Timing Adjustments...Worth it?
 

Has anyone collected data on taking timing out of factory specs and adjusting for economy? I have read many of you have done it, but I might have missed any concrete results.

The only way to do it right is to get a piggyback ignition controller and tune it on a dyno. Thats a large chunk of coin to drop for the little increase your going to get in efficiency.

Coyote X has experimented with his ignition timing and I believe will tell you that advanced over stock is best.

Too much is bad though.

Also, I believe I've found that you may want to set ignition timing to match your driving style. EG medium to high-load P&G won't work with the timing advanced as far as it will work for target driving, or "driving with load" (DWL). P&G is more likely to cause pinging when loaded up.

I've recently backed down my timing to permit more load during pulses, but I'm still a few degrees ahead of stock.

Timing - The cam
 

Ignition timing can show a definite benefit. I've timed by ear since '82 with no detrimental effects yet. Advance until you get ping in your usual driving then retard 2 or 3 degrees. Runs smoother, 1 or 2 mpg better.

So what about the other timing, the cam? Has anyone advanced the cam timing to optimize power production in the low rpm regime? Should be worth a few MPG. I'm currently testing a 7* exhaust cam advance on the Kawasaki, much improved low and mid range due to decreased valve overlap and increased dynamic cylinder pressure. This is a DOHC motor so it's relatively easy to do. Once I run out the old gas from the winter there should be some good data to post.

Many of us have single cam motors and data on these would be helpful. CoyoteX did you experiment with cam timing? Results?

with stock cam timing i would bump ignition timing up about 2 degrees over stock. That seems to be the biggest gain. Not much else to be gained by going more usually. But like most car tuning it depends a lot on how you drive and how the engine is running.

On a stock cam Metro bumping the cam timing up 5-10 degrees advanced will get you up to ~5mpg if you adjust your driving style to match the lower shift points and don't drive fast. If you are a fast driver maybe 2-3 degrees advanced would show more gain since the top end will still have something left. The XFi cam is already pretty good so 2-3 degrees advanced is all it can really handle. The XFi cam at 4 degrees advanced can accelerate the car at 800rpm in 5th gear without a lot of effort. The car as nothing left over 3750 though.

A lot of this is mainly going to depend on driving style so there is no absolute answer. But in general advancing the cam to increase low end power so you can shift earlier and the torque peak is lower gains you mpg. The timing is really dependent on the car, gas, and driver/engine load.

Most cars are tuned from the factory on a steady state dyno so it is a pretty simple matter of making a perfect spark map that way. But the problem comes in when a car has to be sold in a lot of areas they have to cut some of the timing out so it is more tolerant of crappy gas. So in the case of an obd1 Metro the timing can be bumped up about 1-4 degrees depending on driving style without knocking and will get the timing much closer to ideal than stock timing will.

An actual vacuum gauge will give you a good indication of your cam/ignition timing changes. The smoother the needle without any vibration and the higher the vacuum the better.

http://www.amazon.com/Actron-CP7803-Vacuum-Pressure-Tester/dp/B0006V2BS2

This is the gauge I have mounted in my car and it is way better at detecting problems early than any other gauge you can buy. Everyone should have one stuck to their dash somewhere, they really are that handy to have :)

Coyote X,
Thanks for the detailed info...perhaps I can steal more of your insight...
Max speed that I drive is 65. Here in my part of Idaho, Reg gas is 85 octane due to the higher elevation. Is 65 too fast for the 5-10 degree cam timing that you are suggesting? The engine is running pretty good after cleaning out the EGR and replacing the plugged PCV valve, but is has a pretty rough idle after it is warmed up. Perhaps that is indication enough that I need to advance my ignition timing?