TURBO SYSTEM OPTIMISATION
A guide to setting up your turbocharger from Garrett Advancing Motion
In this article, Garrett Advancing Motion explains the Turbo System Optimisation process, covering auxiliary systems and how to properly calculate, install, and identify problems, as well as tips for how to correct common problems that arise from incorrect installation.
AIR FILTER SELECTION
It is important to appropriately size the air filter for the maximum flow rate of the application. A target face velocity of ≤130 ft/min at redline is used to minimise restriction and to provide the turbo with the air necessary for it to function optimally. If the turbo does not have access to the proper amount of air, excessive restriction will occur and cause:
• Oil leakage from the compressor side piston ring, which results in oil loss, a fouled intercooler and potentially smoke out of the tailpipe.
• Increased pressure ratio, which can lead to turbo overspeed.
• Overspeed, which will reduce turbo durability and could result in early turbo failure.
OIL SUPPLY AND DRAINAGE
Ball bearing turbo:
An oil restrictor is recommended for optimal performance with ball bearing turbochargers. Oil pressure of 40 – 45 psi at maximum engine speed is recommended to prevent damage to the turbocharger’s internals. In order to achieve this pressure, a restrictor with a 0.040” orifice will normally suffice, but you should always verify the oil pressure entering the turbo after the restrictor to ensure the components function properly. Recommended oil feed is -3AN or -4AN line or hose/tubing with a similar ID. As always, use an oil filter that meets or exceeds the OEM specifications.
Note: oil leakage should not occur on a properly functioning system if restrictor is not used, unless the system pressure is excessively high.
Journal bearing turbo:
Journal bearings function similarly to rod or crank bearings in an engine – oil pressure is required to keep components separated. An oil restrictor is generally not needed except for oil-pressure-induced leakage.
The recommended oil feed for journal bearing turbochargers is -4AN or hose/tubing with an ID of approximately 0.25”. Be sure to use an oil filter that meets or exceeds the OEM specifications.
In general, the larger the oil drain, the better. However, a -10AN is typically sufficient for proper oil drainage but try not to have an inner diameter smaller than the drain hole in the housing as this will likely cause the oil to back up in the center housing. Speaking of oil backing up in the center housing, a gravity feed needs to be just that – the oil outlet should follow the direction of gravity +/- 15° when installed in the vehicle on level ground.
If a gravity feed is not possible, a scavenge pump should be used to ensure that oil flows freely away from the center housing.
When installing your turbocharger, ensure that the turbocharger axis of rotation is parallel to the level ground within +/- 15°. This means that the oil inlet/outlet should be within 15° of being perpendicular to level ground. Be sure to avoid undulations in the line or extended lengths parallel to the ground; draining into oil pan below oil level; deadheading into a component behind the oil pan; and the area behind the oil pan (windage tray window) where oil sling occurs from crankshaft.
WATER LINE OPTIMISATION
Water cooling is a key design feature for improved durability, and Garrett recommends that if your turbo has an allowance for water-cooling, you hook up the water lines. Water cooling eliminates the destructive occurrence of oil coking by utilising the Thermal Siphon Effect to reduce the Peak Heat Soak Back Temperature on the turbine side piston after shut-down.
In order to get the greatest benefit from your water-cooling system, avoid undulations in the water lines to maximise the Thermal Siphon Effect.
For best results, set the orientation of the center housing to 20°. Significant damage to the turbo can occur from improper water line setups.
The above is an abridged version of a full technical guide which can be found on the www.garrettmotion.com website.
The full guide includes additional information and a video on all of the above plus additional topics including the formula to calculate the correct air filter; calculating the correct charge tubing; charge tubing; blow off valves; vent to atmosphere for manifold absolute pressure engines and by-pass for mass air flow engines; wastegates; system testing; and system monitoring.
For more information, visit www.garrettmotion.com or the Garrett Advancing Motion YouTube channel.