Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

[GinsuGuy585]

Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

So I wasn't able to find a specific answer on which one of the available options is best.

What I think I know:
Straight Pipe - should offer the best performance, since it has no obstructing or distorting properties. Also will have more raspy sound.

Hollow - cheapest (duh) should be less raspy then straight pipe.

Test Pipe - Best sound? I would assume the resonating features remove higher frequency sounds. Worst performance, also assume that the baffles are somewhat restrictive.

What I don't know:

Are my earlier statements correct?
How hard are cats to hollow out?
Sound and performance - trade off or is there an ultimate solution? (micro black hole?)

What would/did you do?

[greasemonkey]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

test pipe and straight pipe are the same thing. Simply put, if you have 02 sims then go with a straight pipe. If you have to go through the sniffer or visual inspection, go high flow cat. They may hinder 1-2 horses at best. As far as sound go, you may end up rasping more if you don't have a decent muffler.

Its hard to answer your question because hollowed out cats, straight pipes, and test pipes all flow the same.

[GinsuGuy585]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

The test pipe style I'm referring to is resonated so maybe it's a little worse.

So hollow cat and straight pipe are the same? There isn't some difference in flow due to the expansion and contraction of the exhaust in a hollow cat?

[IDoVoodoo]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

just get a dynomax bullet. you won't lose any horsepower and it'll take some of the rasp away.

[silvachris1]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

There isn't some difference in flow due to the expansion and contraction of the exhaust in a hollow cat?

According to volumetric flow properties, no. A fixed volume of gasses exits your engine, when RPM is steady, and flows out your pipes. For the most part, those gasses have a fixed speed since the variation doesn't change if the RPM is at a steady rate. Given those factors...... the flow of the gasses will slow down when the diameter increases, but will speed back to the same rate when the diameter decreases.... assuming that the diameter returns to the exact same size.

It's like water flowing from a hose, if you increase the outlet of the hose (like when removing the spray nozzle) the water will flow out, but if the nozzle is on and water is forced through the smaller hole, it shoots out. The flow in the hose is still the same until the diameter changes, but conversely, it must change again when the system changes.

To continue this Fluid Dynamics lesson, the air is moving at a fixed flow rate, measured in cubic feet (or inches) per minute (or second). The gasses must travel within a fixed area. Since our stock pipes are 2.25", the area the gasses flow over is (pi)[(2.25/2)^2] = (pi)(1.125^2) = 3.976in^2. To get the volumetric flow rate, we need the velocity of the exiting gasses.

Since I don't know, and google gives me nothing to go by, we're gonna make up a number. Here's where things get hairy, but this number won't matter anyways, since I'm just going to use it to show the rest of the calculation. The stroke length of the 3800 is 3.4", and let's pretend this thing only has one cylinder so I don't have to take other things into account. Let's assume the engine is at a steady 2000RPM. The exhaust valves are open on every other revolution, so we only have gasses exiting part of the time (duh right?). So in one minute, at 2000RPM, the exhaust valves will open 1000 times, pushing out all the volume contained within all the cylinders. 3.4"x1000 is 3400" per minute, or 283' per minute. That's 4.72' per second. Anyways, since our area is in square inches, let's get a velocity that is measured in inches. 3400/60 = 56.6" per second That's our hypothetical (and most likely very incorrect) exhaust gas velocity for this cylinder. Anyways, wrong or right, the rest of the calculation still works out the same way.

So, we have our Area and our "Velocity". Volumetric flow rate is Area*Velocity, so (3.976in^2)*(56.667" per second) = 225.307 in^3/per second.

And with all that crap out of the way, you can see how changing the area in which the gasses flow will change the volumetric flow rate. Therefore, and furthermore, I'm done with trying to impress people with stuff that's prolly not right anyways.

[f-tothe-ill]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

Just get a highflow and be done with it. The minimal loss of flow won't be at all noticeable and it will help out a lot with the rasp issue.

[RadRacer]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

Like everyone says. The flow rate is very similar in all 3, but the high flow will give a better sound. You may lose 1-2HP, but what's that matter if your car sounds a lot better? If you don't care about sound, then straight pipe it (I did it) and leave it alone. It'll flow abit better than a hi-flo cat, but not enough for you to really see a difference, and you'll save some cash.

[GinsuGuy585]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

Silvachris1: Thanks!

For now I'm going to try hollowing out my cat, and if the rasp drives me nuts :banana: I'll order a bullet asap. I can't remember if the previous owner welded everything, if he did I gotta go talk to a friend at the local muffler shop.

I looked at the setup I have a little more and I don't have a muffler at all (thought I saw an inline before) it turns out I have a normal cat -> flowmaster resonator -> Y-pipe -> dual exhaust. So when I hollow it out... might need some hearing protection. Surprisingly it sounds very good without a muffler; I got pulled over for speeding a week ago and the officer let me off with a warning saying he loved the V8 camaros the state troopers have (didn't correct him, just silently counted my blessings :D.)

I'll try to get a pic and some videos when I get home from work.

[silvachris1]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

Silvachris1: Thanks!

Welcome.

[GinsuGuy585]

Re: Test Pipe (resonated) vs. Hollow vs. Straight Pipe: Which is best?

So the sky is falling and all car work is off until I get a place I can do it indoors.

On the upside, I love being able to powerslide/drift with 180lbs of sand in my trunk, using less than 1/4 throttle :rock: