flamethrower13b

Ok so start out I have a 2nd gen 13b with a single turbo. Street port. T04 67mm p trim turbo with .69 ar on center hotside. Anti surge comp. 550cc primarys and 1680cc secondarys. Electromotive Tec 2. This is in a sand rail or dunebuggy. I had my last motor running great until it sprung a huge oil leak and blew oil everywhere! The motor still started and ran fine. It cracked the front Iron housing near the oil feed line comes from the motor going over to the turbo.

So took it back to the guy that rebuilt the motor the last time. Tore it down. Said the motor looked good inside. Kept the rotors ecentric shaft alum rotor housings. Had all the seals changed. Changed out the irons and ported them had some trick bolts from Mazda trix installed. They said this would solve the problem due to less twist and keeping from cracking housings. The motor was already dowel pinned. So I am not sure if they had to do more work for these bolts or not. Anyhow I got the motor back put it back in the car. I could not get this thing to start. I had a bunch of problems. Starting with a stuck injector. To a improperly adjusted TPS sensor causing faults. To a crank sensor mysteriously taking a ****. This sensor was the biggest headache. Cranking cranking cranking puff puff BOOM! shotgun loud backfire! So finally figured this one out and had good spark to leading and trailing plugs and still couldn't quite get it to start. Could tell it was close though. Upon putting the engine together they had put a heavy coat of grease on the rotors inside the motor and when the motor spun over it coated the plugs with a grease gas mixture that was not flammable. So I fought this for a week with repeatedly removing the plugs wiping them clean and playing with the cranking fuel map to no avail. Finally Saturday pulled the car out of the garage hooked a tow strap to it and pull started it with my pick up truck. Got it running for about minute. Drove it to the end of the street to clean it out a bit. It sounded good a little cold and loaded up still but good. By the time I got to the end of the street to turn around I look back to back up and see OIL spraying everywhere! Shut it off and pushed it back down my street. Spent the rest of the evening trying to clean up the huge mess of oil I left in front of my neighbors driveway and all over the street. So in running my new engine less than 2 minutes mind you I managed to crack the rear Iron housing right underneath the oil filter. WTF!!! I never hit 6000 rpm and was not full throttle and it ran for a minute and a half tops! What in the world would cause this? How did I break another iron housing with super beef bolts? I started the engine once more after I got home and added some more oil just to see if I blew a AN line to an oil cooler or turbo because there was oil everywhere and I wanted to see where it was coming from. It fired right up and ran like a champ as it sprayed oil out of a very large crack in the housing!





I was told by the motor guy the last time this was due to too much boost or too much timing or advance. The boost was set at @ 18 psi at the time of let go. My timing was not too aggressive I think but not sure.

rnz520

iTrader: (10)

maybe it was cracked before he rebuilt it and he just missed it.

rotaryinspired

iTrader: (3)

i have cracked 2 rear plates both S4 TII plates. Both times was from a rich mixture causing a misfire.(I can explain further how it misfired and what caused it) One interesting thing I read in RE by Kenichi Yamamoto is that once there is a misfire it is carried over to the other 2 faces of the rotor actually causing 3 misfires. This causes extra stress on the block and the weakest link breaks unless your lucky IMO.

It sounds like this is your cause to me. I do not know if you got it into boost or what not. These are just my findings after doing this a few times. I know have a new S5 rear plate. Changed a my plug wires, made sure they were not touching and covered and made some other adjustments in my maps. Make sure there is no misfire underload.

Hope this helps some.

flamethrower13b

You think so? I just realized a huge mistake I made that might have contributed to it. I was having so much trouble getting it to start, that I thought the race gas in the tank might have gone bad. So I drained it and took apart my fuel filter and changed it and bought 2 gals of pump gas to see if that was the reason it wouldn't start. I premixed it but it was just going to be used as break in gas mostly for idle to bring the engine up to operating temp a few times before actually taking the car out to really drive it. The only reason I drove the care was cause I actually had to tow it to get it started. Could you really break a cast iron housing at half throttle in under 30 seconds with 87 octane gas when the boost is set at 18psi? I feel like an idiot right now.

I need to post my timing map and see if I am out of line. I just read a thread on dowel pinning motors and from what I gathered its my fault by bad tuning that this happened. I really have had great success with tuning a 1000+hp big block Chevy on a Fast XFI and am about to tune a 500+ hp small block Chevy on a Accel DFI system. They are both Naturally Aspirated. I have gotten this 13b to run better than 2 dyno shops with this archaic Electromotive Tec2 in the past. But ever since I have stepped up the turbo to a much larger aggressive compressor I have seem to shot myself in the foot! My knowledge of rotary motors is limited as to what the timing limits are when the boost comes on. I have also just noticed my map sensor is reading 160 KPA with the engine off when it should read @ 100 KPA. I wonder how long its been messed up. But wouldn't that help matters by pulling timing out earlier and adding fuel?

rotaryinspired

iTrader: (3)

The fuel should have been fine. I run 16 psi on a T67 on 91 octane w/ no issues.

The good news is you can just swap the rear plate and be good to go as long as the bearings look good when you open her up. Not that big of a deal.

Because our motors are sandwiched together it puts extra stress on the dowels when its not running properly. Especially on a misfire. It tries to twist the block. Also if the extra dowels were not properly done they could have weakened the plates.

I have no experience w/ the electromotive units as all i have tuned are haltech, power FC, and aem, but if it was pulling timing and adding fuel it wouldnt' have helped. Also did you make sure the CAS was aligned properly when you put it back in?

Check your turbo as it could have starved for oil when the rear plate let go. I lost a turbo this way. Bearings were toast.

I will help out anyway possible. I have been there done that. Good news is that its an easy fix.

rotaryinspired

iTrader: (3)

oh and make sure the plug wires are shielded from each other and the CAS wire when you get her going again.

rx72c

iTrader: (8)

What ecu do you have?

Maybe the plate was already cracked and your engine builder ripped you off?

Maybe who over studded the engine wrecked it?

Maybe the stud kit is ****?

Trots*88TII-AE*

iTrader: (11)

do you have a log of the 1 minute of run time? Curious to know how much boost it ran before blowing. And what does the crack in the iron look like? Is it something extremely noticeable that your engine builder should have seen, or a hairline crack that could have gotten by a lax inspection?

diabolical1

iTrader: (3)

could you clarify this? photos would be great.
at this point, i count three possible causes that could have been individual or in any combination: (1) the machining for the dowels/studs, (2) the original detonation that cracked the front housing, and (3) the huge misfire you described (though i think this is less likely). i can't say i've heard of dowelling AND studding (i assume you meant studs since i'm not aware of "trick bolts' available from Mazdatrix) in tandem. perhaps i'm missing something. however, the sad truth is at this point it is all speculation right now. pull it apart and let's see.

zayrx7

What is you timing set at