Rear housing

Rear housing. Are these chatter marks from improper lubrication?

Rear housing

Rear housing.

Rear housing

Rear housing
Hey everyone I thought I would share my long term engine teardown pics and findings and ask for advice from more knowledgeable rotary owners than myself.

I’ll give a bit of a history of the car, its general use and the engine parts used in the build.

It’s a 2001 fd rx7 that I use as my street car as well as competition on track. Time attack as well as some autoX. I have lost count of the track days but it might have done about 20-30 track days on this engine and about 40,000km of total driving. It was tuned to about 461whp on pump fuel with water meth injection but I turn it down further to about 400-ish for track driving as the hot tropical weather we experience is quite brutal and to try to keep heat down and be on the safe side.

The engine was built in 2011 re-using the original housings and plates which had about 60,000km using the oem seals on them. Engine mods are as follows:

- ALS 2mm seals
- Turblown oem sized stud kit
- streetport
- OMP removal

The main reason for the rebuild was an internal coolant leak although the engine’s performance did also start feeling weak. Compression before tear down was 75psi front and 60psi rear.

On teardown, I thought the housings looked quite worn but I am not sure if this is “normal” for a total of almost 100k km on them?

Also worth mentioning that the coolant leak was on the rear.


Front housing

Front housing

Front housing

Front housing

Front housing

Rotor dimple from detonation at some point of the engine’s life.


The pics were taken immediately after removal and the parts were not touched up in any way. Maybe a light wipe down with a cotton cloth for clearer pics.

To me it seems that the rear rotor with the coolant leak looks worse. I am wondering if the coolant messed up the lubrication of the premix.

I also ran a power fc with the fuel cut on decel enabled just as factory, which I am now reading may not have been the best thing to do. Although I wasn’t careless about it and would clutch in at some times.

I can try to get some other pics or measurements if anyone wants to see something specific.

Would you class this as normal wear or would you say the seals were aggressive on the housings?

I am not using back these housings, just trying to assess the performance of the ALS seals. Using brand new housings and plates for my new build.

Thank you for looking and for any advice.

Mayank Ramlakhan

 

More cooling will help the area around the leading spark plugs. (That's easy to say and hard to do, yeah?)

You definitely need more oiling, upping the ratio will help a lot. At your power level you may need 3-4oz/gallon to really keep the rotor housings happy, but all in all they don't look abused, just gracefully aged.

I also see lots of chatter which tends to be because of loose apex seal to slot clearances. I am unfamiliar with the ALS seals but the Atkins seals are "nice" in that they seem to wear the seal more than the rotor, so rotor life is increased. I've taken out Atkins seals after 100k km that were worn to 1.7mm thickness but the apex slot clearance was still excellent with new seals.

 

Thank you for the advice man! I’ll definitely add some more premix. I was using a 100:1 and 80:1 for race days which works up to about 1.5oz to a gallon I am guessing.

As for the cooling I’ll do some more research on the forums to see what can be done further beyond what I have currently (koyo radiator and upgraded sakebomb dual oil coolers).

Would a “colder” plug help in this regard? Most of the time I run 9 leading and 11 trailing plugs and only because the 9 leading resists fouling better. I know many rotary owners don’t want 9 range plugs anywhere near their engine 😂 but I found that for street driving the 10 used to foul a lot easier. Maybe I can try a colder leading plug as I have a stronger ignition system now (Ign1a coils vs the hks twin power I used to use).

Thanks again for the advice peejay.

 

i feel like we have seen housings that were a lot worse than those, or maybe at lower kms

you might try a cooler thermostat, if i upped the power on mine (currently ~300hp), i'd go to a 75c thermostat

for plugs there was this little tidbit recently
https://www.rx7club.com/single-turbo.../#post12607886
"Personally, I prefer starting with the coldest plugs and then moving hotter after reviewing. IMO starting hot is approaching the answer from the wrong direction."

 

Thanks. That is good advice.

 

Oh jeez, naturally aspirated I ran 10s leading and trailing. I never had fouling issues but I did have ignition breakup issues with the 9s on longer straights, that was solved with the 10s. (NGK numbers obvs)

I also premix at about 50:1, again at only 270hp. My rotor housings look better than that after a long time.

 

thanks for sharing.

what heat range plug? pretty serious plug boss cracks.

chatter is caused by spark plug mountain and you certainly have a lot of apex seal lift. too much heat at the plug

it also appears you have a lube/premix deficit.

please post a pic of the side of your rotors.

t looks like you may have a depression in your rotor face or perhaps it is just the picture. if it is a dent that would be pre-ignition which is caused by the trail plug. solution is a surface gap plug.

i am surprised at how coated your rotors are. AI generally delivers pretty carbon free internals.. .

 

Thank you for commenting. I ran 9 leading (😅😅 sorry, Howard) and 11 trailing for most of the engine’s life. I only just started reading your thread on spark plugs. Very good info. Thank you.

I will try to get a pic of the side of the rotor and upload tomorrow.

You are correct, there is an indentation on one of the rotor faces. Thank you for your suggestion about the surface gap plug. I’ll do some research on it.

Yes the rotors are pretty coated but in fairness I have not been or been able to drive the car very hard over the last few months so it saw very mild driving and not really using much water/meth injection.

Thank you for the advice. I had never even considered the localized heat at the spark plugs would in part cause the apex seals to chatter.

 

I’d recommend 8.5 CR S4 Turbo rotors. I was just talking to another forum member recently how imo lower CR is perhaps under-rated by many enthusiasts here. While they are heavier, if you’re making good turbo power reliably then the engine will accelerate just fine. To the point I’m convinced even lower CR is justified.

Which I’m also a big believer in balancing the rotating assembly regardless, and this negates mix/matching different engine model components. Lightweight rotors maybe for a high strung NA engine, but even your picture of the one detonation-dinged FD rotor demonstrates the point.

What’s not really understood is how it’s not just the lower CR that’s a sole benefit, There are other unique Wankel factors involved that also result in additional power benefits wrt filling & stuffing the intake phase cycle. A recent example was Rob Be Dahmed’s 700+whp S4 TurboII Rx7 w/Garrett G40-900 turbo video on youtube.
.

 

Nice suggestion. I was always really under the impression that s4 8.5cr rotors were more of a “big” power (600+hp) kind of mod and that the heavier weight a was more of a disadvantage for road racing.

I don’t have any first hand knowledge to doubt that s4 turbo rotors would work just as fine for road racing if not better though. I know many rotary owners choose the s4 turbo rotors over the s6.

For this build it might be a bit too late as I already purchased two new s6-8 rotors. But maybe someone else reading this thread can give it a try.