TURBO BUILDS 101
Turbo Parts Explained for Dummies -
Downloadable Complete Turbo Parts checklist HERE
Turbo: A turbo works by providing a ‘boosted’ amount of air flow through the engine. In addition to the standard intake air flow, the turbo also utilizes air flow from the exhaust to power the engine. When choosing an appropriate turbo, there are many turbo options to choose from. You can get a small turbo, for quick spool & low-RPM power but that may have power limitations. Or, you can go with a big turbo which may take some time to spool & get power, but can take you to maybe 600, 700 or 800HP (really whatever desired HP you’re shooting for). “Spool” is referring to the time it takes for the turbo to speed up enough to create positive boost pressure. (That’s when you feel it go fast)
An example of an entry turbo is the precision 5431, capable of making 500HP, but also usable in a 300HP setup. A budget turbo, with still a reputable brand, is the Borgwarner SX300/400 series of turbos. You really don’t even have to purchase a new turbo to boost your set up, you can use a turbo from a stock application as we did in the Honda CRV. With the Honda CRV we used a stock Mitsubishi EVO 8 turbo which you can find around for $150, this did require custom fabrication. The customization and options are endless.
You may also have heard the terms ‘ball-bearing’ versus ‘journal-bearing.’ This refers to the type of bearing used within the turbo charger, which affects how the turbo spools up. Ball-bearing turbos are the ‘baller’ turbo (pun intended). Ball-bearings can be close to twice the cost of a journal bearing turbo. Journal bearing turbos take longer to spool compared to the ball-bearing equivalent.
Turbo Manifold: A turbo manifold is what the turbo is mounted to. A turbo manifold replaces the engine’s exhaust manifold (also known as the header). There are different styles of manifolds such as a top mount turbo manifold versus a ramhorn manifold which may carry different power limitations and power band widths. Turbo manifolds are specific to types of engine and types of turbos. The flange pattern where the turbo meets the manifold will additionally need to match (from the turbo manifold to the turbo) . What we most commonly see is t3, t4 & t4 divided in turbocharged 4 cylinder applications.. You can check out our manifold collection here.
Wastegate: The wastegate is responsible for releasing exhaust pressure from the turbo manifold in order to control the turbocharger’s speed and therefore boost pressure. When the wastegate bypasses exhaust out of the turbocharger and into the atmosphere, there is less exhaust gas going through the turbo spinning the turbine wheel. Therefore, the turbine wheel slows down, which in turn controls the boost pressure.
Without a wastegate, a turbo will free spin up to the highest boost pressure possible and be uncontrollable. There are 2 types of wastegates - external & internal. External wastegates are connected to the turbo manifold. Internal wastegates are built onto the turbocharger. A build can have one or sometimes even two wastegates depending on the turbo size, manifold choice & size of wastegate. In addition to the size of the wastegate, the wastegate has differential internal springs which guide the boost pressure range. It is important that the balance is there for the wastegates, turbo and turbo manifold for optimized power. Most common sizes we see for wastegates are 38mm & 44mm.
Dump tubes: After your wastegate, there will be piping attached directing the exhaust flow. This piping is known as dump tubes. These dump tubes are typically 1.5” (Vibrant #13032) for the 38mm wastegates and 1.75” (13034) for the 44mm wastegates.
Intercooler: The intercooler’s job is to cool down the hot compressed (boosted) air coming out of the turbocharger, before the air gets to the engine. When air is compressed inside the turbocharger, it becomes very hot. It passes through the charge piping that is connected to the intercooler. Having an intercooler appropriately sized for your turbocharger setup is critical to maintaining good intake air temperature for maximum horsepower. There are two types of intercoolers; air-to-air and air-to-water, both of which the purpose is to cool the boosted air coming out of the turbocharger. Air-to-air intercoolers are the most common, cheap, and simple types of intercooling, they are designed similar to a radiator using air passing through the fins to cool down. Air-to-water intercoolers are more complex, this is a sealed unit that passes water through the fins on an intercooler to cool down the charge air. This needs a water pump to circulate the water from a reservoir through the intercooler, which may be filled with ice and water to cool down air temperature more than is possible by air-to-air intercooling.
Blow Off Valve: The purpose of a blow off valve is to release the boosted air that is within the charge piping to the atmosphere. When the throttle body is closed while the turbocharger is making boost, the boosted air will start to go backwards through the charge piping. The blow off valve will open upon this condition, releasing this boosted air. Without a blow off valve, the boosted air will go backwards through the turbo, which can damage the turbocharger. This is called “compressor surge”. The blow off valve requires fabrication. These are fabricated onto the charge pipes (the piping that comes off the intercooler) before the throttle body.
