Granatelli 307525D 2.5-Inch Electronic Exhaust Cutouts – Set of 2

What Does an Electronic Exhaust Cutout Do?

A traditional exhaust system forces exhaust gases through components such as:

• Mid-pipes
• Resonators
• Mufflers
• Tailpipes

An exhaust cutout creates an alternate path.

With the valve:

CLOSED

exhaust continues through the normal exhaust system.

With the valve:

OPEN

exhaust exits through the shorter cutout path before reaching some of the downstream sound-control components.

The result can be a dramatic increase in exhaust volume.

Depending on the engine and exhaust combination, the shorter path can also reduce downstream exhaust restriction.

Don’t Assume an Exhaust Cutout Automatically Adds Horsepower

Opening a cutout can reduce exhaust restriction.

That does not guarantee a specific horsepower or torque increase.

The actual result depends on:

• Engine airflow
• Camshaft
• Headers
• Exhaust diameter
• Catalytic converters
• Muffler restriction
• Turbocharger configuration
• Cutout location
• Engine tuning

A highly modified engine restricted by a quiet street exhaust may respond noticeably.

A mostly stock engine with an already efficient exhaust may primarily become:

louder

Sometimes considerably louder.

Our How to Install Exhaust Cutout the Right Way guide covers installation, placement, wiring and common mistakes in detail.

Designed for 2.5-Inch Exhaust Systems

The 307525D is intended for:

2.5-inch / 63mm exhaust tubing

That makes it useful for many dual-exhaust systems found on:

• Muscle cars
• Street rods
• Trucks
• Restomods
• Naturally aspirated V8s
• Mild turbo builds
• Custom exhaust systems

Measure your exhaust before ordering.

A 2.5-inch cutout does not magically become a 3-inch cutout because the rest of the build is cool.

Reducers can be fabricated, but every transition adds complexity and another potential leak point.

Set of Two for Dual Exhaust Systems

The D configuration gives you a pair of cutouts.

That makes it particularly appropriate for true dual-exhaust vehicles where each side has its own exhaust path.

Examples include custom systems with:

• Dual headers
• Dual mid-pipes
• X-pipes
• H-pipes
• Separate mufflers

Depending on the system layout, one valve can be installed in each exhaust bank.

For more information on dual-exhaust layout, see our X Pipe vs H Pipe: Which Sounds Better? guide.

Electronic Operation

The advantage of an electronic cutout is simple:

You don’t have to crawl under the vehicle and remove a block-off plate every time you want to change the sound.

An electric motor operates the cutout valve.

That allows the system to switch between:

NORMAL EXHAUST PATH

and:

OPEN CUTOUT

from inside the vehicle when used with the appropriate Granatelli controls and wiring.

Granatelli’s electronic cutout systems use a geared electric motor design intended to move the valve fully between the open and closed positions.

Granatelli One-Touch Cutout Technology

Granatelli’s complete electronic-cutout systems use a one-touch control strategy intended to prevent users from continuously holding the switch against the mechanical stops.

That’s useful because repeatedly driving an electric valve motor against its stop can place unnecessary load on:

• Gears
• Motor
• Valve mechanism

Granatelli describes its system and cutout range on its official exhaust cutout page.

Stainless-Steel Construction

The 307525D is sold as part of Granatelli’s stainless-steel electronic exhaust-cutout family.

That’s important because cutouts live in an unpleasant environment.

They are exposed to:

• Exhaust heat
• Condensation
• Water
• Road debris
• Temperature cycling
• Vibration

Corrosion resistance matters.

So does correct installation.

Even good hardware doesn’t enjoy being mounted directly in the blast furnace behind a header collector.

Keep the Cutout Away From the Headers

Granatelli’s installation instructions specify that the electric exhaust gates should be installed as far from the headers as practical and:

no less than 18 inches from the collectors.

Granatelli rates its electronic cutout system for short periods at temperatures up to approximately:

800°F

Moving the electric valve farther downstream can reduce the thermal stress placed on:

• Electric motor
• Wiring
• Bearings
• Valve mechanism

You can view Granatelli’s official electronic exhaust cutout installation instructions.

Where Should You Install an Exhaust Cutout?

Placement depends on the vehicle and exhaust system.

