Im planning some lite mods to my 03 sedan,, after I have fixed all the common issues. Intake wize, it will get the motordyne plenum spacer, and an ebay throttle body spacer. Already has a z tube,, will also get a high flow filter.

So, I want to also mildly mod the exhaust. Wanting better flow, less weight, slightly louder. A common suggestion is to get the coupe mid pipe section. So, does it flow better? Is it less weight,, if so, how much less? Is it louder? Is there an aftermarket equivalent? Going to stick with factory muffler style, so is there an aftermarket that flows better and fits like stock?

The car will also eventually get some light weight rims and good all season performance tires. Just want to make it quicker, more efficient, and sound a little meaner. The z tube is fantastic sounding inside the cabin. I havent been able to listen from outside yet.

 

I did a quick search and found some catback exhaust systems, but only the high price items make any claims to higher flow. What about the y pipe? Is one design better than another? Theres the long twin tube design, then theres the wide design with a short single tube at the rear,, theres the one that is shaped close to stock but made from shiny stainless..... whats the performance difference?

 

Some pictures of the different y pipe designs. There are versions of these for around 400 bucks, and also for around 110-200 dollars. Of course the popular tuner brands are more expensive,, but the cheaper versions look exactly the same. My concern is which design offers the better performance gain.

 

Usually the reason behind the name brand systems costing more is they actually spent the time and money on R&D to prevent cabin drone and tune rasp to an acceptable level while maintaining a high level of quality assurance from one part to the next. They usually dyno tune their systems and have had multiple revisions before finally settling on the final product and their cost is set higher to recoup the initial investment they spent in designing the system, as well as the higher quality materials used during manufacturing.

After these systems have been around for a while copycats start to show up, they don't typically involve any actual testing aside from basic fitment, the QA is spotty at best and usually just involves the welds but does little or nothing for fitment, the materials are much lesser quality with thinner walls, thinner flanges, and materials that don't have much corrosion resistance. Usually a muffler shop will be required (or someone with a table bender) to make slight corrections to the pipe because fitment will be a little off, drone can usually be alleviated. Drone can be alleviated by adding resonators and changing mufflers, same with rasp.

Knockoff systems (and even some name-brand ones) usually have little in the way of exhaust scavenging or pulse tuning, don't think of the exhaust as a solid stream of air, it's a rapid fire series of smaller pulses and depending on WHERE it creates velocity in the system it can actually pull the air behind it (scavenging) and take some of the work away from the engine thus freeing up even more horsepower, this is where dyno testing and proper R&D pays off, a well designed system will be able to make HP claims that are backed up and dyno proven and have better results than their competitors.

The coupe midpipe is used mostly to tune the exhaust note a little deeper, don't expect much in the way of performance, the most restrictive components of the stock system are the catalytic converter and the muffler, pipe diameter is an issue as well and you really need to replace the entire system to feel results.

I think average gains fall in the range of up to ~10hp for a well designed catback and ~8hp for a HFC/test pipe.

You need a proper tune to really bring the whole system together.

 

Since you're doing minimal mods the mid pipe will give your exhaust a better sound! All the other mods like the y-pipe will be a waste of your $$ since you'll see zero improvement! Your idea of plenum spacer and mid pipe will make your G more enjoyable to drive, without all the mod headaches!
Gary

 

Thanks guys. Ill look for a good coupe mid pipe then, and possibly a free flowing muffler. The ztube really makes the car feel faster in the mid range I think mostly because the louder growl sound. So the acceleration seems to match the sound,, hence "feels" faster. Im sure the actual effect is minimal, but yeah, more enjoyable for sure.

 

Magnaflow makes a great replacement muffler for your G you can buy direct from them, have a muffler shop install it! Nothing is better than having a job done right, no concerns down the line...Gary

 

Don't waste your money on a throttle body spacer, they're worthless.



Look at getting a Turbonater, they're the shizz.

 

Whizzzzz!

Plenum spacer is all you can do on a reasonable budget. The intake noise from it combined with a Z tube (or a capped G tube) is very nice.