Downpipe flange ID? Possible downpipe alternatives?

[KJWOLKE2010]

Hey guys, I've been spitballing the idea of looking into cheaper alternatives for a 3" downpipe, namely running open header.

First off, what is ID of the oe downpipe flange? Is it less than 3"? Does it matter?

Second, is flange for the 2014-2019 Fiesta ST the same? It seems like if I'm running open header what the catback end looks like doesn't matter as long as I can tack hangers to it.

Third, if I were to find a flange that bolts to our turbo, could I run an aluminized steel 3" 90° elbow to a straight pipe with O2 bugs (rear with a defouler) hangers at the end and call it done? Is there any kind of tradeoff here using aluminized steel as opposed to stainless?

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[KJWOLKE2010]

Thank you, sir. It is appreciated.

 

[colinl]

Hey guys, I've been spitballing the idea of looking into cheaper alternatives for a 3" downpipe, namely running open header.

First off, what is ID of the oe downpipe flange? Is it less than 3"? Does it matter?

Second, is flange for the 2014-2019 Fiesta ST the same? It seems like if I'm running open header what the catback end looks like doesn't matter as long as I can tack hangers to it.

Third, if I were to find a flange that bolts to our turbo, could I run an aluminized steel 3" 90° elbow to a straight pipe with O2 bugs (rear with a defouler) hangers at the end and call it done? Is there any kind of tradeoff here using aluminized steel as opposed to stainless?

is this a daily driver, and if so, have you ever had an open header before?

 

[KJWOLKE2010]

Yes it is, and yes I have. Lol.

 

[colinl]

OK. Can't say I have any desire to wear earplugs daily, and without a resonator the Maverick ecoboost sounds terrible.

But if you want to do that anyway, turbo exit exhaust has to be protected from rain, dust and other debris on a daily driven car. Just because we've all seen hood exit turbo exhaust doesn't mean you could do that on a DD. At least, not for very long.

 

[KJWOLKE2010]

Been running with only OE downpipe all weekend and I love it. It feels eponymous with the fact that we as a community are experiencing something special: Ford saw the hot hatch and, even for a brief time, made an affordable pickup truck that could be tailored to the owners most specific desires, whether it was a grocery getter, a nimble offroader, or even a modern day hotrod. It feels like a paradigm shift on par to when Iococca gave Shelby carte blanche over the K Cars.



Now that I've made an overly empassioned monolog, back to our regular programming.



As much as I'd love a fire-breathing hood exit downpipe (especially with an exhaust flapper to keep the outside out) for me the there's too many packaging concerns to overcome. A stack in the middle of the hood would drive me insane, and either the turbo is in the way of making it exit from the passenger side of the hood or the battery is in the way of a driver side exit. Even if you moved one or the other to make concessions for the hood exit, I can't think of a scenario where you don't end up chasing the dragon in regards to packaging. That leaves us with routing a larger downpipe along the same route as the oe pipe.



The way the fuzzy math works out to me as long as the downpipe isn't any closer to sound deadener or sheetmetal than the factory pipe is, and the end is pointed down at at least 45° so exhaust gases are cooled by ambient air before possibly coming back into contact with the underside of the vehicle, there should be no safety concerns to speak of. This should also help mitigate soot deposits along the bottom of the vehicle.



Best I can tell, there is effectively no back pressure concerns on a turbo vehicle because the turbo is effectively causing any and all backpressure the engine needs. Making the only concern regarding flow to be minimizing resistance to cause free flow.



So that gets me to the meat and potatoes of my question: What's stopping us from welding a K03 flange to a 3" 90° elbow and a straight pipe down to the hangers and calling it done? And is stainless necessary in this application?



The older focus st downpipes look very similar to ours aside from using what appears to be a V band to mount to the turbo (which given space constraints around the turbo honestly seems to be the better design). That said, is there a K03 to V Band adapter that could be used to make the ST downpipes a viable solution?

The flange for the '14-'19 Fiesta STs looks very close to ours. Can anyone confirm if the KP39 uses the same flange as the K03?

 

[colinl]

Not safety related. I'm talking about water, dust and debris intrusion on the compressor side. This is mostly an issue for rain into a hood exit, but definitely can be an issue for short/no piped side exit also. If you meant to have full length straight pipes that is different than what I thought when you said 'open header'.

Regarding aluminized vs stainless, stainless lasts longer. If stainless feed wire isn't used when welding you should expect rust to start at the welds.

 

[Dueces]

I didn't make my exhaust out of stainless, and for some reason, on the Maverick it rusts WAY quicker than the exact same piping on my Honda Insight! Same kit, same diameter, blah blah blah. But yes, it will rust. Use a quality high temp paint and it should help, but even with that mine has surface rust all down it.

I still do open downpipe runs every now and then when I'm tuning. There is no way I could do that all the time. My full 3" exhaust is very loud, even with two Vibrant mufflers on it, lol.

I would concider making your downpipe, but leaving it slipfit like I originally did so you can modify your stock exhaust to go back on. Trust me, you will get sick of the open DP!

On the flange, I believe the opening right off the turbo is closer to 3.5 or 4 inch, so in reality, you could build a larger DP 90° that then necks down to 3"....

 

[colinl]

If someone lived near me and did what you described, worked on a vehicle and briefly ran it once open header, no big deal. But if they drove it like that daily, 100% I'm walking over and talking to them politely about it.

It's definitely going to cause hearing loss and headaches, I was not exaggerating about earplugs.

A long time ago, my DD for almost 2 years was a '65 Chevelle with a warm sbc and dual 3" flowmaster deltas. A good HS friend ran open header on a 240z for nearly a year.

 

[KJWOLKE2010]

That's weird. My neighbor's full exhaust 1.8T dub is louder than mine. LOL.

But with kids quite possibly being a thing in the future, I see your point. Might weld on a 3" header flange at the end with a diy bolt on turndown for now, but I can quick bolt on a header glass pack later.

 

[KJWOLKE2010]

On the flange, I believe the opening right off the turbo is closer to 3.5 or 4 inch

So to my understanding the K03 is more of a design less of a model. Is this correct? Is there some sort of model number I should look for as far as finding a flange that fits our specific model?

 

[KJWOLKE2010]

You are a Saint and a scholar, sir.

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