I have an REW swapped RX8 running an Adaptronic Rx8 PNP ECU. OMP is deleted and I've always run between 10 - 12mL/L (~1.25 - 1.5oz/gal) (100:1 - 80:1) of Idemitsu. After 1500kms of engine break-in at 4500rpm or less and no boost the engine was cold compression testing at 120+ psi on all 6 rotor faces. After this I started slowly raising RPM limit up to 8300 and introducing boost first at 10psi then upping it to around 15psi. Shortly after this, over a very short amount of time I started noticing my idle vacuum and overall smoothness of idle start to decrease. I compression tested the motor again and found rotor 2 to be exactly 21psi on all 3 faces with rotor 1 showing 100+ psi still.

Below is a summary of the results I found after engine teardown. Any input on likely causes and how to prevent this on the rebuilt will be greatly appreciated. Please note this is the first engine teardown I have ever performed.

One thing to note is that during break-in and even as I started introducing boost, my spark plugs ALWAYS came out of the engine very black after very short amounts of mileage (~500ish kms only). Here is a typical result on BUR9's.





Here is two videos of my initial review immediately after tearing the engine down:






Here are photos of my warped apex seals along with some general photos of my setup. This is a large street port engine with stock UIM/LIM and EFR 9174 iwg on a custom manifold that is very similar to the Turblown cast shorty:














Important to note that my ECT never saw higher than 190F as measured on the back of the T-Stat housing. IAT measured just behind my Rx8 TB which would be located at the front end of a greddy style elbow never saw higher than ~90F temps at idle and typically 10-30F higher than ambient while moving. My manifold/downpipe is wrapped in DEI heat wrap and I have DEI heat shielding on my LIM. Turbine housing has a generic heat blanket on it as well. Unfortunately, even though I have EGT ports in my manifold, I had not yet installed EGT probes/gauge.

Looking for any input on likely causes of this so I can do whatever needs to be done to prevent this on my rebuild. Goal is for ~15psi on 94 pump gas for around ~400-450 whp.

 

More photos of my setup in the car for reference:






If one truly wishes to do the deep dive on this build, please see the link to my Rx8Club build thread below in my signature. TIA.

 

I am not a rotary-engine expert, but...
The #2 seals don't look warped to me, but they ARE obviously severely worn. I'd be looking for an issue like a stuck or otherwise screwed-up fuel injector or something else washing down #2 and eating the seals there for lack of proper lubrication. Anything else that would cause that extremely rapid wear might also do that, but what it might be, I have no idea.

BTW, that is a VERY well prepped car! Good luck !

 

sorry to hear about your problem.

i have never seen such a mismatch re apex seals. based on the condition of the crown of the seals and lack of heat related blueing i highly doubt the height differential ocurred while in the motor.

please measure and post the height of your corner seal springs for each of the rotors.

i may have missed it but didn't see AI? heat is the primary challenge of any single turbo rotary. AI is one of the necessary components needed to deal w heat. cold spark plugs are another requirement. 9s shouldn't even be in a break in single turbo app.

if you look at the close side of the rear rotor exhaust port you will see an inordinate amount of carbon. at the close, two thirds of your apex seal isn't touching the housing.

i can't tell if the rotor housing longitudinal striations are grooves or oil traces. do they feel bumpy when you run your fingernail over them laterally?

i do think you have more than one thing going on in your motor and you will need to fix all of the items. please post a pic of your front rotor housing exhaust port.

 

Aftermarket corner seals?

 

see how worn the side of the apex seal is on the Right side corner seal area which corresponds to where the apex seal height is also worn down?

Aftermarket corner seals are poorly made and you have to drag the feeler gauge through the slot with all seals in rotor and sand/file the corner seals to have proper clearance. Its a known issue.

So, the corner seal was too tight to the apex seal and the apex seal could not easily get pushed down into rotor slot and so wore at high rpms.

Stock parts are the best.

 

i didn't catch the angle re the wear. from the pics/videos.

the contact section/crown of the worn apex seals look normal, albeit w the typical micro gouging you would get from Atkins seals. i see no evidence of extreme heat nor do i see a significant flatting on the shoulders. yet they are missing a tenth + or -. and at an angle.

it would be reasonable to look carefully at the (OE) cornerseal slot. minimum clearance is .0015. yet it is doubtful that one rotor would have a corner seal slot clearance problem on all 3 positions and the other rotor wouldn't. was there any machinework done on the rotor? also check the seal to groove clearance. you will normally find around .003 in the center 2/3s and a bit more towards the corner seals. there should be no tight spots... what is especially weird is that all 3 of the seals had the same problem??

i note that the majority of carbon on the rotor housing is on the rear side of the plug holes and exhaust port. this lines up w the mis-alignment of the seal. since it did wear (at an angle) against the housing it would have wiped the carbon off on one side and the other half would be less pressured.

there seems to be an irregularity on the rear side of the exhaust port. i blew it up a bit and it is hard to tell but it would be in the area where we are looking for answers.

whatever the cause, it is common to all 3 apex seal positions.

nice car .

 

Stock corner seals without the inserts.

 

This is a good observation, appreciate that input, these are supposed to be stock corner seals but I’m not 100% sure how to confirm that on my own.

 

No I don’t have any AI (and I’m familiar with your website and how much you praise it). It’s something planned but the intent was to get things running at relatively acceptable limits as is on pump gas first.

I will do my best to measure corner seal heights for you, what is the best way to do this? Micrometer? Is there a specifics technique for measuring the springs?

