VVE table warm vs cold ect

[RobZL1]

If you really want your mind blown... rpm is corrected too.

I'll bite. What in the world is rpm corrected against? I assume it must be a sensor or noise correction and not something like the pull of gravity affecting the crankshaft? LOL

[DSteck]

I'll bite. What in the world is rpm corrected against? I assume it must be a sensor or noise correction and not something like the pull of gravity affecting the crankshaft? LOL

Charge temperature.

[GHuggins]

Via a multiplier or how it's figured into the torque model?

[DSteck]

You gotta stop bringing up the torque model.

[GHuggins]

You gotta stop bringing up the torque model.

Well, it does So as a multiplier then. OK...

[GHuggins]

Another point in cold engine tuning is to understand only vaporized fuel will burn. A cold engine cannot vaporize fuel like a warm one can. So while cold the OL enrichment will target numbers much richer than stoich. This is so hopefully enough fuel was vaporized to burn normally. Bottom line you do not want to tune OL enrichment to match commanded AFR.

A example would be while cold commanding .85 at idle but wideband reads .96-1. That would be perfect.

That's entirely different from what the OP or myself are talking about. The engine is already in closed loop and going through it's entire temperature range while still showing the VE lean. The VE won't show correct until it gets within 30ish degrees of operating temp and sometimes later than that.

If you're running a SD only tune, then yes there is a way to correct the VE for temperature changes. You can do it the same way you correct the MAF temperature and it's relocation changes.

I'm still waiting to get a log back to see if the IVT table had any affect on this although I do realize I mis-spoke earlier, as it was pretty late and still going on about 3hrs of sleep right now, but the open loop tables you increase to add fuel and all of the other multipliers you remove to add fuel...

[TheMechanic]

I don't get it. RPM is a constant. How do you "correct" a constant.

[DSteck]

Well, it does So as a multiplier then. OK...

It's got nothing to do with the torque model.

I don't get it. RPM is a constant. How do you "correct" a constant.

Refer to smokeshow's comment about the speed of sound. The VE RPM correction is enabled stock, and I am staring at the line that uses it.

[GHuggins]

Is it just using it at idle or all of the time? Anything one could log to see if it's causing a particular issue? Could it cause surging?

[RobZL1]

Charge temperature.

Love it. Physics is fun. Thanks for sharing from behind the curtain.

[GHuggins]

I mean...if you need to. There's a world of OL calibrations to be dialed in before engine reaches operating temperature... But none of them should inform the airflow models. That part should be done beforehand.

OK, even though as you put that it shouldn't affect one model more so than the other or models in general this is what I found by adjusting the ivt table solely off of the VE fuel error, I was able to turn the 20ish VE error into 3 to 6 % errors as the engine was getting to temp with some random 10% at a couple of specific temps which seems to come and go for those temps depending on the log. It also seems to have not affected the MAF side of the calibration, which I was surprised about to be honest. I've used this table to help with some colder temp closed loop fueling issues on gen 4's in the past where I was working around some other problems, just not VE specifically. Wasn't expecting it to only affect the VE side like it seems to have in this case. Guess cause it's cammed, loping and leaning more that way? I don't really know on that one. The last temp column I left stock and tuned the VE at temp like normal. Guess I'm going to have to go back to better correcting these tables going forward.

[smokeshow]

Not surprising that it didn't affect VE....because its completely independent lol. Open loop (cold) enrichment is mostly governed by two effects...one being the impaired ability of the fuel to actually vaporize and participate in combustion, and the other being the poor dispersion/charge homogeneity effects that result in vaporized/burnable but otherwise uncombusted fuel leaving the cylinder. Neither of those effects has any relation to VE or a MAF calibration.

[GHuggins]

Not surprising that it didn't affect VE....because its completely independent lol. Open loop (cold) enrichment is mostly governed by two effects...one being the impaired ability of the fuel to actually vaporize and participate in combustion, and the other being the poor dispersion/charge homogeneity effects that result in vaporized/burnable but otherwise uncombusted fuel leaving the cylinder. Neither of those effects has any relation to VE or a MAF calibration.

Well it did affect the VE separately, but otherwise that's what I always thought, so not sure why it helped the VE side of the calibration so much while not affecting the MAF side. Even helped with some cold drivability according to the owner.

[smokeshow]

Well it did affect the VE separately, but otherwise that's what I always thought, so not sure why it helped the VE side of the calibration so much while not affecting the MAF side. Even helped with some cold drivability according to the owner.

How would you even measure that lol

[GHuggins]

Back calculating error in a temperature defined table taking an average for those temp zones. Then fuel correction I just do the inverse I use for correcting the other fuel multiplier tables.

[smokeshow]

Back calculating error in a temperature defined table taking an average for those temp zones. Then fuel correction I just do the inverse I use for correcting the other fuel multiplier tables.

That doesn't tell me anything. What goes in, what comes out?

[GHuggins]

Sent you 2 pm's. Second has the VE formula. You'll think it's stupid

[smokeshow]

Seems like you meant to send the one you forgot and then sent another equation entirely?

Open loop mults cannot be helped by any fuel trim feedback. The simple reason is that, where fuel trims are trustworthy...open loop multipliers are 1.0. This is by design and a fundamental behind ICE engine function. There has to be a physics based reason for applying an error correction.

[GHuggins]

Yes, I grabbed the first one quick as it's my usual fuel multiplier correction equation then when I went to send it didn't even think about the VE equation. It's also not using fuel per say to correct the table, but only use fuel to correct the MAF error, so as long as that part of the system is already dialed in I would think the airflow correction part of the formula should work. Don't know, it seemed to work, but errors do change log to log as I've been keeping an eye on it. I've used that equation while in semi-open loop (st ft corrections in open loop - guess that's what it's called) for correcting the ivt table even on 4th gen vehicles. Not the VE one for that, but the density / fuel multiplier one so yes it would be solely trim correction with that one. Always seemed to work there too and as I stated you might have to make a few passes due to the fuel vaporization and so on playing into it. I always assumed the OE was using some sort of fuel correction ratio to come up with the tables in the first place?