Pinking under boost with just 9 degrees of advance

[bertelli_1]

I have been running my mk2 Golf on 99RON fuel since the engine conversion but now fuel costs a small fortune I have switched to 95RON. Ignition advance is 9 deg around 3000 rpm at 180kpa, above and below this area I can run a lot more ignition - its like I have a 'hole' in my map in this area. The car runs fine with this amount of advance (although I'm going to have to take more ignition out to cope with 95). I have been considering swapping to a colder spark plug but even the high output versions of my engine (VAG 1.8T) use the same heat range. I have verified my base timing.
So do I just run with such a small amount of ignition, try colder plugs or something else entirely?

[stevieturbo]

What compression ratio ? Are you intercooled ? what are the charge temps like ?

Lots of things can affect pinking or detonation.

Simple answer is...if its doing it, change whatever you have to, to make it stop doing it.

[bertelli_1]

Comp ratio is 9.5:1, it is intercooled, my manifold temperature is generally around 10-25 deg c above ambient (not excessive) although I am working on a cold air feed.

[Boosted LS1]

Reading your plugs will tell you if they're in the correct heat range but I suspect something else is wrong. Your problem is at peak torque? Are you sure about the advance at that load site and the fuelling is?

[bertelli_1]

I am confident my base timing is fine - and I'm assuming the ecu is adjusting the spark timing correctly! AFR is around 11.8 - 12.1 in that area of the map.

[eliot]

what plugs are you running ant? - are they projected or retracted tips, and have you tried going up one step colder?

[bertelli_1]

E - I'm running BKUR6ET - the standard plug for the engine. The high output versions (225bhp) use a PFR6Q. I haven't tried going colder but may give it a go (PFR7Q are available). Not sure what tips they are, ngk list as a 19mm reach.

[eliot]

yes, somewhat different construction to my old skool plugs.
I had a little tinkling on mine the way back for your work the other week chasing matt in the trev and that was on vpower also.

[stevieturbo]

You could try a 7 heat range... It probably isnt needed at all, but wont do any harm.

[ringram]

What about engine temps? Can you run it at say 80*C. Normal engines seem to be around 98*C
That might also help.

There is a couple of good articles here on running high combustion pressures.

http://www.popularhotrodding.com/enginemasters/art...

http://www.popularhotrodding.com/tech/0605phr_pump...

Sainsbury's also sell 97 octane not much more than the 95 stuff. I know 99 is way expensive. Perhaps you should try something in the middle to help as well.
Made a big difference for me, I was running 11.2:1 NA.