Originally posted by cobrAA
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Like I said, oil pumps are application specific (hence the different oil pump specs, based on the engine the oil pump is fitted to).
Reimax sell a oil pump that's similar to the Tomei oil pump and that's for forged Group-A RB26 engines. It doesn't have external pressure adjustment like the Tomei oil pump, but has higher volume and pressure (the gear is chromoly, SCM430H, 85mm vs N1 that's 77mm or 81mm, depending on the year of the N1 oil pump and 1mm bigger teeth).
The upgraded N1 gears (made of chromoly, SCM430H, stock oil pump gears are sintered alloy) from Reimax are for N1 engines (stock internals) up to 500hp at engine (what the engine is reliable at in a 24 hour race).
Many have run N1 oil pumps on a forged RB26 and found the oil pump (using it outside the intended rpm, application) was the cause of the failure of the bottomend bearings.
Tomei mention why the Tomei oil pump is needed here (increased oil pressure with rpm, etc) -
From what I understand:
Increased volume = forged engine
Increased pressure = higher rpm (or more boost pressure, which is similar to increasing the rpm)
N1 engines failed (bottomend bearings) due to lack of oil pressure at higher rpm with the stock oil pump, so was not just the gears. I think N1 oil pump has a shim on the relief spring to increase the pressure to prevent this problem from occuring. Shimming the stock oil pump relief spring is nothing new, as has been done in the US on some engines.
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