15 replies to this topic

[The Joker]

Hi there :)

I've been driving my mini for a while (about two months) With the engine pinking. When I first heard it I just assumed it was one the front spotlights rattling. But after research (due to my limited knowledge ) I realised it was pinking.

 

The engine seems to pink when accelerating and occasionally when I let go of the throttle/change gear.

 

I have just changed the dizzy cap and the timing seems to be very close (though it hasn't been properly configured with a strobe.etc). I have tried adjusting the dizzy cap but this doesn't seem to have affected the pinking much.

 

I also use Shell V Nitro+ Unleaded with a Millers VSP plus Lead Additive.

 

Just wondering how much damage has this potentially caused to the engine after 2+ months of pinking, and how can I stop it from pinking?

 

Thanks

 

Kapil

[KernowCooper]

Set the timing with a timing light to get it correct, and retest. excessive pinking under load all the time is not good but light pinking should not have done any lasting damage.

[carbon]

Is your engine and ignition standard or modified in any way?

 

If it still pinks once you have reset the timing then there are some other checks you can make :

- make sure cooling system is working well and not overheating

- are sparking plugs correct grade

- check mixture is not too rich or too lean

- if engine has done reasonable mileage then do a full decoke

[The Joker]

Thanks for the help! It seems to have stages where it pinks and doesn't pink at the moment but I will look into the spark plugs and the possibility of it needing a de-coke. The timing and the cooling system is fine :) The mixture is also set right :)

[carbon]

If you're running right at the limit (where it is just about to pink) then the weather can have an effect.

 

On (unsettled/wet/damp) days with low atmospheric pressure you should be less likely to see pinking than on days with high atmospheric pressure.

 

The swing can be from about 970mbar (low) to about 1030mbar (high) in the UK. It makes a measurable difference to the power output, which is why all good rolling roads will use a correction factor for atmospheric pressure on the day.

[Kt1966]

Use the higher rated (more expensive) petrol. I find that helps.

[carbon]

The Joker is already running Shell V Nitro+ Unleaded with a Millers VSP plus Lead Additive...

 

But he has not yet told us what CR his motor is running.

[The Joker]

Ah ok I see, It has been having mixed moments. I suppose the weather could have an effect on this as in cold mornings it does appear to pink more although this isn't always the case.

 

On some occasions it doesn't pink at all when then suddenly it does.

 

Sorry to sound stupid but what do you mean by CR? :)

[carbon]

CR = compression ratio

 

If you run with a high compression ratio in your engine then you can get pinking, poor petrol or wrong ignition timing can make this worse.

 

If it's really bad then you can get detonation which is to be avoided as this can result in very expensive engine rebuilds.

[The Joker]

Ah I see I'm not too sure what my compression ratio is at the moment. What ratio should I be looking for? :) And what would be considered bad?

[Cooperman]

If an engine is allowed to 'pink' it can cause the piston rings to snap and then the bores become scored leading to a re-bore & new pistons.

Pinking is caused by too much ignition advance at certain revs and/or poor quality fuel with an octane rating too low for the CR.

[The Joker]

Ah I see, I'll get the Compression Ratio checked soon then :) can this be checked with simply a compression test?

[Cooperman]

No, you have to remove the head and measure the volume of the combustion chambers, the volume of the piston dish and the distance the pistons are down the bore from block deck le4vel at TDC. Then you do the necessary calculations.

[69k1100]

Timing will be easier for a mechanic to test. If it's the compression ratio it's quite involved to change it.

[carbon]

Doing a compression test won't give you the exact CR of your engine, but it may still be worth carrying out if you have the kit.

 

Do the compression test once the engine has been thoroughly warmed up. If the readings are all over 215psi then you are getting to the point where you really need to take the head off and do full dish & chamber measurements as suggested by Cooperman.