Yes, I blew another. That makes 3 but this one is different sounding. It doesn't have a hard time starting, but knocks like a piston engine with a spun rod bearing. Anyone ever heard anything like this?

 

Knock=Detonation and Detonation=#1 killer of rotary engines. In simple terms detonation occurs when the fuel mixture is too lean. If your engine is knocking at idle then you probably have some really bad injectors, how did all this start? Did you take it out for a hard run and then it just popped? What are your mods? Who built this engine?

 

This not is not a "click", it is like some one is hitting the engine block with a hammer. If you ever hear rod knock on a pistion engine it sounds the same. I car heard the noise from 10 feet away with the hood shut. Something is wrong with the engine and I have never heard a rotary knock.

I just bought a mazda remanufactured engine from a guy with 4K on it. It drove fine. I was adjusting the A/F ratio with my wideband Lambda A/F meter and Wolf 3D. I decided to see how much difference there was between that and my ported engine I blew last FEB. It was very rich on the top end. I decided to give it so boost and around 4,000 RPM at 10 psi it detonated like a million times(it seemed). So I retartewd the timing and tried again. Same thing. Car still ran great. So today I am checking the timimg with a timing light and retard the scale a good bit....all withing Wolf specs. I go and drive it and before I even a block from my shop it starts knocking and I kill it. I started it again and it knocked and drove it back and parked it. I didn't even have time to put the car under any type of load. It just took a ****. Now I have 2 blow engines in my shop. I guess I could rebuild them and make one good one from all the pieces. Or set fire to the shop and claim it on Fire Insurance. Mainly I am frustrated.

 

You only get one knock. After that its pretty much over. It was probably over the first time. Replace fuel filter, Have injectors cleaned. Go back to the Stock ECU and Stock boost till you get everything under control. The Stock ECU will retard the timing when it senses knock coming on. Replace your 02 sensor, Sounds like the Apex seals are toast. You can probably do a minor rebuild and be back on the road.

 

When a rotary is knocking, what does it damage ? apex seals, rotors, housing ???

Thanks

 

It causes the apex seals to crack which is what "blows" the engine. Without the apex seals you get little to no compression. Sometimes the seal will fall out of the rotor and scrape up the housing and rotor.

 

I hear you man. Tuning an FD is a very complicated and dangerous task. It sounds like you leaned it out too much pinged once and blew the seal. There is 0 margin for error with these cars. I'd recommend taking it to an experienced rotary mechanic for the tuning. Rotary Performance is in TX, check them out.

 

You got it

 

I have tuned the car before with the Wolf. It is easier than you think. With the wideband A/F Meter, it made tuning a snap. My problem was with the timimg. I set it according to specs and believe me it was retarted plenty. I did this with the motor before and no problems, but this one.....it was very strange. I have tuned more than one car. My friends 13BT runs great. I tuned it in for him. I know it was never lean, I have 1600 secondaries and the car never saw less than 11.5 A/F ratio. This is one of those things I will probably never understand. Crazy thing is that the car will still start and idle with no problems. Unlike every other blown rotary I have dealt with.....it just knocks.

 

mine ides around 800 ? the car kinda gurgules a tad. Nothing is wrong right?

 

I think the masses do not understand your question. They are only thinking of detonation knock and/or do not know as much about the engine as they think.

The clearance between the rotor near the apex seals and the rotor housing is very small. If a bearing gets too worn or the rotor housing is warped, it is possible for the rotor face to actually hit the surface of the housing. The Mazda Comp manual has a cleanance test for this and even recommends grounding down the rotor face if the cleanance is too small.

Thus I deduct that is the source of your idle knocking.

 

Good diagnosis, Chuck...

It is also possible that one of the stationary gears is damaged, allowing a rotor to contact the housing wall, creating the "rod knock" sound you're hearing. More likely, since the stationary gears in the '93-'95 motors are hardened units, it is possible that the pressed-in internal gearing ring in one of your rotors has spun (just like a crankshaft bearing might) putting the rotor slightly out of "time" with the eccentric shaft, causing it to contact the housing wall at some point in its rotation.

Stationary gears...
http://www.rotaryengineillustrated.c...nat-sgear.html

Rotor with gearing ring...
http://www.rotaryengineillustrated.c...nat-rotor.html

 

Jimlab,

Ditto!

 

What would it run me in parts to fix this? What could be damaged? I have another engine with a good housing and rotor. Only problem is the engine in the car is stock and the one I have as a spare is ported, 3mm seals, a pettit built engine.

This all started after adjusting the timing at idle. I set the timing and checked to see how the engine would rev (pulled in the throttle cable) and it backfired internally. Not through the exhaust, it was a definate backfire just muffeled by being inside the engine. I then heard something "tinking" in the engine then it stopped as the engine kept ideling on. This happened with in a few seconds. Car still ideled well and boost didn't change. No knocking yet. It sounded like a piece of thin wire banging around in the engine. Then I drove a block and the knocking began.

 

At the very least, you'll likely need one housing and one rotor, and probably seals and springs. Since you have one ported engine, I'm assuming that the exhaust ports were ported also. Therefore, you'll need a rotor housing with an exhaust port to match. The intake ports should be fine, since they're all in the end plates on the 13B-REW.

Worst case scenario, you have something flopping around inside the engine and not only do you need a rotor and housing, but you'll need a new intermediate plate and rear plate, because of gouges or scarring, and something may have left the engine through one of the turbos (I'm voting for the rear rotor) and you'll need to replace the exhaust wheel. Hopefully there's no damage to the stationary gear(s), they're somewhat expensive too.

 

Well looks like I better get to work and do another tear down.