Closed loop load limit
 

Was bored and poking around earlier today, and saw these tables; sparked some memories with some issues the competition is having and figured I'd give it a shot.

By default, these tables are set to 2.5 load (which is where the issue the other guys have). For shits and grins, I set mine to 1.75 (as I'm pretty much over 1.8 all the time when wot.

Both sets of pulls on both 1.75 and 2.5 maps (which is the ONLY difference between the two) were done AFTER flogging the shit out of it before hand to get the trims settled.

With some more testing, it might be safe to rename these to "Fuel Trim Load Limit" instead of closed loop since they obviously effect "open" loop as well.

Food for thought; logs attached.

I guess I'm missing what this means. Is there some sort of closed loop to open loop slow transition that causes the slow downward drift in AFR? Is there any associated transition time that can be changed.

No. There are two types of fuel trims, both of which have limits.

The closed loop fuel trims show up in the stft and ltft numbers; the open loop fuel trims do not.

The closed loop fuel trims are inactive at/after the targets specified in the "Closed loop open loop threshold" tables, whereas the open loop fuel trims have no visible (loggable) value, and are inactive at/after the load specified in the "Closed loop load limit x" tables (which is a bit of a misnaming for the tables, honestly). Once you are past the values set for the end of the open loop fuel trims, it defaults to ZERO trims.

Basically, if your ECU is adding 10% fuel up to the load value specified in the "Closed loop load limit x" tables, and you go a little further load wise, you lose all trims and will run 10% leaner (or off target, if you will).

That's why this is important to have control over.

Another example: You're spraying a metric fuckload of methanol, but have enough injector overhead to not need it. Let's also say you never go over the value specified in this table.

The ECU will compensate for the meth, and if it ever shuts off, you lose all that fueling headroom and immediately run lean. If you're on pump gas, you lose the motor. If you had this turned down to below the threshold where your meth starts to spray, you basically wind up hitting your AFR target instead of running rich when your meth fails.

So during the initial tuning phase's when one is dialing in the maf curve. Would a smart approach be to lower this limit as to see the wot portion of the curve in true open loop and dial it in. Then raise the limits back up?

Or just raise them if load conditions get near the limit?

http://www.quickmeme.com/img/b0/b009...beb5c481ce.jpg


Almost a year to the day - http://www.mazdaspeedforum.org/forum/foru...3/#post2764561

Nice work! I stare at the code till I'm cross-eyed, but I don't always see what it's doing.

Thanks for taking the time to experiment and log!

:You_Rock_Emoticon:

Personally, when I start a new map on the new motor, I'm going to set this to the same as OL/CL transition so I can do a legit full MAFCAL. I'll raise it after to a bit below where I'll start spraying meth, so it doesn't compensate for that any longer in the tune.

If I wasn't going to spray meth for aux cooling, I'd do the same but set it back up to above what I'll be hitting at WOT for safety after the load is dialed in.

So...was I the first one to actually test this...A year later?

@Enki; Since I missed the point originally, I'll try this again and see if it's similar to what you are saying. When I started spraying Meth in my GenPu, it obviously messes with the AFRs. Plus, the GenPu corrects some open loop. I tried to make it so that when spraying, I was just under where the ECU could correct, and if the Meth fails, I should have that 8% or so correction to help save my motor?

Let's say you're hitting 2.3 load when WOT. With these tables set to 2.5 load, it will correct for meth; you target 12:1 AFR, you get 12:1 AFR, even with meth spraying. If your meth setup fails, and you don't have enough fueling headroom to auto trim (which would happen after current WOT pull, I believe), you will run lean.

If you set this table to 2.0 load, have a spot on MAFCAL and target 12:1 AFR, when spraying meth you will run rich. If it fails, you'll just hit target AFRS.

In OP you said "competition had some problems" are you referring to a company that produces a port to access our ecu?


Also has anyone ever tried running our car as a fully closed loop system (ie set the transition value above whats achievable)? Might not be possible thinking about it because it probably uses throttle position too. If so is there a table for that? My 135i uses a fully closed loop system and has fuel trims at WOT, tuning is a breeze. There's one table for each "bank" so there's no messing around with CL/OL tables.

i have tried the fully close loop and with a good maf curve the afr curve is just perfect.Off course you have to make all tha changes for ign and afr at the close loop tables

Awesome! Do you still currently have it set up that way or did you go back for any reason?

No i m open loop.The basic reason i went back to open loop is to hold at a steady % my idc% so that i can play with my aux fueling.

Technically with these tables set up you're in a sort of hybrid closed/open loop with an individual (probably third and thus unviewable) trim. I wouldn't think staying closed loop full time would be a good idea due to reaction speed of the trimming system (it's not terribly fast).

It seems like this third trim carries over the LTFT it was last at and makes adjustments for the next WOT pull rather than trying to do it immediately.

When I'm done with my build I'll probably set these to the same as the open/close threshold, MAFCAL properly, then re-enable it after for safety (up to the point where I start spraying meth, which I don't want compensated).

Thread revival :)

If the ''closed loop load limits'' tables are set to 3.0 load, will this extended the open loop trims to 3.0 load...or is the ECU limiting this to 2.5 and lower load!?

Im asking because I inject lots of meth, and want to scale the MAF at a minimum...

Yes, I had a terrible time dialing in my afr targets with meth before I saw these tables. Upped limit to 3.0 and now afr are on target with meth on. Didn't even have to scale the maf.

Edit: this is with single d07 nozzle. I tried with a single d10 and ecu couldn't trim enough to hit targets, which then I actually had to scale my maf for that nozzle size. Since you say you are spraying lots of it, you will prob have to scale maf as well.

If you want to scale the MAF, you should reduce these tables, not raise them (if you aren't using meth as aux fuel, anyways). Let it run a bit rich, and if it fails, no big deal as you'll be on target vs rich.

Im running 4 X 0.6mm Aquamist nozzles in the manifold ports (about 15gph, 100% meth)...scaling is absolutely necessary

Necro-ish

I have been reading alot of late

this caught my eye

Strong post, strongly worded

I keep my jizz intank, but still.....

food for thought

I have just done a bit of work on timing with OL

Seems the CL tables are normally left alone

they normally transition well..........but i the gap is large

I don't think 4 days is enough to call it an necro.

sent from my Pixel XL

...but i the gap is large.

Sent from my XT1254 using Tapatalk

Not on my car; might as well be only one set of tables.

Enki is this table / function specific to the Gen 2 ECU?

No, every gen most likely. This thread is about my genwon, so it's obviously in the 09 version of VT at a minimum.