I am just starting to look into adding some extra performance but trying to keep the sound levels as close to stock as possible (don't mind a slight increase). I've read on other posts that keeping the stock muffler but adding after mkt headers and cats is one option to increase performance but keep sound levels under control. My question is what are the gains by taking this approach and is it worth the time/money to do this without replacing the stock muffler?

I love the sound of some of the after mkt mufflers but have requests from family to keep it under control.

Thanks.

 

There have been many posts on this subject, so suggest you do a search. Bottom line seems to be that performance gains are obtained only when less restrictive cats are put on. The headers etc. seem to be more meaningful when combined with the cats and perhaps higher performance mufflers. But any gains from exhaust changes are quite limited. Most claims of improvement are subjective, not measured.

 

https://www.6speedonline.com/forums/...d.php?t=119461

 

I have switched my mufflers back to the stock PSE and still run the AWE cats and Evo headers and intake. Still can be loud when I want it, and can be quite when it is needed.

 

I switched my muffler back to a stock (not PSE)muffler while maintaining the AWE headers and Cats and I am very happy.

 

Using stock mufflers with more open cats and free flowing headers makes no sence at all...plus not doing any of these mods with out re-programing the ECU makes even less sence. WASTE OF MONEY.

 

Not true at all. Up to a point, freeing up the exhaust flow increases the intake flow which increases the MAF signal and which increases the fueling.

 

The standard mufflers on a 997S aren't particularly restrictive - have a look at AWE's site - there are plenty of dyno graphs and they clearly show little gain by going to a 'straight-through' muffler design. Adding well-designed 200-cell cats will show gains - the standard ones on the 997S are quite restrictive. Headers tend to give more top-end at the expense of a little mid-range - up to you which you want.

Bear in mind that the standard restrictive cats do a lot of the silencing of the exhaust on these cars. Simply swapping cats will give you power (16-18 BHP wheels) but your car will be as loud as if you'd swapped the mufflers for a medium loud sport design but retained the standard cats.

As for mods requiring a re-map; yes, to get the theoretical full benefit from any mod, the ECU should be re-mapped. If you change the volumetric efficiency of an engine at a certain rpm, the timing requirement can change. Fuelling map changes are normally unnecessary as the MAF will simply measure the increased airflow and add fuel accordingly to reach the programmed air/fuel ratio for any given combination of load and rpm. However, external, bolt-on mods make only small gains (10% more power if you're lucky) and the difference in timing requirement for this amount of change is usually small. Hence why these mods can work reasonably well with no remap.

Ian

 

Anyone had a chance to compare results of X51 type header (short primary)and long primary tube (Awe, et al) type? Interesting article on header design above courtesy of Ian. Gerry

 

Wrong. I feel a significant difference even before I had APR put their software on the ECU. What I have got improved performance with less noise. It is still noticeably louder than stock but with the Stock exhaust most of the noise is behind the car. Shortly I will be trying a Remus exhaust which is supposed to be quieter than other after market mufflers but better flowing then stock.

 

+1

The Cats give the biggest gains in power, and the mufflers the least. I am running stock software and the car runs smooth.

 

My feeling is :
a) either keep the car bone stock.
b) mod this for efficient performance .

This half and half scenario may get the feet wet but it's not swimming . Better off to stay dry .

 

I don't agree, I think that we need to make compromises and different things work for different peoples needs. 911fun wants a little extra power and some unique sound levels, but doesn't want to be too loud. He is definitely on the right track to achieving his compromise.

 

Usually a long primary will give more power. But if they are to be very effective you will need to change the ECM. That is just the way it is.

 

I agree with dndodd as im running awe cats only.I had awe cats and fabspeed muffs previously and found it to be very loud.Also non turbo daily driven street cars need a little back pressure or you end up with a very narrow powerband.