Home | Mailing List | Specifications | Care and Feeding | Modifications | Vendors | Literature


Electric Exhaust Cut Out

new 4/16/2004

                                        Special thanks on this project to:
Ian Macoomb, who helped me find my cutout, and helped with the plan for installation. My Dad, without whom this would never have happened. At times, I thought this project would never be completed.


Here's a drawing of what I ended up building: (click to view picture)

I had intended to remove the resonator at the same time, but the time was not available, so its still in there awaiting removal at a later time. When this project is complete, the McCord Power Plate 2 will me mounted to the cutout, and the resonator will be replaced by a strait pipe.

Parts and supplies:

Parts Needed:

The Jegs cutout, designed for a mustang, I used the 2 3/8" cutout, it can be found here:
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=102162&prmenbr=361  $26.99

The McCord power plate 2, found at their web site: http://www.mccordcg.com/mpp/mpp.htm  I spent $120.00 on mine, but it varies depending on options.

Red or copper silicone gasket.

An exhaust step down pipe, just a small one, that will fit outside one end of the cutout, and inside the stock exhaust pipe, can be found at Advance Auto.

Factory style exhaust flange for 2 1/4" pipe. if you can find one, let me know where! I had to build one.

3 lock washers, and nuts that will fit the cutout, I'm not sure of the exact size of them though.

Assorted tools and supplies. wire ties etc...


This project is manageable in a weekend, it took me 2 days, with a week in between since I put on my cutout before my power plate arrived.

My tasks for installation:

Looks of the exhaust before work began, I thought one of the most difficult parts of this install would be to get the old exhaust off the car...

My first attempt on my own to break the bolts loose was useless, too much rust, but with some liquid wrench, a long torque wrench, and two people one on either side pushing and pulling on it, all but one of them gave, a cutting disk and a chisel took care of the last remaining bolt, and inadvertently marked the flex pipe so that I could find the right location later to reinstall it. As for parts, I bought my cutout from Jegs, its the 2 3/8" mustang cutout, I meant to get the 2 1/4 one as it would be the same size as the factory exhaust pipes, but I made a mistake, no problem though, the slightly larger cutout worked perfectly. Other parts I found at advance auto parts, being the adapter pieces to fit into the end so that the cutout pipe could be fitted to the slip fit and C-clamp connection behind the 3rd muffler. The hardest challenge of this install was the single bolt flange that I would need, they are nowhere to be found, absolutely no one sells them. It had to be manufactured.

With the flex pipe removed from the car, we traced the flange onto a piece of 1/4" steel, and cut it out with a cutting torch.

It was a work in progress, we took a grinder to it to shape it better and smooth the edges, then using a drill press, we cut the 2 3/8" hole in the middle, and spaced and drilled the bolt holes as well. After a quick fitting on the car to determine and mark the direction that the flange needs to be attached, the flange is welded to the end of the cutout on the front side. To slide into the clamp fitting on the rear, we welded an exhaust adapter from advance auto, they've got all kinds of fittings and adapters there, we found one that fit the bill perfectly. The adapter is welded to the rearward facing end of the cutout pipe.

Now its time to remount the cutout, if all went well, everything should fit back into place, rebolt the flex pipe, and the cutout pipe. Since the factory gasket will not seal around the new pipe, high temp silicone (copper) was used to make a new gasket, since it is still flowing through 2 cats, the temp will be within the 700 degree temperature rating. Speaking of temps, some engine block paint was used to help prevent rusting with the pipe itself, its rated for 500 degrees, I'll see how well it holds up. Ian found with this cutout installation that the exhaust hanger on the passenger's side had to be cut off in order for it to fit right. I was able to leave it on there with just the cutout, however the MPP2 unit would hit the hanger, so it had to be removed when the motorized component was added.

Now for adding the MPP2 unit. Installation took a bit longer than expected, but not too bad. I was able to route the wire for the controls up through the rubber grommet in the passenger's side floor, the hole proved to be slightly too small however, and I had to use my Dremel to make it bigger so the plug would fit through, the wire is pretty small, but the plug is huge. After that I used some silicone sealant to make sure the original grommet would stay nicely in place, since now its hole is bigger than it should be. The mechanics of the MPP2 interfere with the passenger's side exhaust hanger. So I had to remove that. No cutting luckily, I just had to remove the 3 bolts that held it in and take it off. Without that one side, I can see the flex pipe hanging just a slight be lower than it was before, so in a temporary setup, I used a wire tie to hold the exhaust up higher, I wrapped it around the exhaust hanger under the car, and on the exhaust, basically does the same thing the stock rubber hangers do, but it doesn't stretch to let it hang down too low, but still allows the exhaust to move. I drove the car for an hour and then got under it, and was able to touch the exhaust hangers on the pipe, they are far enough away from the exhaust that they stay cool, so heat shouldn't be a problem. The single rubber hanger held it up nicely but after a couple of days of holding the whole thing up on its own, it got all stretched out. Installation of the MPP2 itself was pretty strait forward:

Use some high temp silicone to form a gasket between the power plate and the cutout, I didn't think about it at the time, but one of the gaskets supplied with the cutout probably would have worked just fine, so silicone didn't have to be used.

