Gone back closed loop

[stigmundfreud]

Hi all,

Yesterday I finally returned the car to closed loop with ltft enabled. The car is running much better than the last time it ran closed loop (as I've tuned as carefully as possible) but I have a few questions regarding the logs.

I'm now logging STFT and LTFT, the STFT average is 0.3% and the LTFT average is settled at -1.3% - is this good? The next is I'd like to see a map to show how the trims are at different rpm/manifold pressure - I presume I just create the map with rpm vs manifold pressure logged against the LTFT?

What I do see is a bit of difference between bank 1 (the bank I tuned for) and bank 2 but it isnt much and to be expected. Unfortunately I can no longer log my LC-1 as I had to remove it to plug in the narrow band (as I wanted to start returning the car to as stock as possible).

When looking at the stft and ltft trims what is a guidance to say its pulling or adding fuel, I guess a - figure is for rich and a + is for lean?

Has anyone ran the O2's in combination with PE mode? I noticed there is a setting for this and would like to know if it does help get a more accurate PE or is it not fast enough so better to use the VE table?

Cheers

[eboggs_jkvl]

- numbers mean your car is running rich and the computer is pulling fuel from the mix to get to commanded fuel A/F

+ numbers mean you are running lean and the computer is adding fuel to the mix to get the commanded fuel.


You want to be slightly negative on all LTFTs to keep the ECM from adding fuel during PE.


PE mode runs from a table of preset values. The trick is to get it (your tune) set so that the ECM doesn't see a need to "help" and mess with the fuel mixture.

Elmer

[stigmundfreud]

thanks Elmer, I'm aware of the PE but there is an option in the tune to enable O2 feedback during PE mode and just wondered if anyone had used it. I presume it uses the switchpoint to register the clmode so it can aide the PE to maintain the desired fuel (its spot on in SD as it is so I am happy with it but wondered if anyone had used PE + 02 feedback)

[5.7ute]

thanks Elmer, I'm aware of the PE but there is an option in the tune to enable O2 feedback during PE mode and just wondered if anyone had used it. I presume it uses the switchpoint to register the clmode so it can aide the PE to maintain the desired fuel (its spot on in SD as it is so I am happy with it but wondered if anyone had used PE + 02 feedback)

What is the table number for this mode? None of the cal files I have seen have O2 feedback for PE as it is in open loop.
Also since a narrowband O2 sensor is next to useless away from stoich the feedback it recieved IMO would be dubious at best.

[joecar]

Mike,

Go back to the basics:

CL: commanded AFR = stoichiometric B3601.
OL: commanded AFR = richer of CFOL B3605 or PE B3618 (if PE the enables trigger).

WOT: PCM goes to OL... but it adds the LTFT's if (and only if) they are positive, as Elmer(eboggs_jkvl) said.

PE is strictly open loop as Mick(5.7ute) said.

Cheers,
Joe
:cheers:

[stigmundfreud]

sorry Joe I was working from memory - just looked and it is the b4206 enabler which appears to enable STFT to work when using OL table. As my 3605 is commanding 12.95 at WOT (PE table is 13) it is using 3605 during WOT conditions as it is richer yes? So if I were to enable 4206 it would then use STFT to correct the trim when in OL mode?

[VTC_WS6]

Considering the NBO2's real accuracy lies only in the area of stoich, why would you want it's input to the PCM when you have the ability to assist WOT with the PE table anyway?

[stigmundfreud]

Considering the NBO2's real accuracy lies only in the area of stoich, why would you want it's input to the PCM when you have the ability to assist WOT with the PE table anyway?

its not something I'm actively considering but its an option thats there and would like to check out what others have found from it (if been used)

[joecar]

sorry Joe I was working from memory - just looked and it is the b4206 enabler which appears to enable STFT to work when using OL table. As my 3605 is commanding 12.95 at WOT (PE table is 13) it is using 3605 during WOT conditions as it is richer yes? So if I were to enable 4206 it would then use STFT to correct the trim when in OL mode?Mike,

I think this will work in a similar manner to semi-open loop in COS3/COS5... it will use STFT's to trim close to stoichiometric... I don't think it's capable of trimming any AFR that is significantly far from stoichiometric... but hey, this is interesting, if you were thinking of playing with this I'd still be interested in your results... I have wanted to play around with this, and now I'll have to make time for it... :cheers:

Cheers,
Joe
:cheers:

[stigmundfreud]

Aaah, strange trigger really and shame I've taken the lc-1 out now. Would have been interesting to see if it was only disabled by PE mode, I dont use PE I just use the commanded table. This trigger, to my limited understanding, just doesn't make sense. I can understand semi-openloop but that is easily triggered by tripping into or out of stoich but this seems to suggest that whatever is commanded that when in OL mode it will still try to run stoich unless PE is triggered. Perhaps thats why it was not used? I'd like to do a guinea pig for you but I'm happy as is now ;)

btw if you are CA based we're over at the end of August start of Sept and I do owe you a few beers!

[joecar]

We can go and have lunch... :cheers:

[stigmundfreud]

We can go and have lunch... :cheers:

sounds spiffing old chap, hooters?

seriously if you're up for it drop us a line via a PM!:beer:

[5.7ute]

You should be able to log commanded fuel & the O2 sensor voltages to test your theory. If you are commanding anything other than stoich & the voltages still switch it would tell you that STFT are active. I am positive though that STFT will only occur when B3605 matches B3601 which is in effect an EQ of 1.0. I run open loop full time so can not test on my vehicle.

[stigmundfreud]

I might have a play but it was my understanding that the voltage will still switch even in OL just the ecu ignores the input back from the sensors. Certainly stft is being logged at WOT loads but it mustn't be fed back in by looking at the voltage constants on the sensors.

Maybe worth me lowering my PE table below the OL commanded table to see if this completely cuts feedback off. Fuel prices have limited my current testing abilities for the time being...