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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Due to demand from our customers we will be expanding our kits to cover many more marques and models. If you want more whine....Contact us for details!