detonation pre-ignition (pinging) noise

[Europa73]

Hi all,

Not sure if the hot weather has anything to do with it - but -

I have allot of detonation pre-ignition (pinging) noise when using over half throttle in gears 3 through 5.

I have put in a octane booster and checked the timing.

Timing is bang on manual specification.

Any ideas out there on how I can eliminate this?

Many thanks,

[BDA]

 What compression ratio are you running? Did you check your timing at elevated rpm eg. 5000 or 6000? Could you be running lean? What do your spark plugs look like? Does it happen on acceleration or does it also happen when cruising?

[jbcollier]

Yep, need more information.

Describe the engine state of tune.  Stock?  Or?

Fresh engine?

Using a timing light, check the timing at idle, 2K, 3K, 4K, 5K, 6K and report the results.

[EuropaTC]

Hi there,
The only time I can recall getting "pinking" was when I'd carefully adjusted the timing so it was too advanced, so I'm of limited use here. 

I'm guessing (with no real justification) from your comment about half throttle & 3rd gear upwards that this isn't happening at high revs but low/mid range when the engine comes under load ? 

As my case was down to timing and you've checked yours, I think I'd look at the plug condition and plug grade you've got in as first & easiest option, followed by checking to see if  the distributor advance is sticking. You might pick that up with a timing light and running up and down the rev ranges - check at say 4-5k first and see if it drops back as the revs drop, but personally I think I'd just pull the distributor out and make sure the springs/weights are free to move. (That's making another assumption that you're on a TC engine with Europa73 as your nickname ?)

The other normal cause is fuel but if you've added octane booster and it's no better then I'd rule that out of the first check list.

Brian

afterthought - how hot is the engine running ? with the "hot weather" comment, is it running hotter than normal ?

[Gmg31]

I had this for a while when I finished my restoration.  Eventually after much trial an error I found the right fuel and my car’s performance improved dramatically. No more pinging faster smoother and more efficient. I’m going to post a thread at the end of the month  with data but my conclusion is simple.  Tesco momentum 99 Ron. 

[Pfreen]

My question is when did this begin?  My tcs with SU carbs and 10.25:1 compression ratio never pings and I run 37degrees max advance and 17 degrees idle advance.  I run 91 or 93 octane unleaded.  Whatever I can get.

A lot of combustion chamber deposits can cause this.  I have seen burnt valves cause the symptoms of pinging.  Lean a/f ratio can cause pinging.  And of course, overly advanced timing.

[E Paul]

too much timing. you checked that at idle, but if it comes in too fast...detonation.
too lean. Check your plug color if you don't have an O2 sensor.
Too hot. Normal temps?
Recently change plugs? Heat range?
Hot spot in combustion chamber...usually a plug with a too sharp, uncooled spot.
How old is the gas? If there is any ethanol separation, it absolutely kills the octane. If its old, drain some into a clear jar and look for any separation or milky color.
More description of engine would help. Change your plugs to one of the recommended ones. If still happening, read your plugs...there are many articles online on how to do this. Report back.

[Europa73]

hi all,

Many thanks for the information.

As always very much appreciated.

I will have more information on timing, plugs etc tomorrow.

Cheers,

[Clifton]

Timing at idle and timing when it's knocking are different. For example, 40 degrees at light load cruise would work but a light load would cause knock. I would pull 3 degrees and drive again. If you have a timing light with a knob you can check your full advance with all the mechanical in.