Oil Cooled Pistons : RB26DETT Tech

Oil Cooled Pistons : RB26DETT Tech

This is a N1 piston that came apart, when we lost oil pressure. The cooling channels are visible in the top two pieces

The RB26dett has something with the pistons, that is fairly unique in the engine world.  Unique doesn’t always mean better, but it is something to consider.  OEM RB26 pistons have oil cooling channels in them. The block has squirters, that spray oil up under the pistons. Unlike many squirters that just splash the underside of the piston, the RB26 piston has a supply hole, drain hole, and channel in the piston to help cool it.  Most all aftermarket pistons, do not have cooling channels in them. 

Most oil cooled pistons on the left, RB26 stock pistons on the right
How do piston cooling oil jets work? 
Oil jet cooling discussion: Bobistheoilguy
Piston Cooling
Pistons and engine testing
Piston cooling gallery configurations
Temperature distribution in gas and diesel pistons


  • Cooler pistons
  • Possibly less detonation

  • Heat added to oil temperature
  • Oil whipped up in bottom end
  • Cost
  • Complexity
RB26dett pistons with cooling channel- Tomei data

We all know that RB26 move a lot of oil, and if you run them hard, they all put a lot of heat into the oil.  If you change from OEM pistons, most will not have the cooling channels in them. It is a special process to make them in the OEM  STD, and N1 pistons, and the only aftermarket ones we know of are Reinik, and Tomei with oil channels actually in the pistons.  It seems that Tomei no longer makes the cooling channel pistons, and Reinik has been renamed Reimax, but still offer cooling channel pistons.  Was the benefit not worth it, cost?  My bluecar has Tomei oil cooling channel pistons in it, was a nice surprise to find the last time it was opened up.  I like the idea of them, of helping to control the piston temperature, but on a max effort car, perhaps piston crown coatings are more of a benefit.  The oil hitting the bottom of the piston has to add some weight, and does add a lot of windage. 
SR20det Oil cooling channel pistons

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Published at Mon, 06 Apr 2020 14:46:00 +0000