DIYEFI.org Forum

Just stuff I am thinking about
Calculating of true load
I have seen where different gears on a flat ground will allow for different timing advance allowing more power to be output
At the same time say you are traveling up a hill in that same gear, it may not torlerate the same ammount of advance.

thinking of ideas

Why would ground angle change the amount of advance that the engine can tolerate? Surely the advance is just changed slightly to allow for a bit more torque up hill rather than peak hp.

Because BTUs.

crazyafrican wrote:Why would ground angle change the amount of advance that the engine can tolerate? Surely the advance is just changed slightly to allow for a bit more torque up hill rather than peak hp.

throttle angle changes to keep the same rpm
its more of how long it stays at the rpm
the more load and longer it takes and more likely it will det of course.
of course heat has to do it as well
But I do know from experience from testing my own vehicle using same boost level and flat ground that a tune in 1:1 gear will never be optimal for other gears where you could get away with more or less timing giving better drivability

Fred wrote:Because BTUs.

^ this.

Because BTUs.

please explain

It's not necessarily an issue of prolonged load (unless your engine is overheating), it's more of an issue of increased cylinder-filling (greater air/fuel charge = higher pressure) causing flame temp and speed to increase, and incompletely-tuned spark maps.

When you are going up an incline, you have to open the throttle farther to maintain the same speed, so the ignition map will reduce timing (maps generally reduce timing at higher load). If there is still too much timing it means the spark map hasn't been tuned correctly at that load (how many people actually tune their spark map other than to get rid of knock at WOT?).

The way to properly tune the spark map is put the engine on a steady-state dyno and hold the engine at rpm vs load to get a grid of data points that are evenly distributed across the spark table in both dimensions, adjusting timing advance to attain peak torque under each condition. The engine's propensity to ping at any load point will be discovered during this process and timing adjusted accordingly. This is what OEMs do, although peak torque is usually ignored in the interest in improved emissions, fuel economy, and/or insurance against bad gas.

Once the above procedure is performed, you should be able to cruise up inclines with no pinging issues.

Your first sentence seems to show that you didn't read his first post well? Granted, he's not great at articulating himself :-) The others are accurate, however I don't think they're on-topic.

And yeah, I tune my ignition map elsewhere (every few years when I get a chance at all...). Furthermore, peak efficiency/torque is not the only thing to consider when tuning a complete timing map to work well (as opposed to a single cell in isolation to work well). There are many examples of where/when non-optimal timing is in fact optimal.

Fred

I was responding to his second post in the first sentence. I didn't realize there was a mandated order of sentences???