Engine experts..opinions need! Solve the mystery!!
 

Ok,

So.....I am going to get straight to it. I had a bad coolant seal about 2 years ago. I pulled the motor and rebuilt it myself. Upon doing so I did a full single turbo setup.

info and build pics can be seen in my Build thread (badly needs an update haha) Check like page 2/3 for the build stuff.
https://www.rx7club.com/build-thread...diary-1052687/

ANYWAYS, fast forward...I break the engine in properly and have it tuned by Steve Kan.

Running conservative timing, ~20 psi, water injection, PFC

car put down ~415whp.

Ran like that for the last year roughly with the only problems being fouled plugs. I am running a OMP plus premix (1/2 oz per gallon). I am running RA super seals so I wanted the extra lubrication to help with housing wear but think I was premixing too much and fouling the plugs.


FAST FORWARD:
Anyways the car was a beast and pulled great. One day not too long ago I was out racing my buddy on his GSXR 600 and did multiple pulls...took him a few times ;-)

Upon slowing down to a light after the runs the car was idling pretty roughly. Vibrating pretty bad and didn't sound right. The more RPMs I gave it the better it would feel and it would actually boost to 20 psi but just didn't feel as powerful. After checking the basics I decided to check compression. This was done on a cold engine as I didn't want to do more damage if i had a crack seal somewhere grinding around. Videos are below:

Front Rotor:

Rear Rotor:

I also used a videoscope probed through the spark plug holes to check for any internal scarring/damaged seals but everything looked normal.


I am getting 3 strong audible compression pulses from the front rotor (backed up by the compression reading)

I am only getting one decent compression pulse from the rear rotor with 2 much weaker sounding puffs.


WHAT COULD BE THE PROBLEM? DOES THIS SOUND/LOOK LIKE A BLOWN MOTOR?



This is just part one....engine is out of the car and ready to be opened. I just wanted some feedback/opinions first.

and a fun picture because who doesn't like pictures...ignore the white thing in the background

http://s22.postimg.org/qgxz9et7h/IMG_2163.jpg

iirc low rpm badness, and other things you described, sounds like it blew...

Can't see the vids but, if compression is low.... :(

But I am far from expert

Blown rear rotor. All the pulses were pretty weak. Cranking speed has a lot to do with compression readings too sine the front rotor only looked like it was giving out about 60 psi. 1 strong pulse and two weak ones is a broken apex seal.

Matt

SO here's the curveball.....opened up the engine and I can't see/find anything wrong or damaged. Things are exactly as they were when I built the engine 2 years ago. Engine only had around 5K miles on it.

During the original rebuild the engine had around 60K on it. All the internals were good and I was somewhat on a budget at the time (rebuild + single conversion is $$$).

I ended up reusing one of the rotor housings and purchased a very very low mileage one. Also picked up 3 very very low mileage irons. Had everything street ported.

Reused the rotors. Reused the corner and side seals (one of the shortcuts I took). Installed all new springs and RE Super Seals.

All new bearings.

Now for the tear down pictures. I really only detailed the rear rotor and seals as that was the one that I lost compression on. All apex seals were in tact and not stuck as were all side seals and corner seals.

Not a single scratch on any of the irons or the housings.

The low mileage housing that I purchased during the original rebuild was installed as the REAR housing. It has some interesting marks around the exhaust port that I am not familiar with. Could this be a result of an apex/compression issue?

PICTURE ALBUMS:

Rear Rotor:
https://flic.kr/s/aHskcCmjQF

Rear Apex Seals:
https://flic.kr/s/aHskcBodDk

Rear Housing & Center Iron:
https://flic.kr/s/aHsk94zdL1

Front Housing & F/R Irons:
https://flic.kr/s/aHskbZj1xu

I will add that I did NOT have the apex seal springs in when I reassembled things for the pictures. When I did the tear down all the apex seals and springs were still intact and functional.

Have you checked the injectors? you might not be getting enough oil to the apex seals to build compression.

Oil injector were brand new as of ~5k miles ago when I did the rebuild. Lines were filled when I was tearing down.

Again....symptoms started immediately after doing multiple back to back highway pulls against a bike.

Check your RA Super seals...

Trust me on this one...

I did almost the exact same thing to mine after rebuilding it myself.

Stand them on edge and look down the edge that seals on the housing.

I would bet money they look fine otherwise but looking down the sealing edge the look like a bow about to shoot an arrow.


J.

