AuxJection FAQ

What is AuxJection?

AuxJection is an auxiliary fuel system for LT-based platforms designed to work with the factory ECU strategy. It adds supplemental fuel when the direct injection system reaches its limit, without relying on a standalone controller or traditional port injection setup.

How does AuxJection work?

AuxJection does not spray all the time. It delivers a calculated fuel pulse only when the direct injection system can no longer meet fuel demand on its own. In other words, it supplements the factory DI system when airflow and fuel demand move beyond what DI can support by itself.

Will AuxJection make the car run rich all the time?

No. AuxJection is designed to add fuel only when needed. It is not constantly dumping fuel into the intake regardless of load.

Will AuxJection still behave like stock?

Yes. The goal of AuxJection is to integrate with the factory ECU strategy as if it were a factory option. The system is only used when needed and should require very little maintenance outside of normal vehicle maintenance.

Please review fitment before ordering. AuxJection compatibility depends on supercharger setup, throttle body, intake tube, and belt drive configuration.

Stock LT4 Kits are only compatible with stock LT4 supercharger platforms and LT1/LT4 Whipple 2.9L/3.0L
Magnuson 2650 Kits are only compatible with supported LT1/LT4 Magnuson 2650 applications
Compatible with stock throttle body up to 103mm bore
Adds approximately 1 inch to the supercharger snout
Depending on your intake, minor tube or coupler modifications may be required
This product does not fit Camaro ZL1 with a standard Roto-Fab intake
Roto-Fab Big Gulp and JLT large tube intakes are compatible with minor modifications; fitment of other large tube intakes is not guaranteed
May have belt-to-throttle body clearance issues with aftermarket idler relocation brackets; fitment is only guaranteed with the stock belt drive setup
A custom throttle body to intake tube coupler is currently in development to simplify Camaro intake tube installation (expected availability: June/July 2026)
DO NOT use with VP Import, Q16, or other MTBE oxygenated fuels

Why use AuxJection instead of larger direct injectors?

Larger aftermarket direct injectors for LT platforms can get expensive quickly and still come with tradeoffs. In many cases, an aftermarket high-pressure fuel pump is also needed along with the larger direct injectors. AuxJection provides supplemental fueling while keeping the factory ECU in control.

What kind of power can AuxJection support?

Power support depends on the full combination, especially the low side, high side, camshaft fuel lobe, and ethanol content. We have made over 850 whp on a stock LT4 high side, stock cam, full E85, and a low side maintaining 70+ psi. We have also made over 950 whp on full E85 with an aftermarket camshaft and +30% fuel lobe.

Can AuxJection support full E85 on a stock LT4?

Yes, depending on the rest of the setup. Low-side pressure may drop slightly at higher RPM, but AuxJection factors low-side pressure into the injector flow calculation to account for that.

What does the rest of the fuel system need to look like to take AuxJection to its max potential?

For maximum potential, an aftermarket camshaft with at least a +30% fuel lobe is recommended so the direct injection system can operate at its highest potential first. A strong auxiliary low-side fuel system that can maintain 70+ psi is also preferred. We have had great results with DSX auxiliary pump systems, including the DSX dual-bucketed pump for Camaro applications.

What applications are currently supported?

The current focus is factory LT4-based supercharged applications.

Does AuxJection work with stock throttle body and 103mm throttle body setups?

Yes. The current LT4 AuxJection kit fits both stock and 103mm throttle body setups. The flange inside diameter is 103mm.

Does AuxJection work with Whipple setups?

Yes. The current LT4 AuxJection kit supports Whipple 2.9L and Whipple 3.0L supercharger LT1/LT4 setups.

Does AuxJection work with Magnuson setups?

Yes. AuxJection is available for Magnuson 2650/2650R LT1 and LT4 applications, including Camaro, Corvette, and CTS-V platforms.

Does AuxJection work with ProCharger, turbo, or centrifugal setups?

Not currently. We do not recommend AuxJection for ProCharger, turbo, or centrifugal applications until more testing is complete. We want engine dyno data and validation for that configuration before offering a kit.

Does AuxJection work with LT1 applications?

LT1 applications are currently supported only when using a stock LT4 supercharger, Whipple 2.9L / 3.0L, or Magnuson 2650 supercharger setup.

Does AuxJection work on Global B applications?

Yes, but Global B applications are not part of the standard public release yet. Global B support is planned for a later release in 2026.

Does AuxJection work with an existing flex fuel sensor kit?

You can reuse your existing flex fuel sensor, but the AuxJection harness and fuel lines are designed to be installed a specific way. Existing flex fuel kit hardware and wiring may need to be removed and replaced with AuxJection components according to the installation instructions.

How many auxiliary injectors does AuxJection use?

The AuxJection plate uses two FID 2200cc injectors.

Is AuxJection easier to install and easier to revert than a full port injection setup?

Yes. AuxJection is designed to be a straightforward supplemental fueling solution and can be removed much easier than a traditional full port injection setup.

Has cylinder-to-cylinder distribution been tested?

Yes. We conducted engine dyno testing with AuxJection and reviewed cylinder-to-cylinder fueling distribution during testing. Results are published in our tech blog.

Does AuxJection make more horsepower?

AuxJection is primarily designed to add fuel capacity, not act as a power adder by itself. That said, some combinations may pick up power from the cooling benefit of ethanol being introduced into the supercharger.

Will AuxJection help with intake air temperatures?

Yes. We have consistently seen significant charge temperature drops when AuxJection is actively spraying ethanol into the supercharger.

Will AuxJection damage the blower or rotor coating?

Based on our early testing, AuxJection has not shown visible signs of rotor coating wear. Since the system is designed to replace traditional methanol injection, it does not affect the rotor coating any worse than a properly set up methanol system. We currently have test vehicles with over 5,000 miles using the kit.

When should I send my tune file?

Do not send your tune file immediately after ordering. Each AuxJection kit includes an instruction card with your personalized unique kit ID number. Once you receive your kit, use your VIN and unique ID from that card to email your tune file for modification.

Where do I send my tune file?

Email your current tune file to:

AuxJection@wisherperformance.com

What should the email subject line be?

Use your VIN number and unique kit ID in the subject line.

Example:
1G1Y82D47L5000324_#010126_01

Including both the VIN and unique ID helps avoid delays.

What file types are accepted?

Accepted tune file formats are:
.HPT or .BIN

How long does the tune file process take?

Most modified tune files are returned within 1–3 business days after the tune file is received.

Do I need to “Write Entire” on the first flash?

Yes. Once your modified file is received, the first flash MUST be done using “Write Entire.”