Dyno Day 1

The first order of business was to establish a baseline against which I could compare all future modifications.  The first couple of runs, or "pulls", were very consistent so I felt comfortable in using them as a baseline.  These runs were conducted with the truck in completely stock trim and with a full tank of 87-octane fuel.


I was eager to see if Nissan's claim of 265 horsepower on 87-octane gas was a good one; using the old tuner's correction factor of a 20% horsepower loss through the drivetrain with auto transmission, I expected to see about 210-215 horsepower at the rear wheels.  I was pleasantly surprised to see the dyno's computer spit out a reading of 221.5 peak horsepower (SAE corrected) at about 5650 RPM.   I'll take that to mean that either Nissan's power claims were conservative or that drivetrain losses were less than average--either one is good news!  Three different runs were very consistent, so I believe that we got a good reading.  The graph below confirms what the butt-dyno had  told me--that this engine is a little peaky for a truck engine, with the power really building in the upper RPM ranges.  You'll note that the graph shuts down at just past peak HP about 5750 RPM, well below redline; we elected to run the tests in third gear and that's where we ran into the speed limiter, apparently set at 110 MPH.

The second graph shows the torque curve; peak torque is 230.10 ft/lbs at about 4100 RPM.  Once again the torque curve is a bit peaky, but it is a nice flat delivery and stays above 200 ft/lbs all the way to the speed limiter.  Sweet!