Info on NPR piston rings

[ApexHunter]

I bought some 2g NPR pistons and rings off ebay, and i'm trying to figure out the material of the 2nd compression rings. I've got it narrowed down to either cast iron or nitrided steel, based on the information on the NPR site (i've got 3pc oil rings).

I'm trying to figure this out so i can gap them correctly. They didn't come with any info on the suggested ring gap nor have i been able to find any floating around on the net.

If anyone knows or could let me know the correct gap that'd be great. TIA.

 

[fivestardsm]

I had to do the same thing with a set I had. I will try and get you the info tonight if no one else does.

 

Quoting ApexHunter:
I bought some 2g NPR pistons and rings off ebay, and i'm trying to figure out the material of the 2nd compression rings. I've got it narrowed down to either cast iron or nitrided steel, based on the information on the NPR site (i've got 3pc oil rings).

I'm trying to figure this out so i can gap them correctly. They didn't come with any info on the suggested ring gap nor have i been able to find any floating around on the net.

If anyone knows or could let me know the correct gap that'd be great. TIA.



What did you gap the top ring at? I usually gap the rings base on how the motor will be used.

Steve

 

[ApexHunter]

I haven't gapped the top ring yet. Any suggestions are welcome.

BTW, as far as how the engine will be used: 91 octane, ~11:1 AFR, SAFC/KD stage III chip with 2g timing maps, s16g, 18-20 psi max but most driving will probably be in the 14-15psi neighborhood. FMIC from a saab 9-3 viggen (substantially bigger than stock but not big). BPR7ES's, 0.028". I'm rebuilding the head, but basically all stock with the exception of bronze valve guides. Street car w/ possibility of a track day every once in a while.

 

.019-.020 on the top. .023-.024 on the second ring.

Steve

 

[ApexHunter]

So for the top ring a little bit bigger than what is specified from the FSM, and on the 2nd ring the large side of FSM spec....makes sense. More power = more heat = more expansion i presume.

Thanks for this info Steve. What kind of rings were you using these gaps with?

 

I use those specs on most of the motors I build. I would say I have
used every ring out there with those specs. I have the NPR rings in my DD with those specs
and don't have a problem running 36psi on pump daily. This motor has been in
the car for a few years with many different turbos but currently runs the
PT6262.

Steve

 

[ApexHunter]

Sounds good Steve, thank you!