The idle air control is a control system used on fuel injected cars. The idle air control or IAC valve controls the idle speed of the engine. The IAC valve is controlled by the ECM (computer). The computer gets it’s information from the rpm which is supplied by the distributor, crank or cam sensor. The IAC valve moves in and out to bleed air behind the throttle plate. This air bleeding is the same as opening the throttle plate. The idle speed can be controlled precisely the throttle plate which isn’t controlled as well. Air conditioning will drop the idle speed down and will kill the engine if the IAC doesn’t work well. The idle air control will be located on the side of the throttle body. The IAC can become sticky after time and will cause the the engine to surge, rev or stall the engine. The valve can be removed and cleaned if not too severely worn. Usually the valve needs to be replaced. Make sure the gasket looks alright. Also make sure the idle air control is secured well and doesn’t leak air, or the engine will rev up.
Go carts can be complex racing carts or simple back yard projects. Many of the racing carts have pre built chassis that are design specific for racing. Most people will purchase a cart for racing instead of building one. There are three popular type of racing carts oval dirt carts, briggs and stratton and tecumseh type carts for pavement racing and shifter type pavement carts for faster road courses. Homebuilt carts are not so critical and can be built from steel tubing or even wood depending on the chassis required. The engine is usually a small four stroke engine such as used on a garden tractors or lawn mowers. If this type of an engine is used the transmission of power is usually a centrifugal clutch running to a sprocket on the drive axel. This limits the cart to be a one speed. Another option is to use a two stroke engine from a snowmobile or an off road bike. The high power and multi gear ratios of both vehicles make them both very fast drivetrains to use. You will want to use a very good brake set-up for one of these drivetrains. A cheap used snowmobile has everything except the chassis all integrated together and gives the cart far more power than it needs. The snowmobile transmission is variable and is fully automatic as it doesn’t need to be shifted. Shifter carts use the engine and transmission from an off road motorcycle. This requires the driver to shift but is also very effective and fast.
A standard car’s distributor ignition coil can be tested by checking the ohms reading. Ohms can be read on a volt/ohms meter. Ohms is a unit of measure for the resistance that a wire or coil has. Ignition coils should be measured on the primary coil between batt and tach terminals. The batt is the coil ground. To check the secondary coil, check the ohms between the batt terminal and where the coil output wire plugs into. If the ohms read zero the coil connection is broken and the coil is no good. An open coil reading zero is the usual culprit of coils. Don’t test through the output wire though. The primary coil should read between .7 ohms and 1.7 ohms, if outside this range replace it. The secondary coil should generally read between 7.5K ohms and 10.5K ohms. If the ohms are not within the specified range for that paticular car, replace the coil. Coil resistance will also change and vary if the coil is hot or cold. This a generalized ohms range that fits most distributor coils. Another thing to remember is that sometimes a coil will only read bad after it gets hot. It may work intermittently after it gets hot also. Coil packs will generally read around .3 to 1.5 ohms on the primary side and 12.5K to 13.5K ohms on the secondary side. These figures will get you reasonably close to where the coil’s ohms need to be to work properly.
Sea doo has long been known for being the fastest and most competitive jet skis on the water. Sea doo was not scared to go to fast when other manufacturers were. They used high horsepower rotax engines and efficient pumps for excellent acceleration and top speed. The two stroke rotax engines also had the ability to produce much more power than they did stock. Sea doo hulls were very well designed and recieved excellent feedback from the racing community. Models such as the xp, gsx, and gtx have sold many models due to there good qualities of performance and reliability. The xp has won races repeadiately for years and was the benchmark for speed and performance through the 1990′s and yet today. Sea doo has also dared at making special models such as the hx which was a direct attack at the very successful yamaha blaster. The hx made more power and was an excellent ride with a first ever shock absorber for the seat. The high performance continues today as sea-doo continues to push the envelope of performance and engineering.
Intercoolers have been used on turbocharged and supercharged engines for quite some time now. When used on a supercharged engine they are often called aftercoolers. Turbos are the most common usage for intercoolers though. Any engine that uses an air compressing device such as superchargers and turbos can benefit from intercoolers. When the air gets compressed it can heat up dramatically, up to 300 degrees F. This dramatically reduces the compressed air density and limits the maximum boost. The high intake temperatures can increase the chance of detonation in the engine, causing major engine damage. An intercooler can fix this problem.
Chainsaws are generally reasonably easy to troubleshoot and repair. Most chainsaws use two stroke engines due to their simplicity, light weight and high power. Common problems with chainsaws are generally fuel related. Either a leak in the fuel supply hose or a clog in the fuel tank filter can cause a fuel supply problem. Chainsaws are usually stored with gas left in them. The diaphragm carburetors will have problems with the supply fuel needle sticking, diaphragms drying out or tearing and build up of old varnished gas, filling up the low and high speed fuel jets. The jets can usually be cleaned by using a small strand of wire and carefully passing it through the hole. The jets are soft metal so don’t force something hard through them such as a drill bit or you will damage them. Primer bulbs may also collapse, they will need to be replaced same as dried out gaskets or damaged diaphragms. Compression on a chainsaw should be around 120 psi. Many chainsaws call for large amounts of oil to be mixed with the gasoline. Such ratios ensure that the piston is not damaged due to the severe beatings that chainsaws will endure. The extra oil also helps to keep the piston lubricated when the chainsaw runs out of fuel.
Engines are simply an air pump. The more air you can get in and the more exhaust you can move out, the more power you can make. Superchargers are one way of packing more air into an engine. Superchargers or blowers as they are sometimes called have been around for a long time and are still currently being used on some production vehicles. There have been many different types of superchargers made but I will focus on the two most popular versions. One being called positive displacement or roots type and are generally referred to as blowers. These are the style most used on muscle cars due to the ease of setup on a v-8 with a carburetor. They are also widely used on drag cars for street and professional racing. Some of these cars make insane horsepower in the thousands. The blower has an advantage, because it compresses air even at very low speed it also creates alot of torque. This gives the engine very good response and power from idle up. That is why drag racers like them so much, they are very predictable from launch and have almost no lag time.