055 | Optimising ignition timing / MBT timing - Haltech

Thanks for the webinar.

It would have been (more?) interesting if the A/F, EGT, TPS%, and Manifold pressure was shown (and logged) as the spark sweep was preformed.

A few questions: 1) How was the engine/throttle held at -60Kpa for the run (manually or throttle servo? (2) Was the engine in open loop or closed loop (3) Was the A/F being read at the tailpipe? (4) Assuming EGT changed as the spark was advanced, did the EGT have any impact on the WB AF?

Based on what I have read on exhaust scavenging (http://www.formula1-dictionary.net/exhaust_road_perf.html), it would be hard to imagine that the spark sweep didn't have any impact on the engine's breathing (thus why it would interesting to see the A/F/MAP during the sweep). Can you help us understand this. Perhaps these questions can (also) be addressed in a subsequent webinar and maybe of interest to the "enthusiast" tuner

Since we are mapping the ignition with manifold pressure on the load axis, the aim is to stay in the middle of a specific zone when going through the torque optimisation process. I'm doing this manually on the throttle. At a fixed throttle the MAP will fluctuate slightly as you sweep through the timing but realistically not enough to warrant any real attention.

The AFR is being measured via a wideband lambda sensor in the exhaust system at the collector and the engine is running open loop fuel control.

Here's a common misconception - AFR will be affected by ignition timing. This isn't actually the case though so let's look at why. The AFR is simply the ratio of air and fuel being combusted. This ratio is fixed at the point where the intake valve closes on the compression stroke and hence there isn't much that the spark timing can do to influence the AFR unless a misfire occurs.

EGT on the other hand will vary as we sweep the timing. Unfortunately we don't have this engine equipped with EGT sensors so we can't show this.