I've read before that it's advised to tune your car in hot weather. I'm trying to figure out the reason.

Will the ecu-controlled boost compensate for temperature and elevation changes? Right now I'm trying to get my WDC numbers zeroed in so I can have my boost desired engine load with the right numbers.

So if one tunes their car in the lower elevation/lower temp area then wanders into a high elevation/high temp area your car will be pushing less air and reach lower load so the ECU will try to correct and raise the boost in order to get to the target load numbers right? But the WDC numbers are MAX numbers if I remember correctly so you won't get any higher boost and your load will never go higher.

On the other hand, if you tune for high elevation/high temp and you wander into a low elevation/low temp area your turbo will be pushing a lot more air in than before and cause higher loads so it'll lower the WDC to get into the desired load numbers.

So one way you get your ecu doing corrections and one way you don't. Or am I incorrect about this? Any advice would be appreciated.

 

I'm pretty sure there are people trying to work out the barometric tables so that we can tune the weather adjustment to be a little better that what it is. The main reason people suggest tuning in hot weather is because that's more of a worst case scenario as far as power / knock / boost etc. However, if you tune for 23psi on a hotday 100 w/90% humidity for example I'm not sure the ECU will be able to correct for a 40 degree 40% humidity day. My car is tuned at 23psi for 100 degree weather and it seems to want to overboost a little when the temp drops. I figure I'll have to remove some more duty around the boost spike after summer is over. It hasnt been enough to re-tune yet but it's inched towards 24 psi but doenst have any knock so I've left it alone.

 

WGDC values are baseline values. They will be offset be the error correction table if target boost is not reached or exceeded.

The ECU has a temp correction table built in, but I'm not sure what values it alters for the correction. I assume it's the MAF reading, bt I'm not sure. Some have said that it isn't perfect from the factory and can benefit from tuning.

I personally feel that it would be ideal to tune your car in moderate weather for your location. For instance, if the low in your area reaches ~20º in the dead of winter and 100º in the blistering summer (like here in Alabama), I'd tune at a temp slightly above the median of the 2 ... around 65º or 70º.

Since this isn't always possible, I'd simply suggest skewing the WGDC table for an offset load value and let the error correction (TBEC) table make up for it. For instance, it's been 100º+ here for about a week. I'm aiming for ~23.5 psi. Since I know that it takes a higher WGDC value to reach the desired load in this heat, I can tune the WGDC for a lower boost level while leaving the desired load value where it needs to be for 23.5 psi. This way the TBEC table will increase the WGDC to meet the desired load while it's hot, but won't have to correct down so far when it gets cold.

Here are some theoretical numbers as an example ...

Desired Boost = 24 psi
Load required for desired boost = 270
WGDC required for 24 psi in current 100º heat = 60%

Tuned values ...

Boost desired engine load + Offset = 270
WGDC = 55%
TBEC = +/- 5% @ 17.5% error

Results ...

@ 100º

Uncorrected actual load = 255 @ 55%
Corrected actual load = 270 @ 60%

@ 70º

Uncorrected actual load = 270 @ 55%
Corrected actual load = 270 @ 55% (no correction needed)

@ 40º

Uncorrected actual load = 285 @ 55%
Corrected actual load = 270 @ 50%

I hope this makes sense ...

 

Absolutely, but like the above poster I'm not running the 3port yet so to achive 23.5 psi (159 + 100 offset), I have the solenoid pill removed and WGDC damn near 100% except for the boost spike area. Are you suggesting raising the offset to make BDEL around 270 so that duty can be lowered and have more "headroom" to play with?

 

There's also afr's that lean out with colder weather.

 

I believe that's what the temp compensation table tried to take care of.

I'm not recommending raising the desired load value, but tuning the WGDC values for a lower load value and letting the error correction take up the slack. This will allow the error correction table to work more reliably in cooler weather.

 

I guess I am lucky because here in SoCal we do not see extreme variation in temperature. From the begining of June to the the end of September (considered to be summer) the average temperature where I live is ~73* F. So when I tune, I check the weather forecast at www.wunderground.com and make sure that the temps are between 72 and 80* F.

I see little reason to tune for extreme hot weather since I do not beat up on my car in extreme hot weather. If I ever take my Evo to a road course then I will use 100 octane gas whether the weather is cold or hot. Since the car is tuned for 91 octane and I am running 100 octane, then that will give the car all the protection from detonation it needs.

 

If given the choice, I wouldn't beat on mine either ... but, the Auto-X season lasts through the summer ...

 

We have 9 mos of hot/humid weather down here. But it's tuned for those conditions. Probably 4 or 5 months of 100+ degree weather where the ambient underhood temps are 135F.

Actually I think extremely cold weather would be harsher on a vehicle than extremely hot weather. The car's engine runs the same temp all the time (at normal operating temp), just start-up and intake temps can vary quite a bit. In a cold start the engine oil does not offer as much lubrication. As long as the car is tuned for the intake temps I dont see how it would hurt it at all.

 

Does the Auto-X class that you are in allow you to run 100 octane gas? That would solve a lot of the heat induced problems.

 

In my area, we have all four seasons and temperatures range from 0 F to 100 F . Very hard to tune for. I got tuned last week in 82 degree weather with 80 % humidity. Personally, I would always tune for the worst. Like someone else said, when it's hot, the probability of knocking is the greatest. So if you're not knocking at 23 psi in 90 degree weather, you're not going to be knocking at 23 psi in 20 degree weather. Just keep in mind that you must adjust the boost controller when the winter rolls around.

And like someone else said, the car tends to run leaner with lower temps, but how does this exactly affect the car? I wouldn't think it affects anything. If anything, just adds a few HP.

 

It overcompensates if left with stock values.

 

double post.

 

The temp compensation, AFAIK, reads mainly from the temp taken at the MAF sensor.

Mitsu probably did this because of ease and cost of packaging. A better place to read intake temp would be right before the throttle body, much like stand alones do.

The way the evo does it, doesn't take in consideration the cooling our intercooler does so it can and will over compensate for hotter conditions at the MAF.

I've seen the ecu richen up the mixture 1 full AFR point on a hot day on the track. I leaned it out to compensate for this and the car ran 1 full point too lean on the drive back home that night in cooler temps.

The perfect and safest way to tune the temp compensation table would be to put a temp sensor right before the throttle body and adjust the compensation table based on what air temp your engine is actually seeing, not what the MAF is seeing.

You have to be very careful and know how you much you should change the table based on the actual intake temps you are seeing. Heat will kill a motor fast if the fuel can't help cool it down.

 

Thanks for the replies. Maybe I should've just asked if the WGC tables are base or max numbers, but not I know the numbers can be adjusted both ways by the ECU.

...as long as the WDC numbers are all 100s of course.