alexb76

I was at my local shop who's very reputable and have done on all my cars and was debating the X51 headers, PSE, and even chip.

He said their custom exhaust for another 997.1 C2S customer added 17 Wheen HP, while some folks who had chips and headers gained max 2-3 HP (they got dyno at the shop).

Anyone else with such gains with custom exhausts? I really trust these guys so I am sure their claim is legit.

dianic

For a Turbo yes. For an NA, well... its not as easy. But I dont know for sure.

Edgy01

It's a subject of considerable debate as dyno results can be manipulated very easily to point to anything. Very few aftermarket designers have access to the amount of engineering data that has gone into the fluid dynamics of a Porsche--enough that they can manipulate it to such gains. It simply isn't cost effective for them to replicate that engineering.

alexb76

I agree in principal, but how can you manipulate the dyno? If they did a custom exhaust with higher flow CATS, shouldn't that affect anything? I am sure Porcshe gets the most out of these cars but they are limited to meet all the emission and MPG standards of all continents!

Edgy01

Dyno results -- before, and after, can vary considerably.

For example. if atmospheric pressure, temperature, humidity,--any of those things are not exactly as they were during the BEFORE test, will add an element of variability to the AFTER results. You may chose to attribute the delta to improvements by the hardware changes, but it will be due to these other variables.

kdurg

There are many ways to manipulate dyno data. Engine temp significantly affects power output. Dyno runs done during different levels of coolant, engine and oil temps will have drastically different results, with the cooler runs producing more power.

Redirecting external cooling fan air can have tangible effects on data. The best dyno operators will use high velocity fans directed at areas of the engine and drivetrain in order to simulate real world conditions.

The 997S has four ignition timing maps to choose from depending on the amount of measured knock activity present. On 91 octane fuel found in California, the fuel injection ECU jumps to a less aggressive ignition timing map resulting in a lower power output than on the 93 octane fuel found in other parts of the US.

The list goes on and on. In short, you need to trust the shop/operator and research their credibility. When marketing and product profitability are added to the mix you can understand how some HP claims can be inflated.

With that said, a freer flowing sport cat and lighter mufflers will certainly help the car exhale and pull stronger in the upper rev band. But keep in mind, you may lose low end torque ( where these cars need it most !! ) due to reduced back pressure.

alexb76

The guys I've worked with, do all the prep work right. The got a HUGE fan blowing air into the engine, and are using the latest Dyno system and software, and I don't believe they will manipulate dyno intentionally, although results may vary quite a bit due to tempreture, coolant temp, etc. They were the shop who managed our local team (997 GT3 RS) in 24hrs Daytona this year.

I've seen quite a few dynos there, they tune their race cars with it. I saw a GT-R added about 20HP after exhaust (average of 3 runs before/after)!

camhabib

I think the question you should be asking isn't how much HP you can gain from doing various mods, but how much HP do you need to actually make a difference in the real world. Every little bit helps I suppose, but in the end, whats gained from that help?

Sean in Texas

I am not as familiar with the 911's exhaust system as I am the M3's, but I will assume that since you mentioned headers, that you're contemplating more than just a 'cat-back' replacement. I will say that I know several people who have dyno'd in the +15ish hp before/after from just adding an x-pipe to the E92. Throw in a Race muffler and +17hp doesn't seem too outlandish.

One fella I know was dyno'd at DriverSource on Memorial... They don't have the greatest front fan setup in the world and it can get pretty warm in their bay. I believe they have a fairly decent rep however.

alexb76

Actually the reason I was considering was that I am looking into getting PSE, but for just about the same cost (maybe a tad more),I could get the custom exhaust which supposedly adds extra HP.

Just wanted to know what's real-life experience of folks with custom exhausts.

mdrums

All sorts of ways to manipulate the dyno...its down to the operator and the values he inputs for a given run. Also as other have mentioned, aur temp, humidity different dyno brands put out different HP/TQ readings. Take dyno information with a grain of salt as there are too many variables.

dianic

PSE was a great and unexpected treat in my C4S. If my car didnt have it, I would definitely not pay for it, and go with aftermarket like you say. I think there is a certain point where the increased sound (be careful not to end up with noise) makes up for a possible shortfall of quoted increase in hp.

RonCT

Take a look at some of my older posts from a few years ago. I shared my "real world" findings based on track performance / telemetry data. For about the price you'd pay for PSE I think you could get X51 headers, AWE low-flow cats, and Softronic software to manage it all (stick with the stock mufflers). I didn't care less what "number" a dyno might find and didn't even think to dyno the car. But I did see the performance gains on the track. Was it 10, 20, or 30 HP? Who knows or cares. What I cared about was the car sounded fantastic, felt quicker / more responsive, and the other guys I used to run neck-and-neck with were falling behind (ie: same exact entry speed into a long straight and by the end of it we both knew for sure there was a change). My TraqMate demonstrated (my own data and data comparisons with other guys that did not change their car when I did change mine) also proved out that there was a positive change.

But, we're talking small increments. Even if we were to say that my mods got me 30 HP, that's not significant in terms of how it will feel to you on a day-to-day basis. 0-60 might go down a fraction of a second from 4.9 to 4.8, but the original 4.9 is silly fast already.