Electric Exhaust Cutout Kits

Short answer: assume off road and track use only, and check your own state before you buy.

Two separate laws apply and people confuse them constantly.

Noise law. California, Maine and Montana use a hard decibel limit of 95 dBA measured under SAE J1492. Most other states use vague "excessive or unusual noise" wording, which in practice means an officer's judgment. For reference, most factory exhausts on powerful sports cars sit under 75 dBA, so an open cutout clears the limit easily.

Muffler bypass law. This is the one that catches people. California Vehicle Code 27150(a) names cutouts and bypass devices specifically and prohibits them on registered vehicles, regardless of how quiet you keep it. A California citation can now be an immediate fine rather than a fix it ticket. Several other states have similar bypass language.

Emissions is a separate question. Mounting the valve behind the catalytic converter does not remove or disable any emissions device, so it is not federal Clean Air Act tampering. Mounting it ahead of the cat does bypass emissions hardware and is illegal everywhere in the United States.

Practical guidance: drive with it closed on the street, open it at the track or on private property. That is how the vast majority of our customers run these kits.

Some seepage when closed is normal on every electric cutout ever made, including ours. Anyone claiming a permanent gas tight seal is overselling. The gate operates in a housing that cycles from ambient temperature to over 300°F, and thermal expansion eventually opens a few thousandths of an inch at the seal face.

What that means in practice: a faint change in tone at low rpm, not a loud leak. Most owners never notice it.

Drone is a different issue and it is mounting related, not a defect. Cabin drone happens when the open pipe exits under the passenger compartment. It is almost entirely controlled by where you weld the valve in.

To minimize both: mount the cutout as far rearward as your build allows, ideally just ahead of the muffler, and orient the outlet downward and rearward so exhaust is not directed at the floorpan. See the mounting position table above for the full comparison.

This is the most common failure in the entire category across all brands, and it is largely preventable.

The mechanism is straightforward: water enters the housing from road spray or a car wash, and it either freezes solid or carries road salt that corrodes the gate track. A valve that has sat unused for four months is far more likely to bind than one that gets exercised.

The single most effective thing you can do: cycle the valve fully open and fully closed once a month, every month, all year. Also cycle it once after any car wash or after driving through standing water. Thirty seconds of maintenance prevents the majority of cold weather failures.

EVIL ENERGY current specification: operating range 32°F to 302°F (0℃ to 150℃), 12V. In sub freezing conditions, cycle the valve once before driving to break up any ice at the gate. If a valve seizes due to a manufacturing or material defect rather than neglect, send photos to our support team.

If you park outdoors in a heavy salt state year round, this is worth factoring into your decision honestly.

Depends on which kit you buy, and the honest answer is that most people should budget for a shop.

What is genuinely DIY: the wiring. Every EVIL ENERGY kit includes the controller, harness and roughly 11.5 ft of extension wire, enough to route from the valve to the cabin. Basic hand tools and a fuse tap are sufficient. Budget one to two hours.

What is usually not DIY: the pipe work. The valve has to be spliced into your exhaust with a proper seal.

Typical shop cost for welding a cutout in: $40 to $150 depending on region and how accessible your exhaust is. This is one of the cheapest labor jobs a muffler shop does. Any independent muffler shop can handle it.

Two things to prepare before the shop visit: know your pipe outside diameter so you buy the right size the first time, and decide your mounting position in advance so the tech is not guessing.

If you have no welder access at all, look for a catback Y pipe kit in this collection, which uses clamps rather than welds, though a welded joint will always seal better long term. Pair it with our narrow band exhaust clamps for a clean slip fit.

Realistically, less than the internet tells you, and possibly close to zero.

You will see "20+ horsepower" claims all over this category. Treat them skeptically, including when a competitor makes them. Here is the actual mechanism, which makes it easy to predict your own result.

A cutout does not create flow. It only frees up power if your exhaust was restrictive in the first place, by letting gas exit ahead of the restriction. So the gain depends entirely on what is downstream of the valve right now.

• Stock restrictive muffler on a modified or boosted engine. This is the best case. Your engine is making more exhaust volume than the factory muffler was designed to pass, so opening the valve removes a real bottleneck. Expect a gain you can actually feel.
• Stock exhaust, stock engine. Small. The factory system is adequate for factory output, so there is not much restriction to remove.
• Already running a high flow catback. Close to nothing. You already solved the restriction when you bought the catback. At this point you are buying sound, not power, and that is a perfectly good reason to buy one.

Where a cutout genuinely wins is value, not peak power. A full catback exhaust system runs several hundred dollars and permanently commits you to one volume level, whether you are at the track or leaving for work at 6am. An electric exhaust cutout kit starts at $155, gives you factory volume on the commute and open pipe volume on demand, and comes back off if you sell the car.

Buy it for exhaust sound control. Treat any power gain as a bonus.