Ltft skyrockets

I've been working on lowering my BRAF due to chasing spark being pulled when cruising steady. It seems to correlate to the IDLE ADAPTIVE SPARK CONTROL table overspeed/underspeed [12647] & [12649]. The changes do seem to help, so I have been slowly creeping up on what feels best to me. After I flash in my most recent changes, I am watching the trims in the idle area when all of a sudden, the LTFT shoots through the roof! Why would this happen all of a sudden? Was there some type of test that ran that could cause this? Any info would be helpful and appreciated.


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Thanks

Clearly your ECM has made some long-term adjustments for short-term problems. Happens more often than not on cammed applications. Ideally you'd adjust the cals for enabling long term correction...but most just disable them. I do when necessary.

If it's only right after flashing - look up rich after flash - your injector temp offset table needs dialing in ;) Also just for a rule of thumb - ignore fueling for 20 minutes of driving - if making fueling adjustments....

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Originally Posted by GHuggins

Also just for a rule of thumb - ignore fueling for 20 minutes of driving - if making fueling adjustments....

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This needs to be the banner on the main forum page honestly. All the software is sitting on the init values, none of the diagnostics have run...the controller doesn't know up from down. Have to give it time to learn in again after a flash...

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Originally Posted by smokeshow

This needs to be the banner on the main forum page honestly. All the software is sitting on the init values, none of the diagnostics have run...the controller doesn't know up from down. Have to give it time to learn in again after a flash...

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Yeah gen 5's are the worst when referring to this. Takes up to 2hrs of drive time on some to get idle timing and behavior to where it's supposed to be just so you know you're making the right adjustments or adjusting something that needs to be adjusted in the first place.........

Thanks fellers. I'll do a drive cycle when the weather breaks and see how it does at that time. I was surprisingly shocked to see the LT's shoot up like that and got all excited.

Greg, i'm slowly leaning into tuning that offset table. If I remember correctly; from a cold start, let it idle for a good while until it reaches max temp?

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Originally Posted by LS ROB

Greg, i'm slowly leaning into tuning that offset table. If I remember correctly; from a cold start, let it idle for a good while until it reaches max temp?

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From a cold start it doesn't matter... The engine is at ambient temp, just like the injectors. But on a hot restart after flash, the controller initializes the injector tip temp to engine temp, which is obviously an overestimate. So the model has to stabilize first, which isn't something you can monitor. As we mentioned, data immediately after a flash is unreliable and should be discarded...but if you'd like to get rid of the richness after the flash anyway, set that injector temp offset table to zero across the board. Just set it back when you're done with the rest of the calibration so if your injectors ever do get that hot, you don't have an engine that refuses to start.

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Originally Posted by smokeshow

From a cold start it doesn't matter... The engine is at ambient temp, just like the injectors. But on a hot restart after flash, the controller initializes the injector tip temp to engine temp, which is obviously an overestimate. So the model has to stabilize first, which isn't something you can monitor. As we mentioned, data immediately after a flash is unreliable and should be discarded...but if you'd like to get rid of the richness after the flash anyway, set that injector temp offset table to 1 across the board. Just set it back when you're done with the rest of the calibration so if your injectors ever do get that hot, you don't have an engine that refuses to start.

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Thanks for that info smoke.

Ummm. Not sure we're talking about the same thing here. A value of 1 would add a full millisecond of injector on time to the pulsewidth on startup and be Super Rich. A 0 would be no influence in this case...

I actually dial the temp table in as a lot of blower applications will hit those really high temps and I personally like consistent calibrations. Even a NA vehicle will hit high temps on hot restarts. The way I do it is to have my customers idle the vehicle to temp of course having the MAF dialed in fairly close in this region - shut if off - reflash and then log trims as injector tip temp comes back down to normal operating temp. Haven't had this cause ill effects as of yet - not to say that it couldn't. I still leave 80c and up a little richer, but not much - maybe 4 or 5 percent. Everything from 80 down is pretty well dialed in. Unless it's a blower - I've seen their calcs hit 90 to 100 Celsius hot lapping, so I try to dial them in better up till there most times. At least this is the way I do it.

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Originally Posted by GHuggins

Ummm. Not sure we're talking about the same thing here. A value of 1 would add a full millisecond of injector on time to the pulsewidth on startup and be Super Rich. A 0 would be no influence in this case...

