720 Exhaust Options

[Dimka247]

On 6/16/2014 at 8:09 PM, datzenmike said:

If you have no smog testing, loose the cat and run 2" pipe all the way back with the largest muffler you can find that will fit the 2" pipe. If getting custom bent system, maybe go 2 1/4" pipe. There is no magical hidden horse power increase with the exhaust, and headers are a money pit of disappointment. The makers won't tell you that the stock system is pretty good by itself.

No. The car will run worse, so a hard NO. Exhaust scavenging is when a properly shaped exhaust manifold and a proper diameter exhaust pipe create a sort of vacuum that completely evacuates spent gasses from the combustion chamber and even help to draw new air in when the exhaust and intake valves overlap open. Back pressure is when the opposite happens; when restriction in your exhaust prevent gasses from completely evacuating the cylinder. Stock exhaust systems aim for maximum scavenging but are hindered by cost and their primary purpose - which is to keep things quiet. A good exhaust system starts with a properly shaped manifold that will route the exhaust pulses so that they enter the exhaust pipe one after the other without conflict/turbulence (which is why you see headers twisted to create different lengths for each cylinder). The pipe following should not be too small because it will create back pressure; but it shouldn't be so big that the exhaust gasses expand too far and lose momentum (which will in turn create back pressure). Exhaust fabrication on a professional level is an art beyond just pretty welds - a lot of math goes into it. On an amateur level I wouldn't recommend any excess since you are likely to waste money with no or worse results than stock. For our slow cars even a $10k custom exhaust will give no noticible gains, I would just focus on the kind of sound you want and invest the left over cash into something else. If you MUST do something a slightly better flowing ebay header and a pipe 1/4 inch over stock to a budget throaty muffler should do the trick. Sorry if I come of rude but I hate to see this lie about large exhaust systems keep spreading decade after decade.