I downloaded the freeware version (for now) of Tunerpro last night and have been looking it over, and needless to say I have many more questions (but only a couple for now).

First off, concerning my rich coldstart cycle; I was looking through the editable menus of the bin and I am trying to figure out what I need to look at to lean out the coldstart idle. Is it the "Open Loop A/F ratio", or the "RIch/Lean Offset VS Coolant"? Or is it something else entirely?

Second question for now, what can datalogging while in open loop tell me that my nose and eyes can't (running really rich)?

TIA

 

Data logging allows you to visualize input components and develop relationships between those..

Take an example, I have been trying to smooth out my idle lately ($8d 730 ecm). I noticed on the datalogging that my spark advance modulation matched my rpm's bouncing. There is a couple tables in $8d that advance or retard the spark based on error in idle speed. In the tables they are all the same (~5*) for 50,100,150 rpm error.. I looked at the trend in the data log, then I tried smoothing out the correction tables (5* for 150, 4.5* for 100, 3.7* for 50). It made a noticable difference. I'm still tweaking, but its getting better.

Granted, this doesn't answer your cold start question, but it illustrates the value of data logging and visualizing the trends that are there (by graphing different sensors/outputs). I've found that you have to formulate a hypothesis with the datalog, translate your hypothesis into editing the bin, then testing and making notes.. That's how you learn the relationships of different components and the interaction of various settings, as well.

 

datalogging in open loop? not sure what it will tell you. when you go closed loop per log check your temp gauge. mine flips to CL about 160 F if i recall. my issue is exact opposite of yours. super lean especially in cool environmental temps. i pretty much live with the lack of choke function but summer driving was no big deal. i can see if very riich will cause you concern! i would do a search for info on all those cold start"constants". make small changes and note results. i think seat of pants on OL will be what you go on. i have a WB so that is a huge help for me OL/CL/AE/PE. understand a large investment ($$$). hope this info is accurate.

 

I assume this is a tbi with a 7747 ($42) ecm? If so, make sure you get the right ecu file.

Your going to basically have to tweak the tables untill you get the motor to run the way you want if you dont have a WB-O2. Its not very precise but if it gets the motor to run well and have fairly good drivability when its cold then mission accomplished as far as Im concerned. Thats how I set mine up. Exaust smelled like an old lawnmower when it was cold but it didnt bog out, sputter, and it ran good at high loads if I had to go in a hurry.

The first thing youll want to do is to make sure your volumetric efficiency tables are as close as you can get them using the BLMs outputted through the ALDL. Not as good as directly measuring with a WB in open loop but itll get the table roughed in pretty good. That alone may solve alot of your problems. In the stickies TRAXION talks about how to do this. There is probably also more material floating around. Theyre working with a different SD ecm but the theory is the same.

This is off the top of my head and according to my $4D ecm. The truck ecm you have may be different.

The next things to look at are the open loop AFR vs. cool temp and added AFR vs. MAP. These two added together basically define your core AFR. The first table defines a base AFR with respect to coolant temp. At cold temperatures, the motor is going to need a richer mixture with lower AFRs to run properly. The added AFR vs MAP table provides a way to control the AFR as the engines load changes. As the load increases, the AFR will decrease.

There will also be a choke afr and a choke AFR decay multiplier. The choke is basically just what it sounds like. It richens the mixture initially so the motor wont be lean. The choke AFR is subtracted out from the AFR value from the previous two tables. This lowers the AFR and richens the mixture. The choke decay multiplier provides a way to slowly reduce the choke. Just like a carb runs like crap with a stuck choke, so would your motor if the ecm didnt take away the choke after a bit. The choke decay multiplier slowly reduces the choke by the percentage shown in the table every two seconds or so. There may also be an initial choke as well. In mine there is another choke afr that quickly richens the mixture for a second or so after the motor as started.

There is also a base pulsewidth multiplier table. This provides correction to the fueling since the properties of air and other factors will change with temperature. This one you probably shouldnt touch without a WB O2 telling you otherwise. Changing these values without one is pretty much a stab in the dark.

So, basically the AFR vs temperature and added AFR vs vacuum provide your base AFR when you add them together. Lower AFRs will obviously mean richer fueling. The choke afr adjustment is just like a choke on a small engine. When its cold out your going to want to put the choke on so you can get the motor started. This is what the choke AFR vs coolant temp does, turns on the choke. The higher the number, the richer the motor will initially run. And, just like that small engine, we have to turn the choke off after a bit. Thats what the multiplier does, slowly reduces the choke as the motor gets going and eventually turns it off.

 

Please excuse my ignorance, but how are the VE tables calculated? I know they use imput from the MAP and O2 but what else? TIA

 

The volumetric efficiency tables arnt calculated, you determine the values experimentally using the BLM/WB-O2 or whatever you have at your disposal. The VE is a measure of how efficient a motor is at moving air. Basically, its the volume of air moved over the volume displaced by the motor. For example, say you have a cylinder and piston that displace 1L. Assume that the pump can move .75L per stroke. Since the total volume is one liter and it only moves .75 liters per stroke, this would mean that it has a VE of 75%. If your motor is 5.7L and it has a VE of 80% then it can move 4.56L of air every two revolutions Its important to note that the VE table is relative and the VEs youll get from testing are dependant on other things like how accurate your injector constant is and such.

The computer needs the VE tables, manifold pressure, and other things to get some idea of how much air is going through the motor so it knows hoe much fuel to add.