performance effects of advancing ignition timing

Just curious. What exactly are the performance effects of advancing the ignition timing? I always set it to 5-6 degrees BTDC when I have to take the car for a smog check but thereafter reset to 8-10 BTDC (just because I once read the slight advance is good). Not sure if I've really noticed any difference in mileage and power, although I have noticed increased knocking in hot weather when climbing steep grades with the 8-10 degreee advance.

What would you Metro folks advise as the optimum timing and what performance effects should one expect at that timing?

Mike
95 Metro 3 cyl, 5sp, 93,000 miles, 47 mpg and running like a top

If you advance the timing on the car, you increase combustion chamber temperature, and can melt a plug. That knocking and pinging is not good at all for the car, and you may create more headaces than you want. It may hurt the engine internally, resulting in a teardown and repair. Go with a better flowing exhaust, better intake filter, install a light-weight flywheel and an underdrive pulley set. Although these may add up to a few bucks, they won't cost half as much as an engine overhaul.

Typically, I retard the timing in hot weather just a bit. It doesn't knock under normal conditions -- only when I am advancing up a steep hill in 2nd gear. And that's only for a few seconds.

As an aside, when last I changed the plugs (about 100 miles ago after a 20K interval), they were in tip-top condition. No glazing or oily deposits or anything. I probably could've reused them but, for the price of three new plugs, why bother?

But, again, my main question is: what are the performance-enhancing effects of advancing the timing? Better mileage? Improved power? Decreased emissions? Anything else?

Thanks!
Mike

I just advanced the timing on my 99 nissan. I was a littly wary of it at first but I got some excellent advice here on the forums and did it. I advanced about 6-7 degrees above the base stock setting of 20. I noticed a slight increase in performance. I don't know about the effects on mileage yet because I havn't used a full tank yet. I'm going on a 500 mile trip this weekend so I'll let you know how it is when I get back. One more thing: are you running premium fuel when you do the 8-10 degree advance?

No. I always use 87 octane gas. So far, no problems.

(Knock on wood.)

Mike

Advancing timing basically means that your spark plug will fire earlier before TDC. What this essentially means is that it allows combustion to happen a little earlier BTDC than normal. This will give the combustion more time create the pressure from the explosion so when its going down on the powerstroke, it tends to 'hit' harder. This will be more noticable in lower to mid rpm ranges. However; it will hurt high rpm. This is mainly since the pistons are traveling faster they don't need that extra time to create the combustion pressure. Too advanced timming will cause pinging and pumping loses high up the powerband. Retarded timming will do the opposite, helping more on higher rpm and less on lower. Of coarse as far as performance goes, its always best to have the timing as far advanced as possible, but not to the point where it starts to ping (and thats when you know its too far).

Engines are already designed to change timming accordingly to a point, so whenever you do decide to advance a little or retard a little you should consider how its going to effect the engine.

The short answer is that anything advanced past optimal will hurt power and emissions. The question is, where's optimal? On a stock car with stock ignition, typically the stock setting is spot on or close to it.

Advancing more than 1-2 degrees from stock will probably not help power production at all and may reduce it significantly, as well as put stress on engine internals from that knock.

I agree with you curtis in that there is an optimal setting, but I'd like to add something. That optimal setting depends on the octane level of the fuel used. In most non performance cars 87 octane fuel is used because the stock timing setting is optimized for this fuel. Any more advance will cause knocking and pinging. The higher octane fuel you use the more advance you can run and not have detonation. The base timing in my 99 nissan altima was set at 20 degrees BTDC. I switched to 93 octane fuel and advanced the base timing to 26 degrees BTDC and have had no loss of power, knocking or pinging.

Very true, however given the internal parameters of an engine like compression ratio, cam, and flow characteristics, it won't add any power either. I was able to get about 5 more hp from my LT1 by leaning the WOT mixture, advancing timing and thereby requiring higher octane fuel, but that's not a rule.

You're right, it can help, but usually doesn't help enough to make it worth the 93 octane :)

It's good to know that there are folks out there that do stuff like this. I've paid for 3 homes by fixing cars that have been "tinkered" with. Yeah, go ahead with the advancing thing...yeah...that.....and rev it up too. By the way, if you drain out all the coolant, oil, gas and trans fluid, the car will be lighter and you'll get better gas mileage too, what the heck, take out the seats, rugs, windows, spare tire and stereo. man what weight savings, it'll be a screamer by the time you get done. And what about that big metal thing under the hood? all it does is suck gas and make noise. If that gets taken out the car will be really light and won't use any gas. WOW. Don't mess with the timing.