Putting a stronger seal in a shallow slot only results in it wallowing out excessively, sooner

 

Interesting idea, then why did they develop ceramic apex seals?

Anyway, I like the older RX7 size apex seals, in Renesis rotors, which need EDC to enlarge the groove.

 

same here. Now side seal development is a another story.

 

A little birdie told me that it is hard to get decent compression with these deeper seals - anyone want to throw any light on that ?

 

3 blind mice, see how they post ...

 

Just watch out for the farmer's wife...

 

I have over 65k kms on my build. 3mm NRS ceramics installed, EDM procedure on my NA renny.
Compression is fabulous. 3 years and loving it.
(hoping I didn't just jinx myself)

 

If it was FI miles then it would be a big deal. However in NA application the initial compression versus current compression test camparison would be interesting.

I am sure your setup in a FI in a precision built and balanced engine will yield good results.

 

I agree. When this motor craps out I am installing a FI REW though.

 

Who did your engine and what was the cost, also, what was the cost of the EDM cutting of the apex groove on the rotors?

 

it seems like a milling would be cheaper then edm

 

yes, but the slots need to be really accurate, so the mill takes a really talented operator to be successful.

the slot not only has to be the right depth, which isn't bad, but it needs to be the right width, AND needs to be square, which is hard, especially on used rotors

so has it been done on a mill successfully? yes. has it been done on a mill really badly? yes

 

with a good mill bit, good placement, and some good cooling it doesn't seem that hard

 

yes, it seems more simple than it is. concept is easy, execution is the hard part

 

I have some bad rotors that I will try with CNC mill with really good encoders. should do the trick

 

McMaster-Carr

 

No engine builder worth a damn starts with used rotors for this procedure, let alone f'd up ones

which is fairly typical here ....

 

so you would use brand new parts to conduct a test that could potentially destroy it?
you sir must be swimming in cash.

I plan to test the machining on some bad rotors and see how it works, if its good then I will run the procedure on my good parts.

 

I'd never use new rotors unless mine were out of spec.

Its like buying a new pair of jeans everyday versus washing your old ones.

 

I can see using used rotors if there is a chance the machine shop could **** things up. But otherwise on my next build new parts will be used regardless of the specs of my parts. Pay now or pay later.

 

the procedure is doing great everthing is coming into spec, I am with shadyscrew, I'll be happy with used parts to spec.

new becomes used very very quickly......

I am sure your engine will last a long time 9krpmrx8 good folks built your motor!!!
and a maintenance ***** drives it :P

 

Which is why I found a very low mileage engine that was all beaten up from an accident and paid good money for it .........

 

I have been searching and I am trying to decide on the depth of the cut

Rx7 specs
8mm tall apex seal
9.7-9.9 apex seal depth in rotor (measured)

1.7-1.9mm for apex springs

Rx8 specs
5.3mm tall apex seal
6.3 apex seal depth in rotor (measured)

1mm for apex seal springs.

I plan to use rx8 springs, so far the two test I have done on the rotor go down to 9.5mm deep, without issue.

 

IIRC you need to use RX-7 springs due to how it sits on the seal. I am not 100% as I haven't compared them side by side but when I was building a 13b-t it seemed different.

 

They are different but they both work the same. Atkins rotoy lists them as fitting all rotors and I found some threads on rx7club about folks upgrading to rx8 springs