Turbo Charging 101
The advent of improved international standardized manufacturing techniques and standards has led most folks to come to the realization that cars are made a lot better than they were ten years ago. Simply put, improved mechanical tolerances and increased reliability have greatly increased. If anything, that should encourage you to coax a little (or a lot) more power out of your car.
A lot of folks go down the path of traditional powertrain modification. They do your average "breather mods" (intakes, headers, exhaust), play with fuel maps, modify ignition timing. Those with more time, know-how, and money on their hands resort to headwork -- porting, polishing, cams, etc.
However, it's the dream of many an automotive tuner to seek power through forced induction (turbocharging, for one) and creating more power from less displacement, which, essentially, is what turbocharging is. There are some VERY expensive aftermarket turbo kits out there. Those with money will trust experts to install such a setup. For those who don't have so much money but KNOW WHAT THEY ARE DOING, there are turbo setups that are more cost effective. This article is just to give you insight on some of the possibilities that exist.
IF YOU DON'T KNOW WHAT YOU ARE DOING, don't proceed! Turbocharging your engine improperly is a VERY easy way to cause thousands of dollars in damages, not to mention serious risk of damage to one's self.
For the laymen who can't distinguish a camshaft from a halfshaft, here's turbocharger theory 101 in a nutshell.
Engines are designed to work like a pump. Air and fuel are mixed together, and then ignited. The explosion provides power. Air and fuel must be combined in a specific ratio -- 14.5 of air to one part of fuel. If there is too much fuel in relation to air, the engine runs in a state of "richness". This leads to poor performance and lower fuel economy. An excess of air in relation to fuel will cause the engine to run in a state of "leanness". This leads to bad bad things -- detonation (explosions happening before they should, when the engine is in a poor position to receive the benefits of it), and high combustion temperatures (which, if hot enough, WILL melt parts of your engine). The point is to maintain that magical "stoichiometric" ratio of about 14.5 to 1. Pay attention -- this part is where power comes in. The more of this 14.5-to-1 air/fuel mixture you can force into your engine and ignite, the more power it will make. A turbo charger is essentially a double-sided pinwheel. The rapidly flowing exhaust gases spin the exhaust side (the hot side). This is connected via a turbine shaft to the compressor side (the cold side), which spins up in the range of tens of thousands of RPM. This action pressurizes the air intake charge -- thereby forcing more air into the engine. Now, if you've been following along this whole time, you should be asking yourself, "won't all this extra air cause the engine to run in a state of leaness?" That's correct! Specially designed fuel injection setups provide the extra fuel your engine needs.
At this point, you reach the two most important questions involved with turbocharging. 1) How do I get a turbo attached to my car and 2) how do I provide enough extra fuel in the right amounts at the right time to accommodate this influx of air?
The easy way.
If there is a turbocharged version of your engine on the market, you'll have an easier time finding parts and doing the installations. This makes things MUCH easier and cheaper, seeing as A) chances are, your car's manufacturer has designed proper clearances and tolerances into your car to accept turbocharging and B) these parts will be quite plentiful.
The parts you'll need from your car's turbo big brother will include the turbo, oil lines, turbo manifold, intercooler, compressor bypass valve (more commonly known as the blow-off-valve), downpipe, ECU, injectors, fuel pressure regulator, fuel pump, air flow meter and as much as the intake/intercooler piping as possible. Here's a breakdown of what each part does.
It's the power adder. When picking one up used, make sure the turbine wheel spins freely. Also, make sure the wheel has no play. It should spin--period. It shouldn't wobble, it should wiggle, it shouldn't move in and out. Try to get the factory oil lines that go to and from the turbo. You will need to tap the sender line into your engine block someplace and the return line into the oilpan to ensure a flow of oil through the turbo.
Turbo Exhaust Manifold
This replaces your stock exhaust manifold. Rather than guiding spent exhaust gases straight into your downpipe and out of your exhaust, the turbo manifold directs the exhaust gases into your turbo to spin it. If one isn’t in existence for your vehicle, it can be fabricated by an experienced muffler shop.