The power plate bolted up perfectly to the Jegs cutout, but you can't really get a socket down into the groves around the mounting holes. It's hard to describe without a picture of it, but a single lock washer allowed the bolt to stick out far enough to get a socket on it until it was tight, a lock washer is a good idea anyway.

Run the power and control wires though the grommet on the passenger's side foot well. As described above, I had to make it bigger to fit the emissions connector I had them install. But from the looks of it, the regular connector is just as hard. It may be easier to cut the wire and reattach it afterwards, the wire itself is small, the connector is huge.

Remember to tie the wire up under the car, it would be really nasty if it snags something and pulls half your exhaust off with it.

Mount the switch and connect to power. I mounted mine in my switch panel below the stereo head unit, but for closer to stock cars the swing down cigarette lighter tray is a good place to mount it. Only two wires need to be hooked up the old fashioned way, the power and ground, which are attached to the switch. I happened to have ACC terminal blocks in my car which are perfect for it, but if not, it uses very small wires, and is fused at 5A, so the cigarette lighter power would be more than adequate.

Test it out, if all goes well, you're done!

Heads up on the functioning of the switch, it is a two way rocker, one way is open, the other is close, but one press doesn't open or close all the way, it just activates the motor until it reaches it stopping point. so to open it you have to hold the button until its all the way open. I was a bit disappointed at first, but then I thought it does give the ability to open the plate to any position, so you can maximize backpressure and torque at lower speeds, and still have the awesome sound.

Performance of the cutout:

I've heard before that the rumors about backpressure being needed for low end torque is just a hot-rodder's myth, but honestly, the butt dyno shows a noticeable loss in low end torque when the plate is opened. But on the other hand, it turned every head at the CCVT car show today! The sound with the plate open is unreal! Although it may not improve performance in the quarter, it really sounds good. Not that the car is without power with the plate off, it still pulls pretty well, but it just doesn't feel as fast way down low. The high end definitely will benefit from the increased air flow, but being non street legal when opened, I couldn't try out the high end performance. I'm thinking that after the power plate is installed, I can hit the switch just after launch at the track, should be about perfect timing for maximum low end, and maximum high end.


I remember one of the guys on this list added one of these to his car, I was curious where you put it. I was thinking of putting it where the 3rd cat is located now.



I think Ian put it in place of his flex pipe..



You need to leave the flex pipe in place, it keeps the exhaust from tearing itself apart when the engine moves, replace your 3rd cat with it.



I put mine where the 3rd cat was. It's bolted right to the flange of the flex-pipe. The cut-out is then connected to a straight pipe which is in place of the resonator. Unfortunately the cut-out didn't last the winter but I'm picking up another tomorrow. There's a brass rod that actuates a microswitch that turns on an LED to tell you when the cut-out is closed. It seized in place and prevented the motor from turning and one of the gears in the motor lost a tooth.

The new one I order without the rod and microswitch. I didn't need an LED to tell me when the cut-out was open.


It should be noted that as far as I know, Ian was the first to do this.


Very true, and Iíve noticed that the LED doesnít even work that well, it doesnít turn on until the cutout is almost completely open, and you hear the roar from the engine at the first crack. Sucks that your cutout bit the dust, I painted mine with engine block paint hoping that being behind the cats it might survive, the paint didnít make it though, the cutout is still fine. I might try to find an even higher temp paint and keep working on it, something to keep the salt off. Oh, and when you put your cutout back on, I would advise using something to close off the opening in the heat shrink around the motor, my motor died because of salt in there, replaced under warrenty, but I missed it! I probably should not have had it on at all during the winter time, but its supposed to be okay with it, anyway, they sent me a new motor and let me rebuild it myself, so I protected it from water all the way down to the electrical connector.



My thanks to Mike who once again came through with a comprehensive write up on how to do this project. I was able to see and hear Ian's car at the Fall Lapeer Drag outing. AWESOME is one word to describe it. When he opens the gate, there's no doubt that the soul of the beast is heard!


Hey Larry, can you add this to the cut-out page:

(from one of my posts on TCCA) A good muffler shop should have a flange that they can weld on and bolt it up to the stock flexpipe.

I almost forgot, get the cut-out installed with the Mccord power plate installed on it. Otherwise you may run into problems mounting the MPP. I got lucky with it.

I had some problems with my cut-out on Sunday. I was attempting to re-install the power plate (I take it off for the winter as the salt will kill it) and managed to break the remaining two studs. I had previously broke the first one. John Hamilton got out a grinder and ground off the heads of the studs and gave me a couple of nuts & bolts to replace the studs with. The studs on the Jeg's cut-out are actually nuts that have been welded to the cut-out. Using bolts instead of the studs will allow you to replace them every year without having to fight the rust. They get pretty rusty after a couple of years.



Contact Information