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Old 07-19-2018, 07:26 PM  
They call me Garrett
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Join Date: Nov 2010
Location: Detroit, Michigan
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Posts: 4,040

Zero/Sports Downpipe

Hey! It's been a while since I've posted in this, and I finally got something worth posting about. I'm gonna tie this post in with the modification as well as some tuning stuff in a post below, so read both!

Alright this one is a simple one.

I bought a Roger Clark Motorsports downpipe for a twinscroll turbo. It was too short. I didn't feel like dealing with welding because I'm lazy and sort of wanted an excuse to get a different exhaust anyways. I searched for a while looking at some JDM length exhaust options, and honestly the used marked for JDM length exhausts is a large amount of bullshit. Certain importers, I won't say names but it starts with a J and end's with a DM Racing Motors, have used dented up exhausts for more than they are to buy brand new on a site like Japanparts... trash. And it's not just them, but every other importer everywhere.

So I looked at some new exhausts.. meh... didn't really want to spend the money to have unknown fitment, sound quality, and the inability for the exhaust to be sold back if it didn't fit.

So I started to look at GDB F-G type downpipes, which are the same length as the USDM ones.

I came across this Zerosports downpipe in great shape. Decent price. Let's do it.

Got it in, and it's definitely gonna fit.

I liked the fact it had a small resonator on it at the end, but sort of didn't like the fact it had a cat.

Here's the important bits compared to the OEM downpipe.

I'm not really sure of the benefit of the extra half circle section, or if there is any.. but the OEM downpipe definitely has a more open bellmouth that's smoother because of the casting and not welded together pieces.

Where the Z/S one IS nicer is that in right after that initial area, it opens up to a wider 3in pipe as well as has a smoother transition in piping. Hard to tell in the pics, but that's the situation.

I was going to post the pictures I took, but they are pretty useless. The Z/S downpipe has a webbed cat, but it's MUCH less dense than the OEM one, as well as skinnier. I'm ASSUMING this promotes better flow, but I'm a software engineer and it doesn't have beeps and boops so I can't say for sure.

I wasn't super thrilled it had a cat, but oh whale. I can always stamp it out later like some sort of lunatic. Glamor shot of the badge before it gets covered up by the heatshield

Got everything on, and turned the car on.

Volume is just a SMIDGE louder, and clarity of sounds is much better. I really, really like it.

I didn't toss a tune on the car yet because it seems like the OEM feedback system can handle the boost fine, but I haven't done any purposeful high boost, low speed testing yet.

It definitely likes to spool the turbo up a lot easier now. I dig it. Time to up boost a little!

Here is my log from a small 1-2-3 pull:


You can manipulate data and look at it with the full log here, or for the lazy/phone users:

Not a super telling pull, but enough to see that it's not gonna be huge issue without a tune.
Tuned Detroit - Automotive Blog, check it!
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