A car is purpose designed for economy and comfort without for performance enhancements which is why we say stock sucks. A turbocharged car is likewise purposed design and its engineers have therefore explored all possible design and build including fail-safe measures for both reliability and performance. If you must want a turbo you are better off with a purpose designed turbocharged car instead of converting.
Aftermarket turbo kits – Because of the significant initial expense and careful maintenance thereafter, it is therefore wise to makes sure you can achieve more than 30% power increase to be cost effective. Otherwise, consider a supercharger instead or modify and upgrade the engine for higher compression and better flow. Unless you have or trust an experienced tuner, you’re probably better off buying and accessorizing and pre-configured kit specifically for your make and model instead of Ala-carte. This will ensure that everything will fit and work well together whilst maintaining a safety margin.
Before you splurge, consider the following : are you planning on an engine swap? Is it going to be daily driven? Is your engine capable of handling the additional stress of a turbocharger? Is your fuel system up to the task? Do you have the space to fit the bolt-on items? Finally, do you have deep pockets for frequent petrol stops, to rebuild and recover if there is a breakdown? The answers are best discussed with the tuner. Cars best suited for turbo-charging are healthy, low-mileage manual driven engines that haven’t been stressed. Have a full systems check to test suitability. Change your engine oil to synthetic – 50W, install performance spark plugs (change to colder plugs after turbo install) and cables, new belts, water pump and run a compression check to test your rings, valves, and seals. Free your intake with a short ram – open pod design, and your exhaust with larger diameter (at least 2.5 inches) piping, high-flow CAT (a.k.a racing CAT), and a straight-through muffler. Install a “piggy-back” engine management and have it dyno-tuned to get your maximum power at the wheels for reference. Now, you are all set for a turbocharger.
Pre-configured turbo kits are usually designed to work on stock engines. Some kits include upgradeable components like Blow-off valves, Wastegates, Intercoolers and Boost controllers. Most of them will supply injectors and other fuel management hardware if the manufacturer deems them necessary. You should also consider higher capacity injector’s, fuel regulator, a more powerful fuel pump, and piston upgrade (strong) if running high boost.
Intercooler – There is a danger of knock when air compressed into the cylinders by the turbocharger. Knocking happens when the temperature of the air rises until they are hot enough to ignite the fuel before the spark plug fires (pre-ignition). Therefore, an intercooler is use to channel compressed air cooling it off before it enters the cylinder. Intercoolers are especially important if boost numbers goes beyond 8 psi as the air inlet temperatures can rise to over 200 degrees Fahrenheit, making detonation probable. There are two types of intercoolers – Air-to-air intercoolers are inexpensive and easy to maintain, but may be large and must be in a good airflow path like in-front of the radiator to be effective. Some may be mounted just above the intake manifold, but you would need a functional hood scoop just above it. However, intercoolers are not fully efficient as their charge temperatures only get to within 80% of ambient during engine operation. Air-to-water systems is more compact hence placement freedom and efficiency. An air-to-water intercooler does not need a supply of fresh air and can be well over 100% efficient (when filled with a cooler then ambient liquid), but they do need an external reservoir of coolant and some means to extract heat from that coolant.
Parasitic loss – Having a turbine in the exhaust flow path increases the restriction into the exhaust system. This will weakens our positive pressure difference between the intake and exhaust sides of the engine, and causes both cam timing and exhaust sizing to again become extremely important to making good power. That means on the exhaust stroke, the engine has to push against a higher back-pressure. This subtracts a little bit of power from the cylinder that are firing at the same time. It is said that it would take around 45 or more horsepower just to drive the turbo even for a small unit. So the horsepower numbers that tuners try to impress your with should be discounted.
Drivability – Turbocharged compressors are not positive displacement i.e it doesn’t have reliable airflow corresponding to the respective rpm, but only produce maximum boost at about 3000 rpm and slowly tail off. Though getting high boost quickly may seem desirable, but this results in uncontrollable wheel spin and loss of handling making driving somewhat dangerous. The driver will be forced to back off and lose the benefits of this power. What you don’t want is maximum power at 3000 rpm from a standing start, nor do your want power reducing when you go higher up the rev range. However, there are ways to mitigate this problem with extra technology and cost.
Turbo lag is another side effect of turbocharging. It can be explained as the amount of time between the accelerator pedal being floored and the turbocharger being able to produce enough boost to get the engine performing. Below 3000 rpm, the engine does not seem responsive as it takes time and a specific amount of exhaust flow to start creating boost, but once this point is reached (called boost threshold a.k.a lag time), all hell breaks loose. Moreover, bigger turbos, although providing superior airflow take longer to spool up (worse lag). A number of technologies have made significant strides in reducing turbo lag and improving boost response. These include divided-inlet turbine housings (twin-scroll), tangential turbine housings, and high-efficiency compressor and turbine wheel designs (ball-bearing). Turbos rapid increase in power (shock loadings) has a negative effect on transmission components that like gradual torque increase and not sudden violent increases. That means all turbos will wear out clutches and gearboxes more quickly.
Heat – Higher pressures and temperatures will encourage detonation which is the engine killer. High under bonnet temperatures in a turbo car will make everything hotter hence reducing power and life expectancy of equipment such as wiring looms and hoses. There is also a higher potential of fire due to the extreme heat of the turbo unit and manifold – some manufacturers used ceramic coating to mitigate the extreme heat. You will need to keep things cool like an oversized (thick) Aluminum Radiator with an upgraded fan (efficient) if the car is to be driven daily. Also consider reinforced (multiply) silicon radiator hoses and a 68 degree thermostat that opens earlier to maintain a slightly lower engine operating temperature. An oil catch tank and radiator cooling plate (the latter help channel ‘stray’ air towards the radiator) should also be considered.
Increasing power levels can stress engine internals and generate heat. Heat changes the viscosity (thickness) of oils; therefore you must always use thicker (50w) fully synthetic oils with a turbocharged engine. Moreover the turbo units are oil-cooled requiring the extra protection and resistance to heat break-down. An aftermarket oil cooler is also recommended, as this will further reduce temperatures between 10 to 15 degrees during high speed driving. Consider also a Turbo Timer to execute the cool-down period by automatically shutting the engine after “soak” time when the ignition is shut off. This is to prevent premature turbo wear and failure because it is important to allow the compressor assembly to cool from the lower gas temperatures in both the exhaust and intake tracts.
At the same time the lubricating oil from the engine is able to circulate properly so the turbine rotating at high speed won’t burn the lubricating oil that would otherwise be trapped within the charger. For those with automatic transmissions, consider using synthetic based automatic fluids. Be careful when using high boost on an automatic transmission, this may cause slippage, killing your auto transmission.
Dyno – it is important to re-map the engine management system and run a baseline check for leaks and proper Wastegate operation at a dyno shop. The tuners will do a series of tuning runs to dial in the boost controller, fuel management, and other tunable parameters. The horsepower and torque your engine puts out can be compared against your earlier chart to measure gains. Make it right the first time to have peace of mind, your car will be safer and perform better.
Most applications fitted with an aftermarket performance turbocharger kit will see typical power increases among the 40-to-50 percent range. Increases up to 100 percent (double the original output) are possible on some specific applications. Higher order increases (that triple or quadruple the engine’s original output) are generally the result of combining an upgraded engine foundation with a high-performance custom turbocharger system. There is no better solution (except Nitrous for a substantial power increase than a well-designed and well-matched turbocharger system .
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