1Revvin7

I have tried .004/5/6 and Pete is right.. I wish someone would have told me that back then



Would have saved me a few bucks and endless hours of time...

13BT-RX3

I am willing to sacrifice 5% power for a motor that will live with a little abuse. I would rather loose a little than have a catastrophic failure. Thanks for the input guys.

RICE RACING

Ditto.



I have a production line of brand new "clone" RR 13B-REW's that I do for people all around the world and when I saw the result of the 2 piece V's 1 piece it simply shocked me. I could feel the difference simply turning the engine by hand off the stand



To put numbers to it. Two seal designs (same end clearance)

100psi one piece

125psi two piece



When I use up my last 4 sets of one piece ceramic apex seals in customer jobs I will only specify 2 piece for any future specification engines that have my name on them. Some people do want the one piece as 13BT-RX3 for various reasons which are legitimate.... at the end of the day its a pure price point thing as the multi piece construction in full ceramic is prohibitive for most people anyway. hahaha even ANY ceramic people bitch and moan about the costs

13BT-RX3

How far have you pushed the two piece seals?

RICE RACING

They take as much power as the one piece design, in my view they are actually stronger

The only one I ever had fail *during detonation* cracked on the one piece end and not on the other side as would most would think.



If you can stretch the budget then 2 piece is the only way to go

1Revvin7

Its more than 5% power..

13BT-RX3

What is? From .004-.006, from .0015-.006? If the NRS come with .0055 clearance how can you have data with less clearance. I am running a very high overlap motor so the cylinder pressure is lower at cranking RPMs. I was getting 90psi on all faces, if Peter was getting 100 PSI with the one piece seals that sounds like a very small loss. I have heard stories of cars that wouldn't even start under their own starting system making well over 800 HP. In my case i am not asking about a street driven car, i am asking about a 900+ HP methanol engine that will never drop below 7000rpm from the start.



Thanks to the people contributing!

RICE RACING

Yeah it's single digit power loss, I have seen around 8% to 9% personally which is quite large .



My typical engines (porting as on my site) on one piece NRS apex seal will do 95psi to 100psi range (as new or 100% new motor) the exact same porting and mechanical specification with the 2 piece apex seal will do 125psi+ (have had higher figures of 130 to 135+psi) it is a massive difference in compression. I have one customer who circuit races and he too reported the highest ever compression on his full bridge port N/A motors when switching to the 2 piece.



I had another who only a few days ago switch over back to steel two piece type from one piece NRS (crack 2 seals from over boosting but with no further engine damage) and he reported a gain in HP and easier starting.



Can't type strongly enough that there is for sure negative effects of low cranking compression going through to power at 7,8,9,10 thousand rpm. I personally have seen one car that I controlled all variables on which dropped 15psi cranking pressure and it went from 430rwkw region to high 390rwkw consistently with all same parameters. This motor was border line and could start with (tested at 600m altitude) 80psi cranking but below 65psi did not really want to do it once warm.



If the apex seal end clearance or construction mean you will loose a fair bit, then so long as you know the negatives then you can make a correct choice for you

13BT-RX3

Thanks for all your advise Peter! Very good info.