Basic Bolt ons: Exhaust Headers/Flex Pipes

[Dung1sm]

theres a o2 cheater you can do... or just drive with the check engine light on like me...lol

[icase81]

Originally Posted by S0C0nFused

The most restrictive part of any exhaust is the cat. Remove it/them and the rest is comparatively fine tuning. You may also look at it the other way. Mounting a header with a trailing cat, gain would be effectively zero, as any potential gains from the header would be negated by the cat.

Not necessarily true. This all depends 100% on the cat. I'm from the 1.8T/VW world originally, and we've done tests with a 700+hp 20v motor that with the OEM VW cat vs a straight downpipe. The cat caused an effective loss 7hp on an engine dyno, which would be even less at the wheels. If you're pushing even less air through the motor, you're not even going to see THAT much loss. However, as I am fairly new to the Focus world, I don't know what the situation is with the factory cat. If you wanted to pony up for an appropriate high quality metal substrate cat, you would probably not lose anything. Especially since a mildly modded 2 or 2.3L n/a motor isn't flowing all THAT much in comparison to a forced induction motor. The main reason to not run a cat is either because of cost of putting a proper one in, or the complexity of the install making it unfeasible.

[icase81]

Originally Posted by BowerR64

It was a cat case or somthing but it was stripped of all the stuff in it. It was just a pass threw.

Is this what you mean?

http://www.siliconeintakes.com/produ...290a0f9afd2114

[S0C0nFused]

Originally Posted by icase81

Not necessarily true.

I have to agree with you, only in that the devil is in the details. 1st. Please post a link to an appropriate "high quality metal substrate cat". I tried once before to find one and came up short. But the point was/is. Assume stock build. The D2.0 makes it's torque low in the RPM range. This negates somewhat the overall performance hit of the cat (low volume as you mentioned). Mount a header though, and you move the curve 2K upwards (to around 4500RPM), So now you trying to push a whole lot more volume, and it runs into the cat. So right when the benefits of the header should be coming in, there getting killed. Hence, A header (no cat) is worth about 7-10hp (real world), A header with a cat? Maybe 2-3HP? So it would prob be best to state that it is just not cost effective.

[BowerR64]

Originally Posted by S0C0nFused

The most restrictive part of any exhaust is the cat.

What if you get a setup that is designed for a larger engine, like say a 6 or 8?

You put on a header but then everything else is like 3" (or for a larger engine)you have all the stuff, cat, muffler, resonator but everything is so large it flows as good as a 2" race setup?

Or does it not work that way?

I would think with a setup larger then whats designed for the car emmisions wise would pass but be so much more un restrictive it would help the engine breathe better.

[BowerR64]

Originally Posted by icase81

Is this what you mean?

http://www.siliconeintakes.com/produ...290a0f9afd2114

Well i never really seen one my brother was talking about them when he ha da honda and was doing mods to his. At the time i didnt even really know what a cat was or what they did actualy.

[BowerR64]

Originally Posted by felixthecat

You need the flex pipe, for the movement the motor has being sideways. All FWD cars have to use some sort of flex for the exhaust, even w/ vf engineering mounts or similair mounts. As far as muffler shops, could put a header on, they would want some kind of conver added to. Legalley I don't think they can. Any how you would be missing out of all the fun you would have, adding a new mod, to your car, don't you think!

Thats what i thought but i seen a post were a guy put a bracket on the end of the header and bolted it to the tranny or somthing. Made everything rigid.

Maybe the header being more solid is better but after that?

Ill try and find a picture.

So where is the flex in this setup?

[S0C0nFused]

Originally Posted by BowerR64

What if you get a setup that is designed for a larger engine, like say a 6 or 8?

Or does it not work that way?

Correct! It does not work that way.

[BowerR64]

Originally Posted by S0C0nFused

Correct! It does not work that way.

Can you explain? not sure i understand why.

[Buickboy]

Pic above is a zetec/svt car- different from ours. the flex is the part that goes over the front subframe (cant see it).


also, a few posts up there was a question about the ebay OBX header having two flexpipes. It has two and theyre different lengths to fit both auto and manual cars