Is there a space between these faces?
It is hard to see from the picture.
If there is... how about the front rotor apex seals?
Are they bowed the same amount?


Attachment 624774








This image below shows the reason why they bow and bend. Your housings show signs of the distortion.
Think of the temp islands as topographic map that the apex seals must rock over.

Did you wipe the rear housing off the same way that you did to the front housing in the pictures?

Barry

Attachment 624775

When lining up the REAR apex seals there is little to no gap between them. (flush)

This is the same with the FRONT apex seals.

When doing this though I noticed a difference between the two sets.

It appears that a decent amount of the REAR apex seals have been "ground down"....?

I have uploaded close up pictures detailing this as shown below. What gives? Could this be the culprit?
https://c1.staticflickr.com/9/8819/1...0e0bfded_z.jpgIMG_2417 by FDeeManTT, on Flickr

ALBUM:
https://www.flickr.com/gp/37634398@N02/9B22s5

The first three pictures are of the rear rotor apex seals sitting on the apex springs in the grove for a free standing height picture. The next three pictures are the same but instead are of the front rotor apex seals. Not sure if this helps or not but I took the pictures.

Also included a lot of picture of the exhaust port on the rear rotor housing.


My experience would lead me to next investigate the housing surface and the exhaust porting. Both of which are smooth to the touch and the beveling on the exhaust port is identical to what was done on the front housing.

Help?!

Are the exhaust ports ported at all?

yes they were streetported by a reputable rotary shop. The porting was the ONLY thing I didn't do myself during the build.

See my pictures if you are curious to see what they look like.

Were they the cause of the ground down seals?

Maybe, but i wouldnt expect the wear to extend all the way to the ends of the seals, only where they move across the exhaust port. Did the apex seal springs have the same shape to them between the front and rear rotors?

Apex seals front and rear look the same and look in great shape.

ALL the springs look like the only have ~5k miles on them (which they do)

I am no expert on the many failure modes of the rotary, but I see a couple interesting items here.

1 - The rear apex seals are uniformly "ground down" as you pointed out vs the front. This is a LOT of wear in my opinion.

2 - The area above the rear exhaust port on the rear rotor housing has a lot of black/burned appearance compared to the same area for the front rotor. At least it looks that way in the picture - perhaps it's just the angle of the lighting but to me the rear housing looks much worse. Burned-looking areas make me think "heat".

Combine those two things and I think either the rear rotor is getting no oil leading to friction wear of the apex seals OR something is causing premature mechanical wear of the seals (and particles in the chamber). That "something" could be too much spring pressure such as stacking two sets of the apex springs (I am sure you would have noticed that), or maybe the exhaust porting is eating/chipping the edges of the seals. Although if that were the case, I would have expected more wear in the middle where the port is. The exhaust porting doesn't look that great to me from the pics, but "not that great" vs. "caused your failure" are two different things. If you take a fresh seal or a seal from the front housing and run it over the exhaust port with your hands, does it "catch" or is it nice and smooth?

Anyway, my first guess is lack of oil. Premix is your friend! *Edit* I just read you ARE premixing at 1/2 ounce/gallon + the OMP - that should be good if OMP is working *

Test out the oil metering bolts by blowing through them with your mouth - can you blow through them? Are you sure the OMP lines are not clogged?

Thanks for your reply! Great ideas.

You are correct that there was a lot more 'burned; areas on the rear rotor housing right after the exhaust port. I'm not sure if the pictures show this 100% because I may have already tried to rub the area out with my finger. The entire housing is smooth and this darkened away wiped away without a whole lot of effort.

I have run both the good and 'bad' apex seals I have over the exhaust port and nothing catches or hangs really on either set.

The OMP lines were checked and verified to have oil in them. I had just purchased new injectors from Ray during the initial build so these have roughly 5k miles on them. I WILL however test them out to be sure...(at least the rear rotor injector.) Both injectors received direct filtered air as to not clog with any debris.

The wear on the seals imo is substantial as well. I'm just wondering if this IS the source of my engine problems (compression/ect) and if it is...what caused it? I also want to know why the housings look great. With the exception of the weird discoloration pattern around the exhaust port...it looks great. I will try to take measurements the housing when I get some time. I am just thinking that if it were a lubrication failure that there would be some pretty decent wear on the housing itself.

I want to also say that I might of been putting a little more than 1/2 oz per gallon of premix in sometimes because I was still playing with mixtures. It did smoke a bit and I seemed to foul plugs pretty easy. Lubrication was one of those things I wanted to make sure was adequate.

