Turbocharging the Nissan MR20DD Engine! Part one, the External MR20DD Architecture

The MR20DD has an unusual arrangement where the exhaust ports for the center two cylinders are Siamese’ed.  The non-direct injection version of the engine has 4 exhaust ports. Although this seems disastrous for performance, it is not as bad as it may seem, as these cylinders are as far as possible apart in the 4 stroke cycle. So we don’t have to worry about cross-contamination of the adjacent cylinder. We think Nissan did this to conserve exhaust heat to speed cat light-off during cold start, which reduces emissions. Although the large exhaust port volume of the center cylinders can be less than optimal for velocity and VE, the exhaust heat can help spool a turbo faster.  We were also looking at the stock exhaust manifold and were thinking that it could easily be modified into an effective turbo manifold!

Another interesting feature is the super high volume EGR system. It is reminiscent of what can be found on some diesel engines without urea injection.  It has a big metering valve and a water-cooled EGR gas cooler. It is the silver box on the left side of the engine in the pic above. We think this engine has high EGR flow for 2 reasons; to reduce NOX emissions due to the direct injection enabled high compression ratio (12:1) and to reduce pumping loss at part throttle by filling the cylinders with inert gas, reducing intake manifold vacuum. Interesting stuff!  The water for the EGR cooler can be tapped to cool the turbocharger’s center section.

You can see the large EGR transfer tube on the right side of the engine.  The thin wall plastic intake manifold is going to limit the amount of boost we can run without it failing.  High boost would require a fabricated intake manifold most likely. We think that the stock manifold is probably OK for 10 psi or less. We’ll see!

This is the large EGR control valve. It is bigger than some small engines’ throttle bodies! We are going to get rid of this system for our off-road turbocharged use, as it will probably wreak havoc with performance tuning.


  1. This is the kind of content I hope leads to more new cheap fun cars. Nissan had a project 370Z a few years back that turned out to be very similar to the new Z. Fingers crossed this leads into a new Sentra SE-R or, fingers crossed, a competitor to the Twins.

  2. OK, love it… obviously I can’t fault playing with known enthusiast cars (in good, detail oriented ways) but doing something Good And Weird is stuff I live for. Look forwards to seeing where this goes! And also wondering how temperature tolerant that EGR valve is, because I’ve been thinking about air bypass antilag lately…

  3. I’m willing to bet it has pencil thin connecting rods.

    Is Nissan trying to find another easy opportunity to over-advertise their cars?

  4. I just purchased this car. Gave up my dream car for a while.
    It’s an interesting car.
    Have you thought of super charging it instead of turbo charging it?
    Or does Nissan only want to see how a Turbo would work out.?

    And congrats, having Nissan contact you for this project must feel pretty darn awesome!

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