Can a Leaf Blower Work as DIY Forced Induction?
Despite many efforts a few years back, tinkerers are still attempting to source extra power using this peculiar method.
For as long as people have tinkered with engines, so have they thought outside the box when adding more power to them. There are countless tricks hotrodders utilize to extract every ounce of power, both common and almost mythical, with forced induction occupying a mighty chapter of it all.
Those less-traditional tricks, however, are some of the wildest. Including today's subject, the history of using leaf blowers as forced induction. It was actually one of its more recent attempts at a LeMons endurance race that caught our eye and made us ask, "Could it actually work?"
Really, why not use one of civilization's greatest, most inexpensive inventions as a DIY turbo? Why not use a leaf blower to get more power? Well, turns out that there are a lot of great reasons not to, as well as one that might have you hit up Home Depot.
Here's the Thing About Forced Induction
Let's first take a step back and discuss what forced induction is, and why introducing more air can make more power.
Forced induction, simply put, is increasing an engine's volumetric efficiency. 100% volumetric efficiency means the engine is making the most it can at its displacement. So turbocharging and/or supercharging increases this to over 100%. That means it's sucking in more air and fuel to produce more power than it otherwise would.
However, it's not about just moving more air, it's about moving compressed cool air. Remember, cool air is denser, thus more efficient. The Germans call superchargers Kompressors for a reason, and not because that one early 00s C Class was a tad compressed-looking.
Turbochargers utilize exhaust gases to spin a turbine that compresses and sends a more oxygen-rich charge to the intake valves. Superchargers are belt-driven off of the crankshaft at a certain ratio to do so. Some forced induction systems utilize both, such as some Lancia Group B rally cars, and also, weirdly, a couple of newer Volvos.
The compressed air charge is referred to as boost and is commonly measured in this country as pounds per square inch, or PSI. Both turbos and superchargers utilize diverter valves as well, which open up and expel unused boost pressure to avoid creating issues when drivers let off the throttle. Check out our explainer on forced induction terminology for more on the different players in the forced induction process.
Electric superchargers are becoming increasingly more common as well, which use—you guessed it—electricity to spin the air-compressing components inside the supercharger. This leads us into using every HOA member's favorite pre-dawn lawn tool: leaf blowers.
The History of Leaf Blower Tuning
Trying to circumvent HKS or Garrett’s pricing has been something searched for since the dawn of YouTube. One of the furthest-back examples of utilizing leaf blowers to create positive pressure is Mighty Car Mods' attempt.
The channel's Marty and Moog hooked up two small lithium-powered Ryobi leaf blowers to the hood of a heap-spec Daihatsu, fired them up, and attempted to force enough air into its teeny intake to show a noticeable increase in power on the dyno. They were not successful.
Conversely, Motor Trend's RoadKill added 20 hp at the wheels on a 350 small block mounted up in a '78 Chevy Monza. Their method? Five 700 CFM gas-powered leaf blowers in the trunk all hooked up to one intake tube. Though the real-world difference wasn't that noticeable, they concluded that all five couldn't quite force enough air to feed the hungry 350 at high RPMs.
Then, there have been more than a few other folks in the greater YouTube community making their own attempts with mixed results.
The Rub About Attempting to Create Boost Via Leaf Blower
The key reason why leaf blowers don't add as much power as conventional forced induction components is, simply put, they don't compress enough air, if at all. RoadKill was able to create a measurable five PSI of boost from a host of leaf blowers. But even that wasn't enough to make an overall difference, despite what the dyno said.
Typically, atmospheric air pressure on an average day is 14.7 PSI at sea level. Thus, adding another five might've shown up on the dyno, but it wasn't enough to feed the engine, as it craved more and more air higher up the rev band. However, if they made just a few pounds more, that probably would have had a more noticeable effect.
Compressed air is the key, but it must also be met with added fueling to ensure the charge isn't too rich and that more power can indeed be made in each combustion chamber. You can't just do one without the other.
And Yet, Leaf Blowers
Recently, a LeMons team came up with a very neat and cleanly mounted method to add Leaf Blower Boost (LBB) to their competition car. It's entertaining to see, and who can deny the gumption? But if I may, I think there are actual benefits to utilizing leaf blowers in a race car outside of trying to gain power.
Ask anyone who's dyno'd a naturally aspirated car and they'll tell you immediately that heat is the enemy. When I dyno'd my Mazda 2 last year, there was a noticeable drop in power between pulls simply due to underhood heat building up and decreasing the intake air's density.
Though, when we popped the hood and aimed a fan directly at the air filter, there wasn't really any horsepower gain. But there wasn't much of a loss, either. This might not be as noticeable of a difference as adding power, but having consistent power availability has its own benefits on track.
More consistent power could mean: improved on-track fuel economy (especially crucial in endurance racing), more power available during battles with other cars, more power available when the car is on another car's bumper and the fresh air stream is impeded, more power available at corner-exit before a straight, more power available in slower corners (not as much outside air is flowing through), and more. This is also assuming that the leaf blower feed is well-insulated from heat.
Could is the keyword here, though. It'd be quite cool to see if this pontification is someday put to the test with real-life scientific (er, somewhat scientific) testing. If anything, even just using leaf blowers to blow more cool air on radiators and intercoolers—and having an aerodynamic method of pulling that air out afterward—might bode just as well in this scenario.
However, some of this is dependent on how the leafblower gets its power—if it's drawing from the vehicle's own 12V charging system, that could be a parasitic horsepower loss as it's taking away from other components' functions, like coil packs and spark plugs.
I think The Drive ought to do its own test of all this ourselves someday. Hint, hint, editors. It'd make for a hell of a fun day and I've already got experience buying questionable test mules from auction. It's time we expense this kind of stuff.
(Editor's note: I'll think about it.)
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