Hi.

Well,this might seem like a simple question:

What does detonation/pinging/knock sound like?

I have heard the sound on a boinger before,but never on a Rotary.

Thanks

 

Helo?
Anyone?

Come on,its not a difficult question!

 

....'boom'?

 

Hahaha!
I`am running a NA.I think the timing is too advanced,but i dont know what to listen for.

(I live in neighbourhood where i cant rev it past 4000 to set total timing.It way too loud)

 

Kinda like popcorn poping, or like someone is hitting the exhaust manifold with a little hammer.

 

Metalic sound, makes me cringe

 

Thanks!Now i know what to listen for,when doing my timing.

Karis

 

yipes, no, check the manual, NEVER attempt to get detonation, this can be very very bad for your engine

 

No-no-no-no!
What i meant was:Now i know,when to retard the timing!If/when i hear the mentioned sound,i will retard the timing.So that i dont get detonation.

:-)

 

I woud say its kind of a weird sound. The first time I heard it I thought the exaust shield was loose, Its a Klinging sound. I dont think itll blow your engine real quick but its not a good thing

 

Rotaries should NEVER ping! Serves no purpose. Don't time your car that way.

B

 

He doesn't want to make it "ping". He just wants to know what pinging sounds like so he doesn't set the timing where is pings.

 

Hmm you should just stick to the manual procedure to set the timing, rather than waiting for ping and then adjusting it. My $0.02

 

Use a timing light.

 

Check T1 and T2 wires. peejay and I have had them accidentally reversed and you can't get on it because it will detonate like a boinger.

 

In the old days, HotRod tuners would advance the timing on a boinger until it rapped too much even for them, then back it off a tad. The common belief then was that resulted in the best timing, which was not supported by dyno tests.

B

 

There is one boinger out there that actually thrives on detonation. It's called the Bourke engine. Do a google search if you're interested.

 

This is long winded, but I like to write.

Popular opinion is that detonation is damaging to the engine. To some degree, this isn't true.

Combustion doesn't happen all at once, There's a combustion flame front that moves through the combustion chamber. Before the front is the air/fuel mixture, behind it is combusted products.

As the flame front moves through the chamber, the pressure in the chamber increases. This pressure can increase to the point that the air/fuel mixture will ignite somewhere away from the combustion event.

At this point, there are two combustion events going on with flame fronts moving toward each other (and away from each other). When the two fronts meet, there's a bang. This is the most common cause for pinging. This is typically non-destructive.

I say typically because there can be times, especially in a turbocharged car, that the pressure can grow fast enough with two or more combustion fronts that it can cause damage to the engine. In general though, most engines aren't as sensitive to the faster pressure build-up.

 

Some good answers!
Well,just for reference :My 12A is BP,(as per my sig)so i`am currently working off the dizzy advance chart,seeing that it doesnt idle below 1500 at all.

I retarded it alott last night.Right down to 0 BTDC(so its right on TDC)Went for a test drive.It was revving very slow.So today,i`ll advance it more,trying 20 BTDC total advance.
The difficult part:I have 70`s Rotorhousings,and `82 Rotors,so the timing cant really be set to a spec.Why? ?Because the plugs sit at a different location than in the 80`s rotor housing.

Karis
Ps: Sorry about the long post

 

Karis, I'm going to have that problem when I build my '73 12A with '83-'85 rotors. Any suggestions for where I should set my timing. It's only got big street ports.

 

sound like gravel in your engine