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Should you run a 4 inch exhaust?

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Recently we have had a rash of tune inquires focused around 4" exhaust systems on the F150 trucks, specifically about trying to tune back in some lost power they have developed with these systems.


From the factory, the stock exhaust is engineered to create the proper back pressure for the size of the stock turbo, and stock calibration. When opening up this airflow, there is a considerable loss in low end power and torque because of the loss in back pressure, especially without running a performance tune to help compensate for these changes. Specifically, this is due to an increase in turbo lag.


With a 4 inch exhaust specifically, we see a much more exaggerated negative impact due to increased turbo lag, which results in a decrease in low end power. Additionally, we are seeing people complain of poor gas mileage, poor driving feel, and reduced towing capabilities, all because of having to lean on the truck harder to do the same things it did before with less throttle input.


For these reasons, we decided to properly size our Thunderstorm exhaust, so as to find that balance of back pressure necessary for quick spool up times, yet ensuring enough flow at high RPM/Boost to ensure no restriction of power capabilities. So, in short our Thunderstorm exhaust will keep the responsiveness you love while still increasing hp/tq!


If you have any more questions or would like to contact us about exhausts to fit your truck, give us a call or visit our website.


(313) 561-5500



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This has been an ongoing problem with Ford trucks...back in the day when I had a 5.4 normal aspirated truck, people were complaining about the same lose of power when they switched from the stock exhaust to a true dual exhaust system.  I changed to a catback system and did not experience any lose of power. Although those late ninety vintage trucks with the 2V 5.4 didn't have a large amount of power/performance to begin.

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