When turboing a 2rz/3rz Tacoma, there are sometimes limited and unlimited options. When it comes to certain things there are very few people who make certain items and some things are very universal. Hopefully after you read this you will understand what it takes to turbo a 2rz/3rz. Its not always easy, but in the end it is very worthwhile.
Basics of turbochargers
Turbos have been around for a very long time. However, with the more recent low displacement engines, many manufacturers are adding it as standard in their vehicles. Additionally, they are becoming very popular due to their ability to make great power from small displacement.
Turbos are sometimes referred to as the replacement displacement. This is a great way to explain it. In a larger displacement engine, it naturally draws in a large volume of air, mixed with fuel, compresses it and then ignites it. Turbos work on the same principle that more air and more fuel equals more power. Turbos force in more air than the engine would normally draw in on its own, just like a larger displacement engine with the amount of air and fuel it takes in.
There are several differences between turbos and superchargers. The most obvious is the way they make boost, or compress the air. Superchargers are basically a belt driven compressor. They are driven by a belt connected to the engine's crank pulley which spins the impellers inside the supercharger which creates boost. This is why (in my opinion) turbos are better than superchargers. Turbos work off of wasted energy (exhaust gasses) that the motor is already getting rid of. A turbo is essentially a set of two fans on a shaft with housings around them to direct airflow. On one side of the turbo (the hot side), wasted exhaust is forced though a housing past the blades on the wheel (the fan). This spins the shaft with the other wheel on it, which compresses the air it draws in.
To my knowledge, there are three companies who make turbo headers/manifolds for the Tacoma 2.4 and 2.7 liter engines. They are: PSI racing, Paradise Racing, YotaShop & LC Engineering. There used to be a couple more, however, either they went out of business or their product was sub par. Both the PSI units and the Paradise Racing headers are awesome quality, fit, and finish. I have never heard a single complaint about either. I have, however, heard a couple reports about the LC Engineering ones cracking from time to time with the old design. LCE has changed to the Steed Speed design. Even though the selection of turbo headers is very slim, I believe that is ok. The Steed Speed, PSI and Paradise Racing models are outstanding, and you should expect to spend about $550-$750 on one and probably a little more depending on options, such as external wastegate flanges and such.
Turbo size and brand
This is the most open of subjects when it comes to the entire turbo system. Size most defiantly matters when it comes to turbos. You could go with a smaller turbo and make boost at idle. On the flip side, you could go with too large of a turbo and never make boost by redline. Granted, these are extreme situations, but it is more than possible when you pull a turbo from a diesel (or other large turbo engine) and do not research proper turbo sizing. Most people desire maximum boost in the mid to lower through the rpm range. This gives you a decent power band and a little better top end is possible. Personally I like to start spooling up about 2,000 RPMs and make full boost by 3,000 RPMs. To do this, a .57 cold/.48 hot sized turbo will do just that. However, don’t get just that size. Some people prefer to have the turbo make boost higher in the RPM range. Some likely reasons would be that its easier to drive around town out of boost, which generally leads to better fuel mileage.
Larger turbos typically produce less heat than it makes as far as the air entering the engine. This is because it is more efficient, there's less friction, and less heat. This is why a small turbo is not recommended for quick boost in low RPMs. When lots of heat enters the engine, the engine pulls the timing which results in less horsepower and possible engine damage.
There are many places to purchase turbos (eBay not being one of them), however Luis at Paradise Racing is a good resource for helping you determine what size turbo is correct for your truck.
A very important (and commonly overlooked) element of forced induction is the need for more fuel to compliment the extra air. There are several ways to go about adding more fuel. However, I will cover a few options that work.
First (and the best option without going standalone) are the piggyback units such the ones that Underdog Racing Development sells. First up is the Split Second PSC1-001. It’s a piggyback unit with a map sensor (to sense boost) for a more precise tune when your engine starts off n/a and gets converted to turbo as in the case of the 2rz/3rz’s we are covering here. It modifies the signal coming from the mass airflow unit to the ECU to manipulate the air/fuel ratios. The second option is the APEXi SAFC and SAFC-II - both of which are fine units. They do about the same thing as the PSC, however they don’t have a map sensor, and lack some adjustability for fine-tuning. Also, with the fuel tuning units, don’t forget to get a larger fuel pump to provide enough fuel to the engine. If you are running high boost, you will need to upgrade the injectors as well. The size of injectors you need depends on your boost levels and power goals. If you plan on tuning your turbo setup, you will need a wideband O2 unit. When price comparing to a regular O2 sensor gauge, a wideband unit seems expensive. However, a regular gauge type O2 sensor gauge will not tell you enough to tune your truck. For information on tuning, check out Gadget's guide to tuning here: http://www.gadgetonline.com/U-Tune.pdf
Blow off valves
This is the best part of turbos, in my opinion. There are many types, shapes, sizes, and sounding blow off valves. Some make lots of noise and some make very little. What you need comes down to personal preference, the sound you desire, and your horsepower goals. There are two main types of blow off valves: the ones that vent to atmosphere which make the loud noises; and the ones that recirculate the air back into the system, which are often called wither diverter valves or recirculating blow off valves.