I actually dial the temp table in as a lot of blower applications will hit those really high temps and I personally like consistent calibrations. Even a NA vehicle will hit high temps on hot restarts. The way I do it is to have my customers idle the vehicle to temp of course having the MAF dialed in fairly close in this region - shut if off - reflash and then log trims as injector tip temp comes back down to normal operating temp. Haven't had this cause ill effects as of yet - not to say that it couldn't. I still leave 80c and up a little richer, but not much - maybe 4 or 5 percent. Everything from 80 down is pretty well dialed in. Unless it's a blower - I've seen their calcs hit 90 to 100 Celsius hot lapping, so I try to dial them in better up till there most times. At least this is the way I do it.

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That's what I said :p Yes, I meant 0. As in no contribution. Fixed the post.

Its good to get a cursory look at that part of the cal, but a reflash before will still give you unrealistic data, as the modeled temp doesn't match actual. So it compensates for an error that isn't there. ITT tends to peak around 10-15 minutes after a shutdown, depending...so a good test would be waiting til the hottest weather you can manage, dial the fans off for a little while to build extra engine heat and then restarting, without a reflash.

Appreciate you guys clearing that up. I'll do what I can with this cooler weather and then re-visit on warmer days.

I've tested or at least verified it in real world race and customer tunes. Keeps fueling correct in really really hot lapped engines and regular hot restarts like filling up at the pump. Scott discovered the problem and came up with this solution for it years ago - seems to work even with all of the numbers going through a reset...

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Originally Posted by GHuggins

I've tested or at least verified it in real world race and customer tunes. Keeps fueling correct in really really hot lapped engines and regular hot restarts like filling up at the pump. Scott discovered the problem and came up with this solution for it years ago - seems to work even with all of the numbers going through a reset...

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If I run into trouble on this, I may reach out if that's ok?

No problem Rob.

Much appreciated Sir.

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Originally Posted by GHuggins

I've tested or at least verified it in real world race and customer tunes. Keeps fueling correct in really really hot lapped engines and regular hot restarts like filling up at the pump. Scott discovered the problem and came up with this solution for it years ago - seems to work even with all of the numbers going through a reset...

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Yeah, not sure how that could steer you the right direction unless by coincidence. Probably get lucky with a blower or other metal intake because the injector mount point temps are closer to ECT and the overall ITT pulse width contribution is small relative to the total (in which case, you would not set the table to zero for restarts). But with plastic intake manifold, NA applications like this one, the corrections based on data after module reset will not be representative and probably cause issues elsewhere.

Realistically, that table is a part of the injector data as it characterizes the sensitivity of the solenoid to high coil temperatures. So it isn't a something to tweak any more than injector flow rate is.

This is true, but we have to work with what we have. I don't personally ever 0 out the table. Causes too many lean hot start issues and yes you can address it elsewhere, but the ITT always seems to be the best way to do it.

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Originally Posted by GHuggins

If it's only right after flashing - look up rich after flash - your injector temp offset table needs dialing in ;) Also just for a rule of thumb - ignore fueling for 20 minutes of driving - if making fueling adjustments....

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So any guide on "injector temp offset table" adjusting and what adjusting actually does?

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Originally Posted by TheMechanic

So any guide on "injector temp offset table" adjusting and what adjusting actually does?

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if u have bigger injectors i find that dividing the table by how much bigger they are from stock get u in the stadium then u have to fine tune further from there if it needs, so if the injectors are double the stock size then i halve the ITT offset table then monitor what its like and adjust further if some cells need it or if im only a few % richer i call it good, alot does go on with startup tho so have to also make sure its the table in play or what others are, also IVT will be doing some adding as well until CL if stock settings are used

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Originally Posted by 07GTS

if u have bigger injectors i find that dividing the table by how much bigger they are from stock get u in the stadium then u have to fine tune further from there if it needs, so if the injectors are double the stock size then i halve the ITT offset table then monitor what its like and adjust further if some cells need it or if im only a few % richer i call it good, alot does go on with startup tho so have to also make sure its the table in play or what others are, also IVT will be doing some adding as well until CL if stock settings are used

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What he said pretty much. Your final table will be considerably lower than the OE - your making .0078ms pulsewidth changes. If it's 10ish % rich then start by taking out .0150ish and see how it effects it. I've also found the IVT table to be in play for closed loop and not just open loop as it's labeled or located in the software. I use the IVT table for colder engine adjustments (after start) - works good for this after optimizing injection timing and open loop tables for the same thing. I've found that the open loop tables - as directly labeled for in gear and park for E and gas to be the only real ones used for solely open loop, so I try to get these close to closed loop operation or slightly richer and then use the IVT table for closed loop cold engine operation.