Snow Performance 30 PSI Hobbs Switch

Automatic Boost Safety Shutoff for Water Methanol Injection Systems

The Snow Performance 81081 is a 30 PSI Hobbs switch designed for use with water methanol injection systems where automatic shutoff protection is required when boost pressure drops below the injection engagement threshold. A Hobbs switch is a pressure-actuated electrical switch that closes when system pressure reaches the set point and opens when pressure falls below it. In a water methanol injection application, the Snow Performance 81081 serves as a safety interlock: it enables injection fluid flow only when boost pressure is at or above the 30 PSI set point, ensuring water methanol is not injected into the engine at low boost conditions where the charge air temperature and detonation risk do not warrant its use. This protects the engine from unintended fluid delivery during startup, low-load driving, and conditions where the turbocharger has not yet reached target boost. The 81081 is the Stage 2 replacement Hobbs switch for Snow Performance water methanol injection kits and can also be used as a standalone pressure-activated safety switch in custom injection controller wiring.

Key Features

• Snow Performance 81081 30 PSI Hobbs pressure switch for water methanol injection safety control
• Automatically enables injection flow when boost pressure reaches 30 PSI, cuts off below that threshold
• Air pressure actuation for fast, accurate response to boost pressure changes
• Stage 2 replacement Hobbs switch for compatible Snow Performance water methanol injection kits
• Also compatible with custom injection controller wiring as a standalone pressure-activated safety switch
• Compact, lightweight design for easy mounting in the boost line or intake manifold

Specifications

What's Included

• 1x Snow Performance 81081 30 PSI Hobbs pressure switch

Frequently Asked Questions

A Hobbs switch is a pressure-actuated electrical switch that remains open (no current flow) below its set pressure and closes (allows current) when pressure meets or exceeds the threshold. In a water methanol injection system, the Snow Performance 81081 is wired in series between the controller power and the injection pump or solenoid valve. When boost reaches 30 PSI, the switch closes and enables fluid delivery. If boost drops below 30 PSI, the switch opens and disables injection, preventing methanol delivery under low-load or off-boost conditions.

Yes. The Snow Performance 81081 is listed by Snow Performance as the Stage 2 replacement Hobbs switch. If the original switch in your Stage 2 kit has failed or been damaged, the 81081 is the correct replacement to restore automatic pressure-based injection control.

Yes. The 81081 is a standard pressure switch and can be used with any injection controller or relay circuit that accepts a normally open (N.O.) pressure switch input. Confirm the electrical specifications (voltage and current ratings) match your controller's switch input requirements before installation.

Yes. The 81081 is used in Snow Performance diesel Stage 2 water methanol injection systems where the injection engagement point is set at 30 PSI of boost. High-boost diesel applications such as performance pickups and competition diesel trucks commonly use a 30 PSI Hobbs switch to trigger water methanol injection at peak boost loads.

If the 81081 fails closed, the injection system will deliver water methanol continuously regardless of boost pressure, including at idle and low load. Continuous injection at low boost can potentially cause engine roughness, dilution of the fuel charge at light throttle, and in some cases fuel system issues depending on the injection nozzle size and fluid flow rate. Inspect and test the Hobbs switch periodically if injection system behavior changes unexpectedly.

If the 81081 fails open, the injection system will not deliver water methanol at any boost level, effectively disabling injection protection. On high-boost applications relying on water methanol for detonation suppression, this removes that safety margin. The engine will not be immediately harmed by a loss of injection, but the detonation threshold may be reduced at peak boost on aggressive tunes.

Snow Performance's product description for the 81081 refers to it as a 30 PSI Hobbs switch. Verify with Snow Performance's current product documentation whether the threshold is factory-fixed or field-adjustable, as some Hobbs switches include an adjustment screw. For a variable-threshold switch covering a wider pressure range (such as 2-15 PSI for lower-boost applications), Snow Performance offers separate adjustable boost pressure switch models.

The Snow Performance 81081 should be tapped into the boost pressure reference line per the wiring diagram in your Snow Performance kit instructions. Typically, this is a small-diameter hose from the intake manifold or the outlet of the turbocharger intercooler. The switch threads into a fitting on the boost reference line. Electrically, the switch is wired in series with the injection pump or solenoid relay so that injection activates only when the switch closes at 30 PSI of boost.

Installation Instructions

1. Identify the boost pressure reference port in your Snow Performance water methanol injection system per your kit's wiring and plumbing diagram.
2. Thread the 81081 Hobbs switch into the appropriate fitting on the boost reference line. Use thread sealant on the threads if required by your fitting type. Do not overtighten; tighten to the torque specification listed in Snow Performance's documentation.
3. Route the Hobbs switch electrical leads to the injection controller or relay wiring harness.
4. Connect the switch in series with the injection pump or solenoid valve circuit per your kit's wiring diagram. The switch should be wired as a normally open contact that closes at 30 PSI.
5. Secure all wiring away from heat sources and moving components using zip ties or existing wiring looms.
6. Start the vehicle and verify the injection system does not activate at idle (below 30 PSI boost).
7. Perform a boost run under safe road or track conditions and verify injection activates at or above the 30 PSI set point using your injection system's LED indicator or data logging.
8. Inspect all plumbing connections for boost leaks after the first test run.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.