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Tuning Ignition Timing at Higher Boost Levels

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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If performing process of advancing the timing incrementally when working near or close to Wide Open Throttle with high boost, are you actually listening for the knock and then backing off. Or what is process to get optimization with hurting the engine?

Andre has discussed this a time or two, but in 'most' instances power/torque will level off just before detonation starts, so monitoring that can be a good start. I said 'most' because some engines will keep increasing power/torque right into detonation - I think this was when one was using too much compression and/or boost and/or too low an octane fuel? Sometimes running a little richer will allow one to advance the timing until the drop-off is reached.

So, watch the torque and keep your ears open.

However, I would advise checking with several sources to confirm, or not, that.

Hi Jeffrey, yes we listen for knock and creep up on that point. Obviously at higher power levels you want to be very mindful of knock and not stay in the throttle though. This also depends on the specific power level of the engine. A low power engine will be much more tolerant of light knock than a very high power engine so you need to keep that in mind. Generally with the drag engines I tune I'll be a little conservative on timing and use a little more boost to get the power where I want it.

Is there a specific engine and vehicle we're talking about here?

Yes.

The engine 430 inch Ford Windsor motor, running on E85, Holley HP EFI. The forced induction is supplied via a Procharger F1R supercharger, estimated 1000 hp. The setup is in a Mustang for drag racing. Trying to determine how we get from conservative tune to optimal tune without hurting the motor on the dyno.

For me, easiest thing to do, if you can keep consistent temperatures between pulls:

Baseline WOT pull.

Add 1 or 2 degrees, do a pull. Record how much power gained (for simplicity sake, let's look at peak power number only). Let's say it's 20 hp for the first increase because you are far from optimal.

Add another 1 or 2 degrees, do a pull, write down result. Let's say we picked up 12 hp this time.

Repeat until the incremental benefit is a lot less. As you increase more, go in 1 degree steps for sure. The threshold of "it's not worth the extra power benefit to keep adding timing" is a bit of a judgment call. say 2 or 3 hp. Then you stop adding timing, or back off a degree or two.

Keep in mind that with E85, there is significantly less knocking tendency. Each time you add spark, you increase cylinder pressure, even if you aren't knocking. So you will stress engine components. I hope you have tough parts in there.