I have a 05' ST. I deleted the 2nd cat when I installed maglow flow catback 2 months ago.
The sound of my car is much louder than before, but
I'm not really sure if I gain some power from that.
Could someone tell me the truth? Thanks!
I don't think anyone is stating there would be no measureable benefits from removing it - just not as much as some might think. Like mievil says - till we have a dyno before and after, we'll never be certain.
Wow, you actually got my back. I'm getting all squishy. Apparently, there seems to be a confusion as to my statement. I am talking about the exact same aftermarket exhuast, with a removable middle section. You dyno with the 2nd cat in place, and without the second cat in place. Then we see what exactly the gains or restrictions are. Yes, it is obviously a restriction, but as Peloton stated, there's really no huge benefit removing 1 unless you are going to be removing both. A fellow Jetter and I both ran at the FS Dyno Day. We both had the FS Sport exhaust. I have mine modified to maintain the second cat, he was using the FS resonator. I actually pulled a few more horsepower than he did. So apparently the 2nd cat isn't as restrictive as some might think. Now considering the build consistency with Ford, exact hp numbers don't mean much, so lets just say that we were about even. So I'll tell you what, for sake of argument, lets start a fund. I'll pay for the gas up there and back, and we'll dyno my car at FS, with there resonator in place on one run, and the second cat in place on the next. That will give us our numbers. Who wants to contribute?
The 2 inch collector on the manicat limits flyweel HP to around 160-165 approximately.
The OE flex portion (removeable on some Duratec fitments), though it has a 2 inch in/out, is actually quite a bit smaller in inside diameter than that.
Then the second cat, with it's 2 inch in/out has to be a bunch more restrictive that a 2.25 inch perforated core muffler (such as the one found on the FS Stealth system)...
So I'd say, based in prior speculation, that deleting the second cat AND improving the diameter of the flex portion should yield at least a 2-3 HP gain if the intake is freed up a bit with the addition of a CAI...
Well, then the statement overall would still be as we have been touting since they became available. The best power maker for our cars is the CAI, not removal of any of the emissions gear. 2-3 hp (in theory) is not quite a huge step in my mind. Goes right along with pulling out the HC trap for ~3hp. Oh wait, I still have that in as well.
And just so we don't open up another jumbo can of worms. Obviously, the more mods you do, the more you are going to want that 2nd cat out of there (as in a racing setup), but my statements are based on a very lightly modded daily driver. So don't someone come along and start talking about if there was FI, or cams, or any of that junk.