"I'm doubting that you'll get any significant HP gains out of a muffler swap on our cars. Che's headers bumped mine 15 HP ... but mufflers are advertised to give 3-4 but they are full of crap if you ask me. It's all about changing the sound with a muffler."
Interesting that you got that kind of HP bump with headers, must be the 2.5L engine. I just got a few HP on the dyno when I put headers and 100-cell cats on my 2.7L. I have used several mufflers and only have the butt dyno to go by, but when added to my car with headers and cats, they seem to make a difference, but not necessarly the way you would expect.
For example, when I put the Gemballa muffler on the car, I could swear that it was slower and not as responsive, albeit very loud. I have been running the stock 2.7L muffler most of the time I have had the headers and cats on the car while I have looked for a higher flow muffler that does not have the 2-3 K resonance.
One of the characteristics of my car with the headers/cats setup is when you get on it, it accererates pretty well from 4K until it hits 5.5K then there is a noticable jump in accereration moving quickly to 6.5k.
Well, I just installed a Dansk OME-style "sport" muffler, which has higher flow rates than the stock muffler. It is only slightly louder than the stock muffler but has no resonance issues.
I definately can tell a difference via the "butt dyno" with this muffler. When I get on it, the car pulls strongly from 4-6.5K without that transitional jump at 5.5K, something differrent is going on. I have dyno figures with the stock muffler (little over 200 hp at the wheels), when I get a chance, I will do a run with the Dansk muffler and see what the numbers say.....
Ed