Intercooler Piping, Couplers + Clamps: Intercooler piping, AKA charge piping, is piping that connects the turbocharger to the intercooler, and the intercooler to the throttle body/intake manifold of the engine. This piping is typically made out of polished aluminum (this is recommended), but may also be made from stainless steel or steel. It delivers the compressed (boosted/charged) air coming out of the compressor housing on the turbo to the intercooler. Once through the intercooler, there is another charge pipe coming off of the intercooler that attaches to the throttle body to feed and boost the engine. Couplers are typically made out of 3-5ply silicone in various sizes, colors, adapters, and bends. This is the connection from the turbo to the charge piping, the charge piping to the intercooler, and the charge piping to the throttle body. Once the couplers are slid onto the components, you use clamps to hold them together. “T-bolt” style clamps are recommended for all boosted applications, however worm-gear style clamps can be used for very low boost applications. You can check out our collection here.
Turbo Oil Feed Line,: For the turbocharger to function, it needs to be lubricated in order to prevent failure. Turbochargers spin at a very high RPM, as much as 150-200,000 RPM. Oil is used to cool and lubricate the bearings in the turbocharger. Typically oil is fed from the engine block’s oiling system to the turbo with a hose, called an oil feed line. The size of the turbo oil feed line is usually a -3AN or a -4AN hose and fittings. Some turbochargers will require an oil restrictor, to restrict the amount of oil that can pass through the turbocharger. Too much oil can be a problem, blowing oil out through the oil seals into the exhaust and therefore smoking and can lead to a failure. Too little oil, and the turbocharger’s bearings will overheat and fail, which can then damage the housings, wheels, and oil seals. (Requires male feed nipple from the turbo - dependent on turbo application) - popular fittings/flanges can be found here.
Turbo Oil Drain Line: Once the oil passes through the turbocharger, it needs to be returned back into the engine through the turbo oil drain line. Normally we recommend using a -10AN size for the oil drain line and fittings. The drain line/hose connects from the bottom of the turbocharger to the engine’s oil pan, returning the oil back to the engine. There may need to be a -10AN bung welded onto your oil pan to be able to connect the drain hose. (Requires drain flange from the turbo - dependent on turbo application) - popular fittings/flanges can be found here.
+ Oil Pan gasket will need to be replaced when removing the oil pan to have an oil return bung welded to the oil pan.
+ Oil Change
+ Clutch - your clutch and possible flywheel needs to be upgraded to handle whatever your power goals are. A stock clutch will slip when too much power is applied to it.
Depending on your engine and turbo set up, you may need to upgrade additional parts such as springs/retainers, head studs, etc. to safely handle the boost the engine will now be handling.
At a minimum the following components need to be upgraded in order to support turbocharged power. The entire fuel system is EXTREMELY important for the reliability and longevity of your engine. The more power you want to make, the more fuel needs to be fed to your engine and all the components work together.
Fuel Pump - There are many sizes and styles of fuel pumps. What pump you need will be based off your power goals. Walbro 255LPH is an example of an entry fuel pump upgrade, providing enough fuel to support 4-500HP.
FUEL INJECTORS - Fuel injectors spray the fuel into your cylinders. The size injectors you need to upgrade to are based on the power goals of the build and type of fuel you are running. For example, using pump gas takes about 30% less fuel to make the same power as a fuel such as en ethanol based fuel such as E85. Your turbocharged car will make much more power on E85, if your fuel system can support it due to its characteristics. Too small of injectors, the engine will be limited on how much power it can make due to not having enough fuel. Downsides to having very large injectors is idle quality/drivability can be not as smooth. Some good brands are Injector Dynamics, Fuel Injector Clinic, Bosch, Precision, RC. A quality set of fuel injectors is crucial for driving and idling characteristics, power production, and reliability. Cheap brand injectors can fail which can cause cylinders to not have enough fuel and become “Lean”, this can quickly lead to engine failure.
Optional (BUT NEEDED WITH HIGHER HORSE POWER):
Fuel Pressure Regulator - The stock FPR will need to be upgraded after a certain power level. It’s always a good idea to have one as it not only flows more than stock, but allows you to adjust to the desired fuel pressure.
Fuel Lines/Hoses - Fuel lines and hoses will need to also be upgraded when power exceeds how much the stock fuel lines can flow. For Honda’s, this is typically in the 4-600HP when they need to be upgraded.
When turbocharging your car and upgrading all these parts, you will need a way to tune the vehicle. This is done by modifying the Engine Control Unit, or ECU with hardware and/or software depending on the type of vehicle. In some cases, replacing the stock ECU entirely with an aftermarket unit can be a better option.
Popular tuning platforms for Honda’s are Hondata, Ktuner, Crome, and more. For older Honda/Acura’s running B/D/H/F series engines, you will need an OBD1 ECU to be modified for either Hondata S300 or Crome. For Honda’s running K series engines, Hondata Kpro is a great option which is installed into 02-04 K series ECU’s. For newer Honda’s 06-present, Hondata flashpro and Ktuner will be the go-to options.
When you turbo your car, the exhaust manifold will no longer be used. Instead, the exhaust will be built off the turbo which requires a ‘downpipe flange.’ This flange will depend on the turbo you have. Additionally, you’ll need piping to build the exhaust off that flange. Depending on the power and set up, you will want to modify the size of your exhaust.
Downloadable Complete Turbo Parts checklist HERE