For most performance builds, consider:

• Header collector location
• Catalytic converter location
• Resonators
• Mufflers
• Driveshaft
• Transmission
• Fuel lines
• Brake lines
• Wiring
• Floor clearance
• Suspension movement

For street-oriented applications, placing the cutout downstream of required emissions equipment avoids using the valve to bypass catalytic converters or oxygen-sensor functions.

Our complete How to Install Exhaust Cutout the Right Way article walks through selecting a safe location.

Don’t Aim the Outlet at the Floor

Cutout orientation matters.

The open exhaust outlet should not direct hot exhaust toward:

• Fuel lines
• Brake hoses
• Wiring
• Transmission components
• Plastic underbody panels
• Floor insulation

You also need adequate ground clearance.

This becomes especially important on lowered vehicles.

A beautiful electronic cutout hanging an inch below the rest of the exhaust has effectively volunteered to become the vehicle’s speed-bump sensor.

Is the Granatelli 307525D Universal?

The 307525D is a:

universal custom exhaust component

It is not a vehicle-specific bolt-on exhaust system.

Fitment depends on whether your vehicle has:

• 2.5-inch exhaust tubing
• Adequate installation space
• Sufficient ground clearance
• A suitable weld-in location
• Safe electrical routing

Custom fabrication may be required.

This is exactly the kind of component where measuring before ordering matters.

Weld-In Installation

The 307525D is associated with Granatelli’s:

stainless-steel weld-in electronic cutout system

Proper welding provides a strong and leak-resistant installation when performed correctly.

The work typically involves:

1. Selecting the cutout location.
2. Measuring the exhaust.
3. Fabricating or installing the appropriate branch/Y-section.
4. Positioning the electronic valve.
5. Tack welding everything.
6. Rechecking ground and component clearance.
7. Completing the welds.
8. Wiring and testing the valve system.

If you’re not comfortable welding exhaust tubing, use a professional exhaust shop.

Granatelli itself recommends qualified installation when the owner isn’t experienced with exhaust fabrication.

This Is the Cutout-Only Set

This is important for your product listing.

307525D is sold as the 2.5-inch electronic exhaust cutout-only set of two.

Do not advertise it as including every component required to convert a stock exhaust system.

Depending on the existing exhaust and how you intend to control the valves, installation may additionally require:

• Y-pipes
• Wiring harness
• Switch/controller
• Fuse
• Connectors
• Exhaust tubing
• Welding
• Heat protection
• Mounting hardware

Granatelli sells complete electronic exhaust-cutout kits separately.

If a shopper wants the entire system rather than replacement/add-on cutout assemblies, verify the appropriate complete Granatelli kit before ordering.

307525D vs 307525K

These part numbers are easy to confuse.

Granatelli 307525D

2.5-inch electronic exhaust cutouts only — set of two

Best for customers who already have the necessary exhaust plumbing or are building their own custom system.

Granatelli 307525K

Granatelli lists 307525K as its dual 2.5-inch stainless-steel weld-in electronic exhaust cutout kit.

If you need the entire installation package, verify the complete-kit contents instead of assuming the 307525D includes everything.

Granatelli’s current lineup is available through its electronic and manual exhaust cutout catalog.

Will a Cutout Change Exhaust Sound?

Absolutely.

Opening the valve bypasses downstream sound-control components.

Depending on placement, that can bypass:

• Mufflers
• Resonators
• Long sections of tailpipe

The result can become:

• Louder
• Sharper
• More aggressive
• More raw

Cammed V8s can sound dramatically different through open cutouts.

Turbocharged engines can also become much louder because less of the downstream exhaust system remains between the turbine and atmosphere.

Closed Cutout for Normal Driving

When properly installed and sealed, closing the electronic valve directs exhaust through the conventional system again.

That allows the vehicle to retain its normal:

• Mufflers
• Resonators
• Tailpipes

This is one reason electronic cutouts are attractive to street/strip enthusiasts.

You can build a relatively controlled exhaust system for normal driving while retaining the ability to open a shorter exhaust path when appropriate.

Our Catback Exhaust vs Axleback: Which Wins? guide explains how the other major exhaust-system configurations affect sound and performance.

Will It Improve Torque?

Maybe.

But don’t advertise a guaranteed torque gain.

Exhaust-system performance is more complicated than:

less backpressure = more torque.

Exhaust velocity, scavenging, pulse timing, pipe diameter and engine configuration all matter.

