's that static pressure is only half the equation. The equation for the "equivalent" pressure at the exhaust port is P-pv^2, the static pressure minus the exhaust density times the square of the exhaust velocity at the port. A 5" pipe may see a slight reduction in static pressure but will kill off the velocity making it harder to push the exhaust out. Some tuned header systems can make the exhaust velocity high enough that the engine effectively has a lower amount of backpressure than the atmospheric pressure! This is known as exhaust scavenging and is what separates good headers from bad ones.

In the case of a turbocharged car, everything is different. They can run a huge exhaust pipe, like the HKS 5" pipes and see a performance gain rather than loss. The reason is the turbine. The exhaust coming out of the cylinders only sees the velocity going into the turbine. The velocity drop across the turbine doesn’t effect flow. On a turbocharged engine, there is no need to worry about the exhaust velocity downstream of the turbine. The size of the header primary tubes and collector, or the exhaust manifold design, still plays a larger role in determining exhaust velocity, but the pipes downstream of the turbo are a lot less important.

As for the turbo itself, you want to maximize the pressure (and temperature) difference across the turbine for the highest efficiency. A low velocity of the gasses exiting the turbine won't make it any less efficient; in fact, it can theoretically improve the efficiency of the turbine. So the exhaust on a turbocharged car can be designed to minimize static pressure, without concern for the exhaust velocity.

So what does all of this mean? It means that while a 5" exhaust would be desirable for a 350 hp turbocharged Supra, it would be a very bad idea on a 350 hp naturally aspirated Camaro and an awful idea on a 1.8 liter naturally aspirated Honda."
-ragtop