ECMlink Open Loop VE Table

[Yamahaulin]

My car is a 2g with v3 full. When i first start my car hot or cold while in open loop the car idles lean, but as soon as it goes closed this problem is fixed as I have my airflow per rev where it is supposed to be and deadtime adjusted so that my combined ft are at 0 +/- 2. I'm not seeing an open loop ve table other than the speed density tab. My car doesn't have a map sensor of any kind so i don't see how the speed density table would work. I would have thought in the direct access tables there would be a ve table using the loadfactor but i'm just not seeing it.

 

[Marchev]

The SD ve table will not work unless you are using a map sensor. Also there is no "open loop idle ve table" either.
Try locking the car in open loop during idle and see what the afr is. Adjust your mafcomp sliders accordingly while trying to keep your airflow per rev close to .25. After you get it close to stoichiometric, put the ecu back in closed loop and adjust deadtimes as needed.
Also there is feature called "enable enrichment during hot starts" under the misc tab I believe. Try enabling it and see if that helps.

 

[Yamahaulin]

In the SD ve table what is the left side of the graph? Is that boost, i know the top is rpm but doesn't say what left side is. If it's boost how would you tune in the vacuum range as it starts at 0.

 

[Marchev]

The left side values are atmospheric pressure, not boost. I believe you can find conversion charts online. But basically:
atms -> in/hg-psi
0 -> -29.9
9.2 -> -11.2
14.7 -> 0
25.7 -> 11
40.4 -> 25.7
And so on...

 

[Yamahaulin]

Awesome, thanks for the help.

 

[Kevin Jewer]

The left column units are in absolute pressure (psia), not gauge pressure (psig). It's still PSI. No need for any conversions, just subtract atmospheric pressure from the number there to get psig. For example, 25 psia is about 10 psi near sea level. The easiest thing to do might be to pick a boost level in the log and "track datalog" on that chart and see where it ends up.

Something is funky though if closed loop makes it work right with 0 trim. That should essentially be the same operation as open loop.

 

[Yamahaulin]

Why do you think it's funky that closed loop works with 0 trim. When in open loop all sensors are not used only a ve table to achieve fueling. But when the ecu goes closed it doesn't use a ve table but uses it's sensors to fuel such as maf and o2. I may be wrong but that's my understanding of how it works. Don't take this as me bashing I'm just trying to learn more.

 

[Kevin Jewer]

The ECU doesn't determine fueling directly from the O2 sensor, which your post implies if I'm reading it correctly. The O2 sensor is used only to get a value to offset calculated (or expected) fueling as error correction. In other words, fueling needs (injector pulse width) are determined independent of the O2 sensor, then the correction factor determined by the O2 sensor (fuel trim) is applied on top of that. Along those lines, the MAF is used at all times, not just closed loop as your post implies. Open loop just means that fueling is based solely on measured airflow (MAF/MAS) with no closed loop error correction. With SD, it's a calculation of airflow based on the MAP sensor, displacement, rpm, temp and VE from the VE table, but it works the same way. Fuel trims as a result of the O2 sensor's readings are a modifier to the predetermined injector pulsewidth.

Back to the original point, if your open loop table is targeting 14.7:1, and the calculated IPW is correct (airflow metering, or VE table for SD), you'll get 14.7:1 in open loop. If you were to go closed loop at that time, fuel trim would be 0, since there is no error to correct. If you're targeting 14.7:1, and the VE table is causing a 10% offset in AFR, your fuel trim would be 10% to get you back to target. If you go from open loop to closed loop and there is no error correction (fuel trim 0), then there was no error. To put it another way, you're saying that in open loop your AFR is off, but then it goes to open loop, applies no fuel trim, and is then correct. Why would it then be correct with no correction made to it? The result would be the same that you would get in open loop. That's what strange to me.

Hopefully this helps you understand the ECU's operation a little better and helps in your troubleshooting. This thread is a bit different than your thread on the ECMlink forum, but I think in either case a log of the behavior in question would make it easier to give good advice.

 

[Yamahaulin]

Well that's some good info, I was unaware it used the maf in open loop to change fueling. I thought it was strictly from ve. That makes my situation definitely strange. I'll try to get a cold start log tomorrow afternoon as I can't get it this morn when I get off cause laptop is dead. I cranked up fuel it adds with temp to see if that helps any.

 

[Kevin Jewer]

You work nights too?

To add to what I wrote above, that does assume that your open loop target is 14.7:1 at idle, which it generally is unless you've changed it. When you go to closed loop, the target effectively becomes 14.7:1. If the target was leaner for some reason in the open loop table (really low vacuum for example, or a weird target afr table), it could shift to 14.7:1 in closed loop and have no fuel trim applied. Something to look for in the settings that are included in your log file.

 

[Yamahaulin]

Too bad we can't log what the ecu is asking for. However I didn't lean it out in the octane table if anything I tried making it a bit richer. I've been working nights for 10 years at a duct tape factory.

 

[Kevin Jewer]

Nice. 12 years in one of Intel's wafer fabs.

AFRest should be what the ECU is targeting.

 

[Yamahaulin]

I need to trade you some tape for a CPU, . I appreciate the help a lot. Hopefully I'll have a log for you to look at tomorrow sometime.[DOUBLEPOST=1410870084][/DOUBLEPOST]Well when i started car this morning it was almost perfect guess that coolant temp fuel adjust did the trick. Will have to see how it does when its warmer this afternoon