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Ignition knocking
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DotMatrix
Posted 6/6/2016 12:18 AM (#722193)
Subject: Ignition knocking


Expert

Posts: 4458
200020001001001001002525
Location: Jelling, Denmark		I think i have ignition knocking after my latest engine mishap an the nessecary head skim. Does any of you know a octane booster that actually work?

Edited by DotMatrix 6/6/2016 12:33 AM
Marv_666
Posted 6/6/2016 12:23 AM (#722194 - in reply to #722193)
Subject: RE: Valve knocking


'88 MG METRO 1300

Posts: 1117
1000100
Location: Dudley, Midlands		What are you running now and what is available in Denmark?

I run a 50/50 mix of 95RON and 99RON.

Can find 98RON at most places here.
DotMatrix
Posted 6/6/2016 12:33 AM (#722195 - in reply to #722193)
Subject: RE: Ignition knocking


Expert

Posts: 4458
200020001001001001002525
Location: Jelling, Denmark		I only use Shell vpower 99ron
Marv_666
Posted 6/6/2016 12:47 AM (#722196 - in reply to #722193)
Subject: RE: Ignition knocking


'88 MG METRO 1300

Posts: 1117
1000100
Location: Dudley, Midlands		Shouldn't have a problem unless running massive compression then.

Ignition timing perhaps?
Mine needed a tweak despite nothing moving or being disturbed.

Did they use the fuel in the tank or their own supply when it was last on a RR?
DotMatrix
Posted 6/6/2016 7:22 AM (#722197 - in reply to #722193)
Subject: RE: Ignition knocking


Expert

Posts: 4458
200020001001001001002525
Location: Jelling, Denmark		I am running a very high compression yes. I think that the latest block and head skim might have put it "over the top".

They just used the fuel in the tank.

Ignition is set where it makes the most power but might have to move it to make the knocking go away
DotMatrix
Posted 10/6/2016 9:23 PM (#722208 - in reply to #722193)
Subject: RE: Ignition knocking


Expert

Posts: 4458
200020001001001001002525
Location: Jelling, Denmark		when I changed the petrol which was v-power 99 half from august and half new for some new petrol also v-power 99 but with added octane booster (toluene based). this made the knocking go mostly away.

I then regapped the spark plugs from 0.8mm to 0.6mm which seems to have made it go totally away. I wonder why and how this made a difference
munday
Posted 13/6/2016 6:51 AM (#722222 - in reply to #722208)
Subject: RE: Ignition knocking


Expert

Posts: 5629
500050010025
Location: Letchworth/Basildon
DotMatrix - 10/6/2016 9:23 PM

when I changed the petrol which was v-power 99 half from august and half new for some new petrol also v-power 99 but with added octane booster (toluene based). this made the knocking go mostly away.

I then regapped the spark plugs from 0.8mm to 0.6mm which seems to have made it go totally away. I wonder why and how this made a difference


Regapping the spark plugs shouldn't have made any difference to the level of knocking, the only thing that may have happened is slightly slowing/delaying the initiation of combustion, effectively shifting the combustion phasing to later in the cycle, however this would only be by a few degrees crank angle at most (not the same as retarding the actual ignition timing).

The fuel part of it I'm sure you already know all about, with the volatile compounds that make up the higher octane flashing off over time and reducing the octane content.

Glad you got it sorted!
munday
Posted 13/6/2016 6:52 AM (#722223 - in reply to #722208)
Subject: RE: Ignition knocking


Expert

Posts: 5629
500050010025
Location: Letchworth/Basildon
DotMatrix - 10/6/2016 9:23 PM

when I changed the petrol which was v-power 99 half from august and half new for some new petrol also v-power 99 but with added octane booster (toluene based). this made the knocking go mostly away.

I then regapped the spark plugs from 0.8mm to 0.6mm which seems to have made it go totally away. I wonder why and how this made a difference


Regapping the spark plugs shouldn't have made any difference to the level of knocking, the only thing that may have happened is slightly slowing/delaying the initiation of combustion, effectively shifting the combustion phasing to later in the cycle, however this would only be by a few degrees crank angle at most (not the same as retarding the actual ignition timing).

The fuel part of it I'm sure you already know all about, with the volatile compounds that make up the higher octane flashing off over time and reducing the octane content.

Glad you got it sorted!
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