I’ve read thru a couple of “the 2mm vs 3mm” discussions and left w/questions. My S4 TII rotors were milled to accept 3mm years ago and know wondering if to go back to 2mm since in the process of rebuilding. Just seems to me if you’re boosting why take chances w/2mm. And I'm refering to 2 piece seals, p.s..

Anyways, a claim is that the 2mm seal better. Seal better @ high RPM and/or seal better between the chambers? I’ll never see beyond 7K rpm so I’m not concerend there. If it’s also because it offers better sealing between the chambers, well maybe, because of more spring pressure? Otherswise, I don’t quite understand if the slot clearance are the same.

Another claim is that 3mm wear the rotor housings faster since they are 50% thicker. True there would be 50% more contact but only if they are both worned out flat. But, my guess the 2mm will wear its crown faster than the 3mm. Maybe just supplementing with some premix makes this a non issue.

 

Just in theory i would believe they are stronger and less prone to breaking than 2mm , being the bigger of the two.

As far as anything else im not sure, but i've read rumors of building boost faster with bigger apex seals, but that I can't confirm.

 

guess it's nothing but yawns in response to this thread! so which thread settles the contreversy once and for all?

 

i really don't think 3mm apex seals are necessary, more for peace of mind.

 

3mm apex seals are typically used for rotors with apex seal grooves that are worn beyond spec.

There isn't enough of a difference to even worry about it. Unless you are building a world-class racecar, it doesn't really matter.

 

Exactly.

I'm really not a fan of 3mm apex seals. Notice that engines with 3mm seals are mostly known for the rotor housings being the primary wear item, whereas on 2mm seal engines the rotor housings are generally in great shape, with no huge flaking, even after 200k+ miles.

I've pulled apart a 150k 3mm seal engine that was chattered through the chrome and into the steel liner in one spot. You *never* see 2mm seal engines with that kind of extreme housing wear.

 

There are 2mm apex seals that are plenty capable to handle power, make great compression and will take just as much abuse as the standard 3mm seals on the market.

Go with ALS or RA 2mm Superseals.

 

thx for the feedback. seems the long ago suggested goto 3mm has been proven to be not the route to have gone afterall. i'm now concerned the condition that my housings are in (20K mile later after rebuilt, 87K total miles ) when they come apart shortly.