Bully dog’s rule of thumb for exhaust sizes, Introduction – Bully Dog 81222 Rapid Flow User Manual
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rAPid FlOW inSTAllATiOn
rapid Flow exhaust # 81222
INTRODUCTION
The Bully Dog Rapid Flow Exhaust Systems have been specially designed to allow the lowest mandrel
bends in the industry. The lower mandrel bends allow increased air flow which reduces exhaust tem-
peratures, burns more fuel in the combustion chamber adding additional horsepower and fuel economy.
This instruction set covers the 4” Rapid Flow Exhaust Aluminized Dual Exhaust designed specifically for
the 7.3L Power Stroke.
BULLy DOg’S RULE OF ThUmB FOR ExhAUST SIzES
300 HP
400 HP
500 HP
600 HP
4” Exhaust
Systems for
HP Applications
Less Than
450hp
5” Exhaust
Systems for
HP Applications
Between 450hp
and 550hp
6” Exhaust Systems
for HP Applications
over 550hp
4”
Ceramic-Coated
Exhaust System
for all HP
Applications
Note: This instruction set and the Rapid Flow Exhaust systems included are made for the Ford
7.3L Power Stroke ‘99-’03