How the f*** do you richen cold idle in closed loop?

[Mr. Smith]

Is this real life?
There's an easy to read/understand/tune open loop ECT vs MAP AFR table ("EQ ratio")
but there doesn't seem to be anything for closed loop
So (pretty much) I can adjust my fuel trims for the first minute of starting my car from cold.. say 10 degrees C to 34 degrees C.. but then can't adjust my trims from 34 degrees to 90 degrees.
And there's only 2 tables for open loop too, compared to a dozen closed loop tables.

[dermotw]

Well... you don't, 'cause its in closed loop... so it will always drive towards 14.7 or 14.63 or whatever... If you wanted to do that, you'd have to move the CL enable point to something else, it was likely chosen at 34 to minimise cold emissions... (get it into CL asap...)... well thats my understanding anyway...

[Mr. Smith]

Thanks.
Maybe I am better off running OL until operating temps..
Why would my emissions be worse (when cold) when my fuelling will be more accurate.. or won't it?? I don't see why it wouldn't.

What does everyone else do to adjust cold fuel trims.. or does everybody just leave it? Do you all set your CL to come in later?

Wait..... why would it even matter if it's in CL??? We can adjust our fuel trims in CL, so why isn't there a table where you can adjust the trims/fuelling at certain coolant temps (like the Open Loop EQ Ratio table)?

It just seems ridiculous that there isn't a EQ Ratio table for CL.. when there's one for OL + a thousand other tables.

[Ben C]

The issue is a wideband can only read stoichiometric, so when commanding anything other than that you can't have closed loop operation with a narrow band sensor.

[Mr. Smith]

Aaand my brain just melted.. but thanks for your time and help.
Why can't I simply add a bit of fuel when my motor is cold.. in Closed Loop??????
I'm done here for the night. I want to be able to sleep tonight without thinking about this.. all night.

[Mr. Smith]

God damn it, I'm back.

I just remembered..
Don't I just have to raise my Base Running Airflow Table > Idle Airflow table to richen it up when cold.. or is that in only OL too?

[Eaglegoat]

That doesn't control fueling. Especially in closed loop.

[dermotw]

Only way I know is to set the CL enable temp to e.g. 60C or something, then play with that OL EQ Ratio table below 60 (which I always thought seemed to be astonishingly rich, btw... ).

As soon as the engine is "warm enough" (and GM decided 34 was enough, in these cars anyway..) then CL will give minimum emissions, the cats will work, blah blah... One of the worst times for emissions in cars is cold startup, and any manufacturer would want to get out of that asap.

When its cold (the engine, or indeed the weather) the fueling needs to be rich to ensure it even fires, but there's a whole bunch of unburnt fuel then getting dumped out the back, you need to get leaner & to stoich as fast as the engine can tolerate it!

[jimmyblue]

Are you on the hook for non-warmed-up emissions, or just
concerned in a general way?

What are you really trying to achieve?

[Mr. Smith]

Thanks, guys.

Dermotw, I don't get why switching to CL sooner would be better for emissions. It's not like when it switches to CL the motor instantly heats up to operating temps. Is it a narrowband thing which results in less emissions? And I don't want to be running 10.5AFR during warmup or something... I just want to see 0's instead of 10's in some of my STFT cells when my motor is warming up.
I'll try setting my CL-kick-in temp higher..

My engine is already lean on startup. I'm trying to richen it.. (jimmyblue) because I hate seeing my fuel trims in the red and want them all as 0-ish as possible at all temps, revs, loads, conditions... And 99+% of my drives (for the last couple years) are really short.. like 10 minutes max., so cold start / warmup makes up around 50% of that time... and it's hard for my trims to average out to what they really are at operating temps with such short drives if you get me....

When I see my STFTs during warmup (and while driving) as soon as they start reading, I usually see around +12.5 in my 1,200rpm 40-45MAP cells and when I check my Max Values (+) STFTs after I've saved the log, I'll see 20+ in 800-1,200rpms 35-40MAP cells...
which is just
not
on.

