EA82 detonating on take-off

[subalex]

As in the title, my L-series' standard EA82 ticks away, detonating on take-off thanks to the 27" tyres I'm running and of course it's worse when a) it's a hot day OR b) I've got the air-con on OR c) I've got a boot load of camping gear and three kids with me OR d) any combination of the aforementioned.

Any solutions to this other than an EJ swap? I've got an upgraded coil, I regularly replace the spark plugs (BP6ES's with the standard gap) and oil changed regularly too. I've installed a hefty battery for better current draw when running lights etc. It's manual and I try getting around this by slipping the clutch but of course this makes the clutch unhappy over time.

I wonder if it's possible that the idler pulley and other pulleys could draw too much power froma standing start?

Whaddyathink?

Alex

[littlewhiteute]

Alex, what fuel are you using and what ignition timing is the motor running?

[subalex]

I've always run standard unleaded and in the last year or so I've been adding upper cylinder treatment in every tank. I've found that it helps keep the engine running cleaner, reduces it's desire to ping, doesn't clog the spark plugs between changes and it runs a little more powerfully across the rev range.

I've also dabbled with the timing and after seeing lots of people suggesting running it at more like -10 I've always found it too keen to ping even more so I've left it at 8 bttc or 9 when running this upper cylinder treatment.

I know that I could pull the plugs out and try widening the gap a little - can't remember the recommended setting - now that I've got the GT40R coil in there but I haven't done it yet.

[littlewhiteute]

Ok, sounds ok so far, just get some Subaru upper engine cleaner.
I run the middle fuel or the 98 if it's not too expensive on the day.
I have found recently that if the ported spark is the only hose going to the dizzy then it will retard faster under load rather than the "tee'd" venturi signal added to ported spark, if that makes sense.

[subalex]

Hmm, you might be onto something there. The vacuum adjusted dizzy may well be advancing the spark too soon when the vaccuum is high - when pulling away from a standing start. I had wondered about that but hadn't delved into the solutions since I thought that would not be adjustable. More adjustable is the fuel mixture, which I have adjusted many times via the screw at the base of the carby.

Aside from that, I've also noted that when the engine is cold, and the mixture is rich, I've not had the same trouble. It's only once the engine is warmed up that it pings under load. I've tried increasing the mixture and idle speed but I don't think that's really made an ounce of difference since it's really adjusting other things and not the mixture under load but the mixture at idle and all other driving times. I'm keen to get it working to it's most efficient setting of course as well.

As for the Tee'd port that you're speaking of... I think I know what you mean... you're talking about the vaccuum hose that connects to the dizzy for the purpose of retarding it... I'll have a look see. I'm thinking like you that if I actually have less vaccuum then it won't retard the spark so much.

[Morcs]

Run 95 octane Rated fuel it will stop the pinging and it will have better fuel consuption per kilometer. Price differance is is more then compensated by the more kilometers out of a tank.

[El_Freddo]

I have found recently that if the ported spark is the only hose going to the dizzy then it will retard faster under load rather than the "tee'd" venturi signal added to ported spark, if that makes sense.

Could you please explain this further?

I have a brumby that pings under load at high speed, namely up small to large hills - am yet to check spark plug condition and timing. It runs great at all other times.

I have heard about running the slightly higher octaine fuel - premium unleaded, not the optimax or ultimate. At 6c a litre more its out of our reach with the current fuel prices

Cheers

Bennie