The small engine turbo—also known as “turbocharger”—is a fan that is powered or rotated by exhaust pressure. In actuality, it is an exhaust turbine, and for this reason, it is called a turbocharger. It is basically a turbine that is on the exhaust. This turbine spins a compressor that is called “impeller.” This impeller then compresses air into its intake manifold. Furthermore, this intake pressure eventually increases the amount of air-fuel that goes into the engine. This also results in a more significant amount of fuel mixture that translates into higher power per cubic inch.
A turbocharger is mainly composed of two little fans called “gas pumps” or “impellers” that sit on a metal shaft. Both these fans spin together in synchrony. One fan is called “turbine.” This turbine sits midway along the exhaust stream that comes from the cylinders. Once the cylinders blow hot gas past the blades of the fan, the blades begin to rotate. A shaft is connected to the fan which, in turn, rotates together with the fan. On the other hand, the other fan is named as “compressor.” The compressor sits on the same shaft as that of the turbine. The compressor also spins. The function of the compressor is to draw in air into the car engine and eventually force the air into the cylinders.
The problem with compressed gas is that it heats up. Since hotter air becomes less dense, it rises over the radiator and becomes less effective in enabling the fuel to burn. Hence, there is a need to cool the air that is compressed. To do this, there should be a heat exchanger between the compressor and the engine that would remove the additional heat and eventually would dissipate this heat somewhere else.
Turbo Charging Limits On Small Engines
Turbocharging a 5 hp or even a 10 hp engine will undoubtedly overtax this engine especially for the 50cc – 150cc engines. It is like asking too much from your small engine to make its impeller spin faster. Hence, if you start the small engine, you may end up not getting enough pressure to start it. Moreover, you may end up having serious turbo lag while starting it. One solution to this possible problem is to set up an after-burner when cranking up the boost artificially.
Let’s see how much HP a turbocharge will generate on a small engine in the video below:
Consider also the value of oil pressure when turbocharging. When turbocharging a system, you need to set up a pressurized oil system or an oiling system, because the turbocharging system generally uses oil pressure to have its bearings lubricated. Some turbines, however, do not carry roller bearings. These turbines only run on the oil film. In this case, however, if the oil film is absent, then the turbocharging system will surely cease to function.
Make Sure that The Turbos are Properly Lubricated
For turbos to survive and last longer, they should be properly lubricated and cooled. For this reason, the turbine and compressor wheels are generally mounted on a shaft that is lubricated and supported by water-cooled bearings, encased in a center housing. These bronze-shaft bearings are pressure-lubricated. They also necessitate a steady supply of lubricating oil for handling the tremendous speed of the shaft. For this purpose, it would be good to use synthetic oils which are best for turbos because they can readily bear high temperatures. Filter changes and regular oil are likewise necessary for preventing the breakdown of viscosity and the depositing of varnish and sludge that could eventually damage the shaft bearings of the turbo.
Common Problems With Turbo
Bearing Wearing Off
The primary problem of operating a turbo is the eventual wearing off of its bearing. Because of the high mileage engaged in by turbos, their bearings usually wear easily. Aside from the wearing off of its bearings, the turbo may also experience blade erosion. Moreover, damages to the turbine wheel may also occur once the engine experiences piston or valve failure or once shrapnel has exited from the exhaust port.
Turbos may also be eliciting a lot of noises like hisses and whistles. These noises may be indicative of air leaks within the turbo housing or in the plumbing or connections. Other noises like scraping or squealing sounds may be due to the bad shaft bearings or the misalignment of the wheels with the housing. If there is oil in the housing of the compressor, it may be indicative of a leak in the shaft seals. The turbo speeds and its boost pressure may also be affected by bad shaft bearings; hence, you should occasionally check on this problem. Bad shaft bearing may also cause the turbo to bog down and stop spinning. If you want the turbo to be functioning smoothly and freely, there should be no wheel-to-housing interference.
Imbalance of Wheel Motion
Another potential problem is if the back and forth motion of the wheels within the turbo housing goes above .0035 inches, because this may be indicative of problems that necessitate rebuilding or replacement of your turbo system. In this case, you can replace the shaft assembly and the turbo center housing separately. However, you will often find that remanufactured turbos are usually purchased as complete units with pre-installed wheel housings. It is expedient therefore that you replace or rebuild your turbo once it exhibits imbalance somewhere in its system because balance is critical to the well-functioning of the turbo system.
Faulty Wastegate/MAF/MAP Sensors
You should also bear in mind that the solenoid that typically regulates the vacuum towards the wastegate can cause turbo control issues. Moreover, a faulty wastegate or MAF or MAP sensor problems may also be the culprit in any turbo system problem. Lastly, a plugged catalytic converter can also be the cause of a problem because it can create excessive backpressure.
Pros and Cons of Using Turbochargers
If you are going to buy a replacement turbo, therefore, you should look for something that includes new wastegate, especially, if you are going to set the turbo system on high mileage equipment. Another reminder is that you should ensure that the oil and coolant lines are clear and free flowing to avoid another failure of your turbo system.