I need help to get my closed loop to run as nice as my open loop!

[Paz]

G'day guys.

I've been working on getting my VE sorted in open loop and the car is running better all the time as i adjust, problem is when i switch over to closed loop it runs okay but would say it is 75% better in OL than CL.

I'd like to be able to run it 100% of the time in CL (if i can).

Specs are-
Cam @ .050 233/238 115lsa
Single i/cooled turbo, both O2 sensors about 30" from turbo dump (this is my CL issue i think)
DW 65lb injectors
No MAF fitted (SD only)

When running in CL I've notice from my logs it is nearly always tending to run leaner when at a constant rpm (plus a few other issues), I'm thinking that maybe the reason is my two O2 sensors have been moved from just after the old cast manifolds to now being about 30" from the turbo in the dump before cats (both in the same pipe side by side).

Can also feel surging which I'm thinking coincides with the rich/lean O2 swings.

So far i have tried (from research)-
1.Closed loop proportional airflow stock x 0.835
Closed loop integrator delay stock x 1.1
No change with above

2.Closed loop proportional airflow stock x 0.9
Closed loop integrator delay stock x 1.25
No change with above

3.Min rich/lean from 250mv to 450mv
Max rich/lean from 650mv to 450mv
No change with above either (with same air and delay as 2above.)

I've tried reading everything i can but finding very little information with a similar setup as mine (turbo, dump and O2 sensors)

Thanks in advance, any help would be greatly appreciated.

Also, which tables do i need to adjust so as i can get a constant AFR commanded when tuning VE in open loop (it varied from 14.7), Open Loop EQ Ratio Gas gear/ P/N?

Attached is CL drive, OL drive and current tune.

[07GTS]

im not sure how well the 02 switching will work when both sensors are in the same bank because it cycles hi/low bank to bank and if u have the change from one bank affecting both sensors then it will try to correct that also because it thinks the bank 02's are separate, would prob cause the surging also, for OL fueling make sure all the tables at operating temps are 1.0 all the gas gear ect and OL IVT table ect

[Paz]

Ahhh very interesting GTS, i didn't know that they switched from side to side cycling rich/lean alternatively, that does explain the surging for sure then, open loop full time might be my only option!

Was considering fitting my O2s into the manifolds pre turbo (both banks feed turbo) but also read that they don't deal with pressure too well.

Time to read up on setting up full time open loop tune!

Thanks for the confirm on the tables.

[schpenxel]

Yeah I can't imagine it working correctly with both O2's on the same bank. I'd try them pre-turbo personally. It's not that it switches back and forth between banks, it's that each bank goes back and forth rich/lean independently.

The readings can get weird under boost with sensor pre-turbo BUT you're going to be in open loop anyways in boost so I'm not sure it will really matter.

I'm not a fan of open loop all the time unless you either really like tweaking things all the time or don't have any other choice.

[Paz]

Okay so doesn't alternate banks (sorry most likely me reading that into GTS's post), just adjusts separately, no doubt there would be some overlap which reduces the surge i guess.

I've got a bung in the drivers side manifold already (feeds crossover to turbo), i shall endeavor to get one into the passenger side bank (turbo manifold) but in the mean time concentrate on open loop tuning only.

Is the "Hot Power Enrich Enable TPS Threshold vs. RPM" table the one to get the ECM to kick into open loop when in closed loop?

Currently mine is 15 from 0 to 2000rpm, 11 at 2500rpm and 8 from 3000rpm to 8000rpm, it will drop the commanded afr but still remains in closed loop (as per above CL log)?

[Codes]

Okay so doesn't alternate banks (sorry most likely me reading that into GTS's post), just adjusts separately, no doubt there would be some overlap which reduces the surge i guess.

I've got a bung in the drivers side manifold already (feeds crossover to turbo), i shall endeavor to get one into the passenger side bank (turbo manifold) but in the mean time concentrate on open loop tuning only.

Is the "Hot Power Enrich Enable TPS Threshold vs. RPM" table the one to get the ECM to kick into open loop when in closed loop?

Currently mine is 15 from 0 to 2000rpm, 11 at 2500rpm and 8 from 3000rpm to 8000rpm, it will drop the commanded afr but still remains in closed loop (as per above CL log)?

Your PE trigger is MAP 75kpa. It appears in the CL log it is going to OL once PE enable parameters are met, as your fuel trims are going to 0. Try adding channel "Fuel System #1 Status (SAE).

[Paz]

I'd set my PE map trigger to 75kpa as that was normally when i started to make boost, stock it was 15kpa, that would mean it was in PE nearly constantly when stock wouldn't it?

I've been monitoring "fuel system status" but this could be the wrong one, when the commanded AFR drops from 14.61 to 12.49 it still reads as "stoichiometric closed loop"? My Fuel trim Cell states it is in "9" when the AFR drops.

Added channel, will do a scan after lunch.

Would it help if i upload my channel config?

