Mazda RX8 engine rebuild project

So with this Mazda RX8 engine rebuild completed what did learn about the original hard-start, flooding and accompanying low compression issue?

First, looking strictly at the evidence I found areas on the rotor housings where it appears that the apex seals were not making contact, the apex seals were worn, and the side seal clearances were a bit excessive. Everything else inside the engine appeared to be normal. In my opinion the rotor housings showed reasonable wear and were reusable. Side seals and all seal springs were ok. So what are the conditions or mechanisms responsible to throw the engine into a no-go mode? The answer is not an easy one, but I believe that the new shallow apex seal grooves found only on RX8 rotors coupled with the “short” apex seals might be responsible. Could a situation develop where after x amount of miles on these engines the apex seal springs fatigue and with wear on the already short apexes they get stuck in the grooves? The missed contact patches (see earlier blog pics.) attest to this. Carbon flaking from the rotor’s combustion pockets may be the agent that wedges the apex seals in their grooves. As I mentioned this is a difficult problem to diagnose because it does not mean that all RX8 rotor housings will have patches of no-contact on them. Based on what I’ve found in this project engine those are my conclusions. I have more ideas that I will blog later.

One thought on “Mazda RX8 engine rebuild project

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