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Discussion Starter #1
I was just reading about resetting the ECU and was surprised to find there is also a learned memory for the ignition timing.

Your ECU remembers the signals from the knock sensor and makes adjustments to what's called the basic timing advance map. If you had a crappy tank of gas the ECU sees this on the knock sensor output and adjusts the basic timing map to compensate. Obviously, it retards the timing to avoid detonation.

Even if you put a tank of good 94 octane in it won't matter. It takes the ECU a few tanks of gas to compensate for the increased octane and for it to advance the ignition timing accordingly. (relearn the basic map)

When you reset the ECU you erase the "learned" basic spark advance map and the ECU reverts to the using the preprogrammed timing map and comparing that to the knock sensor signal, the coolant temperature sensor, and the crankshaft position sensor to relearn the basic map.

It might be worth a shot if your truck is getting some shitty gas mileage to put some good gas in next time and reset the ECU. You might just see an increase if the learned timing map is retarding the timing too much.

I know I've reset my ECU before and had the gas mileage come back to normal but never knew why. I thought it had more to do with the fuel trim numbers but it seems timing plays a part in it also.

(SC'd guys ignore this and stick w/ Gadget's advice)
 

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Where were you reading about this from? I know whenever mine pinged after a fill-up, it adjusted very quickly, probably within minutes. I'm surprised that the continuous learning will take so long to go back the other way. I'm wondering where the "few tanks" number came from and how trustworthy it is.
 

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yup, that's why in the TRD S/C instructions the ping is supposed to "go away" after driving a few tanks . . . retard!
 

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creed said:
yup, that's why in the TRD S/C instructions the ping is supposed to "go away" after driving a few tanks . . . retard!
go away my ass :explode:
 

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Discussion Starter #6
not2XS said:
Where were you reading about this from? I know whenever mine pinged after a fill-up, it adjusted very quickly, probably within minutes. I'm surprised that the continuous learning will take so long to go back the other way. I'm wondering where the "few tanks" number came from and how trustworthy it is.
According to what I was sent, the ECU will adjust for knock quickly but it is advancing the timing that takes a long time to happen. If it senses knocking or pinging, it logs that in the learned timing curve and retards the timing accordingly. If you fix whatever it was that caused the knocking the ECU will take some time to adjust for the fix.
 

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Discussion Starter #7
creed said:
yup, that's why in the TRD S/C instructions the ping is supposed to "go away" after driving a few tanks . . . retard!
Like I posted, SC guys ignore this.

Also, I have a friend with a Jetta who is very interested in the SMT. I told him I knew a few guys running them. Do you have the link to the yota tech thread with all the SMT info?
 

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akshunj said:
According to what I was sent, the ECU will adjust for knock quickly but it is advancing the timing that takes a long time to happen. If it senses knocking or pinging, it logs that in the learned timing curve and retards the timing accordingly. If you fix whatever it was that caused the knocking the ECU will take some time to adjust for the fix.
the ecu adjusts for knock quickly because the knock potentially damaging the engine, I guess it takes longer cause the ecu needs to gradually increase timing back to normal while "watching" the knock sensor output to see if the knock has returned, if not it can bump it up a little more. Im not sure how often it updates the timing, some things will only be done once every drive cycle(cold start to complete warm up and some driving time after warm up). If so that would explain why it takes a couple of tanks to return to normal unless you reset the ecu so it can start from scratch with its base numbers that are burned into the ecu memory.
 

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I really don't think the timing works this way at all. It is dynamic and is constantly adjusting all the time. The ECU will constantly keep advancing the advance and keep it at the knock threshold above 3000 RPM. When it sees knock, it pulls timing and a few hundred RPM later it will try to move it back up. This process is constantly ongoing and does not take a few tanks of gas.

Gadget

www.GadgetOnline.com
 

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Discussion Starter #12
knoxtaco said:
the ecu adjusts for knock quickly because the knock potentially damaging the engine, I guess it takes longer cause the ecu needs to gradually increase timing back to normal while "watching" the knock sensor output to see if the knock has returned, if not it can bump it up a little more. Im not sure how often it updates the timing, some things will only be done once every drive cycle(cold start to complete warm up and some driving time after warm up). If so that would explain why it takes a couple of tanks to return to normal unless you reset the ecu so it can start from scratch with its base numbers that are burned into the ecu memory.
Of course knock can damage the engine ;) As for the how long it takes to advance the timing I guess I'll find out when I go home. The guy playing with my truck right now doesn't have a diag. scanner that can see anything about timing info in the ECU. I could watch the timing with my o-scope when I get home. I don't want anybody else playing with that though. Cost me too much $$$.
 

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Thats just a way to get you out the door, otherwise they know you will come back wondering why your truck is making this aweful noise that could be attributed to gremlins or something.
 

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does it reset when the battery is disconnected as well as when u pull the fuse?
 
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