ATTN: solid corner seal users
 

I stumbled on this section of the series 3 training manual, I'm not sure how many people have seen it:

https://www.rx7club.com/attachment.p...1&d=1238340449

I have heard many people deride the corner seal plug as essentially useless. I just wanted to get some reactions to Mazda's explanation of why they implemented this design. What I'm getting from this document is that they needed to use the plug so that they could make a seal with enough clearance for the apex seal to move freely, while still preventing blowby from gaps that open up as the seal itself moves.

It seems like even when they're half melted from being old they would still mostly do their job, right? Isn't the plug more for keeping the apex seal oriented in a certain way, rather than the rubber itself sealing gases?

I've always wondered if the factory three piece seal was the main reason they had the plug and also if it's importance would be negligible with two or one piece seals.

doubtful. The Rx-8's have two piece seals and they still have corner seal plugs. I don't see how the 3rd piece (the top part) would affect the gas leakage they are trying to prevent.

I've taken two motors apart that have not had and plugs in the corner seals. This is the first time I've heard about the "gas leakage." Anyone I've talked to and any discussions on the forums pointed to Mazda implementing the rubber plugs to prevent chatter, not combustion leakage. Furthermore, the housings in the motors I tore down showed no signs of chatter and the lowest recorded compression numbers on the one motor was 110psi COLD...

Technically, the plugs are a Good Idea.

Practically, in engines that see extended high RPM use, they disappear, and compression and drivability don't seem to suffer any from the loss.

Mazda worries about different things than we do. They need new engines to run cleanly enough and efficiently enough to pass the emissions test loop and get good fuel economy numbers, and maintain clean emissions for the duration of the warranty (emissions warranty is *mandatory* in the US, the mileage depends on the year).

We care about stuff not falling into huge intake ports.

:lol::lol::lol::lol::lol::lol::icon_tup: Haha sooo true!

-J