I started this thread years ago and the pics have long since disappeared, yet illiterate users continue to bring the thread back and ask for the pictures.

refer to these threads for current information with pictures included.

REMOVE YOUR ENGINE: https://www.rx8club.com/tech-garage-...w-pics-178937/

REMOVE ACCESSORIES FROM YOUR BLOCK: https://www.rx8club.com/tech-garage-...ctures-178945/


DO NOT BUMP THIS THREAD ASKING FOR THE ORIGINAL PICTURES



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I thought you guys might enjoy seeing some pics of the general process. As time presents itself I have a full removal writeup and another full teardown to shortblock writeup that I have to transcribe and post.

04, 81k, has been burning coolant, now will not start.







Down to the shortblock...





Front cover off...



Front stack removed...



tension bolts removed...

 

Let the fun begin.

Rear iron off...



rut row...



That's gonna leave a mark.



Yup, it did leave a mark.





Rear rotor/housing



I think I see where coolant has been leaking, due to a compromised seal.



Rear rotor. You can see the water on the face, due to water in the combustion chamber from the leaking coolant seal. The water robs the engine of it's coating of oil on the housings, reduces compression, wets the sparkplug, and won't allow the engine to start.

 

Man, that's some killer wear on those stationary gear bearings. What oil have you been using?

 

rear rotor housing off.



Not bad looking once I wipe it off a bit. Mild wear, light chome flaking on the rearmost edge of the housing. This area is where the short triangle assist piece of the apex seal rides, and due to it's sharp tip, it digs out a groove on that rear edge and causes the chrome coating to flake off over time. All used rotary engine rotor housings with more than 30-40k miles will have some wear/flaking here.



Damn, those are some deep *** cracks at the plug hole orifices. These cracks are normally only seen on 3rd gen rx-7 13b-rew TT engines due to the heat created by them.

However on the renesis engines I have torn down I have begun seeing the same cracking as well, indicating these engines have localized cooling issues. This supports the findings of other renesis builders who have developed special waterpumps to try and combat the issue.



Intake/compression area of the housing, looks good, no chatter, light wear.



More shots of rear edge chrome flaking. This is VERY mild wear, and is reuseable. But, every builder has their own opinions, and some builders flatly refuse to reuse housings that have any wear whatsoever. I am not one of them. I would love to build new parts engines all day long, but with the cost of parts being what they are ($1200 for 2 rotor housings alone) I will not force the customer to pay for something they cannot afford.

 

Not my engine. Customer's engine. I am a rotary rebuilder, google the username. I assumed that much would be clear, but I suppose not since I am not a heavy poster on this forum.

Please try to wait for me to finish all the posting until you make comments or ask questions. It will make the thread more organized for later reading.

 

okay, so where were we.

Ah, intermediate iron. You can still see some coolant residue on the face.



Intermediate iron off...front face.



Shaft resting in place after pulling the INT iron off. It's a tricky job with the engine mounted on the stand facing up.



Won't be needing that eccentric shaft any more...







Front rotor/housing...



Front rotor out. That's a lot of carbon there...



Front rotor housing off.

 

Front rotor housing is in about the same shape...



Blurry pic, but the same cracks are on this housing too.



And then you are left with the front iron still mounted on the stand.



Both main bearings were chewed due to oil starvation.

 

On the rotor housing where the cracks are at the plug holes, you see a thick stripe of carbon buildup on the housing. The reason for this is that the cracks expand under heat, and push out into the combustion chamber. Since the apex seals ride over this, that means they get pushed up off of the housing for a split second in that one spot, over and over. Since the cracks are only in the center of the housing, the rest of the housing in that spot remains flat, and blowby occurs there while the seal is lifted off of the housing.

This is further detrimental in that the apex seal is constantly riding over a "bump" on the housing, and so the center of the seal is going to wear more due to this. So, even when the seal is over on another part of the housing that is flat, the "bump" has worn a bit of material out of the center of the seal, and so blowby can still occur everywhere. This means a loss of compression and power.

There are only a couple of things you can do about this. 1) replace both rotor housings with new ones or used ones with less wear, at a significant cost, anywhere from a few hundred for a used set to over a grand for a new set. 2) grind down the cracks lightly so that they will not expand when the housing is put back into use, and the seal will not skip over them. Compression will not be lost elsewhere on the housing, and compression loss due to blowby at the plug hole itself will be minimized.

 

So, here are the cleaned rotor housings, ready to be put back into service. I have doctored the cracks as best I could. I would obviously have preferred to use new housings, but with a bill in the mid 2500 range (installed w/warranty) already, the customer did not see fit to replace them for another $11-1200.









