I know metrompg has an advanced timing sprocket on his car. I would assume this would help with mpg/power, but you would need to get higher octane gas (or water injection). Is there any problems you can run into by running a moderate timing increase?
This is a pain to do with a dohc saturn anyways so I won't do it on my current car. Maybee my next one...
2008 EPA adjusted:
Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
actually, i'm just running advanced base ignition timing. i don't have an advanced sprocket.
(the sprocket i think you're referring to actually adjusts the cam (valve) timing, which is a whole other kettle of fish compared to ignition (spark) timing.)
if you're REEEEAAAALY careful and you know what pinging sounds like in your car, you can adjust your timing "by ear" experimentally.
twist the distributor forward (advance "against" normal rotor rotation) a little, then go for a drive. if you don't hear pinging, advance it a tiny bit more. do another drive. rinse & repeat. rinse & repeat. as soon as you hear pinging (under load, usually when accelerating or climbing a hill), you know you've gone too far and need to back off the timing a notch.
you need to test "hard" acceleration. because you can set the timing so it won't ping when you drive conservatively, 95% of the time, but it won't be good enough for the 5% of the time you stick your foot in it (e.g. merging on the freeway) or going up that particularly steep hill in your neighbourhood. in which case it will "unexpectedly" ping like crazy.
(and don't hold me responsible if you wreck your engine with this technique because you didn't really know what pinging is...)
that's how i've done it in my past few cars, ever since my timing light died and i never replaced it.
and i always start by physically marking the "stock" timing position on the distributor/collar (i score a line with something sharp) so i can return to stock timing without a timing light, if i want to.
i advanced my ignition timing over stock because i *assumed* it would help mpg. my assumption was "the most advanced timing prior to getting knocking/pinging = best MPG".
but maybe it's not true. maybe it's possible to advance past best efficiency, but still not hear detonation....
Perfect example. Rutger's SAE car. We used a Kaw Ninja engine, pretty much stock except for a [fancy] injection and intake manifold system. We used the Electromotive engine management system which also does direct ignition and has programmable timing. The specified fuel was turbo-blue which has an octane rating of something like 115. Obviously an engine designed to run on pump gas is not going to take advantage of that octane. During a dyno run I experimented with timing from the keyboard of the laptop. Torque continued increasing as I jacked the timing up until I reached *55* degrees BTDC! It slacked slightly after that and the radiator temperature rose notably. Incandescent headers were also
Think about this for a moment. More than 1/4 of the compression stroke is spent compressing a burning mix! Narry a knock was heard in this process. - source
it's one of those things i've been doing without thinking very much about it, and i certainly haven't tried testing it with the scangauge. (and it would be an easy enough test to try... in the spring)
One of the things I noticed on the Geo was more throttle and torque at low end with the timing cranked up and using Hess gas reduced the knock. That dyno test at 55 degrees btdc was with some really high octane gas - high octane burns slower so you need more advance to get it to burn before it gets dumped out the exhost. Again this is for power - for fuel economy lighter engine loads require more timing advance to ignite the gas mixture before too much compression occurs making it harder to ignite the mixture. If you have a bigger spark gap it can help also but only if you have the voltage to make the spark jump the gap. In the rambler I indexed the plugs, ran a CDI (Capacitive Discharge Ignition) and solid clear plastic wires and when the gap got too big I would get 2 inch sparks from the plug boot to the engine head. Ran a 0.065" gap in the plug. One thing on the Geo was too much advance / not enough octane in the hot summer months I would be on the highway going 60-65 and if I gave just a little gas to accellerate it would be knocking just a little but constantly and that is not good for the engine at all - the exhost was making enough noise that I could barely notice it knocking - better to be a little retarded at that point. Newer cars have a lot of advance controlled by computer and knock sensors that adjust timing automatically. ScanGauge lets you select it and watch it as you drive - try to keep it advanced as much as possible.
Being mechanically challanged and trying to learn.
How much advanced ignition timing(assuming you can change the timing) is to much for the best FE? Do you want to just take it till the engine pings, for your highest load you encounter, and then back off a couple of degrees or is there an area between base and ping that works better for FE? Has anyone played with this or have links to look at? Also I guess the higher the octane the more advance timing you can run but is it cost effective and will the increase increase FE? Thoughts.