Does weather affect the tune?

[UFGatorGuy20]

I've seen mixed responses in random threads. So, I did a search for "weather tune" in titles and each thread only had one or two responses. I'm trying to understand what different ambient humidity and temperature levels would affect tune wise? You're just sucking in cooler air during the winter right? Not more volume... just cooler air. What's the need for a separate tune? What would be different in a cold weather tune as opposed to a warm weather tune? Timing? I just figured the mass air would adjust accordingly. :shrug:

 

[nolyaw]

subscribing...

 

[96stanggt]

Weather won't affect the tune, IF it was tuned properly. If the car was tuned through the MAF then the MAF will do it's job and compensate for weather conditions. Now if the car was on the ragged edge of running out of fuel when tuned during the summer, you'll have a problem come winter when the car makes more power and needs more fuel. Or you could have an issue where the tuner tried to compensate for lack of fuel (or hell even lack of tuning ability) and ramped up the fuel multiplier thus "throwing" more fuel at the car than the MAF can provide, at that point the car isn't really tuned properly through the MAF anyway.

 

[sprstr1000]

depending on weather depends on how much boost i will run
comparing a hot dry day 28degrees to a cool dense night 12degrees iwill see a 2 to 3 pound diff in my boost which i can feel in the seat of my pants

 

[Brutal Metal]

A bit of topic but as far as DynoJets correcting for High heat and humidity conditions in the deep south I'm calling BS, I've seen 15RW difference on the same dyno between summer and winter.. and that's where MOST custom tunes are done! "Note" the A/F's where similar but the car overall was just down on power..

 

[fiveoh2go]

I've seen 15RW difference on the same dyno between summer and winter.

Heat and humidity will kill power production, isn't that to be expected? :shrug:

"Note" the A/F's where similar but the car overall was just down on power..

I can live with a few less horses when the mercury rises, a blown engine I can't live with.

 

[Brutal Metal]

Of course it will kill power but So Many members on here say 500HP on a Dyno Jet is the same from Maine to Florida cause the electronics are supposed to compensate for the temperature differences and I'm calling BS on that!

 

[adrenaline rush]

The weather technically doesn't affect the tune. However, the ambient conditions will affect the power output. The calibration is the calibration. It's coded into the RAM area of the ECU. When the MAF sensor sends the airflow data, the ecu will compensate for the correct amount of fuel needed. The algorithim is hardcoded, but the A/F and spark is calibrateable. This is what your tuner changed.

When OE vehicles are SAE certified, it is done in an environmental chamber. The conditions are held at a constant. Also each rpm point is held until steady state before the SAE witness confirms that the HP/TQ is certified. This is all done on an engine dyno.

That being said chasis dynos are good to get a ball park figure of your HP/TQ. However, that's all that it is, a ball park figure. There are way too many variables. If your tuner dynos your car at 6 in the morning on monday. It won't be the same number if he dynoed it at 6 on tuesday.


If you had a good tuner, he would of been aware of all of these variables. Therefore, he would of tuned your vehicle via A/F and spark to not run on the ragged edge. Also, good tuners will calibrate in a consistent manner. Meaning that if you 500hp today, you'll make +/- 15% any other time.

 

[P49Y-CY]

^good post

so since cooler air is denser air, then is the maf actually reading more oxygen molecules in cooler air, or does it only measure the airflow?

 

[adrenaline rush]

^good post

so since cooler air is denser air, then is the maf actually reading more oxygen molecules in cooler air, or does it only measure the airflow?

MAF=Mass Air Flow

The sensor is doing both. Most MAF sensor transfer function algorithims within the ECU are in g/s or some equivalent.

 

[UFGatorGuy20]

The weather technically doesn't affect the tune. However, the ambient conditions will affect the power output. The calibration is the calibration. It's coded into the RAM area of the ECU. When the MAF sensor sends the airflow data, the ecu will compensate for the correct amount of fuel needed. The algorithim is hardcoded, but the A/F and spark is calibrateable. This is what your tuner changed.

When OE vehicles are SAE certified, it is done in an environmental chamber. The conditions are held at a constant. Also each rpm point is held until steady state before the SAE witness confirms that the HP/TQ is certified. This is all done on an engine dyno.

That being said chasis dynos are good to get a ball park figure of your HP/TQ. However, that's all that it is, a ball park figure. There are way too many variables. If your tuner dynos your car at 6 in the morning on monday. It won't be the same number if he dynoed it at 6 on tuesday.


If you had a good tuner, he would of been aware of all of these variables. Therefore, he would of tuned your vehicle via A/F and spark to not run on the ragged edge. Also, good tuners will calibrate in a consistent manner. Meaning that if you 500hp today, you'll make +/- 15% any other time.

Great info and well described. Thanks. :beer:

 

[mustangtw]

My car slowed down 2tenths in the 1/8 from when I ran on a cool march night around 50-60deg to a hot and muggy 80-85 deg night. It's still running the same air/fuel ratio and the tune hasn't changed.