Why some aftermarket exhaust have a different design than what we already know is a good free flowing system.

I was looking into the exhaust piping for my old M3 as well as the exhaust on the current g37 and the upcoming GTR... and noticed the all share a very similar structure.

I know on the M3 it was hard to find a aftermarket exhaust that would yield gains without removing the cats/headers. Even while going FI it was better to keep the stock exhaust than to gamble with a aftermarket one that could make you lose hp over stock.

After looking at a few of the exhausts for sale for the g37, g35, 350z.... i wonder why many of these companies didn't keep the original design, or even copy one that's proven to work good.

Of course i'm not a manufacturer and I've never tested the efficiency between the ones in question, i'm really just curious and thought of it as an interesting subject to discuss.

I'll be interested to find out what some of the vendors on this site have to say... i wonder is they test many different ones and how they find a good compromise between cost, efficiency, assembly difficulty, etc.

 

Some designs are more straight than others. Stock is for Fuel efficeny and quietness. Its not always the best though. after markets that want the most power will go for the straightest design to get the power out.

 

correct me if i'm wrong but..... in a N/A motor, isn't there a sweet spot for back pressure that provides better gains as far as compromising hp/tq balance.

 

Im thinkin all that back pressure talk isnt true anymore ... not sure tho...someone else will come along that knows more...

 

To not loose low end power you need a certain amount of back pressure

 

Logically i assume that less back pressure will make you lose low end tq and gain top end hp.... I'm sure this translates into different performance numbers/time.

Now if you throw in intake, cat removal, headers into the mix... how much back pressure is necessary to get to a good compromise in hp/tq numbers that of course will yield better performance.

My point is.... maybe straight is not always better, maybe 2 mufflers instead of one is not better, maybe our engines could use 2.75 instead of 2.5... etc

 

There are a lot of variables to deal with when you start changing intake and exhaust on any car. To maximize performance gains you also need to make sure that you have your ECU reprogramed to take advantage of the new hardware that you are installing. Because the manufactures, like Infiniti, program their cars for a balance of performance and every day living there is room for improvement on the software side too. That is one of the reasons I am excited about Technosquare's ECU reflash that they are working on. It really brings together these types of mods.
The engineers of these cars do a great job with the specs they are given. The problem is that they have to compromise to make the bean counters happy and to sell as many cars as they can. The more specialized they make them the less they will sell.
More fun for us to mod mod mod!!!!!

 

each tunning company has their own idea as to whats the best

 

Back pressure is a bad thing and is the enemy of performance. The only useful side-effect, depending on who you are, is noise reduction. Poor flowing stock exhausts and OEM style chambered mufflers are typical back pressure generators because heat and exhaust gases cannot efficiently escape causing resistance in the motor that the cylinders must overcome during the exhaust stroke. Any effort the cylinder has to make to FORCE the exhaust gas out (because of back pressure) is wasted power.

Back pressure being a "good" thing is a myth and misunderstood by many.

http://auto.howstuffworks.com/question172.htm
http://www.flowmastermufflers.com/backpressure.html

Oh and here is Magnaflow's guide for pipe sizing:
http://www.magnaflow.com/wideopen/performdata.asp