I was reading you tuning FAQ on the DIY-EFI site. Hehehe, I remember reading that a year ago and it didn't make much sense...now it does.

I have one question tho:

If I add timing and the vac signal is lower than before, do I add more timing? Do I keep advancing the timing until the vac signal drops off or until I trigger the knock sensor?

thanks...

 

If the vacuum signal goes down that's a sign that your motor is under less load. Or that you're making the most torque. If the vacuum goes up the engine is seeing more load. When you do this, make certain that you've limited the rest of the tables and that the weather is calm and repeatable. This way of tuning is great for getting the light throttle fuel and timing. It's tedious work but the only accurate way of tuning with the slow ALDL (winaldl or diacom).
Most of the time I don't have access to somebody's car for a long period of time so my practice and patience is nill. The only cars I've done this on is my car. Let's just say I would start at 10pm and not end up getting to sleep until 3 or 4 in the morning. That's with no cars on the road. Oh yeah, and that was after I got rid of that bad fuel pump. Before that it was just too frustrating .
I like to limit the IAC's operation all together when tuning. With it closed I can get the BLMs in the 126-130 range. Haven't tried messing around with the fuel adding vs IAC tables but I'm sure I'll get around to it. Lockers , that's the secret weapon.

 

Ok...I gotcha...

The weather has been crazy lately. I check the barometer on days when it's nice...like today it's 40°F and 30.05" baro. We've been on the weather roller coaster tho...I just keep the Stro in the garage on those days.

I also just realized why you'd want an AE modifier vs. RPM. Seems like a table like that would really help about now.

I made a few chips with extreme changes in very specific areas to help me figure out this bog. I know I've beat this topic to death but this is the only thing keeping it in the garage.

I took out ALOT of AE vs. MAP and timing around 800 rpm x 80 kPa. It helped alot. There is still a nuance of it left but it least it doesn't want to stall. That sucks when I'm makin a left and the engine is drowning in gas and timing.

 

I don't understand why the weather has to be the same. I thought fuel injected cars can adjust for the weather?

 

That's exactly why you want the weather to be the same. You want the computer to do the exact same thing every time so you rule out all the variables except the ones you're working on.

Works for some other things too. Thus the locking of certain parameters.

 

[yoda voice]
....and that is why you fail....
[/yoda]


To do accurate tuning, you only want to change one variable at a time. Yes the ECM can correct for weather. But those corrections are never perfect. The error in that correction then propagates into your new data, skewing your answer.

 

It's really simple to understand OEM efi. Just imagine yourself as an engineer working for say Honda or GM. You can't just go and guess how the vehicle is going to react to things like harmonics, transmissions, tires, pressure, humidity, temp, other gases in the air, different fuels, and thermal properties of various parts over a period of say 10 hours straight towing with oil temps doing funky things and oh yeah, oil properties. It's just SO many variables that even the most expensive simulation software can only come close. True they can be within 1% of your actual VE under all cercomstances but that's only if you tell the software everything. Heck, even gasket materials make differences.
These vehicles are tunded with a base "safe" set of parameters and then field tested. All of their parts go through extensive research which takes time. I'm sure somebody somewhere if given the time, could come up with the near perfect simulation software that takes into account everything but until then you need to field test. This is what GM did but they did it with stock motors and gas/oils back in the 80's. Lots of things have changed since then. This is why we tune our efi. We essentially trust in GM's original code and modify parameters to make certain that the system runs like it would have if driven new from a dealer's lot. There are a few self tuning computers but they don't impress me as much as they should. They usually just use a wideband o2 and a lookup table. That's great and all but who's to say in cold weather with hot oil temps and cheap gas while you're blasting your radio and lots of electrical draw....that the 12:1 afr is what the motor needs.
Don't you love this stuff . Why would anybody want a "bolt-on" when they could have this *** like power over your vehicle

 

[yoda's, mean brother]
.....and that's why there are patches
[/other yado]

Once you move the IAT sensor to be a MAT, and you get your sampling as close to the intake valve as possible, and then have corrections based on MAT, things get sooooo much easier.

Once you get to gathering the best data possible, then the ecm can generate really accurate info..

And wouldja believe Doc and Yado are related?.
Whoda thought.....

 

Hahahaha...I almost fell out of my chair!

...yoda's mean brother...

I wish I knew more about source code...I really want to add an IAT to the 7747. You could say just switch to the 8746 but then you'd need to hack it to get a larger AE vs. TPS table.

AE multiplier vs. RPM would also be nice...