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Electric exhaust cutout ... or convert to full 3"

FlyingEagle

Staff member
Joined
Mar 5, 2005
Messages
1,635
Location
THE Ottawa
Looking at adding an electric exhaust cutout to my car, but also the real possibility of cutting up a complete Borla Hush 140053 3 inch catback system to replace my current exhaust setup, with the help of some extra tubing.

The motor ingesting/expelling the gases is as follows:
4g63t, Cyclone, HKS 264/272, EVO3 stock boost to maybe 18 psi, complete to the rear bumper exhaust (2.5 inch press bent, catalytic equipped).

Muffler is currently a rather forlorn, Magnaflow offset in/out unit, faces left to right. It has seen better days and will be replaced with this unit: Borla 3 inch Hush twin tip (cut off tips and weld in L's, single 3 inch in, dual 3 inch out)

Thinking about adding an electric cutout just after my rear axle. Allows for a switch to open the exhaust just before it enters the muffler. I can even add a pipe to the cutout, to direct all bypassed exhaust out past the rear bumper, to keep fumes from getting in through the rear compartment. Torn on whether a cutout should even be at the back, or closer to the front, so that the spent exhaust, see's none of the stock system, and exits outside/under the vehicle as soon as possible. This modification is a straight line, track use type of thing. /ubbthreads/images/graemlins/devil.gif

So, possible scenario's:

2.5" system to over axle - Hush 3" muffler - no cutout bypass
2.5" system to over axle - electric cutout bypass - Hush 3" muffler

I am not a fan of drone, so leaning away from the complete 3" system. Can I expect to see any gains with a cut-out just after the rear axle, bypassing the muffler?
Got a line on an electric cut-out, just unsure at this point.

Anyone install one in a similar spot or close to the downpipe for side exit?

Here are some pics of what is on the table.
Pics are not mine, but help to illustrate where I want the electric cutout.


img.php


img.php


You can see above (last pic) that just before the muffler is the perfect spot to weld on a pipe before the exhaust takes the bend. Can be made super stealthy with a downturn tip painted black, to not show just at the lip of the rear bumper. /ubbthreads/images/graemlins/devil.gif
 
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mitsuturbo

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Jun 2, 2008
Messages
3,544
Location
Near Seattle, Washington
First, i do believe that a free flowing 3" muffler on the end of 10 feet of 2.5" exhaust pipe is a waste of time. Next, converting a muffler from dual 2.5" outputs to dual 3" outputs is similarly useless. Additionally, if you don't like "drone" then it's probably not a great idea to have a downward facing exhaust exit. Oh, and what are these "L's" you are talking about welding in? How does your muffler go "left to right" under your car? I'm genuinely curious about this, because i don't see how it's even possible.

You seem to be making this far more complicated than it needs to be. The objective here is to get exhaust gases out the back of the car as quickly, efficiently, and quietly as possible, right? If you're not interested in getting the most out of your E3 16g, go ahead with the 2.5" tubing. If you want it to breathe a bit easier, go with 3" tubing and pick a nice quiet muffler. Maybe put an inline tube/bullet muffler in as well. These make great replacements for the kitty /ubbthreads/images/graemlins/devil.gif and quiet things down a bit. Just keep a cat for emissions day, if you must.

If you've got your heart set on an electric cutout, knock yourself out. I'm pretty skeptical about the longevity and usefulness of these cutouts, personally. I've seen what happens to exhaust parts after just a couple of winters. I could be wrong here, but it doesn't sound like yours is the kind of gvr4 that sits in the garage during those nasty canadian winters. I would expect such a thing to rust/leak/seize/fail within 30 months.
 

