I'm happy thus far with what has become a fairly smooth idle on "Shammoo" when in closed loop condition. I'm not quite there yet on the initial open loop side of the idle yet, as the engine warms up. It's still stinky rich

As I understand things, (and likely I'm wrong) since the conditions for closed loop haven't been met yet (BLM's still locked, low temp) I'm really not using my low RPM fuel chart yet on my $8D -speed density bin in the 7730 ECM.

So how do I lean out my warm up idle while still in open loop. Is this as simple as an entry in a Fuel (pulse) vs Temperature chart. I know it's not truly Crank pulse per say as that is simply a startup chart until the ECM takes over at 400rpm. This is well past startup as I am in the first 3-4 minutes or so warmup What am I neglecting to do to, or failing to grasp conceptually to take more fuel out in open loop idle during warm up conditions? Although I'd rather cut the fuel in open loop, is there a way to get it to closed loop faster to unlock my BLM's if I can't cut fuel?

As always, Thank you for taking the time to read this. Additionally, more thanks to those who respond.

... God bless Grumpy...
Dave

 

Basically, for open loop there are two tables. One is vs MAP, the other is vs CTS. They are a percent change from the stoich value.


Note that after start (choke) AFR is in affect for a short while after start up. So this too can contribute to being excessively rich.

RBob.

 

Is your BPC correct for your application? I believe changing it will affect OL A/F.

 

OK, I'm finally getting back to this with winter being over. I didn't follow what RBob was trying to educate me about, and unsure of the acronym of BPC means.

I believe RBob is trying to tell me to lower both settings, but didn't comprehend the posting? Is change by 5% a good starting point?

 

In open loop the AFR is lowered by the percentage in those two tables.

Start with the CTS table, 5% is fine but 10% can be faster for rough-in.

BPC = Base Pulse Constant, not used in 730/8D. The equivalent in $8D is the injector flow rate and cylinder volume values.

 

Thanks.. will post results

 

just realizing I never followed up on this thread.

Cutting fuel in the open loop "vs temp" helped a great deal to get my initial open loop idle less rich. In retrospect, the mistake I made was lower everything in the chart by a given percentage. The result after a while was having hot restart issues going too lean.

I should have just modded the colder temp stuff and not been so aggressive in cutting with the higher temps along with it.

 

I went backwards on this issue.

Once the wideband gauge comes up. My afr in idle after starting goesup and pegs at twenty.

It exixhits signs of being way to lean in trying to stumle and cut out.

So i'm going to try to work with temp related issues first. I'd like to enrichen open lopp idle. On the Afr vs temp table. I'm unsure about raisng or loeringr the points on the table.
It will change the afr , but in which direction is needed to enrichen.

Trying to accelerate off of idle is nearly impossible, like simply backing out of the driveway and proceeding dow the street, wants to stall. Gets marginally better as it warms up until closed loop occurs.

 

Might have actually figured out part of my question on my own for a change.

looked at the table "open loop param, AFR % changes vs coolant" and its graph. The higher numbers were already showing increases with colder temps. So I increased the bottom end from where I had it at 18 and went to 25. Starting became instantly better without the tendency to stall out.

I also changed open loop param, idle, % change AFR from 3.5% to 4

Overall, etween the two mods, m AFR on the wideband pillar gauge went from 20 to 15.6, so I know I'm headed in the right direction now.
I'll take readings at different starting temps to nail the specifics "vs Temp" stuff

 

I'll have to find the "open loop vs temp" in my 7730 $A1 tune as I have a similar issue, although I'm not sure the VE tables aren't part of the problem too. This gives me another place to look though. Thanks for the heads up!

 

As morning temps become more erratic as Fall approaches, I've been continuing to tweak th open loop AFR qualifiers better. still not ideal, but coming along.

 

Subscribed

 

whats the correct AFR in open loop? when my car is in open loop my AFR is in the 12s-13s, is that to rich? Also in table "Open Loop AFR% change vs Coolant temp" does increasing that value make the AFR richer or leaner?

 

Part of the answer is that it is not just one number. It should be richer at starts and more so in cold weather (talking upstate New York here)
In general as the engine warms you should be going away from the 13's toward 14.5-14.9 whatever your warmed up engine AFR is happy with.

It won't like 14.5 to start with at 26*F. Once warmed up, 12.3 will be stinky rich and wasting gas.

 

I understand it should be richer in open loop on a cold start. I was just dont want to wash my oil down with fuel. I didnt know if the afr in the 12's was to rich? Also if I wanted to get the OL start afr a little leaner, say 13's would I raise or lower the value in the "open loop afr% change vs coolant temp"?

 

hopefully this helps

"open loop param, AFR % changes vs coolant" ( graph). The higher numbers are already showing increases with colder temps. Increasing the bottom end from for more fuel, decrease for less at any given range of temp.

Dave