Pesky detonation

BX Tech talk
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mnde
Meteor Man
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Pesky detonation

Post by mnde »

Worse with 95 octane, improved but still there with Shell V-Power.

Timing is set at 8 BTDC.

Do I need to retard even further or is there another cause? Like there is a blow in the downpipe somewhere.

I can get the car to pink under strong acceleration in 2nd gear. Even 1st sometimes......

Any advice welcome!

Mark.
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AndersDK
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Post by AndersDK »

There are several causes to pinking :

1) too far advanced timing
2) lean fuel mixture (air leaks on carb/manifold)
3) engine running too hot (air locks in cylinder head)
4) wrong octane rating (or crap fuel !)

The standard for all BX engines should be a static timing advance of 10 BTDC - vacuum advancing disconnected :!: - running on 97 octane fuel.
This should be modified to 8 BTDC running 95UNL.

Remember you can only check the timing using a stroposcopic light.
C U / Anders - '90red16riBreak - '91GrisDolment16meteor - Project'88red19trsBreak
dead cars : '89white 16RS - '89antrasitTRDturboEst - '90white19triBreak
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mnde
Meteor Man
Posts: 1453
Joined: Tue Oct 18, 2005 5:10 pm
Location: Aldershot, Hants
My Cars: 2007 Citroen Xsara Picasso 1.6 16V VTX
1982 Citroen GSA Spécial Estate - gone to a new home
1991 Citroen BX16 TGS Meteor - still out there somewhere!

Post by mnde »

I should have added that I have already carried out a stroboscopic timing check, yes with vacuum advance disconnected - I have read the instructions in Haynes etc. - it was around 10-12 BTDC, I set it to 8 BTDC. Yet it still pinks with 95UL and doesn't disappear 100% even when using Shell V-Power, which I believe to be 98-99 octane.

Re. lean fuel mixture, I guess I'll have to get out the WD40 and spray all around the carb joints with the engine running - not sure what I can do to test the manifold. I have a Gunsons Colortune, but the standard size is to fit 14mm sparkplug sockets - so I have to buy a separate adaptor before I can use it on my BX :x

Mark.
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