Atmospheric blow off valves sound great and let everyone know you are turboed (which is great fun). However, they can be bad for performance and your engines health. When you make boost, the mass air flow meter is telling your ECU that a specified amount of air is about to enter the engine, so it adds a certain amount of fuel for that air. When you blow off to the atmosphere, the air is released from the system. Then you are left with all that additional fuel that was supposed to meet the air that’s not there. This leads to an overly rich condition, which is not good for performance because it can cause the engine to stumble, or even backfire. Also, when all that fuel is dumped into the exhaust, it can deteriorate the catalytic converters, and they can be destroyed which will set off a check engine light and cause degraded performance from a clogged exhaust. The only downside to a recirculating blow off valve is the lack of sound if you desire such a thing.
Now down to the sounds. There are a bunch of different sounding blow off valves on the market. The best way to sample the sounds is to go to www.blowoffvalves.com . They have videos and sound clips of the more popular blow off valves. Don’t forget that you will need the appropriate flange to weld to the piping. Also, you should have a basic understanding of how blow off valves work and why you need one. When you hit the gas, hopefully you make boost. When you let off the gas, the throttle body plate closes and the air compressed inside the pipes has to go somewhere. The path it would take without a blow off valve is out through the turbo (which it just came in from). This would be acceptable if it wasn't for air traveling backwards through blades spinning at thousands of RPMs. This is known as turbo flutter, and the sound is unmistakable. This will cause severe damage to the turbos seals and bearings, and is very bad for the turbo.
How blow off valves work is very simple. It’s essentially a plunger that has a spring over it. When your engine is under boost, there is a force from the boost going though the vacuum line, forcing down the plunger, and thus sealing the system. When you let off the gas, the throttle plate closes and the engine begins creating vacuum, and it is this force that pulls the plunger up and releases the air though an opening.
Oil for the turbo
Believe it or not, things spinning at up to 26,000 RPMs create friction and need lubrication. Turbos use the engine's supply of oil for lubrication. The oil has to be forced into the turbo by the oil pressure of the engine, and can't just be taken from anywhere. On the 2rz, there are two plugs that are removable on the same cast unit that holds on the oil filter. Those plugs can be removed and replaced with a threaded fitting to provide oil to the turbo. This is the most common place for the oil feed for the turbo on a 2rz. To get the oil to the turbo from the fitting, you will need a stainless steel braided line. You can buy these lines from several places. However, the best quality (and ironically) the cheapest place I have found one is at the local performance shops that carry nitrous lines. If you go this route, ask for a 36-inch long –3an stainless steel braided line. Mine ran me about $20 or so compared to the $45 ones elsewhere.
Now that you have oil in the turbo, you need a way to get it out. You can run a regular oil hose here. However, turbos generate an immense amount of heat, so I strongly recommend stainless steel braided line for this as well. I would also recommend running a –10an sized line for the drain. If the drain line is too small, it will back up oil into the turbo and blow out the seals and cause you to smoke and put oil into your engine. In order for the oil to get back into the engine after the turbo, remove the oil pan and weld in a fitting for the oil line that’s connected to the bottom side of the turbo. Always make sure the oil feed line is on top of the turbo and the drain is on the bottom, since the drain is gravity fed and it needs as little of restriction as possible.
Intercoolers are, in essence, a big (or sometimes small) radiator for the air that the turbo compresses. When air is compressed, it creates friction. And friction creates heat. This is where the intercooler comes in. After a certain PSI (normally about 10-11), the turbo creates so much heat that without an intercooler, the engine would make about the same amount of power at 9psi than 15psi. The air is so hot that the engine has to retard timing to prevent predetonation.
Hopefully, this guide has provided you with the basic concepts of turbo systems.