Alternative ignition timing methods?

[takza]

There are 2 different alternative methods that I know of...which probably end up with about the same result.

How to method 1:

* After the car is warmed up...find a road without traffic.

* Loosen the dist hold down bolt using a 12 mm box end wrench...but just enough to be able to turn the dist and still have it stay in one place.

* turning the dist clockwise...advances the ignition

* Accelerate in 5th gear at approx 2/3s throttle from around 1200 to maybe 1700 RPM...adjust the dist until you have only slight pinging. Retighten it.

* pinging sounds like "clicking" or "ticking" with this car?

** the middle 70's Corollas had a fine timing adjuster on the dist and instructions in the owners manaul as to how to do this...similar to the above method.


How to method 2:

* warm the car up

* using a vacuum gauge teed into the full manifold vac line that goes from the manifold to the HIC valve on the bottom of the air cleaner housing...adjust the dist to where you JUST approach the best vac reading you can find at idle. My car shows around 20" hg at idle.


CAUTIONS: You DON'T want to drive the car with it pinging to any extent. If it only lightly pings in the 1200-1700 RPM range...it won't likely ping at more typical RPMS...usually above 2000 RPM.

KNOW what a PING sounds like.

Advancing the timing can do 2 things...give you more power and maybe better mpg...AND cause your NOX output to increase...keeping you from passing an emissions test....and trashing the air you breathe.

And it might cause your car to run hotter.

So I'm not really recommending this.

[Mac]

really glad i happen to have a timing light...

but i think you can get a cheapo one nowdays for a reasonable price.

[Gasoline Fumes]

Timing lights are great for setting timing to the factory specs, but you might be able to get better results if you play around with the timing.
What I've always wanted to do, but was too lazy to do is:
Pick the RPM range you use the most, maybe 2k-4k? Then measure the time it takes to go through that range accelerating at WOT, trying different settings until you find the most power. Second gear would probably work well in these cars for the test. But I don't know how that will affect things like fuel economy.

[shogun]

i play it by ear, where the car feels best i set the timing to

[takza]

i play it by ear, where the car feels best i set the timing to

That's another method I've used with a car with auto trans...if you advance it too much...some cars won't ping or knock...but will run rougher and "fight" themselves...you can tell they are firing too early and losing power.

If you set the advance somewhere below this...you can feel smooth but still strong power...then you are close to the right area.

This is really *power testing* at higher RPMs and at close to WOT.

[keith]

Whether you use a timing light or do it by ear, all you are setting is the timing at idle. Using a timing light, or setting the initial timing my way, which is to turn the engine till the marks line up (5 BTDC in this case) and align the vanes with the ignitor,



you are setting the timing to what the engineers determined is the best place so that the vacuum and mechanical advances will have the timing at the right place under the loads the engine is most likely to encounter.

Setting the timing at idle based on fastest idle or some other criteria, could result in the timing not being the best when you are actually driving it. To insure that you are getting optimum timing, the first thing to do is ensure that the mechanical advance is working. Sometimes a little shot of WD40 or some other oil sprayed on the weights can make a huge difference in the cars performance. The weights do tend to "freeze" over time. Then check the vacuum advance by first checking the diaphragm for ability to hold a vacuum. Then check that the mechanical arm attached to the diaphragm moves freely and that it turns the plate its attached to.

When all advances are verified, then set to the factory specs. In older vehicles like ours, you may want to play with the timing by a few degrees (2-4) and then check fuel economy over a couple of weeks. If there is a long term improvement, ok. If not, split the difference with the factory specs and check again. Compare the results and pick the best setting.

[Mac]

i set it to 10BTDC at 800RPM then hooked the advance/retard back up. I think regardless of the technique, your still only going to be able to advance it enough so that it won't ping.
would running colder plugs prevent pinging? I run higher octane because Husky sells 90 octane for the same price as 87.


thanks for the heads up about the weights Keith, I'm going to look into that as soon as i can.

[keith]

would running colder plugs prevent pinging?

No. Pinging is when the the pressure front from the exploding fuel air mixture hits the piston before it can go down, causing a pressure spike in the combustion chamber.

The heat range has to do with the amount of heat the spark-plug retains while the engine is running. If it dissipates heat too fast, deposits will build up. If it doesn't dissipate heat fast enough, it will get too hot and burn or melt the tip. Sometimes you go to a colder plug if you do a lot of high speed driving because the average temperature of the combustion chamber, and the spark-plug will be higher.

[Mac]

well, my reasoning is if the tempatures in the combustion chamber are hotter (by advancing the ignition timing), the plug could turn into a "hot spot" and pre-ignite the fuel mixture before a spark arcs across the plug gap.

[keith]

I added a picture to my earlier post.

Mac, I believe pre-ignition due to a hot spot is dieseling. My understanding of the effect of timing and octane on pinging is that higher octane gas has a slower flame front so it doesn't prematurely "slap" the piston. The advanced timing builds greater cylinder pressure when the piston is in the power zone of the power stroke. The power zone is 30 degrees after TDC to 30 degrees BBDC. Compression is also a factor, higher compression increases the speed of the flame front so you need a higher octane to slow it down.

[joecell]

hi - the 84 toyota tercel 4wd is one of my favorite cars ever.

recently I've decided to try adjusting the timing, but this distributor looks dif than say a 84 oldsmobile or ford. that is, it's square, with all of the leads on one side. how do I go about setting the timing forward? is there still one bolt to undo, then twist?

thanks,
uncertain but hopeful

[Typrus]

Why hasn't anyone answered so simple a question...? Or did it get resolved in another thread?
Yes. One bolt to loosen, rotate the dist counter-clockwise (forward) to advance, vice-versa for retard.
Why it looks different is because it has an internal coil. Much like a Chevy HEI, only much smaller package and different layout.

[neonsport]

I've never had a timing light on my Tercel. With my first Terc wagon (back in 1993), I realized that the 3A engine is a pinging beast. I set the timing by sound, and by feel. I've owned over 125 cars, so I'm not really a novice. With every Tercel I've owned, nothing short of racing fuel would completely eliminate the pinging. With my current wagon, I switched to running premium fuel last year, and it did minimize the pinging. however, I started driving the car less conservatively, and it's showed in my fuel mileage. Not that I'm complaining; I was still getting 35mpg. However, I've now run a couple of consecutive tanks of regular through it, and I've adjusted my driving style to suit this. I take off less aggressively, and work less at maintaining my usual 80mph on the highway. I've been rewarded with approximately a 4mpg increase in fuel economy. This was not unexpected; I'd been pulling numbers like that before I took a job with a 62 mile one-way commute. However, with the current cost of gasoline, a 10%+ improvement in economy is nothing to ignore.