OK. Who has heard of "Checkpoint"?


Date: Mon, 19 May 2003 10:22:12 -0700
From: Eric.L.Wells@health.net
Subject: (rx7) Update on blown motor - might not be cracked rotor

Well, the saga of my third rebuild entered the 'wow, a lot of stuff
broke inside' phase. The crack we saw in the rotor may just be a casting
flaw towards the tip of the rotor. We are going to have it Magnafluxed
(along with the housings) to confirm - when we look at the apex seal
slot, it doesn't look like there is a crack. It could be so fine we can
visualize it with the naked eye, so the Magnaflux should confirm.

However, the bits of broken corner seal and broken side seals that fell
out as I took each layer apart definitely indicate that something went
boom. What was amazing was that the motor, in that state (one cracked
side seal and corner seal in EACH rotor) still made a 114 mph quarter
mile pass .... it just hard started and idled like crap. The Hurley apex
seals don't have a scratch on them! I know that some people have been
debating on the durability of Hurleys, but my shop is convinced. They've
not seen side seals break at all - corner and apex seals sure, but not
side seals. Usually the apex goes first. Anyway, my apex seals were
fine.

My housings show a LOT of wear after only 6K miles - looks more like
100K of wear. I'll be joining the group that adds premix to their cars
due to this. Checkpoint has been contemplating building a bypass kit
that routes fresh oil from an external canister to the omp vs. using
internal motor oil .... I'm not sure if I'm ready to try another
prototyping adventure until we get the turbos built correctly. One
prototyped part at a time, please.

So, next week we clean up the parts and send them for Magnafluxing, then
to Cam for dowel pinning, then back home for a good ol fashioned port
job. We are thinking of radiusing the e-shaft and also will install
competition side seals that are available from Mazdacomp for a couple
extra bucks a seal. Per Mazdacomp's website, these have additional
sealing pressure.

We were thinking of putting in lightened 89 NA rotors for added
compression
:-) , but Mazdacomp's website says those will run a cool $2400 .... uh,
I think I'll wait.

More to come....

elw
Marc Wiese