FlyingEagle

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THE Ottawa
Hmmm ... should have stated this is for my 89 Mirage/Colt Turbo. /ubbthreads/images/graemlins/wink.gif

My car is already functional and has had the 2.5" system on it since I bought it in 2004. Still in great shape structurally, but the muffler is on it's last legs ... literally.
The Subaru system is worth darn near $500 new, and it was my cheapest option (you'd like to know what I paid!) to getting into the 3" range, with their fancy stainless blend. If I choose to go full 3" and bite the "drone" bullet, the option will be no more than 50 feet away.


I only wish to use the cutout during those times that I want to hear the motor, in all it's infinite and puny glory considering the size of the frame of my turbo. /ubbthreads/images/graemlins/rofl.gif

The purpose of the tiny extension being added inline with the cutout, is to get the exhaust to the back bumper ... none of the nasty drone will particularly fill the cabin in an unwanted way; much like tips on a volkswagen of any type, that face down - gas or diesel.

Staring at the pic of the exhaust on the lawn, the L's pieces would be welded onto the dual outlet side of the muffler, facing to the right. This allows whatever tips size desired, whether I re-use the tips from the Subaru muffler or use a pair I have lying around, likely from an Impala SS. Any setup I use will have much more volume, than the muffler takes in, so as to not create another restriction.

Also, you can see in the picture of the exhaust sitting on the lawn, that is a C50-C60-C70-C80 type exhaust, when used with a 2WD setup, solid twist beam axle. Maybe the muffler is enough, but for around the $200 mark, I can change the sound when I get to the track, or on some back roads. Personal taste, not looking to drown my neighborhood in noise pollution. I used to work with a kid 3 blocks from my house, could hear his muffler delete (nothing installed in it's place) from a good kilometer away, changing gears, romping on it, till he hit his parents driveway. Nuff said there I figure.
 
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JDM_DSM

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Sep 2, 2006
Messages
66
Location
Calgary, AB
I started looking into the cut out idea a couple years ago, but what was pointed out to me is that if I ever wanted to do any track or autocross events the cut out would probably exceed the noise limitations for the event, so I'd be better off keeping it simple and going with free-er flowing exhaust.
 

FlyingEagle

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Mar 5, 2005
Messages
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THE Ottawa
I see what you are saying. I doubt I will try much autocross, because it's syncro-use-heavy if you can't heel and toe; I'm not there yet nor is my Colt's pedals setup well for that.
Drag strip use or back roads where no one is around, or cares about a car that's still likely quieter than a sport bike ripping on by.

Being that the system uses a turbo, catalytic converter and two 90 degree bends before the last corner at the muffler, things get quieted down pretty good. Cars with completely straight exhausts, much like Subaru's don't have this same noise leveling characteristic built in. They can however accomodate 3" piping pretty well.

I should also add, that I can weld in whatever parts are needed, myself. Fab for fitment, also by yours truly. Recently bought a 14" chop saw with spare blades, access to a welder at the shop (I weld exhaust systems and random bits on top of my usual car repair duties).
 
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tektic

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Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
From what I understand about thermal dynamics, as the temperature drops the gasses take up less volume.
You would most benefit from a free flowing 3" down pipe. Further down the exhaust path it could be reduced to 2.5" for better fit without much or any difference in performance. If i didn't have all this 3" pipe bent to fit I would have had a 2.5" DP Back built.
 

4thStroke

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Joined
Oct 22, 2007
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1,864
Location
Vancouver, WA
You never want to neck down an exhaust towards the back of a car, especially on a turbo car where you want zero back pressure.

My coworker had a cut out on his old VR4, it dumped right behind the driver seat. It was awful.

You are correct that as the exhaust cools it takes up less volume, but on the flip side, the colder gas isn't as free flowing as it was towards the front of the car when it left the motor at 1600*. A lot of people get away with 2.5" downpipes with great results and may see little to no benefit from a true 3" turboback exhaust, a lot of that will be determined by the size of the turbo, larger turbos need larger exhaust systems to help alleviate back pressure.