Some engines may gain power at high RPM when a restrictive muffler system is bypassed.

Others may show almost no measurable difference.

The correct sales claim is that opening the cutout can:

reduce downstream exhaust restriction where the existing exhaust is restrictive.

That is technically defensible.

“Adds torque to every vehicle” isn’t.

Turbocharged Applications

Cutouts can be particularly interesting on turbocharged builds.

Reducing restriction after the turbine can potentially reduce turbine outlet pressure.

However, the actual benefit depends on:

• Turbo size
• Downpipe
• Catalytic converter
• Existing exhaust diameter
• Mufflers
• Boost level
• Engine calibration

Never use a cutout as a substitute for properly designing the rest of the exhaust.

For more information about exhaust flow and performance hardware, see our Best Exhaust Manifold Upgrade for Real Gains.

Wiring Matters

Electronic cutouts live underneath the vehicle.

That means the wiring is exposed to:

• Heat
• Water
• Dirt
• Road debris
• Vibration

Route electrical wiring away from:

• Headers
• Catalytic converters
• Driveshafts
• Steering components
• Sharp sheet metal

Use:

• Correct circuit protection
• Quality connectors
• Heat-resistant loom
• Proper grounding
• Secure harness routing

Don’t twist two wires together, wrap them in electrical tape and call it a performance wiring system.

Eventually, electricity will submit its complaint.

Check for Exhaust Leaks

After installation, inspect the system for leakage with the cutouts:

closed

and:

open

Watch for:

• Ticking sounds
• Soot around joints
• Exhaust smell
• Valve sealing problems
• Loose welds
• Hardware movement

Exhaust leaks can cause unwanted noise and allow fumes into areas where they don’t belong.

Street-Legal Warning

Electronic exhaust cutout legality varies by jurisdiction.

Granatelli’s own instructions warn installers to check applicable:

• Emissions regulations
• Noise limits
• Safety requirements

before installation or street use.

In California specifically, exhaust cutouts and bypass devices can present significant street-legality problems.

Our older Is My Exhaust Legal? FAQ discusses California exhaust-noise and bypass-device rules, although owners should always verify current state and local requirements before driving.

Do not install or operate the cutout in a way that bypasses required emissions-control equipment.

Is 307525D CARB Legal?

Current retailer listings identify the Granatelli 307525D as:

not CARB approved

and some sellers specifically restrict California sales.

That is particularly important for California customers.

Do not describe the part as emissions legal or CARB exempt unless Granatelli provides a valid Executive Order covering the specific application.

Who Should Buy the Granatelli 307525D?

The Granatelli 307525D makes the most sense for enthusiasts who already have—or are fabricating—a:

2.5-inch dual exhaust system

and want two electronically controlled cutout valves.

It is especially appropriate for:

• Muscle cars
• V8 street cars
• Restomods
• Trucks
• Custom exhaust builds
• Street/strip projects
• Track cars

It is less appropriate for someone looking for a completely vehicle-specific bolt-on system requiring no fabrication.

Why Buy the Granatelli 307525D?

Key features include:

• Two electronic exhaust cutouts
• 2.5-inch / 63mm sizing
• Electronic valve operation
• Stainless-steel system construction
• Universal custom fitment
• Weld-in installation
• Suitable for dual exhaust layouts
• Instant exhaust sound changes
• Potential reduction in downstream exhaust restriction
• Granatelli Motorsports performance-exhaust design

The biggest advantage is control.

Build a conventional muffled exhaust for normal operation, then use electronically controlled cutouts to access a shorter, substantially louder exhaust path when the vehicle and local rules allow it.

Specifications at a Glance

Brand: Granatelli Motorsports
Part Number: 307525D
UPC: 802735036794
Product: Electronic Exhaust Cutouts
Quantity: Set of 2
Exhaust Diameter: 2.5 inches / 63mm
Material Family: Stainless steel
Installation: Weld-in/custom
Fitment: Universal
Primary Application: Dual-exhaust performance vehicles
CARB Status: Not listed as CARB approved
Installation Note: Granatelli specifies at least 18 inches from header collectors
Temperature Note: Rated for short exposure up to approximately 800°F according to Granatelli installation instructions

Always verify exhaust diameter, available underbody space, system layout, required installation components and applicable emissions/noise regulations before ordering.