Is this rotor usable?

[RETed]

Originally Posted by TitaniumTT

As far as the rotors... my feelings, it's obviously damaged, gases are going to get in there and do things that it shouldn't do. The pressures can force the apex seal/corner seal harder into the sealing surfaces than they should and cause accelerated wear... I know someone who tried this by milling gas ports into the rotors. Killed the housings in about 5k from what I understand.

That little imperfection could lead to the seal moving back and forth and wear improperly. Also thinking carbon buildup is going to increase in that area as well.

This is basically the primary reason to worry about clearances.
This is why I mentioned as long as the clearances should be measured.
Pics can sometimes distort dimensions, so it's always prudent to go measure everything yourself.

Side note...
There will always be a little blow-by past the seals.
Anyone who has opened up a high mileage motor (with stock OMP still intact) and checked the rotor apex seal grooves has seen the crap that gets lodged under there.
For the most part, IMO, that carbon build-up is relatively soft.
The apex seal is bouncing up and down in the groove and will most likely just mash all that carbon build-up under it until no more can fit under it.
From my experience, just swapping out the stock OMP with pre-mix greatly reduces the amount of carbon build-up in the engine.
Also, having the fuel mixtures tuned right (not excessively rich) will greatly minimize this carbon build-up also.
At the same time, it's a given that your ignition system be working in top shape to fire off the combustion charge, as misfires are just as bad as a too much fuel.


-Ted

[TitaniumTT]

Originally Posted by RETed

This is basically the primary reason to worry about clearances.
This is why I mentioned as long as the clearances should be measured.
Pics can sometimes distort dimensions, so it's always prudent to go measure everything yourself.

Side note...
There will always be a little blow-by past the seals.
Anyone who has opened up a high mileage motor (with stock OMP still intact) and checked the rotor apex seal grooves has seen the crap that gets lodged under there.
For the most part, IMO, that carbon build-up is relatively soft.
The apex seal is bouncing up and down in the groove and will most likely just mash all that carbon build-up under it until no more can fit under it.
From my experience, just swapping out the stock OMP with pre-mix greatly reduces the amount of carbon build-up in the engine.
Also, having the fuel mixtures tuned right (not excessively rich) will greatly minimize this carbon build-up also.
At the same time, it's a given that your ignition system be working in top shape to fire off the combustion charge, as misfires are just as bad as a too much fuel.


-Ted

I agree 100% Ted, what concerns me though is that a gap like that is going to allow more gasses in there which IMHO will lead to more carbon build-up. Yes the Apex seal moving up and down is going to keep it moving freely, but bad things are more likely to happen due to carbon build up than a rotor without that imperfection. Plus you gotta wonder what happended that caused that and what else was damamged that's not being seen.

As for that carbon, fact of life... I've actually got 2 n/a motors in the shop right now that need to be torn down. One with the OMP, one without. I'll snatch a few pics and post them up. For my engine, even while running spot on (.82L under bull load, .96L cruise) and running idemitsu premix, I was surprised at how much carbon buildup there was in a short amount of time. Granted the buildup was softer and not compacted in there, but I was a little surprised. One more reason I'm going to build my FD around E85.

[RETed]

Originally Posted by TitaniumTT

I agree 100% Ted, what concerns me though is that a gap like that is going to allow more gasses in there which IMHO will lead to more carbon build-up. Yes the Apex seal moving up and down is going to keep it moving freely, but bad things are more likely to happen due to carbon build up than a rotor without that imperfection. Plus you gotta wonder what happended that caused that and what else was damamged that's not being seen.

Ever get to tear down one of those way north of 100k+ mile stock engines still running the stock OMP?
Yes, there is a LOT of carbon under there, but the springs (and seals) all look like they still have full travel (well, not measured, but just an eyeball guesstimate).
I'm talking about side seal springs that are almost welded into place due to so much carbon in the grooves, so when you do pull them out, you swear you're going to snap it into pieces.

I'd figure the premixing has got to help in this case?


-Ted

[TitaniumTT]

Originally Posted by RETed

Ever get to tear down one of those way north of 100k+ mile stock engines still running the stock OMP?
Yes, there is a LOT of carbon under there, but the springs (and seals) all look like they still have full travel (well, not measured, but just an eyeball guesstimate).
I'm talking about side seal springs that are almost welded into place due to so much carbon in the grooves, so when you do pull them out, you swear you're going to snap it into pieces.

I'd figure the premixing has got to help in this case?


-Ted

Yup, tore a few down that were north of the 200k mark with the OMP still working and dayum... so yes, I see your point. My concern is, those engines were factory fresh with very tight tolerances when they were first built using all new parts. So, with that gash in there, it's obviously going to let more in than a new rotor. Is it enough gas/carbon to make a difference? I don't know. But it is one of my concerns using that rotor.

On the side seal subject... that's exactely how I lost the first engine after the swap. It was an RE with REW housings. SWEET!!! REBUILT!!!! Comp was 105F/107R so I ran it. The thing lasted 4 hours.... yup... 4 hours before a CARBON LOCKED side seal let loose. I was upping the boost and when the combustion temps/pressures got high enough the seal wanted to move. It couldn't and broke loose wiping out the Apex seals as it went by. Bummer for sure. Upon disassembly it looked like when the engine was "rebuilt" it was just new housings/Apex seals as the carbon buildup on the side seals and oil control rings was out of control yet the exhaust, face of the rotors, were all fairly clean.

Lesson learned.... ALWAYS tear down an unknown engine. It's the only way to know for sure.