rotarygod

Not in the area in question.

saskloppers

Hey Chris, calm down buddy!

The only thing more plentiful than hydrogen in this universe is stupidity. Hehehe. Relax!

I am looking into the possibility of adding the oil control rings to the RX-7 rotors if mine shows any signs of wear. That is only if it is necessary but I suspect that it won't be necessary due to the low compression ratio. I have had a look at old oil seals last night from stripped 13B turbo engines and none shows any signs of wear so I might not have the problem that RG has mentioned. However, I like to keep my eyes and ears open to all possibilities.

I looked at the crack. It is so minute you cannot see it with the naked eye. As a precaution I will be adding dowel pins to the housing and have looked at changing all the other dowel pins as well, just to prevent this "tuning" <GRIN> problem from happening again. I will keep you posted.

saskloppers

Thanks a lot. How would you approach this and what modification would you do to keep them open?

The car has such torque that losing low end power is really not a concern.

rotarygod

You need to leave the rotating sleeves installed as they have a radius at the end of them and take up excess space in the intake runner of the end housings. Remove the motor that turns them and just figure out a way to hold them in the open position full time.

What did your side seals look like? Is there any carbon in the grooves? If it's a race engine then I suspect there might not be much if any. I'd be very curious to see a street engine running these rotors to see what the longterm effects of not having wedge shaped side seals or a cutoff ring are.

GrRx8MaZdA

Hey Rg what is the difference in a race and a street engine??I am getting mine which is a daily driven fd rotors with race seals and we ll port it here and turbo it arround 16psi with mazsport..

saskloppers

Okay, I'll mod them and redo the map. I think this will make mapping a whole lot easier as the APV's don't dump a huge amount of air into the engine at 6800. Also, I think the car will be more driveable as the APV's opening causes a little hesitation before she really chucks up to 9400. In theory the result might be a smoother ride.

As for the seals, they're fine. Remember that I race it at 1.1 bar and set it at 0.5 to 0.8 bar for everyday/street use. There's really no visible carbon build up in the grooves. Another thing, I use 102 octane with my race map. This might help. For street use I fill up with 95 unleaded.

rotarygod

I consider a race engine to be one in a car that has at least 75%+ of it's driving done on a race track under track conditions. A street engine is one driven around that rarely sees track events. Maybe a couple here and there. Unless most of your car's life is at the track, don't build it around the track. Many people want a race car they can drive on the street. It just doesn't happen.

crispeed

You probably had a little pre-ignition or some ignition misfire under load. It can happen no matter how good the tune is. If you're confident that it was not a tuning error and from the looks of it, if it was you would not have been this lucky so far because rotaries leave no room for error when force induction is involved. Your best bet would be to have the motor pinned. Normally if the motor was experiencing any form of detonation for some time it would have shown up in the rotor housing surface area between the top of the housing and the trailing plugs.
From my experience a motor running at 1.0 bar should not be making enough power to crack the housing under normal circumstances anyway. I have made close to 700rwhp on a 13b without any extra dowel pinning done to it.
Now motors can crack at much lower power levels also so that's why pinning is done. It's not to solve a tuning issue but it's done mainly as a safety and durabilty issue.
Do you care to share some tune up info like AFR's, T & L ignition timing, charge air temps etc.?

rotarygod

That brings up a good question. What are you doing for an ignition system?

Jedi54

iTrader: (7)

stupid question alert:
You said the crack was so minute, you could barely see it with the naked eyes. So how did you know you actually cracked the front housing? Did you just trace back the oil leak?

saskloppers

Got Okada Projects plasma coils installed. I ordered a new set yesterday just in case. I also use genuine spark plugs only. No aftermarket leads or anything. I think in this case OE is the safest.

saskloppers

I placed the engine on one of our lifts, ran it and traced the leak. It took a while but eventually I could see the oil seeping out from the dowel pin location. I hate oil leaks or any leak whatsoever. I prefer to fix them immediately. Been through a lot of scrutineering in my lifetime with race cars not to take a chance and leave it. Besides, a small oil leak can just as easily become a big leak. I'm not chancing oil on my tyres with all the power.

saskloppers

Exactly why I decided to go the route of extra pins. I run the AFR rich. Normally 11.5 under vacuum and cruising but anything over 0.5 bar I fuel between 11 and 10.3 depending on the rev range and boost. If my memory serves me correctly we pull back timing around 12 degrees maximum under load. I don't measure charge air temperature and would presume it to be quite low due to the alcohol injection.

I have had one problem though, I have not been able to measure the EGT reliably. I think the sensor is faulty. Any ideas?

saskloppers

If I wanted somethine that was pee'd on I'd have bought a Beemer....

MazdaManiac

iTrader: (3)

Why the hell would you do that? You'll coke up everything insight, not to mention you are giving up a TON of power and working the ignition system to death trying to jump that charge.
In vacuum and cruise, it is simply ludicrous to run anything more rich than stoich, though you can probably see some smoothness in transition into boost by running 13.5:1 or so. That's a bandaid for bad throttle tip in programming, though.
In boost, you can believe what you wish, but the absolute lowest for RBT is 11.5:1. You give up 15% of your power for every 1/2 point richer from there.
MBT is going to happen at 12.3:1 or so.

That is actually fairly advanced for a lot of boost at the torque peak (and probably why you've decided to run so fat).
On street gas, at 1 BAR at the torque peak, you should probably run only 5° - 7° degrees of advance with 10° - 15° of split.
You can go forward 1° or 2° for each point of octane (AKI, not RON).

Who is providing you with this tuning setup and what engine management system are you implementing?

TeamRX8

iTrader: (25)

I suppose it was too obvious to consider that it may have just been a one-off fluke bad casting

MazdaManiac

iTrader: (3)

Definitely possible, though somewhat unlikely since this particular type of failure isn't too uncommon and is traced to one tuning/power scenario or another.

I'm still curious to hear why knowing "that the tuning is spot on" can coincide with a ton of ignition advance and an A/F just short of choke.

dannobre

iTrader: (3)

Deluded is as deluded does......or If your not looking for it you will find something else....or a lot of other quotes come to mind

MazdaManiac

iTrader: (3)

Indeed, though there is probably even more to the saga that is not revealed to us.

TeamRX8

iTrader: (25)

at least he's out there doing it rather than just running his theoretical gob on some forum ..

MazdaManiac

iTrader: (3)

True.
Though, I suppose he's actually doing both.

That is pretty much the function of forums like these for those of us that actually build stuff - its a place to air our intellectual laundry.

GrRx8MaZdA

Hey Sas any news on the problem??Did you manage to install extra pins?

saskloppers

Hello Chris

The housing is being machined as we speak.

I have found another potential problem. I've noticed some faint score marks caused by the corner seals.

I suspect this is caused by some form of vacuum sucking the rings out when they pass the exhaust port, due to the boost. There is not damage as such but I am concerned that it might cause damage in the long term. I'm looking at ways to resolve this one.

Any suggestions anyone?

MazdaManiac

iTrader: (3)

I'm not sure what you are saying exactly.
You have scoring on the irons around the track of the corner seals. What "rings" do you mean?

saskloppers

Sorry, sorry, sorry - The corner seals, not the rings. Forgot to get out of my piston mode. Busy on my racecar as well at the moment. hehehe

There's slight marking of the housing at the exhaust ports where the corner seals pass over the exhaust port. This is very faint and only on the side after the seal has passed the port.