The GFB Whistling Trumpet was developed in response to repeated requests for an alternative trumpet that produces a distinctly different blow-off sound.

As the ability to tailor the sound of a blow-off valve has become increasingly important, GFB first introduced the original Whistling Trumpet (part #5701) in 2004. This version produced a sharp, piercing whistle under aggressive driving, but it was only effective on certain valve types and typically required high boost and engine speed.

To address this limitation, GFB released the 5702 Whistling Trumpet. This updated design is intended for lower boost applications where the 5701 does not perform as effectively, making it suitable for a broader range of GFB valves.

The 5702 can be fitted in place of the standard trumpet on all GFB blow-off valves and is designed to generate the whistling sound more easily than the 5701, and at a slightly higher pitch. As with the original whistling trumpet, best results are achieved when all or most of the air is vented through the trumpet.

Valves configured for partial recirculation—such as Respons valves set to 50/50 venting—typically do not produce sufficient air velocity to generate the whistle.

Recommended for:
GFB Respons and Deceptor Pro II blow-off valves, excluding part numbers T9003 and T9503.