Adjusting for weather while autotuning?

[Chris81]

On the car i'm tuning right now, the other day the weather was cool (IAT's in the 50's) and I got the car to run pretty well for a big cammed stroker motor with a 90 mm TPIS TB.. the car didn't want to die on decel and idled great

Today I did some more tuning and I had a hard time getting it to not die coming to a stop, today the temp was in the 80's and the IAT's were in the 90's..

The car is setup for Autotuning, so no MAF or o2's

How can I correct this?

[Delco]

On the car i'm tuning right now, the other day the weather was cool (IAT's in the 50's) and I got the car to run pretty well for a big cammed stroker motor with a 90 mm TPIS TB.. the car didn't want to die on decel and idled great

Today I did some more tuning and I had a hard time getting it to not die coming to a stop, today the temp was in the 80's and the IAT's were in the 90's..

The car is setup for Autotuning, so no MAF or o2's

How can I correct this?

You can filter for IAT in the logging , once you have the VE table nailed at a set constant average temp then and only then start playing with the IAT temp compensation tables in the custom OS systems , with this you can dial in the correct amount of compensation for different IAT conditions.

One of the biggest mistakes most people make is keep adjusting too many tables with too many variables , get a consistant tune nailed then under consistant conditions before starting to play with the corrections

[Chris81]

I've thought about filtering the IAT's, but since they are all about the same on any given run on the same day I decided not to.

My main problem is the temp as a whole.. the tune went to crap with the weather today, the other day my ben's were very close in that weather, but today they were all off with nothing but the engine and IAT temps changed.

Now, when its cold again i'm assuming the car will run too rich again?

I was wondering if there was anything to do for this other than the IAT temp compensation in CustomOSV3?

Also, if I can get the VE dailed in to my liking in one day.. should I re-enable the MAF then run the ben factors on it? or leave the car in SD to do it?

Turning on the MAF should fix some of these problems since it will work with the VE for fueling correct? Even still in open loop?

[Delco]

I've thought about filtering the IAT's, but since they are all about the same on any given run on the same day I decided not to.

My main problem is the temp as a whole.. the tune went to crap with the weather today, the other day my ben's were very close in that weather, but today they were all off with nothing but the engine and IAT temps changed.

Now, when its cold again i'm assuming the car will run too rich again?

I was wondering if there was anything to do for this other than the IAT temp compensation in CustomOSV3?

Also, if I can get the VE dailed in to my liking in one day.. should I re-enable the MAF then run the ben factors on it? or leave the car in SD to do it?

Turning on the MAF should fix some of these problems since it will work with the VE for fueling correct? Even still in open loop?

If you are happy with the VE table then do a drive loggin the ben #'s if the IAT is different to what you did the original tuning then change the IAT temp compensation to bring the ben factors into line , hardest part is getting consistant IAT and getting enough different temp data to get a good IAT curve.

[Blacky]

Ross and I have been discussing a plan to better compensate for the changes in IAT temp.

By recording the original temperature at which the VE table was calibrated we can make the PCM use the difference in the original temp and the current temp to calculate an automatic adjustment. The PCM does this for the cranking VE table but not the main VE table. We presume because GM meant for the cranking VE table to be used but the main VE table (in a a stock PCM) is really only an emergency backup. So they probably never bothered to implement the adjustment for IAT in the main VE table.
Hopefully it is not a big job and it can be included in all custom OS's.

Until then you may be able to get some joy using the {A0014} IAT VE Multiplier to compensate for changes in VE.
The values (calculated by the adjustment formula mentioned above) that you should use in the {A0014} IAT multiplier table are defined in the attached spreadsheet.

Regards
Paul

[turboberserker]

Wow, nice speadsheet Blacky. Thanks!

[Chris81]

Awesome spreedsheet! I'll have to give it a try

[oztracktuning]

I thought the IAT was a multiplier of the VE table and by doing that - values above 1 would make it richer - values below 1 leaner ?

My car is leaner when hotter and richer when cooler. So it looks to me like the values are around the wrong way. Maybe i missed something somewhere??

[Delco]

I thought the IAT was a multiplier of the VE table and by doing that - values above 1 would make it richer - values below 1 leaner ?

My car is leaner when hotter and richer when cooler. So it looks to me like the values are around the wrong way. Maybe i missed something somewhere??

They normally go richer when warmer and leaner when colder due to the increased air density.

Paul , those values look just about exact for what I ended up with in my base tables in the real world.

[oztracktuning]

Mine seem to do other things. Maybe its because the IAT position in my over radiator air intake is in a warm position and the IAT is saying the air is hotter than it really is when i am idling in traffic??

If this was the case my car would have more density of air than expected when heat soaked and lean itself out - is this right??

[SinisterSS]

Paul, the spreadsheet is nice and all but where is the "I use real units" button?

Haven't seen that many Kelvins since college or in my closet - oops, those are Calvins.

:muahaha:

[Blacky]

Paul , those values look just about exact for what I ended up with in my base tables in the real world.

That's good to know, I only calculated those values based on airflow/temperature theory.
Paul

[SinisterSS]

Imperial...

[Chris81]

They normally go richer when warmer and leaner when colder due to the increased air density.

Paul , those values look just about exact for what I ended up with in my base tables in the real world.

My car runs richer in cooler air, and of course the colder the engine is.. the richer it runs as well.

And, the car in question that i'm tuning has the IAT in the MAF so it sees hotter IAT's than my car.. and it went WAY lean from one tunning session to the next due to the engine temps being over 30 degrees higher and the IAT's over 50 degrees higher in places.

[oztracktuning]

The new table didnt work in my car. It went way lean at high IATs, so i have reverted to 1s and done some logging - it is certainly leaner at higher temps than 30 and richer when colder than 30 !

[vetteboy2k]

Is it just me... I can't seem to open the attached files? Use excel right?