About Blow Performance Exhausts
Blow Performance Exhausts manufacture performance exhaust systems for stock Harley Davidson Sports & Touring models, and some Custom and Chopper Motorcycles with 80 ci to 131 ci. Evolution & Twin Cam Engines.
Our designs deliver increased performance and great sound as well as a variation in looks with our bonus 3 heat shield sets with every kit. We are committed to our customer's satisfaction and stand proud behind our product and service. 4 years in design and testing, we are proud of what we have created for our biker communities’ worldwide.
We wanted to find out exactly how good our Blow Performance Exhausts were so we went down to Maztech of Melbourne, and hooked up with Anthony Rodrigues, undoubtedly one of Australia’s best Dyno tuners.
We compared our exhausts to stock Harley Davidson exhausts and one of the world’s best sellers, Big Radius 2 into 2, by Vance & Hines.
Blow delivered an additional 23.9 horsepower on the stock factory exhausts and a massive 12.1 horsepower on the Vance & Hines Big Radius. This bike was now pulling 89.7 real horsepower at the back wheel by simply bolting on our exhaust kit and a sports air cleaner and having Maztech Dyno tune the engine.
3-Step Tuned Headers
Blow Performance Exhausts are 3-Stepped Tuned Headers. From the exhaust port our header pipe merges into a larger diameter header pipe and then once more merges into an even larger diameter header pipe thus consisting of multiple step ups along the length of the exhaust pipe.
The first step is placed where the exhaust port ends (44.5 / 1.75) and the exhaust pipe begins. To prevent reversion this is left as a step rather than making the pipe diameter match the port diameter thus, preventing exhaust gases from flowing backwards into the combustion chamber after the piston reaches TDC. The second step diameter is (55 / 2.17) is found at a calculated distance and the 3rd and final step diameter is (63.5 / 2.50) is found once again at a calculated. distance. The steps are placed for the greatest performance level achievable by our Blow Performance Exhaust System.
Blow Performance Exhausts are designed for high RPM's and run at greatest performance without collector’s, mufflers, or baffles. The first step helps prevent reversion, thus giving power at low RPM's. Steps placed further down the pipe create pressure drops in the flow of the gases, and increase power at higher RPM's. Our designs work with the exhaust pulse and give a broad power band on 80 ci -131 ci EVO & Big Twin Engines.
Specifically designed and calibrated for piston to valve synchronization, our pressure wave begins to travel down the tube, when it reaches the end of the tube it reverses as a vacuum wave and comes back towards the cylinder. Our tuned headers time that wave to hit right around the closing of the exhaust port, this boosts scavenged residuals out of the cylinder while the intake begins to fill.
Blow Performance Exhausts first primary length is close to the exhaust port. This prevents a sudden drop in velocity due to a volume increase from head port to exhaust tube, from there we start stepping up the diameter.
Scavenging is the effect generated by harnessing the inertial energy of a high velocity exhaust gas pulse. The best performance exhaust system has no back pressure, this is misunderstood and confused with the pressure wave.
A high velocity pulse of exhaust gas carries with it energy; as the pulse moves through space it displaces the following volume behind it. This generates a low-pressure zone like a weak vacuum. Scavenging effect is created, a low-pressure area is left in the vacated cylinder ready for the incoming intake charge. When the intake valve opens the air/fuel mixture can cram in even before the piston begins to travel toward bottom dead center (BDC) — this generates a very mild forced induction effect. I We refer to this as “Induction Boost”
APL Performance Bikes
Windsor Sydney NSW Australia
Address: Unit 2, 18a Walker Street South Windsor NSW 2756
Tel: +612 4587 7557 Mob: 0419 262 311
Harley Davidson 2001 Softail Deuce with 1550 engine producing approx. 65 HP boosted to an incredible 95.2 HP after fitting Blow Performance Exhausts, a Sports Air cleaner and Dyno Tuned by APL Performance Bikes.