[Paz]

Okay, did a short log while driving back to work in car after i flashed a new tune in and seems to be an improvement (feel less surging), still need to do a few ks to get the after flash bugs out to do a proper scan!

I've changed my "O2 sensor R/L vs airflow mode" B1/B2 tables from the above tune (stock settings) to 450mv across the board, might play with them some more.

I've added "Fuel System #1 Status (SAE)" to my channels and you are right Codes, it is going into "OL-Accel/Decel" when it drops my AFR, i'd been using the wrong channel to scan for this.

Regarding the PE Enable Map trigger of 75kpa, am i better off to drop this down a bit more? Reason i have set it at 75kpa is i start to come onto boost at around 100kpa so i gave myself a bit of head room (BE is set to 90kpa)?

[07GTS]

yea i was just meaning the 02's if like mine when one bank is rich other is lean and they alternate constantly for CL, personally i use TPS for entering PE and i also use BE for boost, i have my TPS enable at 11% around cruise up to 2500 and 8% after that, actual throttle is about 40-45% PE enable which is heaps of throttle with the blower for cruising around and is close to making boost also i find the TPS very quick to react so fueling is always where it should be, i tried using the map for enable but it just didnt seem as reactive as the tps was with mine

[Paz]

Thanks GTS, will drop my pedal in the lower rpms a bit and see what i end up with, mines currently dropping into OL around 40% at present.

Interesting to note i am seeing about 190 milliseconds of delay from the time ECM drops the cmd AFR to the time the wideband starts to register a richer afr.

[07GTS]

yea there will always be a small difference because the WB is further from the engine so its that time it takes the exhaust to get from injector into cylinder when commanded then to WB, u can setup filters to ignore that error during the change in EQratio to clean up your logs a little

[Paz]

Well I've conceded defeat at this point in time trying to get closed loop running in my setup and have decided i shall go open loop full time for now via the tune/editor.

Noob question, which tables do i mod in the editor to call for open loop full time?

So far to command open loop i had been using the scanner controls, last tune i maxed out the "ECT vs Startup ECT" table thinking this would cause it to stay in open loop full time as it will never get to the temp, this morning's drive it seemed to be okay but when driving this afternoon (also hotter ambient temps) i noticed that the O2 sensors were affecting fuel so obviously not 100% in open loop?

[07GTS]

yea i just max out ect v start ect and the 02 readyness table also i think it was not sure if it makes a difference or not, look at the stft to see if they are working or not or there should be a OL status pid u can log

[Paz]

Never even thought to look at my STFT tables , thanks GTS.

I've modded all three tables for closed loop now, hopefully it sticks it into OL full time.

Yep monitoring "Fuel system status" and "Fuel sytsyem #1 status" pids.

[Paz]

Question for those that know, if I'm going to be running open loop full time (not too many other choices at present) how important are things such as inlet/ambient air temps etc going to affect how rich/lean i am running?

Effectively I've just got a fancy carby in open loop, is there ways i can fine tune it?

[schpenxel]

Not sure what you're asking. It needs to know air temps to calculate how much oxygen is going into the engine. You can still adjust airflow, maf/VE, like always..

Mine got stuck in open loop for a few days once and it did fine so I'm sure it can be done

[Paz]

Mainly asking how much my OL tune is going to be affected say from a cold day to a hot day?

If i do my VE tuning today at 20 deg C and get it within a few % then in a few weeks time we get hotter 35+ deg C days is it going to run richer or leaner?

Def still running an inlet air temp sensor, just no MAF in OL.

Another question, why does the ECM call for a richer AFR ratio on hot starts, can understand why on cold starts but hot doesn't make sense to me?

My ECM at normal operating/cruising will always call for 14.68 (I've set it this way for tuning the VE obviously), on a hot start yesterday i noticed it commanded 13.52 at start and took around 23 seconds to level out to the usual cmd'd 14.68.

I'm thinking it is to do with the open loop gain tables (particularly Injtemp gain?), no harm to adjust this in the higher operating temps to get rid of the commanded rich starts?

[schpenxel]

If it's dialed in correctly fueling shouldn't change regardless of temp swings. That's why it has things like an IAT sensor..

You can run a MAF in OL just fine if you want

Not sure why GM does that but I'm sure there's a reason.

I wouldn't worry about it unless you're having issues with it being too rich during hot starts or something like that

Log intake valve temp and injector tip temp and you should be able to see what area of those tables you're in

[Paz]

Thanks for the reply Carson.

No chance of me being able to run a maf sadly, got a thumping great turbo on the road haha.

Yep logging both those PIDs which had me looking at the OL gain tables.

It does seem to be running rich at hot starts, have just been comparing my stock injtemp gain table with a stock ZL1 and my stock one is def calling for richer at the higher temps, shall make some adjustments.

[07GTS]

yea could just be the inj tip temp v engine run time in the OL tables if its richer on hot start, i have mine all set to 1.0 still starts fine when hot