Turbocharging the Nissan MR20DD Engine, Part 5, Putting It All Together!

So if you have been following our series on building the Turbo Nissan MR20DD engine, you can read about our analysis of the engine in the first chapter, the engine internals in the second chapter, and what we are doing to the engine to make it more suitable for turbocharging in the third segment. The new Turbo system was discussed in the 4th segment. This week is the 5th segment of our Turbocharging the Nissan MR20DD engine.  In this week’s segment, we will assemble our engine and turbo system to ship it to Nissan Motor Corporation where it will be installed in their Sentra DET concept car that will be revealed at the SEMA Show in the Nissan booth!

When starting our assembly, we installed the main bearings and torqued them down to factor spec in our freshly prepped block.  No performance bearings are available for the MR20DD so we WPC treated the OEM bearings and reused them.  WPC treating can increase a plain bearings load carrying capacity by up to 20% and one OEM that we know of uses it for this purpose.

The next step was to measure the bearing bores with a bore gauge.

The bores were all measured carefully in several spots and the inner diameters were recorded.  The same process was also repeated on the Carillo connecting rods and WPC-treated rod bearings.

Next, our crank was balanced, micro-polished, then cryogenically treated by CTP Cryogenics and finally WPC treated.  The crank pins diameters were measured using a micrometer and recorded.  Subtracting the crank pin diameters from the block and rod bore diameter gives the bearing clearances.  If you are building a motor is it critical to check this every single time and correct any out-of-spec conditions. Poor engine life and performance will result from having your clearances out of spec.  No matter what your engine builder or YouTube expert says, plastigauge is not the way to do this correctly!

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