Bimmerfest - BMW Forums - View Single Post - 540 mods and SC build
View Single Post
Old 12-16-2012, 02:29 PM
geargrinder geargrinder is offline
Crapparatus Bendgineer
Location: AndoverRockport MA & Intl
Join Date: Jun 2010
Posts: 114
Mein Auto: E46 M3Cic6MT, E39 540iT
Originally Posted by LalaRay View Post
Some kid i was talking to at a shop one day while he was getting his car tuned (Lexus GS 430 with a supra motor swap) told me tunes are not permanent or something. That he has to get one in summer than in winter cause of the season change (weather and temperature) or something ? Is this true, cause im not looking to get my car tuned Now than in summer it Blows up or something cause i need to have the whole thing retuned..That tuning Sh*t aint cheap ya know ... So basically im asking if i get my car custom tuned is that it, am i done?! Like am i good to go for life now ? All year around ? lol
Yeah. Sounds like just the kind of thing a ricetard would say.

On an old school motor the issue would be that you could tune hotter for winter air density and temps but would have to be more careful about detonation and exhaust temps in summer when the air is hot and thin.

Anything from 90's on will have IAT (intake air temp) and engine operating temp and MAF (mass air flow) sensor and ambient atmospheric and/or manifold air pressure (MAP) and then compensation constants and tables that ensure the car runs in all conditions as those things go up and down. A good tune and ECU/DME can totally handle all that for you.

Shizzy tuners only know the main fueling / timing tables and don't know the more sophisticated and nuanced stuff which is where you'll hear about guys getting great peak dyno numbers but then when the weather changed or he started driving it on the street the car wouldn't idle right or wouldn't make power or threw CEL's etc.

Only reasons I can think you might "need a seasonal" tune would be:
  • If the tuner didn't KNOW how to or didn't bother to tune the temp or barometric compensation properly for either a speed-density or mass-air type system
  • Running speed-density but the ECU doesn't HAVE an atmospheric pressure sensor or MAP to tell it if barometric is up/down.
  • If the car is running speed-density or alpha-N system pushed to limit so that seasonal barometric changes knock it out of range of trim

Assuming your tune would still be on OEM DME then it will be totally fine. It's a MAF based system with IAT sensor. If the tuner really does crazy stuff and sets you up speed-density with the OEM DME then you might have an issue since it doesn't seem to have an ambient or MAP pressure sensor but that's highly unlikely.

Oh and BTW even if the ric3rs tune did need seasonal changes, he's chosen poorly if he doesn't have a setup these days where he can reflash the tune back and forth himself a la shark injector / etc. etc. style - SO many tuners now use tools where you can flip yourself back and forth from stock to tune and more and more allow you to buy a second tune so you can have street-tune and track-tune for instance and this would be just the same... shouldn't be a big deal even if you have to do it...
2003 M3CicM6 TiAg
2002 540iT 6MT Sport TiAg
1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)
2008 Audi A3 2.0T DSG (hers)
1999 Cherokee Sport 4L (trailer-hitched in-law loaner bomber)

Some Stuff FS
Reply With Quote