bigbd03

Probably not necessary. Occasional wide open throttle will will help clean out the carbon of any engine adequately. Excess wear on engine and other components people cause by overreving and driving the crap out of their car all the time cancels out any benefit of trying to keep carbon build up out of the motor. Of course in my opinion.

UnknownJinX

Redlining occasionally won't do anything, as the temperature won't get to the point to remove carbon. Outside of driving on a track, your engine won't get hot enough to remove carbon.

This thread had some more technical discussion on this topic.

https://www.rx8club.com/rx-8-discuss...posits-268570/

bigbd03

The fuel cleans off the carbon. Hence a lot of smog and carbon problems plague direct injection engines.

Loki

iTrader: (1)

Well that's completely unrelated. In a DI engine the carbon we're talking about is on the backsides of valves and in the intake, its deposits created by unburned fuel and PCV gases. Carbon in a rotary is in the seal gaps, the equivalent of piston ring grooves, from combination of burnt and unburnt fuel, oil, etc. There is no steady supply of fresh fuel into there. You need to get the interior surfaces to get up to self-cleaning temperatures for sustained periods of time. Number of redlines is meaningless, what you want is high engine load conditions for sustained periods of time.

XDragon8

Finally got this car running great with no codes. Not even a P0139 and Im catless! Win.
Still having that 'hot start' issue every time a start is attempted after a drive. Starts up great after 30 min coffee break but what a PITA. Have just ordered a "high torque 14 tooth S2 starter (copy)" as I see my old looking upgraded one only gave 200rpm on an attempted start recently. Really hope this helps as currently service station visits are a no go zone!
Dont think there is much more I can do atm, just drive her and enjoy before the inevitable.

Can anyone elaborate further on the use of RX7 apex seals in our 8s?

Also FWIW I saw 11.2 AFR on multiple WOT 3rd gear pulls on different days. Pulled 1500km new plugs (installed at same time as BHR coils) and they were a beautiful latte' color. Reinstalled for another 5k then will recheck.

Loki

iTrader: (1)

A faster starter should definitely help on the hot start side of things.
11.2 AFR is too rich though. Was this fully warmed up? AFR read via OBD?

XDragon8

Hope you're right on the starter. Will find out soon enough. Im using a Bluetooth dongle and torque pro on the road. I'm looking at monitored and commanded AFR. Hard to view both at wot but they are always near each other. Obviously fluctuate with loads etc. Def warm engine as I watch ECT and others. Plugs show 👍 in coffeeness test! (Yes it's a real word in my world.)

Phreakapotamus

MAZFIX

UnknownJinX

Basically you need a rotary shop to deepen the apex seal grooves on the RX-8 rotor as the RX-7 seals are taller(3mm vs. 2mm IIRC).

A few power users do agree that this has benefits when it comes to engine longevity.

XDragon8

Thanks JinX for the info and Phreak for the linky. No-one around here really gives a crap about 8s so that's why I'm here lots. I'm always learning.

40th8Jake

See I was about to make a thread about this very thing and I SEARCHED. So not only new housings I’m looking at for my rebuild, but also new rotors to modify to fit the Rx7 seals? Ok.

So far what I’m thinking is; Koyo Rad, auxiliary cooling system with aluminum under tray, Sohn adaptor, fresh coils/plugs and wires, and maybe a baffled oil pan? Hoses, incidentals..
Oh and new (exedy?) clutch and lightweight flywheel oh and motor mounts..

very expensive but hopefully life sustaining. Oil and cooling.

Anyhow thanks for the thread and not trying to hijack but this saves a wasted thread and the flame.

TeamRX8

iTrader: (25)

https://www.rotaryengine.com/service.../rx8rotor.html

40th8Jake

Thank you team. I love watching this guys videos on YouTube. When I first got an Rx8 I watched these videos of him building engines and porting irons etc.

Hopefully Lucky 7 can do this to rotors as I would have to ship from SoCal to Canada. I know they use a racing beat template to do the intake and exhaust ports where I’m planning to get my rebuild done.

Other than using a sohn adaptor, is it worth it to do other oil modifications when doing a rebuild? I’ve heard of people going as far as opening oil channels out more?

TeamRX8

iTrader: (25)

Well I don’t use or recommend a Sohn. There’s zero evidence imo that it benefits engine longevity. Otherwise if you intend to get a rebuild through whoever then you should be talking to them rather than posting here. If you don’t trust them then get your engine from someone else that you do trust.

CaymanRotary

Agreed to a point. Agree that premixing and changing oil every 3k miles you should be just fine. However, I like the idea of the adapter though and while it may not help engine longevity it cant hurt. Has to be better running clean oil vs dirty oil pan oil. Not necessary but also not harmful so long as you set everything up right.

