& THE SOUND OF POWER
For years, muscle and performance cars have oﬀered the exhilaration and thrill of both performance and power, and with today's ongoing muscle car wars its only gotten better.
Modern cars today are infused with technology that oﬀer impeccable roads manners, reliability and power levels with advanced cockpits and interior design bursting with technology and gadgetry. Comfort and noise reduction have also improved through cabin isolation technics which is largely contributed to rigid chassis design and enhanced insulation.
These new quiet ride cabins keep road noise (noise vibration and harshness NVH), engine and exhaust note at comfort levels associated with luxury cars. This may be good for the mainstream market, but some of us miss the raw energy translated from the powertrain to the driver, supercharger whine included.
A key element we can all agree on is the importance of power. However, the sound of power is as vital as power itself for many muscle and performance car enthusiasts.
We only have to look to the success of the aftermarket exhaust industry to know this. What would our beloved high horse power cars be today without the spine-tingling sensation and sounds of performance and power?
The staccato sound of a cammed big block at idle, the crackle and pop of the exhaust on the deceleration, the roar of an engine at wide open throttle, the spool of a turbo, and of course, the ever so elusive blower whine of a roots and twin screw supercharger come to mind.
Exhaust may be one of the most popular upgrades when it comes to muscle cars, proving again how the sound of power is as important as the power itself.
The physical sensation of being catapulted forward while being slammed back in your seat from the torque and power may only be eclipsed by the harmonics generated by the drivetrain, exhaust pulses and scream of blower whine. Combined, they generate an experience that’s truly electrifying, to say the least.
I’d like to delve into one of my all-time favorites when it comes to the sounds of power. It commands respect when heard from a distance and stirs the soul when behind the wheel.
Supercharger or blower whine is devilishly attractive, and for many, we just can’t get enough whine. Supercharger whine has been popular since the roots or positive displacement PD blowers of the early muscle car days.
The whine of the old school roots blower coupled with the cogged belt drive systems produced a dramatic eﬀect and a sound many of us have grown to love.
The 1973 Ford Falcon, called the Interceptor in the movie Mad Max, brought the sound of blower whine to mainstream America, introducing the unmistakable noise of a roots style supercharger to the masses.
In modern day, the most proliﬁc example of supercharger whine since, is from the 2003 SVT Mustang Cobra, AKA the Terminator.
When overspun, the Eaton M-112 supercharger produced an undisputable sound generated from the rotor pulses known as whine, fueling the passion and addiction for the sound of power that’s delicious to twin screw compressor fans today.
Terminators later ﬁtted with the larger 2.2L Kenne Bell and the 2.3L Whipple twin screw superchargers, when pulley’d down and overspun, produced some of the most dramatic and primal blower sounds ever heard.
YouTube is a clear example of how popular supercharger whine is today, and that may be because it’s less common in today’s muscle cars.
Interior sound control with insulations, deadening materials, and chassis design have improved while roots and twin screw supercharger manufacturers strive to reduce rotor noise, also known as pulsation eﬀect.
They aim to produce lower noise or blower whine to compete for the mass production in the OEM market where sound level controls have to meet standards which appeal to the broader market.
As supercharger technology advances the side eﬀects of old technology and ineﬃciency, the pulsation or whine eﬀect diminish.
Rotor Whine, better known in technical terms as ‘gas pulsation,’ has been greatly reduced over the years, much to the disappointment of the Whine lover.
Many factors contribute to gas pulsations in positive displacement type twin screw or roots superchargers. In a twin screw, over-compression is a key element. It’s a surge of airﬂow in the compression cycle of the rotors, resulting in supersonic airspeeds which creates a shock wave or sonic blast at the exhaust port or discharge end.
The enlargement and design improvements of the rotors exit port or exhaust port have greatly reduced gas pulsations and the associated whine noise.
New rotor designs have an exhaust slot cut in the rotors spiral channel (a pulsation trap) to improve exhaust ﬂow and end pressure at the port.
Diﬀerent rotor proﬁles also contribute to increased harmonics. 3-lobe male rotors with larger female rotor channels may produce a signiﬁcantly higher decibel rating compared to a 5-lobe rotor with smaller female rotor channels.
However, the result heard by the human ear may appear that the 5-lobe design is louder as the higher pitch it produces can seem more dramatic.
Variance in intake and exhaust port pressures also have an eﬀect on pulsation as well as speed, volume, clearances, length and number of lobes, and position of the discharge port and size.
Understanding how and why rotor whine is generated from the varying positive displacement superchargers made over the years, we can see how it has diminished as technology advancements dramatically reduced the eﬀects of gas pulsation.
This may have satisﬁed the OEM marketplace where broad customer appeal and noise level reduction are important, but for many muscle car and performance-based enthusiasts, the whine eﬀect is greatly missed.
No matter how much twin screw technology has improved in design and eﬃciency, it’s the inherent nature of these systems to whine.
The pulsation and whine will always be present at some level, so bringing the whine back is still possible.
Until Foster SC Mods sound tube technology designed and developed a ‘capture and enhance’ system for the natural rotor pulses, the only options to increase whine were larger open ﬁlter inlet systems (CAI) and overspinning the supercharger.
These two options may work to increase whine, but they have their limits and cost to consider.
Aftermarket open-air ﬁlter inlet systems are commonly referred to as cold air intake (CAI) and have been used to increase whine. Many of these claim to be cold air intakes when in fact, they’re not.
In most cases, they replace a closed air box system that truly does isolate engine heat from the inlet path and draw cold air from the front of the car or fender well. Aside from the lack of heat isolation, their increased size and open nature often allow for an increase in exterior whine. It also helps if the hood liner is removed.
CAI’s come with a high price tag and generate very little increase in interior whine for many cars. Cost is in the realm of $400 to $500 and require a custom calibration which can cost another $400. This proves to be an expensive option for those looking to increase whine.
The other most common option was to increase supercharger speed by overdriving to increase whine.
This works well at increasing the exterior whine, but also comes with a large price tag and some unwanted side affects.
Overdriving creates more boost, more heat and less eﬃciency in many cases, in the process creating a more dramatic air pulsation eﬀect or whine affect. The cost of overdriving a supercharger may seem low at ﬁrst, with a smaller supercharger pulley selling for around $150 depending on make.
However, the reality is, many cars will require supporting hardware such as fuel system upgrades, recalibration, heat reduction, fuel octane enhancement and even internal engine components to support the added boost associated with overdriving a supercharger.
These costs can tally into the thousands to do it the right way and be safe, and the cost to do it wrong will prove to be much more.
Foster SC Mods supercharger whine enhancement system is based on sound tube technology developed for twin screw and roots style superchargers.
This is the ﬁrst product ever designed and marketed to increase the natural rotor whine in the cabin for the driver to hear. The cost is under $150, and the results are dramatic.
The in-cabin whine from 3 to 7 thousand RPM is increased by as much as 100% in many applications.
Foster SC Mods innovators in supercharger whine is currently developing a large velocity stack style Bell mouth inlet system to increase and produce a more dramatic exterior whine affect.
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