I hear some noises sometimes at higher rpms in 4th gear...sorta tiny rattle, almost like rain falling on a tin roof is that like DETONATION or PINGING? Is there such a thing as MILD DETONATION and SEVERE DETONATION?

 

Pinging is detonation. Any detonation on a rotary is severe

 

Severe isnt the right word. Any pinging is dangerous. Minor pinging wont kill the engine as quick, but all it takes is one severe ping, and your engines toast.

 

I don't like creating extra work for myself. I'd rather not build an engine unless I have to. I ***** around with the timing and boost till I'm sure its right

 

how exactly do u know youre detonating? you can physically hear it?

 

It, on my engine, before it blew, sounded almost like a heat shield rattling...

 

ok, cool. thanks, ill know what to look out for. and so what causes pinging and detonation then? low A/F ratio, right? what else? bad tank of gas? ignition timing off, what else?

 

Im not 100% sure. My A/F was fine according to the gauge....I think mine just blew because of a spike due to the S4 manifold

 

a spike? like a boost spike? my friends 3rd gen died for the same reason. what exactly is a boost spike?

 

Where you boost just shoots up too high. I think mine hit 15 psi... Its a big problem with the 87-88 wastegates and/or manifolds. One of the main reasons im putting a 89-91 motor in this time...

 

how do i prevent that from happening? i cant afford another engine right now...

 

The best way to prevent this is to get a 89-91 turbo and manifold, or port the wastegate on your S4 manifold.

 

When you have your foot to the floor, its always gonna read rich... Thats why you need an EGT gauge to watch too

 

I remember a post with a video clip of someone intentionally blowing their engine.
It sounds like chattering.

 

Pinging or detonation is properly called "pre-ignition". That is a very accurate description and explains why it's so dangerous. It means that the air-fuel charge is igniting during the compression phase or "stroke". So the chamber is decreasing in size causing compression AND it is filled with a rapidly expanding gas because the air-fuel charge has ignited prematurely. It can be caused by many things; timing advanced too much, a ridge in the chamber that gets too hot, overboost, etc. In piston engines it breaks rings, punches holes in the top of pistons (burning a piston), breaks the crank, etc. In the rotary it brakes apex seals. Think about the force to blow a hole in a piston and then think about that poor little seal.

 

I beg to differ on Pre Ignition and detonation being the same.

Pre Ignition is the uncontrolled firing of the fuel air charge in advance of normal ignition. Pre ignition can happen when there is a hot spot in the engine (Burning carbon ignites the fuel air mixture instead of the spark plug) or a crack insulator on the spark plug can get hot and get a hot spot.

Detonation occurs at a high power setting when the unburned fuel mixture charge in the rotor housing is subjected to instantaneous combustion. Instead of buring progressively and evenly.

These two can occur together or one could bring on the other.

This is out of my Commercial book for aviation.

James