Rebuild your turbo!

Just starting this section....will be finished soon!

Preface: The turbocharger is an engine enhancing device that uses rapidly expanding exhaust gases to spin a turbine. This turbine is attached to a shaft which rotates a compressor blade which compresses the intake. The pressure difference of the exhaust across the turbine between the engine and turbo and turbo and exhaust tip causes the turbine to rotate. Contrary to popular belief the turbo energy isn't free. A non turbo engine has back pressures around 2psi while a turbo engine with the turbo producing 14psi has engine exhaust backpressure of around 28psi. Turbochargers spin at around 130,000rpms stock and up to 230,000rpms @25psi on the stock turbo. Of course the heat produced above 16psi seriously reduces the life of the turbo and the engine unless other upgrades such as a larger intercooler and fuel delivery is taken care of.

If you had a sudden failure of your turbo chances are you won't be able to rebuild it. Sudden failures happen when internal components of the turbo break or seize, something hits either the compressor or turbine blades, oil or coolant flow is interrupted or the turbo bearings develop enough play that the blades come in contact with the housing. If any of these things have happened then chances are the parts needed for the rebuild (shaft, compressor and turbine wheels and all 3 housings) have damage. Since the turbo charger works on such small tolerances some of these pieces would have to be replaced.

I highly suggest a yearly diagnosis of your turbo. Remove the aircan -> turbo piping and O2 housing. (make sure the engine and turbo are cool and the engine ISN'T running) Put one finger in the intake side of the turbo with your finger gently touching the compressor wheel and the inside of the compressor housing. Use your other hand to try to move the exhaust wheel pushing from side to side and back and forth. If you feel any play on the intake side while doing this then a turbo rebuild is in the near future. Having play in the shaft means a couple things: longer spool up time, higher rpms for less boost, more heat, chances of oil and coolant mixing inside the turbo, oil leaks to the intake and exhaust as well as damage to the shaft since the turbo isn't operating in a balanced state.  

Tools needed:

	Center Bearing Section after intake and exhaust housings removed. Compressor blade already removed.
	The snapring must be removed to access the inner bearings
	Take care in removing the snapring, use your thumb to keep it from springing at you.
	Remove the cover assembly by pushing it out with a plastic or wood stick from the exhaust side of the section. Removing the seal plate will expose the following parts: (a) the compressor seal; (b) the thrust collar; (c) the thrust bearing; (d) the thrust bearing retainer; and (e) 'O' ring
	Remove the rubber o-ring seals using a toothpic or some other "tool" that won't scratch the metal
	This is the order that the parts are removed
	The small split seal keeps the oil separated from the coolant. Take your time removing these from the groove and be sure not to scratch the housing.
	Polish up the shaft using 1200 grit sand paper to remove surface varnish then polish it with some kind of metal polish. For best operation the turbo shaft should shine with no scoring marks or dull spots. Rinse the shaft and exhaust wheel assembly under water to get rid of all the polish. Clean the assembly again with lighter fluid or paint thinner to get rid of any water or contaminants. Coat the assembly immediately (except the exhaust wheel) with engine oil to prevent surface rust which forms almost instantly after cleaning.
	There are a couple things you can do while rebuilding the turbo to extend the life of the rebuild. First off is to polish the exhaust turbine housing to eliminate carbon build up. Same goes for the center rotating housing assembly exhaust end cap. By polishing the surfaces you get rid of adhesion factors and carbon no longer sticks. You get better flow and spool up properties by having greater flow characteristics. Next off is the compressor housing, everything should be polished to a mirror finish for best results and ported to the mating flange. These couple steps reduce heat build up, increase flow and can decrease the exhaust pressure drop.

Reassembly Notes:

 The snap rings have one tapered edge that must face outwards to achieve proper sealing.

Be sure to soak the bushings/bearings in oil for at least an hour before assembling. They have some absorbing properties with oil and doing this really helps during the initial seating period.

Back to Main

© Copyright 2000 Michael Hamilton. All Rights Reserved. 
Email me with any questions or comments mdhamilton@home.com 

This page was last edited 08/03/2001 05:09 PM