IAT temps changing my VE

[Dale]

I have added some new parts to my engine, and this part of the season the air temps can change up to 40degs in a day. I noticed doing data logs during different times of the day are throwing my VE all over the place. I see no place to change this in the "stock" tune. After searching on here I have found:

1. "lock" the IAT into one temp (is there a way in the pcm?).
2. Upgrade to cos5 and use A0014
3. If option 1 is not available, install a resistor inplace of my IAT while doing data logs.
4. Log during the same time every day, which doesnt help really cause even from day to day, you get about 10deg difference.


Now, also, if I go with option 1 or 3, then my fuel is going to be way off if I drive during really hot times, or really cold times correct? Making cos5 really my best choice? Any other thoughts?

Why/how would GM not have some option in the stock tunes to not adjust for this better then it does?

[mr.prick]

atmospheric conditions are going to have an effect no matter what you do.

[redhardsupra]

Dale, there's _a lot_ on the topic on the forums, just search for temperature bias, or temperature modeling, i've done a ton of work on it, it's all on my site, take a look at it, try not to get scared

[Dale]

I have searched on here, but so much stuff. Plus I was just searching on IAT. I'll take a look at your site and the key words you gave me.

[macca_779]

A0014 is a huge help in this regard. I use it religiously.

[WeathermanShawn]

Dale, are you just logging VE values, or is it your intention to stay in OLSD?

Not trying to start a controversy here, but running in closed loop with feedback from the MAF will address many of the air density challenges you are facing.

Not discounting that there are ways to do it with a COS upgrade and many many people successfully run OLSD.

Just adding that I am pretty much successfully tuned and am running Closed-Loop. Did the VE tuning, calibrated MAF, re enabled closed loop, and car is running great (every day).

Living in Colorado where terrain and atmospheric conditions change very rapidly, I have learned to work within the parameters of closed-loop tuning.

Just a thought. You said you wanted any other ideas.

Don't know if this is an option for you, but in any case best of luck.

..WeathermanShawn..

[Dale]

I'm still learning this stuff, but I am infact running SD, no maf as the propper one wont fit in my air intake setup. I use to have one in it, and got killer mpg, but kept getting maf codes so I took it out.

I keep getting OL and CL confused. I have no clue what it is I am running.


The car runs fine. But when my STFT swings -12 on the way to work, and +6 on the way home... I am sure something is wrong and I need to work on it. But the only thing that has changed is the air temp. I'm very surprised the tune doesnt adjust better for air temps, or have a chart that you can tweak.

[redhardsupra]

what are your IAT's on the way to work and back? if they're that consistent, i could probably eyeball a better bias table for ya...

[Dale]

The readings while moving are accurate with the weather channel so I know the sensor works.

The morning on the day I noticed, it was 72degs.
Drive home it was around 95-98deg.

Now the setup I have, when setting at a light it gets radiator heat BAD. Which I am thinking of ways to fix this.

If we didnt have 10days of rain, I would do a morning and afternoon log and post them with my tune. But I refuse to drive this car in the rain for safety of many people.

:edit: Shawn, are you saying if I had a maf sensor in the car it would adjust better? Maybe I need to rethink my complete intake setup and have it so a maf will work.

[WeathermanShawn]

Dale:

Understand. I just started EFILive about 2 months ago. A hundred hours later and a lot of help from this board, I think I finally have it down.

As RedHardSupra eluded to, biases exist in the VE computation concerning temperature. Just look at the denominator in the VE computation (charge temperature). It is a function of IAT and ECT, and how much each influence the charge temperature is dependent on the 'airflow factor' or how fast you are going.

I guess I would suggest going to one of the newer custom systems that allow more accurate commanding of the VE fuel computation as temperature varies.

As you stand now, there is a small error or bias. If you do a SD VE tune in summer when the air is warmer and less dense, at worst in winter your tune will be a little richer (air is cooler and more dense).

My advice is to not let it overwhelm you. As far as open loop or closed loop..I always just try to remember it like this:

Open-Loop: No narrow-band O2 feedback.
Closed-Loop: Narrow-band feedback.

When you set closed-loop enable temperature to 254F, it will never enable, thus you will always remain in open-loop..fuel is commanded by your 'commanded fuel when in open-loop'.

Hope all is this helps. Never any absolutes, but you can successfully tune these cars. And when you do you will be very happy.

Good luck..

..WeathermanShawn..