Myth of Small Superchargers

Myth:
“Smaller superchargers are lighter and cooler so they use less engine HP to drive.”

This is probably the best storyline for those who don’t offer a larger supercharger than a 2.3L. Really? Smaller does better?

Wrong!

Some of this thinking comes from the mindset that a lighter flywheel that performs no real work, compares to precision-machined supercharger rotors. In reality, these large screw-style rotors pump large amounts of compressed air at a high rate of speed into an engine. But it takes engine HP to turn any supercharger.

If smaller superchargers with smaller rotors were truly able to make more power, why in the heck would Kenne Bell continue to build larger and larger displacement superchargers, throttle bodies, intakes, etc. In 1990, we introduced a 1.5L supercharger for the 225 Hp Ford 5.0-liter engines. That was considered a big supercharger for its day. Today’s supercharger is require to support two (2) of these 5.0’s on a 450HP 4V 5.0. ?

The OEM 2.3 TVS supercharger is used on 2013-14 Shelby 5.8-liter engines. Both our 2.8T and the 2.3TVS are capable of delivering the same cfm/boost at 25 psi. At first glance, that sounds great – a little 2.3-liter matching a 2.8 for less money? So if they both are pumping 1300 cfm, why buy the larger 2.8 Kenne Bell?

Well as the saying goes, ”If it sounds too good to be true, it probably is!”

At 25 psi and 1300 cfm, the 2.8 beats the 2.3 by 59 HP in power consumption/parasitic loss.

In reality, the smaller supercharger with a 20% smaller displacement has to spin 20% higher to achieve the same cfm rating and boost figures as the 2.8T supercharger. That is not good. Higher rpm equates to higher heat and increases in air and oil friction. This requires the engine to waste more HP to drive the supercharger.

To put a figure on how much frictional power consumption (PC) is lost, we tested both superchargers on our dyno. In our testing, when comparing the 2.3TVS to the new KB 2.8T at 25 psi and 1300cfm, the power consumption LOSS of the 2.3 was 59 horsepower more than the 2.8.

The Move to Bigger Displacement Superchargers is on!

Even the OEM Dodge Hellcat (2.4L) and the Demon (2.7L) twin-screw superchargers are being updated with Kenne Bell and Whipple 3L and 4L superchargers. The OEM’s continue to engineer more powerful and efficient engines, which, of course, require large displacement and more efficient superchargers – not smaller.

Over the years, we have progressed from that 1.5 to a 1.7, 2.0, 2.1, 2.2, 2.3, 2.4, 2.6, 2.8, 3.2. 3.6, 4.2 and finally a 4.7: supercharger for a Ford 5.0-liter engine. Jim Bell, our owner, admits that there would not be a Kenne Bell today if our top supercharger size was still only a 2.3 or 2.6-liter unit. With the current cot of supercharger HP in the $35-40/HP range (not including installation). Even a 10 HP advantage from PC temp or inlet trait efficiency is a big deal to us.

Why Smaller Superchargers Can’t Compete!

This unavoidable elevated RPM requirement of the smaller supercharger in comparison to the larger KB units creates a number of seldom mentioned efficiency shortcomings:
– Hotter air charge
– Higher gear, rotor, seal and bearing friction heat
– Elevated oil temperatures
– Bearing loss is practically immeasurable on any supercharger. However, the rotor gears must spin faster on the smaller supercharger thereby consuming additional engine HP to drive while then generating higher air temps.

We are not recommending that everyone buy our largest supercharger as there is such a thing as “too big.” But the desire for room to grow and maximizing engine performance is there to stay. But one thing we are sure of – smaller is not better for what we do, nor are the discharge temperatures cooler.

Points to Remember Before You Purchase

In summary, no 2.3 TVS supercharger is capable of supporting more HP as efficiently as a Kenne Bell 2.8T, 3.2T, 3.6, 4.2 or 4.7-liter supercharger. All KB kits incorporate the same basic components (intercooler, manifold, etc.). That is why larger displacement superchargers, for any application, are so popular. “Bigger is Best” unless one chooses to disregard PC. It is also no doubt why Eaton is introducing a slightly larger OEM 2.65-liter system on the 2018 Shelby.

But if someone tells you that the smaller supercharger makes more HP – just know it doesn’t and it won’t!