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TRSCobra 06-06-2011 09:40 PM

Electric exhaust cutout installed w/pics. Best of both worlds?
**Edit: Now with dyno results and videos!**
Due to excessive noise, I sold my HKS catback and reinstalled a stock system. While my neighbors and passengers loved the sound (or lack thereof) I really felt the loss of performance with my 20g turbo. My car had the spool of a 20g with the top end of a 16g. Less than ideal,but since every aftermarket exhaust that I've heard is louder than I'd like, I'm stuck with the stock catback.

A few weeks ago, I had a 3" electric cutout installed on my downpipe to give me the power I spent so much money on when I want it. Turbos love to breathe, and what better way than an open dump a few inches after the bellmouth? This bypasses every restriction in the exhaust system and keeps it nice and quiet when it's closed.

Yes, I've read the stories on the internet of these things failing, and talked to people (none with personal experience) who also said they're garbage and won't last. So I did some research and found most of these complaints were with QTP and Badlandz cutouts. The other two major brands, DHM and Race Ready, seemed to have better reviews in terms of longevity. Since Race Ready has a lifetime warranty, I went with their 3" cutout.

I saw two guys running the cutout right after the bellmouth in a cutout thread on NASIOC, both reporting great results. (I PM'ed them and the one with the Race Ready cutout hadn't had any issues in over a year of use.) This position puts it up high enough to avoid the ground clearance issues that many have with these, at the expense of subjecting the electric motor to more heat--another reason I like the lifetime warranty. I spoke with a representative from Race Ready Performance who suggested that I shield it from heat, but he made no mention of it voiding the warranty. Also, it turns out that it's about a foot away from the biggest hole in the firewall, making wiring this thing a breeze.

Since their 12" stainless Y-pipe would need to be cut down to about 7" to fit between the cast bellmouth and the first bend in the DP, I had a local shop that makes stainless headers and custom exhausts cut an oval hole and use their own 304 pipe and flange. Top notch work.

The notched holes on the cutout flange allows a decent amount of options for mounting. I had them clock the flange so the motor would sit where it wouldn't make contact with the control arm or the chassis and allowed for engine movement.

Here it sits, well out of the way of hitting anything I might drive over:

I know that the placement of the Y-pipe is close to the axle, but there is plenty of clearance for turning and suspension movement. I'm going to keep an eye on the inner boot, since it's exposed to more heat than before. If I run into issues, I'll just wrap the DP.

I don't have any sound clips, but it actually sounds quieter than when I ran my catted DP with no catback. This is possibly due to the exhaust pulses reflecting off of the ground. Still super loud, and the turbo whistle really turns heads at the track.

My first 1/4 mile run with the cutout closed was a 13.8 @ 106mph. I had a crappy launch, but I know I could've had a better time. I doubt the trap speed would have changed by much, though. My next run (cutout open) was also a bad launch, but I hit 13.1 at 112mph. Eventually I hit 12.6, but my trap speed stayed at 112mph. 6 mph isn't bad for flipping a switch. This is with ZERO tuning changes.

The car is tuned for the HKS catback, which flows better than the stock system, but nowhere near as well as the open cutout.

I'm in the process of getting an Infamous tune, and I'm going to try to get some dyno results later this month of the car with the cutout closed and open. More track time to follow, too. :)

Thanks to:
Race Ready Performance
Clear Image Automotive

Grumbles08 06-07-2011 06:41 PM

Let me be the first in saying, that is sick! I'm jealous. Please post video ASAP.

TRSCobra 06-10-2011 06:22 PM

Here's a hasty vid I made today:

Grumbles08 06-11-2011 11:26 AM

Thanks for sharing man! Love the turbo spool. Where did you mount the switch?

TRSCobra 06-11-2011 04:21 PM

Got some dyno results!

Still not tuned for the cutout, but with it open I picked up 46whp and 58wtq over it closed with the stock exhaust! Also, notice how far the curve is moved to the left. :D

Solid lines are cutout open, dotted lines are with it closed.

BTW, I know my numbers are way low. This was a crazy-low reading Mustang dyno, as a GT30 powered 07 STI only put down ~330whp/318wtq.

TRSCobra 06-11-2011 04:23 PM


Originally Posted by Grumbles08 (Post 3424623)
Thanks for sharing man! Love the turbo spool. Where did you mount the switch?

The switch isn't mounted yet. I just routed the wiring under the center console and the switch sits between the console and the driver seat.

GTTuner 06-11-2011 04:42 PM

Nice clean install, I like it. What about flames? any flames shoot out of that thing?

TRSCobra 06-11-2011 04:49 PM

^^^ Got a small blue fireball once they let off on the dyno pull. :)

Look under the rear door at 0:15:

GTTuner 06-11-2011 04:58 PM

That is so cool. Just keep an eye on that CV boot. Looks like you have enough room but I'd peek at it every oil change.

TRSCobra 06-11-2011 06:10 PM

I wonder if anyone makes high heat silicone boots...

BAC5.2 06-12-2011 04:31 AM

Call DriveShaftShop and see if their blue boots fit stock axles. Those things are pretty tough.

Why did you have it dump before the O2 sensor? I've never seen a butterfly cutout that didn't leak.

TRSCobra 06-12-2011 10:11 AM


Originally Posted by BAC5.2 (Post 3425270)
Call DriveShaftShop and see if their blue boots fit stock axles. Those things are pretty tough.

Why did you have it dump before the O2 sensor? I've never seen a butterfly cutout that didn't leak.

Good idea, thanks!

I placed it as close to the turbo as i could, where it would have the fewest clearance issues. I asked infamous (who is working on my current tune) about the O2 sensor and he said it wouldn't be an issue. I don't get a CEL when it's open, either.

This one has a silicone o-ring in a machined recess around the closed butterfly, which helps with leaks. It does still leak a little around the shaft, but not enough to hear or smell, though.

ChefRacer 06-12-2011 03:00 PM

That is really awesome man. I'm still new to these cars, but I was just looking into doing the same thing to my 05 LGT wagon. I love the sound of it, and my wife loves the idea of not spending $800 on a catback lol. Why didn't you put one of those exhaust extension pieces on the end of the cutout that race ready sells on their site, that should help you divert the exhaust gas in a different direction and not have to worry so much about your axle boot.

TRSCobra 06-12-2011 03:36 PM

It exits below and aft of the boot. I'm concerned with the radiant heat of the pipe.

ChefRacer 06-12-2011 05:37 PM

Well wouldn't that be pretty much exactly the same as stock, I mean it isn't really any further in any direction but down. BTW, how many lbs of boost were you running on that dyno pull? Thank you for the inspiration and validation to go through with this outside the box mod. I literally just posted a query about this on the .org seconds before I found this post, and im really glad to see that this forum is still active and growing.

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