Is this rotor usable?

[TitaniumTT]

This is all good info, so post it up as opposed to PM's

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.

Regarding the seals... I'm running the RA super seals. When the fuel filter clogged she ran 13.5-13.7 AFR's and 15+psi and detonated for sure. The seals didn't crack, they didn't chip, but they did warp. IMO they saved the engine though.

[JustJeff]

Originally Posted by TitaniumTT

This is all good info, so post it up as opposed to PM's

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.

Regarding the seals... I'm running the RA super seals. When the fuel filter clogged she ran 13.5-13.7 AFR's and 15+psi and detonated for sure. The seals didn't crack, they didn't chip, but they did warp. IMO they saved the engine though.

I'll create another thread about the PM..make it easier for people to search and find.

You've got good points about added carbon build up in that spot and added wear.

About the detonation...that's what I've read and been told about RA seals. They seem to be more resistant to detonation. I won't be doing Super Seals though. It seems like most of the guys running higher HP and boost are going with the Super Seals. I'm thinking with my mostly stock rebuild and rarely hitting 12psi on my stock turbo I'll be ok with Classics.

I'm curious if you had chatter marks from the Super Seals? IIRC what I read about RA is some chatter marking with the Classics. More chatter marking with the Super Seals.

[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.

[GoopyPerformance]

Hello JustJeff,
Saw your post and photos about your concern with your rotor slots and read through most of the replies on the forum. Here are a few ideas for you and others that have been part of this conversation.

There is obvious damage, but as others have said, you can make it work as many have. However, that damage will contribute to you performing less than optimally.

Agreed, machining to 3mm and using thicker seals can be risky and expensive at best especially given your lack of proximity to machine shop, etc.

What if there were a way to add more material to your slots to fill in the gaps/wear/damage and get your rotors back to factory spec. clearance? That's not really practical, but if there were OVER SIZED APEX SEALS, that would essentially accomplish the same thing ... give you more material to work with.

That is the thinking behind a cost effective solution from Goopy Performance that is inexpensive and requires no special machinery or expertise. Here's how it works.

1. Goopy Performance OVER SIZED APEX SEALS ... for all of the RX-7 Apex Seals that we manufacture. We produce these seals with an additional few thousands of material. So in the example of your 2mm 13B seals instead of being factory stock .115, these seals are .118. By using these seals it is like we just put .003 of new material into your slots.

2. Goopy Performance ROTOR CLEANING KIT ... that includes a high quality flat file that fits into your rotor slots, a .0015 Feeler Gauge (= Factor Clearance), and two stainless steel wire brushes to clean your corner seal slots.

When you try to put the over sized apex seals into the slots they probably will NOT fit, but they will be close. So all that you need to do is CAREFULLY take a few passes with the file on the inside of the slot, keeping the file FLAT and TRUE against the inside walls of the slot and begin to remove some of the rough edges at the top of the slot on both sides.
Do NOT remove too much material at any one time before testing with your new oversized seals again. Probably still doesn't fit but getting closer. Continue to remove material from both sides of the slot and be sure to keep the file FLAT and TRUE against the sides of the slot as you proceed. Remove material along the sides to the full depth of the slot.
Retest and continue to remove old, damaged and excess material until the seals just fit into the slot. Pretty easy, correct?
Now you have another .0015 to go. That is NOT much material so proceed CAUTIOUSLY. Continue to remove material from both sides until you can just fit BOTH the oversized seal PLUS the FEELER GAUGE.
When they together fit perfectly into your slots you now have "FACTORY SPEC" ROTOR CLEARANCES!

No buying new rotors, no machining 3mm slots and hoping your rotors are not ruined, no 3mm seals, no running rotors and apex seals that are way out of spec and leaking compression like and old engine ... just your rotors back to spec!

JustJeff, there is more info. on our web site or feel free to call for assistance.
Reply if you would like contact info., pricing, etc.
Good luck and looking forward to being of help.

Goopy Performance

[rxspeed7]

^I'm totally with you on this. If this is your last hopes for putting the motor together then by all means use it but if you can I know you'd feel better using a rotor you know for sure is good. It's the little things that will always come back and bite you in the ass.

Zack.

P.S. As for me i'm going to be rocking some atkins seals on this motor.

[TitaniumTT]

I would go for the Super Seals... it only takes one good knock. I would say use the classics in an N/A build, the supers in any boosted engine

Chatter Marks - I didn't have any when I tore that engine apart. I'm also running Idemitsu "fuel lube" being injected through the OMP via the RA OMP adapter and I also run .25oz/gal in the tank. If I'm going to be doing NOTHING but highway driving, I'll knock it in half.

[JustJeff]

Originally Posted by TitaniumTT

I would go for the Super Seals... it only takes one good knock. I would say use the classics in an N/A build, the supers in any boosted engine

Chatter Marks - I didn't have any when I tore that engine apart. I'm also running Idemitsu "fuel lube" being injected through the OMP via the RA OMP adapter and I also run .25oz/gal in the tank. If I'm going to be doing NOTHING but highway driving, I'll knock it in half.

Where did you put the reservoir for the RA adapter? I'm thinking of doing that mod also. I saw a right-up for an FB and the person mounted it to the passenger strut tower. On a turbo I don't think that would be the best location.

[TitaniumTT]

Where the airpump once lived on the FD..... running the REW waterpump.

[JustJeff]

Thanks for the posts Ted

I had read your article on apex seals several months ago. In a perfect world I'd go with Mazda seals, BUT I'm already on limited finances from all the bad economy stuff. On top of that I'm trying to get money set aside to start graduate school. I figure now is the perfect time to add some education. There isn't any hiring or moving up going on anyway. Might as well do what I can to pad my resume.

I'll certainly give apex seals some more thought. I suppose I could reuse my pressure plate rather than replace it. Use that money to offset cost between RA and Atkins compared to OEM.

My thoughts on housing wear related to apex seals is that I doubt my housings would be good for another rebuild after this one. So I wasn't as concerned about those. Though I am keeping in mind housing wear and compression.

I hadn't considered wear to the apex groove. I'd like these rotors to last beyond this rebuild.

I took some pics of clearancing my apex grooves. I'll post them up pretty soon.

[JustJeff]

OK...I don't own a dial caliper so this is what I did to compare one corner from the other. Feeler gauges stuck between the apex seal and the groove. I'm sure it's not as accurate as having a dial caliper. But what I was looking for was a comparison from the good end to the bad of the groove.

My old rotor I took to a machine shop and had them measure it. I don't remember the figures and can't find my notes ATM.

I'll be buying a dial caliper tomorrow. The seller seems to be annoyed that I had not measured. I'm annoyed for the obvious reasons.

Bad Corner


Good Corner


As a comparison the rotor in my engine when it detonated
Bad Corner


Good Corner

[2gslse]

I would think that apex to groove clearance is excessive I checked a set of used rotors and they were .002"-.003"

[NoDOHC]

I think that RETed is correct, that leaner mixes will protect from carbon buildup to a large extent, as will careful selection of engine oil or running premix. I get carbon buildup in my '91 driving around town (where it runs open loop and filthy rich) but it goes away after a long highway cruise (due to closed-loop, stoic fuel mix - or maybe just extended operation). My '86 (which run 16.2:1 AFR (lambda of 1.1) everywhere but WOT) never experiences the carbon-buildup-characteristic knocking that the '91 does (although this may have something to do with the 9ish 7,500 rpm shifts that it experiences everyday on the way to work). My 13,000 mile teardown (which is still a sore subject) indicated very little carbon buildup on the rotors (although they were polished).