advancing timing

[nabstud]

My work car (05 Mazda Bravo 2.6) has had a gas conversion. I use Premium unleaded when I run on Petrol. I often do country runs so it has to run well on both petrol and gas.

I advanced the timing a bit so it went better on gas and gave a bit better economy. The way I set it was I advanced the timing a bit, went for a test drive to see if it pinged, adjusted it again, went for a test drive again and so on until it didn't ping at all. Then I retarded it just a bit just to be sure. This was done while driving on petrol.

I recently got the gas tuned and the guy set the timing back to standard timing. He said if it was too far advanced I would bugger up the motor (bugger the pistons etc). The car now feels noticeably more sluggish.

The question I have is will advancing the timing cause any damage, provided it isn't pinging? Is there any reason I shouldn't advance the timing again as I did before?

[91Mav]

My understanding is that optimal ignition timing with LPG should be more advanced than petrol at idle but more retarded than petrol at higher revs. The problem is getting an ignition curve that will suit both fuels but be best for neither. Jaycar sell a kit where u can map two different ignition curves and switch between them both to suit what fuel you're using. The whole kit, including knock sensor and hand controller was around $220 a couple of years ago when I had my old 40. Maybe something to look into.

[skootin]

Pinging - Detonation will cause broken rings and damaged big end bearings in the long term or short term if excessively bad if not corrected.
If you can set the static timing at 10-12 it should be fine. Or advance it slowly with the engine running till you hear the revs pick up a little.

[chimpboy]

The only damage is from pinging so if you are condfident you avoided that then no probs. As 91Mav says you can get an electronic unit to give two different timings, in effect it would delay the spark slightly when running on petrol.

[drr]

91 Mav is spot on. Gas doesn't like lots of advance up high but needs more down low in the revs to perform optimally. Need to remap the ignition timing to do anything about it though. I don't think it's really worth the rooting around.

[nabstud]

Cheers guys, just the info I was after. I advanced it a bit and it is going much better. I am now confident it will be good.