Ripper415

iTrader: (6)

I just installed a set of LTs/ORY and need a dyno tune. Unfortunately, since I'm a student and in class mon-fri, i cant get to a tuner during normal business hours. it looks like the only time i have free during the week would be over christmas break (mid dec to mid jan). i know that colder temps give you worse gas mileage and slightly better hp in normal driving, but how would possibly below freezing temps outside effect my dyno tune if i was to have it done then. another thought is do tuners do their work inside heated garages? the few pictures i've seen of places look like just a big warehouse/garage that would only be a few degrees warmer than the outside temps (like our garages at home). i'd also think they would need to keep the doors/windows open to vent the exhaust produced during the dyno runs. maybe i'm wrong in these assumptions?

WeathermanShawn

iTrader: (1)

You will be O.K.

Assuming a closed-loop system and MAF still installed...

No matter what temperature your car is tuned at as the outside temperature (IAT) changes, the PCM will make the appropriate changes to your injector pulse width (IPW), and change your air fuel ratio (AFR) accordingly.

What you might want to check next summer is how your car responds to very IAT's. Depending on your tune, very warm temperatures will affect your final spark advance. I.E., high IAT's retard spark advance to some degree.

But, short answer is it does not matter what time of the year you tune it. Your car is very smart and will adjust under almost all circumstances.

..WeathermanShawn..

LSWONGTO

iTrader: (3)

If you have a MAF and its not Speed Density you will be fine!!

EarlSS

i had my car tuned in 108 degree weather and it runs fine in warm or cold weather. So if its not a speed density tune you should be fine.

Haans249

iTrader: (24)

it doesn't matter if you're OL or CL, Speed density will work just fine as long as your tuner knows how to tune SD properly. SD will run in any weather condition!!! And please, don't argue this with me, because my speed density tune works just fine in 108 degree weather or this 20 degree weather i'm seeing now....and yes i tuned my car myself.

WeathermanShawn

iTrader: (1)

Haans249:

You might be asking too much of the forum members to not engage in a debate over temperatures and a SD tune.

Without igniting a massive controversy, it really depends on the original posters intent. I assumed from the phrasing of his original question, that he was intending for a 'classic' tune, and was not entertaining the option of a speed density tune.

While I totally agree with you that that with an extremely accurate VE Table, and accurate VE IAT correction factors, speed density tunes work. Humidity is also a factor in computing airmass density, which is always a debate point of MAF vs SD.

All I can say is that I tried them all. OLSD, OLMAF, COS-Semi-Loop, and closed loop. Maybe successful SD tuners just have their tunes nailed, but I always found getting a consistent AFR was a challenge. Heat-soaked IAT errors in summer were tough. Elevation changes were also difficult, regardless of the MAP sensor primarily driving the BARO correction.

To the original poster, were you intending to stay closed-loop? While I have found closed-loop tunes a little more forgiving, if speed-density is your choice, finding that great tuner is especially essential. It is up to you.

In any case, good luck and enjoy your car.

..WeathermanShawn..

Ripper415

iTrader: (6)

wow this has gotten all kinds of complicated. open/closed loop, speed density, etc. i'm not really sure about these things. but i guess the take home message here is that getting my car tuned in sub freezing temps will be OK, so that's good. thanks for the input guys! i feel much better now, like i wont be "wasting my money" on it this january.

Haans249

iTrader: (24)

Good presentation. It is true that getting a consistant AFR is very difficult to do, and in general you just want your AFR to be within +/-1%, which isn't entirely difficult to do given that you have your injectors tuned properly.

But, remember this, even a MAF tune will NOT correct to temperature changes. I've collaborated with one of the best analyst of tuning that is around, and from data that he's gathered and using complicated statistical analysis has found that a MAF tune can be just as bad, if not worse, than a SD tune in keep consistant AFR's. This is from a stock vehicle btw, not a modified vehicle. Interesting stuff indeed.

Adrian

WeathermanShawn

iTrader: (1)

Good point(s) Adrian.

Temperature variations along with the ole infamous cam 'reversion' does make tuning challenging.

It is all worth it, regardless of the tuning techniques you ultimately are successful with.

And yes, to the original poster, tune away..

Thanks for letting us extend the discussion.

Good luck.

..WeathermanShawn..

vettenuts

iTrader: (4)

Just remember that differential temps and tranny temps might be cooler so numbers may be lower as a result due to additional parasitic loss. Just want to throw this in so you aren't disappointed if the numbers are lower than you expected.