Help a dummy figure out his exhaust system! 😉
07-29-2018, 10:08 AM
#1
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Help a dummy figure out his exhaust system! 😉
I'm trying to put together a list of everything I need to redo my entire exhaust system from headers all the way to the tips.
Right now, I'm looking at a set of headers with 3" collectors, a 3" inlet/outlet Thunderbolt catalytic converter, and a 3" cat back system. But I'm getting tripped up at the Y-pipe. One trend I've seen is that nearly all the Y-pipes seem to go to a 2.5" crossover, even if they came from a 3" collector (like the Y-pipe on the Hooker 2055's). I also noticed all but one model of any bolt-on catalytic converter were 2.5" inlet/outlet on Summit Racing, hence the Thunderbolt cat. My plan was to keep at 3" from the collectors all the way back, but either there are performance reasons why most parts seem to circle back to 2.5" piping, or the site is playing it safe and only showing parts that match the OEM specs. If almost everything goes back to 2.5", is there much point in even trying to run even a full 3" exhaust system? I was hoping to install everything myself, but I'm almost wondering if I'd be better off having a local exhaust shop fab the whole system for me if that's the only way to keep a true 3" system front to back. I want to go to 3" pipes because I plan on eventually swapping in a 350, so I can take advantage of the improved exhaust flow now and be prepared for a bigger engine down the road. But I also want to make sure that I do the system right to get the most out of what I install, even if that means I need to let it go to 2.5" at some point just to maintain the right amount of back pressure. Any input is greatly appreciated. 
07-29-2018, 11:32 AM
#2
07-31-2018, 07:53 PM
#3
Re: Help a dummy figure out his exhaust system! 😉
First, back pressure in an exhaust is never a good thing. That doesn't mean that necking down someplace might not be beneficial, sometimes it can increase flow (this is especially the case in exhaust ports and header collectors). Second, as you get further back in the exhaust, exhaust cools and it's volume goes down so to some extent you can gain by decreasing cross section and maintaining flow if you can do it without restriction (and in the process, you can actually end up with a quieter exhaust that flows more). Cats and mufflers are typically restrictions compared to an open pipe that size, but what that restriction looks like to the engine is dependent on the design. Finally, the closer the restriction is to the engine the more it affects power production and vice versa.
What works? Well, that depends on what you're trying to exhaust. Real world, you can have engines making identical power that the optimum exhaust would be different for. As a general rule of thumb, larger header tubes = more power, longer header tubes = more torque. My $02- I started with a set of Headman shorties and modified the y-pipe, 3" intermediate pipe to dynomax ultra flow welded and I'm making roughly 500hp through that without much restriction with something that sounds a lot like stock at idle. I put a cutout in it, not for flow but just because you sometimes want to be a little more roudy than stock.
As far as Dyno Don's stuff... the people that have spent the money on it seem to like them, but I've never seen a back to back comparison between it and anything else done right. I certainly wouldn't expect it to make more power than a set of either headman or hooker long tubes and a properly made cat back. I don't see why they would be any better than what I did with my Hedman headers (I could see reasons why I would expect it to be worse), and for the most part, just find it annoying that the only posts about them read more like advertisements than anything else.
What works? Well, that depends on what you're trying to exhaust. Real world, you can have engines making identical power that the optimum exhaust would be different for. As a general rule of thumb, larger header tubes = more power, longer header tubes = more torque. My $02- I started with a set of Headman shorties and modified the y-pipe, 3" intermediate pipe to dynomax ultra flow welded and I'm making roughly 500hp through that without much restriction with something that sounds a lot like stock at idle. I put a cutout in it, not for flow but just because you sometimes want to be a little more roudy than stock.
As far as Dyno Don's stuff... the people that have spent the money on it seem to like them, but I've never seen a back to back comparison between it and anything else done right. I certainly wouldn't expect it to make more power than a set of either headman or hooker long tubes and a properly made cat back. I don't see why they would be any better than what I did with my Hedman headers (I could see reasons why I would expect it to be worse), and for the most part, just find it annoying that the only posts about them read more like advertisements than anything else.
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