Extreme Engine Tech: Jim Wolf Technology’s Turbo Nissan QR25DE Powerhouse Part 2

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The chamber was also lightly reworked to remove sharp edges and unshround the intake and exhaust valves.  The QR head flows pretty good from the factory and did not need extensive porting to produce some impressive flow numbers, over 20% more than an SR20 in modified form.

Piston coolers are nozzles tapped into the engine’s main oil galley that shoot oil to the undersides of the pistons to help keep them cool.  The Honda piston coolers are nice because they have a check valve so they only open at high rpm when there is a surplus of oil flow.  At low rpm they close and help preserve idling and low speed oil pressure.  Newer QR25 engines have piston coolers and if we were to do this over again, we would have simply used those.

You can see the three angles of the valve seat right here.  The milky band is the 45o seating cut, it is milky because it is hand lapped for better sealing.  The top and bottom cuts help smooth the airflow over the seat.

In this photo of the intake port you can see the porting in the valve bowl and short side radius.  Flowbench testing showed that porting the port’s entrance did not help, likewise the exhaust port only improved after some light massaging of the bowl and short side radius.

On the cylinder head side, the engine is pretty stock.  Flow bench testing showed that the QR benefited from only minor porting.  It also showed that a QR head flows over 15% more than an SR20 head.  JWT lightly ported the valve bowl and short side radius of the intake and exhaust ports, about the only place where flowbench testing showed a significant difference could be made.  JWT also unshrouded the intake and exhaust valves in the combustion chamber to improve flow as the valves open.  The cylinder head deck surface was also milled smooth and lapped for near perfect flatness.

The valves were recontoured for better flow, the recontoured valves are on the left, stock on the right.

JWT finished the valve seats with a 3 angle cut, 70, 45 and 30 degree cuts help smooth the airflow past the valve as it starts to open.  The valve contours were also smoothed to improve the flow.  The valve job and valve re-contouring greatly help flow especially at low and partial lifts.

A close up look at the valve modifications, the seating surface is narrowed and hand lapped for better seal.  The valve contour is smoothed and blended to the seating surface.

The late model crank has a different crank trigger wheel with an inverted trigger pattern.  JWT modified a truck crank trigger to use the old style trigger with the new style crank.  This keeps the crank angle sensor happy.

We ended up using a truck crank trigger wheel.  It has the 4 bolt bolt pattern that the newer crank uses with the trigger tooth configuration of the older 3 bolt trigger wheel.