SFCK problem found, not rectified yet.

Just to recap:
Change to B9ES and use 98 octane fuel.
Check if noise still there.
Quick and cheap way to test before ripping tings down or altering ignition timing.

You could also spray some Start ya bastard around the inlet stub joints when the engine is running to check for leaks.
 
Red's comments about wash patterns suggests that pressure waves might be triggering localised precombustion areas. At 3,000 rpm the piston speed should exceed the flame front speed and it is all down to turbulence to propagate. That is why ignition advance stops around here, turbulence takes over.

That is why I would try cooler plug and/or slightly richer. This makes mixture less sensitive.

Some Keihin carbs for big singles have a vacuum operated enrichment valve for when high speed coasting, or on overrun, to stop the exhaust popping due to initial leaned-up mixture when the throttle is backed off.

Or you could try some smart ecu combination of injection and ignition if you have a spare lifetime to tinker about.
 
Chris I think if there was evidence of detonation on the pistons Red would have seen it.  I'd be interested to see what you are looking at with the bore scope can you send me the images.

Yep remember you mentioning a noise, also remember it was brutally hot and me commenting about you not using 98, and notunderstanding why anyone with a hi compression engine would not want to be running the best octane they can get. But what would I know as i'm only a mechanic  :-X

I would be guided by Red, put some B9ES, use 98 always where available, fatten up down low - mid range.

A lot of what folk call detonation is actually more likely pre ignition as detonation is commonly referred to as the silent killer.


I've told you who the Dyno guys is in Penrith before but will send to you again.


 
Brett said:
A lot of what folk call detonation is actually more likely pre ignition as detonation is commonly referred to as the silent killer.
Click to expand...

You have that arse about Brett.  Or should I call you Brad now?  :D

Detonation makes the pinging noise, so it's not silent. Pre-ignition doesn't usually make a noise (at least as long as the engine holds together) so that's the one that's called the silent killer.

Excellent video BTW. Explains the difference nicely.
 
Brett said:
A lot of what folk call detonation is actually more likely pre ignition as detonation is commonly referred to as the silent killer.
Click to expand...


So Knocking and Pinking is/are the same thing..?
 
Top Video Brett, was able to get my wife to translate, very informative and now Choedon has a better understanding of pri detonation than I do.
Sensational :) :)
Tom
 
Detonation, pre-detonation, pre-ignition... different terms for basically the same phenomenon.  Knock, ping, pink, again, different terms for the same thing, all depends on where you are and how willing somebody is to split hairs. :D  Recognising what's actually going on and why it is happening is the difficult bit.

Reckon the general concensus is that both are potentially dangerous/expensive and should be investigated and corrected as quickly as possible.  The causes for both are closely related and often linked.

piet
 
You must log in or register to reply here.
Back
Top