Why has noone installed an electric exhaust cutout in the downpipe before the cat? - Saturn Sky Forums: Saturn Sky Forum
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Old 05-18-2017, 01:00 PM   #1 (permalink)
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Why has noone installed an electric exhaust cutout in the downpipe before the cat?

As the title says-I'm just wondering why no one has installed an electric cutout in the downpipe pre-cat.

I've seen SRT-4s get over 25whp from the addition of the cutout PRECAT.

Turboed engines really benefit from cutouts.

Anyway, I was just wondering.

I know some have said that the space is limited but I guess my question there is why not just weld a y-pipe at the downpipe (PRECAT) then run the pipe to the bottom of the car where the cutout would be?

Just wondering....
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Old 05-18-2017, 02:06 PM   #2 (permalink)
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Perhaps they do not wish for an idiot light to appear...perhaps.
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Old 05-18-2017, 02:07 PM   #3 (permalink)
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The downpipe IS the cat on the Kappas!



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Old 05-18-2017, 02:17 PM   #4 (permalink)
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^ What HE said ^

No space to install a pre-cat cutout. Some folks have installed a cutout in the pre-muffler pipe though. And others have reamed the cat out or put in a cat-less downpipe.

And Solo does a high-flow cat that has nearly all the advantage of cat-less, yet is still emissions-compliant in most states. (Noisier than stock, though.)
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Old 05-18-2017, 06:40 PM   #5 (permalink)
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When I searched on here about the cutouts it just didn't make sense to me that folks would put the cutout on after the cat. That literally just defeats the purpose of it since it's meant as a power adder by allowing the exhaust to flow around the converter. I had one on my supercharged probe before the cat and it made 12 whp. I definitely would never put that on the car just because I liked the noise.
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Old 05-18-2017, 08:54 PM   #6 (permalink)
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Quote:
Originally Posted by MattM View Post
When I searched on here about the cutouts it just didn't make sense to me that folks would put the cutout on after the cat. That literally just defeats the purpose of it since it's meant as a power adder by allowing the exhaust to flow around the converter. I had one on my supercharged probe before the cat and it made 12 whp. I definitely would never put that on the car just because I liked the noise.
Assuming you have the turbo, you can get some extra HP by installing a high flow cat. Lots of people have done that. I don't think it will get you as much as 12 WHP, but at least 5-6.

I don't like 'noise' mods either .
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Old 05-19-2017, 12:49 AM   #7 (permalink)
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If you put the cut out before the cat, it would be right over the front O2. The fresh air coming in right over the O2 would throw off all your fueling. That's assuming it would fit and you don't mind your exhaust running out your fender millimeters from your battery...or relocating the battery.

I mean, the room there is so tight that to get the cat out of the car requires you to rotate the assembly 180 degrees as you lower it (like a screw coming out of a hole) WITH the engine jacked up a few inches. So you can't run an exhaust pipe next to the cat for the cut out and you don't want it open to the engine bay right in front of the cabin air intake...unless you want to asphyxiate from inhaling the exhaust.

A high flow cat usually gets you about 8-10 hp. I have one because I do like the environment and don't want to be a gross polluter so the extra couple of HP is inconsequential to me.
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Old 05-19-2017, 08:38 AM   #8 (permalink)
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Once you see the area you have to work with you will understand why nobody has done it. The downpipe isn't actually pipe or tubing. It looks like stamped sheet metal to me that is then welded at the seams around the cat. I have attached some pictures I found online to help you visualize space available.
Attached Thumbnails
Why has noone installed an electric exhaust cutout in the downpipe before the cat?-misc035.jpg   Why has noone installed an electric exhaust cutout in the downpipe before the cat?-016-1.jpg   Why has noone installed an electric exhaust cutout in the downpipe before the cat?-2015_13_09_13_12_08_08.jpg  
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Old 05-19-2017, 12:19 PM   #9 (permalink)
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Thanks for those KappaTarbo. I didn't have the time last night to look up a picture of the area or the cat.

MattM, you can see in KappaTarbo's first picture what the factory cat looks like (it's the one on the left). You see the flange at the top that connects to the tarbo...uh...turbo and then the big can thing at the bottom of the "Question mark" (because that's what the stock downpipe/cat looks like to me) is the cat. The O2 sensor bung is in that top "C" portion of the pipe going from the flange to the cat at the part of it that is furthest to the left and it points straight out from there.

In his other shots you can see just how tight that section of the engine bay is too.
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Old 05-19-2017, 02:25 PM   #10 (permalink)
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So... seems like the only option for a cutout (and still be able to pass emissions as long as they don't look inside) is to go with a cat-less downpipe and then add a cutout and cat further along in the system?

Stay clean for emissions testing and normal operations, then open it up when you want the power.

How much would that mess with tuning though?
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Old 05-19-2017, 02:31 PM   #11 (permalink)
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It's just not worth the hassle no matter how you install it.
Get a Hi Flow cat or completely Open Downpipe and tune for that.
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Old 05-19-2017, 03:43 PM   #12 (permalink)
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Quote:
Originally Posted by Elff View Post
It's just not worth the hassle no matter how you install it.
Get a Hi Flow cat or completely Open Downpipe and tune for that.
Pretty much this. Everything after the cat is good until about 400 whp anyway so unless you're going over that there really is not much to gain diverting the exhaust out sooner. And like I mentioned, you're talking low single digit HP gains high flow cat to catless when it comes to the down pipe.
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Old 05-19-2017, 05:10 PM   #13 (permalink)
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Originally Posted by Elff View Post
It's just not worth the hassle no matter how you install it.
Get a Hi Flow cat or completely Open Downpipe and tune for that.
> I < personally agree.

However, worth is gonna be relative to every owner. The subject obviously has some worth to the OP or he wouldn't have fired up a convo about it

More stuff/clarifications:

When I'm talking about bypass I'm not meaning just the cat. I LOVE some of the more aggressive sounding un-muffled systems I've heard. There are plenty of times when I wouldn't want/need to hear all that extra sound.

Also, IF I was to go through the trouble of switching to catless/HF, and/or mufflerless... I would already be under the car and would already be tuning. Not >that< much more hassle >IF< a cutout is something you want.

My reasons to consider a cutout/bypass:

- IF I was back in Cali and wanted an opened up exhaust I have two choices. Either change everything back to stock for smogging, or spend extra time in a one time setup to come up with something switchable. Here in WA? I'd probably be fine with a HF cat.

- When I was driving the car daily, about 20-30% of the time I was in neighborhoods and on base where I really don't want any added attention.

- Currently, I live next to a 50+ housing area and will soon have the mother-in-law with us. I'm not trying to send anyone into cardiac arrest because I hit the gas a lil too hard on the way outta the driveway. :P
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Old 05-19-2017, 05:24 PM   #14 (permalink)
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Something like this plus the HF cat:

Varex Mufflers

Not a fan of the giant can, but I like the quiet or loud option.

What would happen, worst case, if you tune for wide open and then get aggressive with it closed off?
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Old 05-19-2017, 06:07 PM   #15 (permalink)
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The answer is AFR
Since you can't flips tunes on our platform at the same time you open or close the cutout
you will be changing the amount of Air, but have a fixed lambda.
So if you tune for the max air when it's open, when it's closed you will be Rich.
If you tune for when it's close, when you open it, you will be running lean.

As such
TO ME, it's not worth it.
The OP is open to his own opinion after reading our reasons.
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