Noted about the BUR9’s, thanks!

The striations can be felt on top of the exhaust port up to the bump in the housing, and on top of the trailing spark plug hole. The rest of the housing feels smooth and the looks of it are just oil streaks.

 

So these are RA Superseals (not sure if that’s affiliated with Atkins). I’ve ordered some E&J Apex seals for the rebuild. Also, not sure if this matches up with what you are saying about carbon on the back side of the engine, but my assumption os that as per typical build procedure the assist pieces should have been located at the rear of the engine but I’m seeing more wear on the opposite end of the seal from the assist piece.

I will measure corner seal clearances against the apex seals as well as rotor slot clearances as per your comments, appreciate this information thank you. I also agree it would be very odd for it to be so even on all 3 seals on the same side of the rotor even. I am not aware of any machine work needed on the rotors, certainly nothing was requested at the time of the build.

I will get you some photos of the front housing and it’s exhaust port specifically.

Also as an additional note, I have a E&J apex seal tool/precision straight edge on the way with my seals, so it may make things more clear exactly where the apex seal wear is. Not that it isn’t pretty obvious already.

 

So clearance of apex seals inside of the corner seals, I was able to still drag a .002 feeler gauge through them. This is consistent with all 3 apex seals in each of all 6 corner seals.

A .003 feeler gauge with the apex seals fits into the rotor slots but causes them to bind and the feeler gauge cannot drag through it. This was consistent on both rotors with both front and rear apex seals. Important to note that this is on my rotors that have NOT been cleaned yet (still lots of carbon on them). The apex seals themselves slide through the rotor slots nicely and prior to pulling the engine apart the apex seals had nice movement and spring to them through the spark plug holes on both rotors.

Not sure how to measure corner seal springs but “eyeballing” all 12 of them are roughly 1/8” tall when sitting on a flat edge.

 

Photos of front rotor housing below. The complete surface of this housing is all smooth to the touch except for a small area at the bottom of the housing where there is some of the chromium worn (my understanding is that this is a common location for this to happen). The worn chromium is roughly 1/16” in from the rear edge of the housing (shown on last two photos below).

 

Sorry for my 5 times back-to-back posts here lol.

But yes this was also one of my initial thoughts. Injectors will be sent for flow testing and cleaning. Maybe this is just purely from lack of premix due to clogged injector, maybe the slanted wear is explained by a clogged primary injector?


Another dump of info:

Fuel system consists of a walbro 450 in a modified Rx8 in-tank pump basket to accommodate a return line. Supply to engine has an in-line 6micron Radium filter feeding 2 ID1000 primaries then 2 ID2000 secondaries. Using an Aeromotive FPR and my FFE rails are plumbed in series. Fuel pressure has been solid at all boost levels.

Ignition system is IGN-1A coils with Sakebomb plug wires and a Rywire sub harness for the coils. CAS is an FFE Rx8 trigger wheel with their Hall Effect Sensor wired into my stock harness.


Lastly, thank you for everyone’s compliments on the car and your input on all of this has been GREATLY appreciated.

 

Sounds lime corner seal to apex seal was good.

Can we have a close up pic the back of the worn apex seals where the springs contact.

Wonder if the small springs didnt get pushed fully into the center detent and that is what stopped the apex seals from having freedom to be pushed into their slot on that side.

 

In all pictures rear rotor is on top, front rotor is on bottom. Springs left larger indents on rear seals but maybe expected since they were obviously contacting the housing. One other thing I’m seeing now that you have me looking in this direction, the side of the assist pieces on rotor 2 facing the rear of the engine are “blackened” where they would be sitting inside the corner seal while the front rotor pieces are silver:

 

the corner pieces on the rear rotor were out of position on assembly. they were not glued to the apex seal and the spring pushed them away at an angle. when the plates were torqued together the corners were pinched. this misalignment is also confirmed by the missing adjoining chrome on the housings. corner pieces on apex seals should always be glued. the misalignment is probably what caused your apex seal degradation.

your rotor housings should be honed. recommend Adam at REC. confirm your corner seal springs are the real deal (inconel OE FD) and at least .17 high. simple to measure w vernier caliper, change plugs. (see my new Spark Plug Section re a new plug for the trail position), add AI and get tuning.

http://www.colemanprecisionrotaries....ark-plugs.html

 

I initially missed the slant on the worn seals. As Howard says, it's got to be a mechanical issue. His latest post is likely the way to solve this. My fuel cause is very unlikely.

 

Late to the party but wanted to say that’s a great looking setup. Looks like you found the issue. It’s unfortunate that happened. One of the first motors I put together I pinched a corner seal and the corner piece resulting in a noticeable compression issue between two chambers. Unfortunately, I did not catch it and everything was completely installed. I had to disassemble. Lesson learned . Just remember that sometimes learning comes at a cost. Don’t get discouraged.


~ GW

PS ; Howard’s link is most intriguing. I’m running mid 400s with r7420-10s. I plan to investigate this trailing plug this Spring.

 

following

 

But if this was the case, how did he have 120psi compression for at least the first 1000kms when we checked it?

 

🤔

doh!


.

 

I'm guessing they sealed well even with that issue until they wore down from the excess contact pressure and started losing contact. Once they wore down the springs would have been doing little good.

 

Howard, how about replacing the sealing washer with a thin copper crush washer to gain some of the 2mm height? I've done this with other plugs.

 

Is this anything of significance? Noticeably lower than the rest. Not sure if you have these labeled where they came from.