The Ultimate 7

Yep they take forever to break-in.



Scathcart, the seals that warped were factory defects. The detects were inadvertantly cut thinner than 2mm making them very loose in the rotor grove. Thats why they warped.

Drago86

These seals shouldnt take longer to break in then stock mazdas due to there hardness. RWS does not claim there seals are harder then stock Mazda seals. They cannot be, they are through hardend (says so on the site and in the pamphlet they send you with the seals). Stock seals are a bainite structure with a chill hardend 2mm deep section at the tip. If RWS seals were as hard a stock seals all the way through, they would be incredibly brittle and shatter easily. Based on the fact that the RWS seals are much more ductile then stock and are through hardend they must be considerably less hard then the wear are of the stock seals, thus should less time to break in then stock mazda seals. I suspect the extra break in time is due to the RWS's seal design with the wide apex tip. While this design reduces wear on the housings (as per hurley and rws claims) and makes instalation easier, it is not the best design for overall sealing ability. Because two piece seals run zero lateral clearance; when they are cold they are exactly the right length, but as they start to expand the corner piece slides down to acomidate the expansion and keep the seal the right length. with stock seals this compromises the sealing ability in a very small area. With wide corner pieces a much larger area is compromised, thus lower compression then a stock seal design motor. the long break in is most likley the seals slowly wearing their end clearence down over the 5kmiles so that when hot they the side piece isnt pushed down as much, thus more compression. I believe atkins now has an option for small corner pieces on there seals now just for this reason (may be wrong on that, but i think i heard it somewhere). I am in no way knocking the RWS seals, as i myself am using them in my rebuild, they just compromise some sealing ability for other benifits, and a more ductile, softer seal then stock can have benifits (improved overall durability, less wear on housings etc). If you were to clearence the seals end clearence before installation (Judge Ito does this on Atkins seals i think) i think you would avoid this long break in period. Heres a picture of what im talking about so you guys dont call me insain, its kinda hard to explain. I'd like to acknoledge that RETed origonally enlightend me on this issue.

mazdaspeed7

I *completely* disagree with the apex seal clearanceing thing. The coefficient of thermal expansion for aluminum is much greater than that of iron or steel. Therefore, it side length of the apex seals are set for cold housings, when it heats up, the aluminum rotor housing will expand more than the iron seals, and the seals will be slightly shorter than the width of the rotor housing at operating temp.



I havent seen any comparison numbers between RA and OEM, but I know the Atkins and hurley seals are much softer than stock, and the RA seals are considerably harder than the Atkins and Hurley seals.

Drago86

true, but the apex seals run much hotter then the water cooled housing. A quick look up in the SAE papers ive posted before (recent-tech84) shows apex seal idle temps of 120 degrees C and WOT temps above 5k at over 240 degrees C. using a housing temp of 90 degrees C we come out with a housing expansion of .173mm for a theoretical total housing width of 80.173mm. For a seal at 120 degrees c we come up with an expansion of.115, for a total theoretical seal lenght at idle of 80.115mm. At 240 degrees C the seal undergoes an expansion of .230mm, for a total theoretical seal length of 80.230mm. As you can see this is .0574 more expansion at 5k rpm then the housing. Add this to the fact that all 2-piece seals are slightly oversized from the factory ~.05mm





so, final sizes are:

Housing @90 degrees C: 80.173

Apex seal at idle: 80.165

apex seal at 5k:80.280



the seal will be to large at anything but idle.



I'm going to measure my rotary aviation sels right now to get an exact length on them,..

TURBOX2

^^I must say this is very interesting reading..thanks guys!

Drago86

It's hard to get an exact measurement because i dont want to glue them together, but it appears to be more like .025 oversize.

mazdaspeed7

Good stuff.

FikseRxSeven

does the 5000miles breakin go for 3mm apex seals for 12a's or does that go for 2mm seals also... im not looking forward to my breakin..... maybe ill put the car on jackstands and let her fun there with a brick on the gas

Cheers!

ya but the aluminum housing has much greater mass, and thus will take longer to heat up when compared to an object with much smaller mass