Vintage Videos Chronicle First Tests of PSI Supercharger

Perhaps no single performance engine component has endured such a turbulent history as the PSI supercharger. It’s banned in some classes and mandated in others. From political squabbling to well-publicized explosions, there’s hardly a shortfall of opinion on this innovative product.

One of PSI’s original investors, Patrick Hale, recently reposted a number of digitally restored videos on YouTube showing the first time a supercharged engine ran with a PSI blower and also on a blower dyno; plus, there are numerous videos of the initial tests at the track. The PSI originator, Norm Drazy, is shown conducting A-B tests on a Hemi, first using a traditional 14-71 Roots blower followed by the PSI prototype. As you’ll quickly discover, the spirit of backyard innovation is truly revealed in these videos.

“Norm quit his engineering job at Garrett to pursue his dream,” Hale recounts for EngineLabs. “He built a shop in the backyard of his mobile home in south Phoenix. After starting the Roots blown engine in his driveway, the neighbors complained about the noise. That’s why we ran the PSI blown engine in an industrial area in the back of his truck.”

That’s right! The first test of a PSI blower came with the engine strapped down in the bed of a Datsun pickup.

“The initial engine was a typical top alcohol dragster engine that Norm assembled,” adds Hale, who is best known for developing the Quarter Jr. software to help drag racers predict performance. “After testing on Billy Williams’ dyno, that engine was sold with the 14-71 blower. The first PSI blower was then mounted on Mark Niver’s engine for on-track testing.”

As many drag race fans know, Niver died in 2010 following an accident at the Northwest Nationals in Seattle when the chutes detached from his dragster after it crossed the finish line. The dragster then crashed into the safety net at the end of the track.

There’s also a video of testing the PSI on a blower dyno. Drazy and Hale had gathered considerable data from testing the Mooneyham 14-71, recording blower speed, manifold pressure, then compared those numbers against the PSI tests. Hale says he still has all the original data and notes from those tests.

“The high-speed blower dyno testing of the 14-71 and the PSI blowers was done at Firebird because we didn’t know if the thing would explode or not,” says Hale. “And it was also quite noisy.”

A year later a PSI blower did explode during a race, ironically at Firebird, sending some parts into the crowd. NHRA then banned the blower until further redesigns were approved. PSI, or even high-helical superchargers, are still not allowed on nitro engines, but are accepted in alcohol classes and Pro Mod. They’re also quite popular in performance boats.

Overall, a PSI screw-type supercharger is more efficient than a Roots blower. The screw supercharger combines a 4-lobe “male” rotor with a 6-lobe female rotor, which actually turns 33 percent slower than its male counterpart. The PSI acts not only like a positive-displacement air pump — that is, moving air from one opening to another — it also provides internal compression as the air is squeezed when the rotors mesh.

The result is increased boost and lower air temperatures when compared to even larger displacement Roots-style blowers. According to a Hot Rod article published shortly after the first test on the Williams’ dyno, an alcohol engine running the PSI blower (385ci displacement) made 1,260 horsepower at 28 pounds of boost — the same as a 14-71 blower (552ci displacement) running at 36 psi. The difference was lower manifold air temperature (85 vs. 150 degrees) and less parasitic drag on the engine.

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
Read My Articles

Drag Racing in your Inbox.

Build your own custom newsletter with the content you love from Dragzine, directly to your inbox, absolutely FREE!

Free WordPress Themes
Dragzine NEWSLETTER - SIGN UP FREE!

We will safeguard your e-mail and only send content you request.

Dragzine - Drag Racing Magazine

We'll send you the most interesting Dragzine articles, news, car features, and videos every week.

Dragzine - Drag Racing Magazine

Dragzine NEWSLETTER - SIGN UP FREE!

We will safeguard your e-mail and only send content you request.

Dragzine - Drag Racing Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...


Street Muscle Magazine
Hot Rods & Muscle Cars
Diesel Army
Diesel Army
Engine Labs
Engine Tech

Dragzine - Drag Racing Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

  • Streetmuscle Hot Rods & Muscle Cars
  • Diesel Army Diesel Army
  • Engine Labs Engine Tech

Dragzine - Drag Racing Magazine

Dragzine

Thank you for your subscription.

Thank you for your subscription.

Dragzine - Drag Racing Magazine

Thank you for your subscription.

Thank you for your subscription.

Loading