I will check the oil injector and report back.


The engine was working hard when it went so whether is was internal heat, lubrication, build, condition, ect ect I would just like to figure it out haha. I've been around for a while and tried to do everything "by the forum book" to have something decently reliable.

-water injection/omp+premix/conservative tune/yada yada

I want to build it back as soon as possible but obviously you can see I am weary of doing so until I can understand what happened. Thanks

Also not an engine expert but with the gold/brown dis-coloring in those rear seals I would suspect that they were subjected to a lot more heat than the front set that doesn't show any color.

Looks like a lack of premix or improper closing of the exhaust port. The seals on the rear rotor have lost radius. With super seals I recommend 1oz per gallon minimum WITH an working oil metering pump. 1/2oz per gallon just isn't enough. Those seals are super hard and eat housings very quickly without enough lubrication. Personally I would never use those seals again after tearing down a motor with only 10,000 miles on it and seeing how trashed the rotor housings were. Any pictures of the rotor housings and exhaust ports?

I am with Brian/Wargasm. Heavy wear on the rear apex seals indicates the possibility of the lack of
lubrication.... but shouldn't we should see more wear on the housing?

The oil jets are brass with a slotted face and are in the housing (usually very difficult to remove). I check and clean them in place.

I think the items that you are referring to as jets are just banjo bolts with check valves in them.
Their purpose is to not allow vacuum to suck all of the oil out of the lines on decell.

An important note here.... there is a often-forgotten square oring that Mazda added as a revision for racing.
It fills the small area between the jet and the banjo bolt so this reservoir won't need to be refilled before any oil
goes to the housing. So we have hard deceleration and no load.... followed by hard acceleration/load and no oil temporarily.

My guess would be that the rear jet was blocked.... partially or totally and you were running on just premix.

Also Mazda hardens their apex seal faces. I wonder what other suppliers do? That was a lot of wear in a short time.

My thoughts,
Barry

Problem

Engine lost compression on the rear rotor and did not want to idle.

Why did the engine lose compression on the rear rotor?

The rear apex seals are ground down and lost compression? (Is this a true statement)?

Why did the apex seals become ground down?

Observations?

1) Apex seals are ground down (worn) substationally more than the front rotor.
2) No radius exists on the apex seals from being worn so much.
3) No visible bow to the apex seals.
4) 5) All 3 apex seals see this wear and are worn evenly.
5) Housings look great and show little wear.
6) Visible heat marks on housing of rear rotor.


Causes to why?

- seals are too soft, (missed process step or operation at mfger)
- Too much heat destroyed the seals, (but heat from where?)
1) Problem with fuel delivery? (clogged injector(s), problem with ecu, problem with mating plug to injectors, injector faulty)
2) Ignition system missfiring, not adequate? possible rear rotor coil issue? (noticed heat marks by spark plug hole)
3) Friction, Lubrication not adequate?
4) Exhaust port issue? (note even wear though)
5) Improper installation of rear rotor (springs installed with too much tension????)?
6) uneven distribution of air into rotor housings (lean AFR = heat)?
7) Spark plug failure/faulty spark plug/faulty spark plug wire, too much heat for spark plug?


Now looking at the marks from the spark plug area Could this effect the apex seals in the way that is seen above? (I can't view pics at work).


Other muses.

People say super seals destroy housings because they are so hard, these seals did not destroy the housings. obviously the seals appear to be softer than the housing material and wearing the seals. Could this be our golden nugget? seals are too soft and along with some extra heat from the spark plug area on rotor 2 lead to increased seal wear?

I would think the problem doesn't lie with the manufacturing of those particular seals. The chances of getting 3 "below acceptable grade" apex seals and installing them all on the same rotor, while the other 3 seals (assuming purchased at the same time) are perfect - is quite low. I think it was the environment those seals lived in that caused their excessive wear...like others are saying - lack of lubrication or excessive heat.


Looking at the pictures the FRONT housing appears to have encountered more heat than the REAR. More prominent carbon "wings" as well as slight cracking around the spark plug boss.


How is your water injection plumbed? Is it possible the water being injected is favoring one rotor over the other?

This is a very strange one. If you asked me to guess by looking at the pics I would have said the front housing was the one that lost compression. The front housing is showing typical RA super seal wear patterns that will increase rapidly in the next couple thousand miles.

My guess is the Rear housing was Cermet coated in the past. I have seen the Ceramic coated housing eat every seal besides ceramic seals. Can you verify the history of the rear housing?