Thread: Exhaust system....I need your ideas?

Bull GTi, you are underestimating the flow potential of a 3" exhaust. However, you're getting towards the point where you should consider something larger, and like you said if you want to keep the same flow capacity as your current exhaust dump you will want to do something large.

If you can manage to fit a 3.5" downpipe then more power to yah. That will be the most important piece for you. The downpipe. Getting that large and flowing well is more important than the rest of the exhaust. I think as a good compromise maybe you could try for the 3.5" downpipe and then do a 3" exhaust. It should be very similar in performance to what you have now. However if you can afford to do an entire 3.5" exhaust you could do that. It will clear, and it will fit, and it will work. But it will cost you. I think 4" pipe is cheaper than 3.5" pipe, but I could be wrong.

Ideally open yes, but if you're going to run all the way back, you still want to make sure that you have velocity all the way out to the exit. If the velocity is not there you just end up having hot gases pushing cooler gases. Though it may or may not impeed flow that much, it still does.

4" is pretty overkill though. I'm just stating my opinions though. I'm not going to tell you how to do your car. 4" would probably have a cool sound to it though.

I know what you're saying, and it's wrong. Flow analysis calculations (taking into account that exhaust is not an ideal an incompressible fluid) at least do not back that story up. Nor do the real world results. And if you think about it, if that were true, then an open dump would make the least power, because OMG all of a sudden the exhaust has entered a gigantic pipe (the atmosphere) and is now traveling ultra slow and it would cause a backup in the system. Except it doesn't.

NVM

Charles (Snickers) had 4" Exhaust on his 500+HP G20....i say why not go 4" for better flow

If you're annoyed by drone, maybe you should run the smallest/quietest exhaust you can, and run an electric cutout. A 3" exhaust is far from quiet!

It'd be sweet to tie it into the current setup to have the best of both worlds!

^ That's a good idea.

You are basically right don't back down

There are two different things going on with say an open exhaust housing and large diameter pipe. The exhaust is not only moving straight out of the pipe. There is turning and potentially pockets,and swirling and getting in the way of the main stream of exhaust if the pipe is too big. This effect the turbulence is increased with the bends and other flow restrictions found in the exhaust.

I think a good visualization would be pouring liquid out of a 2liter pop bottle (it is not exactly the same physics but just so everyone has a picture in their heads) . There is a point that the fluid flows the fastest out of the bottle. It is not straight up and down as that causes turbulence and the bottle to burp and collapse. At just the right angle so there is a space for air to go back into the bottle and keep the flow of liquid leaving the bottle smooth.

You have to match the exhaust flow to the exhaust pipe size for best results. This is not to say that the car still won't make tons of power, it is just not the most that it can make with exhaust sized for flow.