In this article we will talk about some great ways to extract more horsepower from a gasoline powered small engine. Everybody with a mini bike, go kart or other motors want to get as much horsepower as possible!
Some of the most popular small engines for mini bikes and go karts are the Predator 212, and the Predator 420 or the Predator 670cc. What is your favorite?
These gasoline powered small engines are all copies or "clones" of a previously produced Honda motors. Honda motors and the clones are very popular for mini bikes, go karts and every tool you can imagine. The motors are very well designed and virtually bulletproof. Making a great platform for making more horsepower.
We get asked the question quite often "How do you make a 212 cc predator go faster?"
There are many modifications you can make to increase the horsepower of a small engine.
Small engines need three things: air, fuel and spark. In this case we are going to talk about a predator 212 exhaust.
"When you add more air and fuel into an engine, you get more torque and horsepower, which is the cheapest bang for your buck .https://kartfab.com/go-kart-engines-predator-212cc"
"The stock exhaust is very restrictive. After seeing the inside of a stock muffler, we were surprised our 6.5 hp Honda could even run with the stock exhaust. Upgrading to a high flow header is a big performance enhancement. https://affordablegokarts.com/pages/performance-basics"Â
One of the most popular methods is increasing the amount of fair and fuel mixture introduced into the combustion chamber. Anyone that has tried to gain horsepower from a gasoline engine knows the saying, "Gasoline engines are a pump, more fuel and air in, more power out" right?
For our purpose of gaining more horsepower from a gasoline small engine we will focus on the exhaust flow.
Just increasing the flow is not the priority but maximizing the efficiency of the exhaust flow has produced the best results in our dyno tests of Predator 212 cc engines.
More Horsepower from a Tuned Exhaust with a Stepped Header
Stepped Headers
Stepping the header tube size is one efficient way of increasing the amount of exhaust gas scavenged from the exhaust port. More accurately it provides the most efficient manner of exhaust gas flow. Stepped exhaust headers are one of the popular predator performance parts.
In simple laymen’s terms you start with a smaller diameter tube to keep the velocity of the exhaust gas coming through high.
As the exhaust gas comes through it goes into the next size chamber. This allows the control of the gas while maintaining a high velocity speed.
 "In more complex terms, we look at the pressure waves within the header primary tubes. Engine pulses in an equal-length, tuned header create what is called rarefaction,
 or a negative, low-pressure wave that is partially compressed and redirected back up the primary tube toward the exhaust port. https://www.centuryperformance.com/exhaust-header-tube-sizing-and-length.html "
The animated image below (source: Wikipedia- https://en.wikipedia.org/wiki/Rarefaction) shows a sound rarefaction. By Christophe Dang Ngoc Chan (cdang) - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1386746
The Wikipedia definition states, "a reduction or diminution of an item's density, opposite of compression, especially in air or a gas."
Exhaust gas pulses in equal length in a tuned header produce a rarefaction, or a low pressure negative wave that is partially compressor and redirected up the header towards the exhaust port.
This exhaust gas wave reaches the exhaust valve about the same time valve overlap happens (time when both of the intake and exhaust valves are open at the same time).
Some tuners would state that these rarefactions (exhaust waves) are detrimental. Actually from experience and dyno tuning we have learned to control them and control them to our benefit.
"Step headers actually create additional rarefactions, and the location and size of the steps (usually in 1/8" diameter increments with most headers) affect the strength of the negative pulses.
Increasing the step too much (or having to many) can weaken the initial rarefaction while increasing corresponding negative pulses, which negatively affects the benefit.
This is why most step headers have just one or two steps.
Three-step step headers are not as common. https://www.centuryperformance.com/exhaust-header-tube-sizing-and-length.html"
Getting Better Results with Dyno Testing
"Every racer understands that, without horsepower, that kart goes nowhere.
As dynamometers are the only tool specifically designed to measure engine horsepower,
it's no surprise that top racers want their own.
This article examines things to consider before selecting and using this expensive tool.
Its one thing to know the mechanics of how a stepped header exhaust works.
The only way to build a header that produces the most torque and horsepower at a operating rpm range is extensive dyno testing. This is done from years of experience on what shapes and sizes produce the best results. Robertson's Torque Tubes dyno test their designs and have refined the shape and design for each small engine exhaust that they sell.
This guarantees that your Torque Tube exhaust will extract the best torque and horsepower in a specific RPM range from your gasoline powered small engine.
So at this point you have three choices-
Take your chances and just buy any pipe
Build it yourself
Get a custom exhaust that is professionally designed and built.
Visit our website now to see the selection of small engine exhausts.
Visit http://robertsonstorquetubes.com for all of your small engine performance exhaust needs!
Custom Performance Exhaust Headers for Small Engines.
Small Engine Exhaust Pipe for Go Karts, Mini Bikes, Mudboats, Mowers and other Small Motored Equipment.
Performance header tubes for mini bike exhaust and go kart exhaust are our specialty. Â
All are manufactured in house with performance increase and fit foremost.
Dyno Tuned Exhaust Headers for Predator 212, Predator 260, Honda, Briggs and Stratton, Vanguard and Kohler
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