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Turbo Oiling and Cooling, Part 2

by Julian Edgar

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At a glance...

  • Oil supply
  • Oil drain
  • Water connections
  • Fittings
  • Hoses
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Last week at Turbo Oiling and Cooling, Part 1 we backgrounded the supply of oil and cooling water to a turbo – and the plumbing needed to remove that oil and water. This week we’ll put the theory into practice, installing a turbo on a normally aspirated Toyota 1NZ four cylinder engine.

Oil Supply

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The oil supply for the turbo was obtained from the oil pressure sensor. The oil pressure sensor was unscrewed (interestingly, it uses a 15/16th inch socket size – the only Imperial fitting on the whole car!) and the oil feed banjo fitting to the turbo unbolted. Both fittings were then taken to an industrial hose company (EnZed) that made up a braided high pressure oil line to suit. The line cost about AUD$100.

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EnZed also supplied the threaded T-piece that allows the original pressure sensor to screw back into the assembly. We also sourced a barbed hose fitting that can be screwed-in to replace the pressure sensor, allowing the easy fitment of an oil pressure gauge. Braided line can wear away surfaces with which it is contact so the line was clamped securely in place. Threaded fittings were sealed with Teflon thread tape. A swivel was placed in the line near the T-piece so the fitting could be done up without having to rotate the whole oil hose. Note that even with this apparently minor relocation of the oil pressure sensor, the signal wire needed to be extended.

Banjo Fittings?

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Banjo fittings consist of a spherical union with a pipe attached. The spherical union has two openings in it, through which a hollow bolt passes.

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A hole is placed in the side of the bolt. Fluid can flow up the hollow bolt, out through the side hole and into the spherical shape of the union. From there it flows into the attached pipe. Alternatively, it can flow in the opposite direction. It sounds a complex path to take but banjo fittings are widely used on turbos (and also plenty of other hydraulic hose connections).

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When handling banjo fittings, be very careful that the two copper crush washers (one either end of the bolt) are not misplaced. The copper washers provide the sealing of the fitting; copper is soft enough to deform and fill any surface imperfections in the mating surfaces. If you leave out either of the washers, the fitting won’t seal. If you lose the washers, new ones can be sourced from industrial hose suppliers. If there is any doubt as to the condition of the washers, replace them.

The retaining bolt in a banjo fitting should not be over-torqued, or else the union will become distorted. Most banjo fittings use relatively large bolts (they need to be to have sufficient flow-put) but the bolt should not be tightened to the same sort of torque that you’d normally use on a bolt of the size.

Oil Drain

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The oil drain line went through a number of design iterations before this approach was picked. For the attachment to the sump, EnZed supplied a 19mm barbed hose fitting which they cut off short and silver soldered to a bulkhead fitting. This cost a not-inconsiderable AUD$40.

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However, another approach – which is much cheaper – is to use a stainless steel fuel tank breather sourced from a boating supplies shop. The wire grille is easily pulled out and the opening can be aimed downwards within the sump. Another advantage is that the retaining nut ends up on the outside of the sump! This fitting cost AUD$13 from Whitworths.

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In this case the manufactured fitting was used (arrowed). The drain fitting of the turbo can be seen directly above.

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Installing the sump fitting required drilling a hole (to avoid any likelihood of chatter, a new hole-saw was used)...

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...inserting the fitting and then placing a nut and copper washer on the inside. This required the use of a volunteer with small hands. Access was gained to the internal wall of the alloy sump by removing a small pressed steel cover plate located at the base of the sump.

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The clearance between the big-end bolts and the sump fitting can be seen here. It’s tight – but big-ends don’t move around very much!

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The oil drain pipe came with the secondhand turbo but this proved to be the wrong shape, so a large section of the pipe was cut out before the parts were silver-soldered back together. A rubber hose with a moulded-in right-angle bend was used to join the oil drain fitting to the sump fitting.

Water Supply

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On this secondhand turbo, the water pipe openings came with fittings – in this case, of the banjo type. These water fittings had steel pipes attached, however with the turbo installed, these had the wrong orientation. The pipes were modified by being cut and silver-soldered back together.

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The water supply was obtained by plumbing the turbo in at the point indicated on this diagram by the arrow. As shown, that places the turbo in series with the coolant supply to the throttle body. An alternative would have been to plumb the turbo in parallel with the throttle but it’s physically easier to take the series approach, as the throttle body and the turbo share similar hose barb diameters.


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The trickiest bit about installing the water and oil plumbing on a custom turbo installation is fitting the drain fitting to the sump. The water connections are easy, and the oil pressure feed straightforward to install once you’ve had the braided cable made up and bought the fittings.  So before making the turbo manifold, it’s wise to assess where the sump oil drain fitting will go – this hose needs to be kept close to vertical and if the turbo can be offset to one side by (say) 25mm in order that the fitting is placed in a more easily accessible position on the sump, then you may want to do so.

In the case of the Toyota shown here, the water and oil plumbing came together well – and with no leaks!

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