I have first hand experience with a 1500+awhp car benefiting from the downpipes being cut out and going from a 34psi limit on 6466s to 40+ without an issue due to back pressure within the rear section of the exhaust, that car happened to run dual 3" out the back after being reduced from dual 4," the reduction was made within the muffler. The cross sectional area of dual 3" exhaust supports more than what the car was making for power, but funny things start to happen when you reduce the size of the exhaust through the mufflers, and have two 90* bends on each side before it exits the car... when the exhaust is cooled way down.

I've also seen first hand a 750+whp Honda see no benefit from going from full exhaust to open downpipe, but that exhaust system was damn near completely straight to the back of the car with a good straight through muffler.

I just recently picked up a 60mm Godspeed waste gate that I will be mounting under the car on the exhaust system. I'm a skeptic whether or not my exhaust flows as well as it should for being a true full 3" exhaust, so I'll be doing some research on my own and try to determine whether or not a turned up 30R requires as much exhaust as I currently have. The car will be close to being an open down pipe car when I hit whatever psi the spring is set for in the gate, but won't have to deal with the annoyance of having to flip a switch and wait for it to open up. I can even run a line to the cabin with a valve if the spring pressure is low enough that it keeps opening up in traffic at say... 10psi.
 
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ApexHunter

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Apr 25, 2007
Messages
1,992
Location
Marysville, WA
I just did something like this last weekend to my Evo.

Bought a JIC "spartan de type 2" exhaust system...It's 3" all the way from the cat to the muffler, but the muffler necks down internally to about 2 3/8". Interesting internal design, should have taken a pic of that part. Basically 3" inlet which then opens into a big chamber...then there is a tube sort of "floating" inside the chamber, which eventually connects to the tip. So essentially all of the gas must exit through a 2 3/8" pipe. /ubbthreads/images/graemlins/banghead.gif

12098801893_4b26055720_b.jpg

12098802683_5d86bcbd9e_b.jpg


In its defense, it is damn near as quiet as stock, and i love that part and so does my GF. However i was disappointed about the obvious restriction. So, plumbed a WG into it just before the muffler. Turbosmart Compgate 40mm, using a 14psi spring. It is very compact, which was important for space and to make it as invisible as possible from behind the car. It is fairly lightweight. Nice construction too.

12098860994_1117cea49e_b.jpg


I'm stoked. Quiet under cruise and low load situations, still drone-less on the freeway etc. Sounds loud and rather nasty when it should. /ubbthreads/images/graemlins/devil.gif
 

ApexHunter

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Apr 25, 2007
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Marysville, WA
Not yet, i've got some logging tools on order though. I'd really like to be able to quantify it. Will be making a trip to the dyno soon, i'm hoping to experiment there.
 

FlyingEagle

Staff member
Joined
Mar 5, 2005
Messages
1,635
Location
THE Ottawa
All these options look great guys!

I've been wondering what to do about the exhaust, and as it was still structurally sound and can work with my turbo goals for now, I sold the 3" catback.

Still looking at muffler options, and possible dump setups just for the sound aspect and smile factor, but have a transmission sitting around that needs my attention.

Keep posting your data and exhaust setups, I've got the popcorn waiting.
 

JDM_DSM

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Joined
Sep 2, 2006
Messages
66
Location
Calgary, AB
Was the wastegate just what you had lying around, or was there another reason you used that over a cut-out?
 

EHmotorsports

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Sep 25, 2012
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Location
Beaverton
Wastegates have been proven to be more durable and cost effective vs cutouts.
 
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raptorWagon

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May 17, 2007
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Oak Harbor, WA
Who needs Electric Cutouts when you got these bad boys?
g3ky.jpg


/ubbthreads/images/graemlins/rofl.gif
 

EHmotorsports

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Sep 25, 2012
Messages
1,278
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Beaverton
wow!!! Is that Pipe welded on with caps? hahaha /ubbthreads/images/graemlins/rofl.gif /ubbthreads/images/graemlins/rofl.gif
 
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