I'm trying to figure out if the 2.5" catback from an ST, modded to fit, would be a better choice than the standard 2.25" model for the N/A cars currently...
The 2.5" would have a lower restriction than the 2.25" tubing, however if you go too large you reduce the backpressure too far and start to hurt performance.
Its been discussed that the 2.5" might be a better plan if you are planning on adding additional power adders down the line. If the limit of your modding is an intake and exhaust and nothing else a 2.25" exhaust may work better.
Back pressue is not a factor in direct injection engines, as fuel charge scavenging can not happen, becasue the fuel charge is delivered at full compresion.
Back pressue is not a factor in direct injection engines, as fuel charge scavenging can not happen, becasue the fuel charge is delivered at full compresion.
Soooo if a 5.0L pushrod made 225hp from the factory with 2.25" dual pipes... Why does it gain power moving to a 2.5" system? I daresay that a 2.0L making 160hp from the factory is moving much more air volume than that weezy 2.5L per bank engine.
I honestly don't give much credit to the backpressure theories on modern cars where multiple cats are retained. The cats are a blockage, and force backpressure to be retained for the engine side of things, cancelling out most if not all pulsation in the exhaust flow, and anything post-cat system is made better by open pipes.
I went with the 2.25 from Magnaflow. It sounds good and helped the performance. Just installed a Green Performance air filter. It sounds great and really pulls well.
There's nothing wrong with the Magnaflow. I have it on my car and love it, it sounds greats and the drone is very minimal on the highway. I drive across the state quite a bit and I haven't been annoyed at all by it. It woke up the car a little bit too!
I have the 2.25 as well and it will be fine for now. honestly there isn't enough mods out yet for the 2.25 to hold you back. And at the shop where I had my exhaust installed, they told me that the stock piping was 2 1/8th.
I have had the Magnaflow system on for about 3 weeks now. Overall it is not too loud. No drone at highway speeds. When you accelerate there is an RPM range that it sounds the loudest. I heard it from the outside the other day when the wife took the car to run an errand. It was not loud at all as she drove away. Sounded good. Overall I'm happy.[cool]
I got 'er done. Got the Magnaflow installed and I really do like it. Sounds good...and the car does indeed have a little more zip. Accelerates well and is just loud enough to let you know it's there.
I was planning on seeing mileage increase and initially I thought I had...but I can't keep my foot out of it long enough to say for certain.
Has anyone seen more than 2-3 mpg increase with the exhaust?? Not that it should but who knows its possible to get 4-5 with an intake and exhaust system right?
With the Magnaflow and the Steeda CAI I haven't noticed a change in my mpg at all. It's still roughly 34mpg in the city with winter tires and 32mpg with summer.
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