944 Exhaust Upgrade?

We all know one of the best ways to improve power and performance is by letting the engine breathe better. In a future article we will go over some different options for improving the intake but for the sake of this article, we are going to talk about the exhaust. The two obvious choices for this are intake and exhaust. For our 944's there are also two reasons for replacing our exhausts. One is for performance. We want more pep out of our 944. The other reason is for sound. We want that growl that turns heads and satisfies something inside of us.

Strictly speaking, if you are thinking of replacing your stock exhaust to improve performance you might want to think twice and consider using the money for something else. The stock exhaust of the 944 is already very impressive.

How impressive is the exhaust of the 944? Consider this; the 944 was the first car to test the same on the dyno with and without the catalytic convertor. That's right, the dyno showed no difference or loss of horsepower or response when the 944 was run with and without the catalytic convertor. This is mostly due to the design of the catalytic convertor. It is longer and more free flowing that a conventional catalytic convertor. Additionally the the exhaust headers for the 944 are very well thought out. Some of the 944 models came with a cast header whereas others came with mandrel bent pipes. The 944 exhaust was very well thought out and not easy to improve upon.

So why all the talk about performance, cat back systems and like? In all honesty, it is only about money. They want your money and in order to get it they will make performance claims that just cannot be backed up.

Is there a better exhaust option for your 944? Consider what you already have and weigh options and decide what is best for your needs and desires. Just changing your muffler or catalytic convertor isn't going to give you an improvement in performance. Unless you are willing to do a radical exhaust change, you aren't going to see any notable change at all. That being said, if you have an older catalytic convertor you might want to consider changing it out. Catalytic convertors get clogged up and this alone will cause a significant loss of performance and fuel efficiency. Since you probably already understand how a catalytic convertor works and for those who don't there is a wealth of knowledge already available on the internet, I'll keep it short. This is really a demonstration in flow. The brick in a catalytic convertor is made up of thousands of little holes, passages really that the exhaust passes through. If the catalytic convertor is old or if the car is not running well, burning oil, running too rich, these passages clog and restrict the flow of exhaust.

So now on the topic of replacing catalytic convertors. If you are going to replace the catalytic convertor, you will want to replace it with a high flowing performance cat. Don't just take the sales persons word for it, look at flow, CFM and choose the one with the highest CFM. There are those that will tell you you're wasting your time on a higher flowing cat, you only need enough CFM's to handle the engine out put. In theory, this is true, however, considering that all catalytic convertors are going to experience some clogging, the higher flowing cat is going to give you better performance for a longer period of time. Another argument you are going to hear is for back pressure. We want a free flowing exhaust but we need back pressure for torque. Even with a better flowing cat, you're going to have enough back pressure from the rest of the exhaust that you aren't likely to experience any loss of torque from a lack of back pressure. If you have an older catalytic convertor, you'll absolutely see the difference in performance. However, if you have a fairly functional catalytic convertor, you aren't going to see any noticeable change in performance by changing out your cat.

So now that we've gone over replacing the catalytic convertor, let's look at how we are able to make changes in our exhaust to get some noticeable performance changes.

What we did with our test 944 was to replace the entire exhaust from the headers to the tip. We used an 2 inch mandrel bent, aluminzed steel pipe but on other projects we've used stainless. Both work just as well but the stainless will cost you more. We had a 3 inch, high flow, high performance cat installed. The cat runs to a 24 inch resonator. We used the resonator to help add some back flow pressure and take out some of the twangyness from the exhaust sound. We used a Borla muffler and put it in the same place as the original and finished it all off with a resonator tip.

This exhaust gives us more flow which has improved our performance. We also have a very impressive growl that screams performance and turns heads and makes us want to drive through parking garages. We actually get comments on that growl and how great it sounds.

If you are at the stage where you are ready to replace everything, then do your research, find the cat that is going to give you the most flow and the muffler that is going to give you the sound you want. Pair that with the right resonator to tune that sound and give you some back pressure. If you aren't ready to make that investment just yet, save your money, keep your original exhaust and put your efforts into other performance upgrades.