Cummins J Hook Mod

Increase Boost with the J Hook Mod





Cummins J-Hook The J-hook upgrade for the Cummins turbodiesel is a relatively simple and cost-effective modification. It allows for more turbo boost by holding the wastegate closed longer. This increases the amount of air being forced into the engine, thus increasing the performance potential. Since the Cummins is capable of handling higher than stock boost levels, the modification is relatively safe and effective.


Otherwise Known As:

J-hook, Cummins J-hook

How It Works:

A J-hook for the Cummins turbodiesel attaches to the turbocharger wastegate and holds it closed longer than stock, allowing more turbo boost to be produced. The wastegate is designed to funnel exhaust gases around the turbine of the turbo when a certain amount of boost is acheived. By keeping it closed longer, higher boost levels can be acheived, increasing performance by feeding the engine more air.


• Affordable price tag.
• Noticeable performance gains.
• Lower exhaust gas temperatures.


While the engine can handle the extra boost, you may be pushing your stock turbocharger.

Possible Problems:

A J-hook upgrade should allow you to build around an extra 10 psi of boost, which puts you close to the stock turbocharger's limits.

Est. Gains:

Gains will be more noticeable if you have upgraded injectors or a tuner/programmer.


5.9L Cummins

Additional Info:

On a budget? Many owners build their own modified J-hooks using components available at their local hardware store.













































You may also be interested in the following articles

Turbocharger Guide

Lift Pump Upgrade

Cummins Heater Grid

Fuel Stop Plate