Ignition Timing

A couple of weeks back, the X was experiencing really bad vibrations in traffic jams. I stopped by the Sungai Pinang SC and they diagnosed it to a dirty throttle body. How? The foreman said he couldn't get the a reading and can't update the computer diagnostic tool.

I had it cleaned and that cost me RM80. He also reset my ignition timing back to 16 BTDC.

Now this is the interesting part. So far I've done about 3-4 tanks with the new ignition timing.

On highways, with 16BTDC I'm getting back the high 11.x km/liters in fuel economy.

However the funny part was, mileage driving in town (Penang) has dropped back to below 7km/liters. What is going on?

Before this with 18BTDC highway mileage is between 10-11km/liters and town driving hovers 7-9km/liters.

I don't have conclusive data yet since this is only the 2nd tank of fuel driving in town.

From my reading, N16 users did say advancing the ignition timing did save fuel.

At the moment, I have the following conclusion for tweaking the ignition timing.

Increasing the ignition timing saves fuel when you do more stop-go type of driving involving 0-2500rpm. The increase in ignition timing brings forward the power curve and torque curve. I still can't explain why it uses more fuel cruising at 2800-3000rpm. Maybe more power = more fuel could be use here.

I'll be heading back to reset the ignition timing back to 18BTDC after a few more tanks of fuel.