Also, cleaned and painted irons. Irons should almost always be reuseable in the renesis. They do wear slightly on the faces at the 3 and 9 oclock positions, but this is always negligible and will not significantly affect how the engine runs. And since there are no longer any coolant seal grooves/walls to crack and break on the renesis like the old rotaries had, that will not be a point of failure either. The only way irons will not be reuseable on the renesis is if 1) you break apex seals and the fragments damage the irons, or 2) you run out of oil and continue to drive the engine in such a way to scorch and crack the iron faces.

I am disturbed by the way mazda cast the irons to prevent any significant porting or reshaping whatsoever. I know others have already posted about this on the forum so I will not comment further, other than to say that these engines are basically going to be what they were in stock form, there is not much at this time that can be done to improve them for a stock or mildly modded street car, without making significant compromises.

 

Here are all the small misc parts and hardware for the shortblock, now cleaned and inspected and ready for reuse. Note the new main bearings in the stat gears. I also use new front and rear main seals, rear stat gear o-ring, and the aftermarket solid thermal pellet replacement piece that eliminates the oil thermostat in the front of the e-shaft.



Here are all the seals and springs laid out. Some are being reused, some are new. Side seals are labeled with their individual "letters". In previous rotaries, side seals were cut extra long by mazda, and hand ground to proper fit/length/clearance one by one by the builder. With the renesis, the rotors have a stamp by each of the side seal slots with a letter. This letter matches the side seal that is to be used in that slot, and you order the seals by letter instead of getting universal ones and cutting them to fit.

One thing I dislike about the renesis, mazda runs a VERY loose side seal clearance, 2-3 times what was acceptable in the previous versions. This causes blowby, carbon buildup on the sides of the rotors, and a bit of compression loss. I am pondering on trying a couple of things to run less sideseal clearance and perhaps improving efficiency. To do this I will use the "extra long" renesis side seals that are available by special order, and hand fit them as per previous versions.

I am using aftermarket viton oil o-rings instead of oem mazda, just like in all my other builds. These should hold their form longer than the stock ones, to prevent excess smoking later in life.

 

Cleaned rotors. I use walnut shell to blast the carbon off mine, without harming the coated faces of the rotors and without making a mess all over me and the rest of the garage. You can now see the small bevels cut on the sides of the rotors to help exhaust gases escape.





Rotors with seals and springs installed, plus a used replacement e-shaft.

 

enough for now, will get to assembly later.

 

AHHHHH ! NICE FREAKING PICTURES !!!!

The wear is all the way down to copper, the e-shaft is no longer reusable, bad.

In your opinion, does this have something to do with the 5w20 that Mazda/Ford *recommends* ?

 

Excellent stuff! Expo1 had the same bearing wear as well. One more data point that points to an oiling problem with the bearings either too thin or not enough being injected into the bearing area.

 

Edit: removed due to excessive stupidity.

 

center housing...bearings?

 

Don't mind me, I'm just the local idiot Sorry bout that.
I was at work and trying to talk to my boss and respond at the same time.

This might be alittle more relavent now that I'm home and paying attention...
How much information do you have about this customer's mods, driving habits, milage, etc?

 

Moderate amount of info.

Bought with 8k, had 81k when brought to me. He is a young guy so I would assume he drives it hard. I had rebuilt his 93 rx7 a few years ago but he sold it to buy an 8, something newer with fewer electrical issues and rattling interior plastic. I knew for a fact that he beat on his rx7 so I assume he beat on this as well.

 

Yea, it looks like he was using cheap oil too... I mean fuel economy improving oil

 

Jesus that is a LOT of bearing wear. Why are we getting so much front bearing wear on this engine---i have seen several.?
Those heat cracks around the lead plugs--why is that happening?
oil weep holes need to be larger?
olddragger

 

Even if the oil injection holes were larger, it would not matter, because the OMP and PCM control the oil injection amount being fed to those holes. The volume of oil is very small...flow through the orifice is not the issue, flow supplied to them is.

The reason they want to make the hole as small as possible is so that there is very little compression loss or blowby. The same reason the trailing plughole is smaller than the leading, to minimize compression loss as the seal sweeps over the hole.

 

Im gonna quote myself

Any opinion RR ?

 

Yes, please ask what specific oil weight has he been using if you don't know?

 

All I can say is that I have always, and will always use at least 10-40 or 20-50 in all my rotaries, and have never had issues on engines making as much as 450rwhp. Other armchair engineers may debate back and forth about the merits of the thin versus thick oil, but this is what I have found to work for me and it is what I recommend. I'm not saying I know more than mazda or engineers about the situation, but I would suggest that they had a side motivation to recommend such an inadequate grade of oil for anyone except those in very cold climates...such as emisions or efficiency concerns.

If I get an opportunity to speak to the guy again I will inquire about his oil habits, but he has already paid and taken the car back home 4-5 hours away so I doubt I will talk to him again.

 

+1

nice write up. KL