Brettus

iTrader: (2)

I've run the deeper rx7 apex seals in my boosted engines for many years and think this is an important upgrade for any boosted engine. For N/A i'm not convinced it is necessary. I haven't heard of anyone that's actually done it for an N/A engine let alone done a long term trial that shows any benefit.

40th8Jake

I plan to go boosted in the future, just it doesn’t make sense spending $20k all at once (especially with the economy now) to get a rebuild, and necessary parts. Then a turbo kit and necessary parts such as fueling and ecu. Maybe I could get lucky and be around $15k. But the labor, new housings, mods to rotors for seals, street port, etc you know how it goes.

They only charge 1k to install a kit with the engine in place. I’ve seen the build threads and that sounds like a good price compared to the hours most people spend doing it themselves.

So to me it’s better to have it done and not need it, then to need it and not have it.
I trust them there. They said they intend to rebuild my engine for N/A use to last up to 100k miles.

Thats a big claim for a Renesis, I know. As I will add a turbo kit down the road, I know the life of the engine is expected to suffer, but it is a weekend car.

As to the sohn adapter like Team said I’ll talk to them about it. I trust them. They build lots of Rx7 race cars and have a good track record as far as I can tell.

Brettus

iTrader: (2)

If you have any mechanical ability you will regret not installing it yourself ...if you don't have any ...you shouldn't be going turbo in the first place . IMO

40th8Jake

I have heard this before. It makes sense as in for troubleshooting. I do have mechanical ability, just i don’t know if I have sufficient tools. I don’t have a mig machine or a mandrel bender though. But supposedly the kit I want to use doesn’t require that but they are built to order...so mistakes happen.

I do have an air compressor, pneumatic impact, and all imperial and metric sockets/wrenches. So in theory I should be ok.

Thanks Brett,
Regards, Jake

kevink0000

For what its worth, one of my Renesis engines went 186,000 miles in stock configuration.( Not under my ownership, FWIW.) The side seals, irons, and bearings were in great shape, of course the housings looked horrible, with lack of lubrication evidence throughout. The main failure areas were the apex seals, both on the housing contact face, and the sides where the apex seals make contact with the rotor groove. The apex sides especially were troubling to me, as the fretting type wear took the stock 2mm thickness down to about 1.25 mm in its thinnest spot. The engine failed catastrophically when a seal broke loose on the rear rotor. The front wasn't too far behind. Got home on one rotor though. Impressive in that regard. That type of wear is a killer on a high mile engine in my opinion, and a real Achilles's heel to long life. (I personally consider 200k + street use, and hopefully more, long life, FWIW.) The deeper rotor grooves would surely help here as they would lessen the angle the apex seal rotates through in the groove as it makes its way around the chamber. It would likely lessen the impact forces of those angle changes as well. In my opinion that is a worthy pursuit to building a long life engine, if that is your goal.

XDragon8

Thanks Kevin for your clear explanation of the benefits of the 3mm apex seals. I'll definitely have a good look I to this and discuss with engine builder.

Just an update on the 14 tooth uprated starter motor. It made for rapid starts on my cold high km engine, however it did not help the hot start issue at all. Deflating, but at least I know I have done what I can.

I'll probably keep using the 8 for weekend fun until I can't stand the low compression issues any longer (poor idle when hot and of course the hot start issue). Is there any benefit to rebuilding a high mile engine or keep driving it like I stole it? Goes great while moving, just don't stall it!!

kevink0000

Dragon,

To clarify, I was speaking about the height of the seals, not the width. The RX7 seals are still 2mm wide, but are taller and the rotor groove is deeper than on the RX8, which is what Team was talking about, and what the link he posted was referring to.

XDragon8

Yeah. I'm good with the info. The rotors would need CNC machining or similar to accept these. I will look into this as to cost effectiveness. Thanks again.

Phreakapotamus

Rx8performance also offer a "bolt on" kit that looks half decent

XDragon8

Thought i would share my findings and where i sunk my cash into this engine after catastophic failure earlier this year.
Nothing was used from the original keg!
I got a reputable engine builder to build a standard spec engine using mostly new parts. (His suggestion BTW) All ports were polished rather than ported, then fully blanced before final assembly. Thats basically it other than adding in a Koyo full alloy rad. All came with decent warranty so I'm happy.
Yes it cost a bit but remans are not an option where i live so it's either build, buy unknown condition, or buy new from Mazda...... ouch!
Now i have a great car with an even better engine. Time to enjoy. Hope this helps someone else that is beginning this journey as i have learned a lot throughout the process. 😁
In years to come i can see this car being parked next to a full electric car of some sort. Now they would be polar opposites!!