I want to know what's realistic.....how close to perfect we can get our tunes... if people bother to tune their cold starts / warmup... if it's possible to get perfect 0's at all temps on an ideal day... Max and Min Values at 0 - -1.... or is -1 at operating temps and +15 on some cells during warmup as good as it gets?

jimmyblue.. I'm trying to achieve TUNING GREATNESS! ( )

[dermotw]

When in the warmup cycle (before CL), it is by definition running rich to some extent, and thats not good for the cats! It will destroy them if it goes on long enough, so it has to be minimised. Cats 'like' a/f around 14.7 or slightly leaner. The CL holds the fueling at 14.7 come hell or high water, lol, and thus the cats can operate and cleanup the exhaust emissions some more. Of course, I haven't GOT any bloody cats hahaha...

More modern vehicles than mine/ours are using wideband o2's as standard, which don't switch but constantly measure of course, and can measure fueling fully across an, err, wide band, so THEY are in CL all the time, effectively.

BTW its much worse if you have a carb engine... An injected vehicle can tolerate quite lean startup a/f ratios, and move towards 14.7:1 quite quickly.

Looking at my 'ol '99 ECU, as standard it is at about 12:1 at zero C, OL, by 30C it's at 13.9:1... and so on..

[Ben C]

I've never looked hard at this issue, as it's never bothered me, but isn't there a setting that determines what engine temp the long term trims start learning? Meaning the short terms doing their thing when cold would have no impact on the long term trims.
The fact that this parameter exists (just checked LTFT Min ECT, ) tells me it's unlikely you can get zero trims when cold, or that it's not worth the hassle of trying.

[AutoWiz]

Well if you are experiencing driveability concerns from being in closed loop at a lower temperature you could certainly use the iat spark table to add a few degrees of timing advance in those areas/temps as an alternative to changing closed loop target afr's. Alternatively you could use the closed loop enable ect vs. iat table to save closed loop for a higher temp.

[Ben C]

Well if you are experiencing driveability concerns from being in closed loop at a lower temperature you could certainly use the iat spark table to add a few degrees of timing advance in those areas/temps as an alternative to changing closed loop target afr's. Alternatively you could use the closed loop enable ect vs. iat table to save closed loop for a higher temp.

You mean ect spark table?

[AutoWiz]

lol. yes.

[Mr. Smith]

Thanks again, guys.

Fyi, I don't have any driveability issues when my motor is cold.. it runs great at all temps.
I just don't like seeing +20 STFTs when my motor is cold.. and how it affects my STFT averages....
I've also disabled LTFTs.

I'm going to raise my CL kick-in temp and read up on Open Loop now..

[5FDP]

To me there is just no way to get everything exact on cold starts, way too many variables. Just increase the CL enable to like 130-140 degrees if anything.

I don't even start logging untill the motor is warm unless it's something specific with cold starts and idling that is a problem.

[AutoWiz]

So why not try to reduce your idle airflow at that specific temp?



Why not find the temp where your +20% and multiply that cell by the .95. re test and see where you are at. It's not dropping the idle rpm just closing the iac / throttle blade a little more to force a richer condition

[Ben C]

So why not try to reduce your idle airflow at that specific temp?



Why not find the temp where your +20% and multiply that cell by the .95. re test and see where you are at. It's not dropping the idle rpm just closing the iac / throttle blade a little more to force a richer condition

Maybe I'm missing something, how does reducing the airflow add fuel?

[AutoWiz]

Maybe I'm missing something, how does reducing the airflow add fuel?

afr is a ratio of fuel vs. air. The less air that enters the motor, the richer it becomes. I mean, that's a pretty basic principal right there, right? vacuum leaks don't take away fuel but they sure do make a motor go lean. Haven't you ever seen a choke on a carb? How does it work? does it add fuel? no it closes a flap and restricts air.