Hey guys i have a 2011 RA currently with a magnaflow catback. I want to make it full turboback but don't know which piece i should go with first -- dp or hfc? I don't want a test pipe obviously cause of legality.

basically i want to know which will give me more power and better flow? i know down pipes are usually cheaper so I'd love to not have to break the bank but i want to do this right as well.

any help is appreciated, i did search for this but didnt get the exact answer im looking for. if i missed it im sorry, hopefully i dont get flamed for this.

also, i like it loud so dont worry about which is quieter.

mod list: evo x IC, UR pipes, magnaflow catback, evo x bov, k&n drop in

thanks guys

 

hfc. the stock cat is the most restrictive piece of our exhaust. Depo Racing sells one for $200. I have it and have no issues.

 

Go with the HFC. Downpipe is nearly pointless on this car unless you've already done damn-near everything else and you need to squeeze out that last hp or two, or if you're going with a full downpipe with a modified collector design, but even that...

If you don't want to take my word for it, there's a thread here on evom where AMS did a test and showed absolutely zero change to their car when installing just the downpipe and back-to-back dyno testing. They actually advised customers against the purchase of their short downpipe design and that is one of the main reasons why they made the updated widemouth design.

 

With that said, if you don't want to have a bung welded in your stock DP for a wideband, getting one with it already there is a must.... before any other mods. Everyone on these forums with ANY mods (or even none) should have a wideband for safety reasons.

 

HFC all the way, for all the reason chi said and more.

 

+1

 

would you mind explaining a little more?

 

You can skip the dp bung problem altogether by welding your bung into your HFC, I welded my bung about 2" downstream of the flange connecting the dp to the cat. Works great, and is so much easier to install because you can just take the cat to a muffler shop and have the bung welded in before you install it.
To answer Chaz17's question, you want a wideband to give you a readout of what's going on with your air-fuel ratio. This is important because if something is going wrong you'll be able to see it happening as the numbers change on the gauge. This allows you to see a potentially catastropic lean condition and stop the car before you damage your motor. For example, normally at wide-open throttle (WOT), your air-fuel ratio should be around 10.5 (stock) or 11 to 11.5 (tuned). If you're at WOT and the number climbs past these values, the car is leaning out. If you see a 13 or a 14 at WOT, you'll know to let off the gas and go find out what's wrong. Without the wideband, you'd never see the problem, and potentially wind up with a blown motor.

 

so you can attach a wideband to the bung in your hfc instead of in the dp?

 

You can add an additional bung in the HFC...

 

Yes. My AMS pipe came with a second bung already welded in it (which I am using with much success). Most companies that sell test pipes and HFC's will offer this at the time of purchase for a small additional charge.

 

This is true, but even if you don't have a bung welded in, most wideband gauges come with a bung. Most muffler shops won't charge more than $20 to weld that in for you. Make sure it's welded in upstream of the cat housing part (the part that flares out) of the cat pipe.

 

u guys have any close up pics of what it would look like? and so if i get the hfc and have the bung put in, id also need to get the wideband sensor and an a/f gauge?

 

They are one and the same; tomatoE tomatO

 

Here's a shot of a HFC for an Audi, with both pre-cat and post-cat bungs. The post cat OEM sensor would go to the post-cat bung (obviously ) and the wideband sensor goes into the pre-cat bung. There's the OEM bung for your OEM pre-cat sensor on your downpipe, and most HFCs for the RA/Evo X already have a post-cat bung, for the OEM post-cat sensor.



Here's a diagram of where each bung is in the system. Lolz mspaint



The sensor and gauge generally come together as a package. Usually between $200-$300.