Why is there a need to tune ignition maps if the computer auto adjusts?

[imzjustplayin]

I was thinking about all the work that people go through in order to tune their ignition maps on things like chrome, AEM EMS and their Hondata systems, but I was wondering, if the computer automatically tries to advance or retard ignition timing until it knocks with the feedback of the knock sensor, then wouldn't manually setting the ignition maps be unnecessary? I heard that the AEM EMS has a function that can create ignition and I think fuel maps as well automatically when you first set it up, so I was wondering if it works strictly off of using the knock sensor for that and if it does, how does manually tuning the ignition maps after doing that improve performance. Is there a way for it to "auto" set the ignition maps aggressively?

 

[rfrumusa01]

The ECU does not control timing strictly using a knock sensor... in fact, unless your car is knocking all the time, it pretty much never looks to that sensor. Next of all, honda knock sensors work like shit. So for someone to build a 500hp car and rely on some piece of crap sensor that doesnt work would not be good. The need for mapping ignition timing is simple. Much like fuel mapping, the ecu interpolates values based on several conditions. Conditions such as IAT, ECT, Knock, etc... the ecu then reverts back to this map and calculates a mean value between surrounding values on a cell coordinating to map pressure and rpm. The ecu will like I said, then add or subtract from this timing value based IAT, ECT, and other advanced conditions.

So if you understand any of what I just said, the need for an ignition map is simple. So is the need to tune it. Any changes such as boost to the engine, your timing map will need to be adjusted accordingly to accomodate the denser air charge or your shit will blow up. Oh, and the ecu limits the knock sensors ability to effect timing by + or - a very small percentage to avoid it from blowing your engine in the event the sensor fails and sends false readings. Make sense?

 

[imzjustplayin]

The ECU does not control timing strictly using a knock sensor... in fact, unless your car is knocking all the time, it pretty much never looks to that sensor. Next of all, honda knock sensors work like shit. So for someone to build a 500hp car and rely on some piece of crap sensor that doesnt work would not be good. The need for mapping ignition timing is simple. Much like fuel mapping, the ecu interpolates values based on several conditions. Conditions such as IAT, ECT, Knock, etc... the ecu then reverts back to this map and calculates a mean value between surrounding values on a cell coordinating to map pressure and rpm. The ecu will like I said, then add or subtract from this timing value based IAT, ECT, and other advanced conditions.

So if you understand any of what I just said, the need for an ignition map is simple. So is the need to tune it. Any changes such as boost to the engine, your timing map will need to be adjusted accordingly to accomodate the denser air charge or your shit will blow up. Oh, and the ecu limits the knock sensors ability to effect timing by + or - a very small percentage to avoid it from blowing your engine in the event the sensor fails and sends false readings. Make sense?

How does the AEM EMS do an auto tune?

 

[K2e2vin]

AFR lookup. As far as any aftermarket ECU systems go, I believe there's none that auto-tunes ignition.

The stock sensors do not compensate for max power or lean condition; they're fixed rate and work strictly off of their own lookup tables.