Thanks Barry

Here are the findings so far:

Front (pulley side) housing:



Rear housing:



2 chipped apex seals in the front rotor:



Pieces of metal inside the oil sump but we cut the oil filter and it was clean, no particules inside:



In the past I've read a thread about build up in water passages in brand new 13b engines, never thought mine would be that bad. We have flushed the system few times when we first installed the engine but looks like it didn't help. As you can see from the pic too much dirt inside the passages. This engine had less then 5k miles:

 

Out of curiosity, what coolant mixture were you running? Just waterwetter? 50/50 antifreeze? and if antifreeze what brand and mix ratio?

 

Around 60% antifreeze. I don't know the brand.

 

Alpsta,
Are you using distilled water with the antifreeze?

And do you see what broke the apex seals?

See the stains on the sides of the plug bores... See how the seal can't run flat and must rock over the plug area? This is what warps soft seals and chips hard seals.

You will want to port the water passages to eliminate or minimize this heat distortion.
Barry

 

Suggest reading this thread for more details.
Barry

https://www.rx7club.com/3rd-generati...em-fix-989811/

 

Regular tap water was used. I still don't know what the actual cause of the failure is. If it's tuning related or fuel or gauge malfunction, heat/knock/boost etc. I will port the water passages.

I've read that thread in the past, in fact comment #4 belongs to me When I bought my engine it was a brand new one from Mazda Japan (got it from Ray @ Malloy) so even though I preferred streetporting and water passage porting I couldn't get it done. Now that the engine is open I can do all those.

Is the front housing still usable? Does that line around leading plug bore matter? Can it be machined down?

 

The water jacket corrosion is from using tap water..... and some tap water is a lot worst than others.
The iron and aluminum in the engine cause it to become a battery when an electrolyte is added.
Tap water is an electrolyte!
We need electrolytes in our bodies but it is very bad for our engines.
In an emergency all bets are off! Any water even urine would be OK.

 

The seal broke from high-cycle fatigue.
It rock across the spark plug hump with two spring contacts on one side..... but only one on the other side.
The forth spring tip contacts the triangle which in turn breaks the tip off.





Ways to mitigate this ...
1- Colder plugs
2- Flatter surface

I would reuse the housing but only after stoning the surface to make it as flat as possible. Use a diamond knife sharpener.

Barry

 

Thanks for the illustration Barry. I was using all bur9... when engine failed.

If stoning the surface won't cause loss of compression then I can do that some friends said they wouldn't re-use that housing except if the cracked part was on the bottom of the housing. I have 2 spare damaged engines in my garage I will open them up and see if I have a better housing.

 

I'm thinking you went lean, most likely from voltage drop at the fuel pump. I've had a car run out of fuel with a similar setup to yours. Re-wiring the fuel pump solved the issue. Did you ever pull the logs?

https://www.rx7club.com/3rd-generati...l-pump-847009/

 

Unfortunately I never got to pull the logs, and lost the connection cable. I had my pump rewired since the beginning.

 

I think most everyone is right in this thread. I think having such horrible corrosion in the water jackets is a contributor to the problem. Cooling the housing is key, and I am betting corrosion like that inhibits flow and reduces heat transfer. with the reduced heat transfer it leads to more heat being retained in the housing, which leads to a higher chance of heat retention in area by the spark plug holes, which leads to higher chance of fatigue failure of the seals quicker. you just proved what Barry has found as root cause of failures but accelerated that failure mode with reduced cooling.

The seal wasn't the root cause of the problem, this would have happened with a soft seal as well, just probably would have bent and chattered the hell out of the housings looking even worse than you have.

distilled water only!!!! run a 50/50 mix at a max, more water gives you better cooling as it can absorb more heat.

 

I've seen multiple engines damaged by the PFCs rev limiter, its been a while but its fuel only IIRC and its not particularly fast, giving the engine time to see a lean condition before its unable to combust at all.

 

After the rebuild, I will pay more attention to the details like coolant ratio, water type but regardless of these I wasn't running the engine under extreme conditions at the time of the incident. I will still look into the tuning logs once I buy another connection cable.

At the moment I am concentrating on what I can re-use for my rebuild and what parts I need to purchase for my rebuild. The step after that will be what I can improve during the rebuild (eg. ported water jackets, thermal pellet, seals, new and faster ecu like Vi-PEC or Adaptronic).

I will clean the parts and post pics for comments on which ones are reusable and which ones aren't. For example do I have to bin the old seals or I just need to replace the chipped ones only?

Hmm interesting info. I am planning to buy a new engine harness and a new ecu like Vi-PEC or Adaptronic.

 

Does anyone know how to tune those ecu's? please send me your map when you get it.

 

Yea you don't want to hit the rev limiter. If a customer plans to shift at 8000, I set it at 8500. Its a hard fuel cut and not particularly good for the engine. With more advanced ecu like Haltech or Adaptronic I can set a soft cut, either fuel or ignition.

 

agreed. its ok to hit it here and there, but if you sit on the limiter, it can be bad

 

I know your moving on, but one thing no one has mentioned: You said that the engine was new from the factory. I'm assuming you got it from Ray's "last of the new factory engines announcement". These were a great deal. However, some one mentioned a couple of these engines were reported with rusted water passages. I have no experience with Mazda's engine manufacturing, but I do know that in the past new engines from Toyota had some residual tap water in the coolant passages from the factory QA/QC coolant pressure test. This typically isn't a problem if the time between the coolant test and installation is short. If the Mazda engine factory uses tap water to pressure test all the new engines as a part of their QA/QC and the engines sat around for a long period before being cleared out of inventory or installed in a car it may have had prerusted passages. All water under the bridge, so to speak, since there are no new factory engines around anymore.

 

No they don't. They are in the Motec, Haltech and Vipec bandwagon. It kind of annoys me to be recommended a product not based on the benefits for a rotary engine but instead based on their convenience and laziness.

I've read good things about Adaptronic and looks like there's plenty of support so maybe I get that and not be in need of tuners here.

I will send you the map when I get it.


Yes I've seen the thread about the water passages we've covered it few posts earlier. The "blown engine" gave me a chance to clean them out or even enlarge them a bit. However someone told me on the newer engines Mazda fixed this issue so I may not need to enlarge the passages. Have to check...

 

My mechanic is wondering if the chipped apex seal could've caused ovalling. What I mean by ovaling is if one side of the apex seal was touching the housing more and wearing the housing more, would it cause the housing surface to be uneven. We can't see this with the naked eye or have a tool to measure it. If there was such a problem once we put new seals and springs it'd still be pressing one side more then the other. Other than that the front housing looks ok and reusable.