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Several years before I started the project I found a Dinan turbo manifold on ebay for $100. It was a rough casting, meaning it didn't have any of the flanges machined and no holes were drilled. My local machine shop was able to machine the manifold after I gave him bolt pattern dimensions for the head and turbo flanges.
Here is the turbo manifold back from the machine shop. You can't see it in the pics, but the stud holes on cylinders 1 and 4 are drilled larger to allow for heat expansion of the manifold. After taking measurements I decided that a t25 flange most closely matched the size of the manifold opening. I'd guess that other Dinan manifolds have a different bolt pattern than this but I don't know.
Since I was stuck with a T25 flange I was stuck with T25/28 turbos, and the largest, cheapest T25 I could find is the Garrett T25 from the Nissan S13 SR20DET. Though compressor maps for this turbo are nowhere to be found, from my calculations and studying the compressor map from the GT25R (which is very similar in spec), it should be an excellent match for my motor, plus they are cheap and easy to find. I paid $150 for one in good used condition and also bought a used aftermarket SR20DET stainless divorced port down pipe for only $30.
I bead blasted the housings and ported the inlet of the compressor housing to remove a sharp ridge. I also ported the inlet of the turbine housing to match the hexagon shape of the manifold.
Here the manifold, turbo and downpipe are mounted for the first test fit. Since the cheapest and most readily available downpipes out there for this turbo were designed for a Nissan Silvia, that's what I used. It's not ideal for my application, but it works. I had to grind the bell housing of the tranny to eek by with 3/16" clearance.
Eventually I decided I needed to re-clock the turbo so the compressor outlet was facing down rather than up to simplify charge pipe routing. This meant I had to modify wastegate actuator mounting bracket and tap new holes in the back of the compressor housing. Now that it was now mounted on the back of the housing the rod needed to be shorter so I cut and welded the actuator rod. This was a temporary setup that ended up causing a drop off in boost pressure due to inadequate rod tension. I corrected this by cutting threads on the rod with a die and using an adjusting collar to allow rod tension to be adjusted. Shown is a test fit after reclocking the turbo.
Here's the turbo after installing the oil inlet fitting and checking oil supply line clearance, compressor inlet and outlet flanges, oil drain flange and fitting, and coolant hose barb fittings. All of these components were purchased new from ATPturbo.com.
Oil Supply & Drain
I drilled and tapped a 1/8 npt hole for the oil supply line on a flat area on the return side of the filter flange so the turbo sees only clean filtered oil. The oil drain on a turbo is at zero pressure so it needs to flow down hill and be free from obstruction. I initially intended to weld a flange to the oil pan. The side of the block and oil pan are at a steep angle and to clear the pan flange while keeping a fitting horizontal it would have to sit below the oil level. Because of this I chose to tap the block rather than weld a flange to the oil pan. I had to remove the pan and drill a 7/8" hole to tap a 1/2" npt thread in the side of the block directly under the turbo and as close to the pan flange as possible. The fitting sits horizontal at the block which is about as good as I could get it.
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