Chances are, your factory non-turbo downpipe will not mate up properly with the turbo exhaust outlet. If the turbo downpipe is unavailable for your car, your local muffler shop can fabricate one.
Much like a radiator for the incoming air charge, the intercooler cools the intake air charge to temperatures closer to ambient, condensing it and allowing you to fit more into each combustion stroke. This also helps in reducing combustion temperatures and helping prevent against detonation.
Compressor Bypass Valve (CBV) or Blow Off Valve (BOV).
This is what usually makes that cool pffffsssshtt sound on turbocharged cars. This valve does more than make that funny noise, however. Its main purpose is to relieve the pressure on the intake air charge between shifts. When you shift, you usually let off the gas pedal. That in turn slams the throttle plate shut. Your pressurized intake charge now has no where to go. What the CBV does is vent this pressurized air -- either back into the metered intake stream in the plumbing before the turbo, or out into the atmosphere. If this air is not vented, it will send a pressure wave back down to the turbo, trying to reverse the direction that the turbo is spinning. This is not good for turbine longevity. There are benefits of going with aftermarket units like the Greddy Type S, which is adjustable.
ECU/Injectors/Fuel Pressure Regulator/Fuel Pump
This is primarily, the fuel system from the turbo version of your car. Chances are, the turbo version of your car will have larger higher capacity fuel injectors and have a different air metering system than your normally aspirated car. This system, when functioning properly, will inject the proper amounts of fuel, proportionate with the incoming air, at proper intervals and duration. Several sensors (air flow meter being the major one) detect the volume, temperature, (and in some cases, velocity) of the intake air charge. This information is sent to the ECU, or computer, which in turn computes how much fuel is required to mix with this air. Once this is calculated, the ECU fires the injectors. The fuel pump and fuel pressure regulator are in place to see to the fuel demands of the injectors.
These are very important systems and should not be ignored. Simply put, to remain lubricated and within operating temperatures, a turbocharger needs a constant supply of oil and coolant flowing THROUGH it. Your stock cooling system can usually be teed off with radiator hose and redirected through the turbo to supply coolant. Oil on the other hand will require a certain grade of hose that withstands much higher temperatures. Fittings will need to be created both in your oilpan for the oil drainage line from the turbo and in a source of fresh oil somewhere before the turbo.
This is what holds everything together. This piping, held together by friction fit, hose joints, and clamps, will allow air to flow through the air filter to the turbo, from the turbo to the intercooler, and finally from the intercooler to the throttle. Stock factory pieces are usually made of plastic, but tend to fit fairly well. Pieces that you're missing can usually be made from large radiator hoses or pieces of generic muffler piping of varying lengths and bends. If you're feeling extravagant and want a better flowing system, we recommend taking this task to your local muffler shop. You should see to it that beads are welded into the piping where clamps will be used to ensure a fit that will not come apart should you start running large amounts of boost.
Ideally there are three different gauges you should have when you embark upon this project. First and foremost is an aftermarket boost gauge. Decent units are made by Autometer. Best thing is, these units read in ENGLISH, that is, in PSI. These gauges will tell you what kind of negative and more importantly, positive manifold pressure your turbo is creating. Next is an air/fuel ratio gauge that will tell you how far you are from having a stoichiometric mixture by reading the signal coming from your O2 sensor. Finally there is the EGT (exhaust gas temperature) gauge. When an engine is in good running order, it should be at about 1450 degrees Fahrenheit. Temperatures below that will indicate a state of richness, and temperatures above that will indicate a state of leanness. An EGT gauge is essentially a voltmeter that displays the output from a thermocouple, or pyrometer, that sits in the exhaust stream and converts heat to an electric signal. A full complement of these gauges, coupled with some good common sense, we go a long ways in keeping you from turning your motor into a scrap heap.
What you’ve read are some basics of a turbo conversion. Don’t you consider doing this until you understand turbo selection, advanced turbocharger theory, intercooler selection, fuel management, pros/cons, monitoring, tuning, and installation.