Introducing our latest 9A1 GT4 based engine, the 4.25L GT4.

As many of you know we designed, produced and introduced the 4.0L GT4 engine parts 3 years ago and have since tested, raced and driven them with over 300 hours on the race track, thousands of miles of street use and countless DE’s to refine the tune and test the durability. The 4.0L was available with the added X51 power kit to produce more peak HP but with a little less available TQ as it made power much higher in the rev range. With ZERO failures to date we are proud to introduce our most powerful GT4 engine yet, the 4.25L

As with the 4.0L, the 4.25L engines we produce are built with 2 “personalities”, the “Street/track” and the “Street/Race” versions.

The street engine was designed with TQ as a priority and plenty of HP, we wanted a motor that pulled strong from 2500 to 6000 RPM, an engine that didn’t leave you wanting to “re-gear” the trans just to enjoy the power. Our 4.25L engine in street trim using the stock side intake runners with a Carrera S center section and large TB produced 376.2 rwtq at 5600 rpm and 445.5 Peak HP at 6300 rpm. This combination feels like turbo power when rolling into the throttle and an absolute blast to drive. Dyno chart is below with the original GT4 Clubsport dyno runs as comparison.

porsche gt4 dyno sheet

The “Street/Race” version of the 4.25L engine was developed with maximum peak HP in mind. Utilizing the factory GT3RS intake manifold we mated it to our 4.25L engine to produce 488.5 rwhp at 7900 rpm with 360 rwtq at 6200 rpm. Using the factory intake significantly reduces the cost of the high RPM motor compared to using the X51 kit as we did with the 4.0L engines. This combo is excellent for the street and is perfect for Eating up GT3RS cars on the track.

The second dyno sheet below comparing our GT4 4.25L race to a factory stock 2016 GT3RS. This is the “Street/Race” compared to the same car as stock before conversion.

Here is a comparison of the 4.25L GT4 “Street/Race” GT4 to a Factory stock 2016 GT3RS, I’d be betting on the GT4!!

Below are a few pictures of the development process, pistons, intake adapters as well as some shinny engine hardware parts to drool over. 

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