Turbos cut out occasionally when boosting in cold weather.

[maltbie]

That was exactly my experience while traveling when the temp was around 35F before I got a ECU tune. Unfortunately, I don't know of any fixes other than tuning. Also overboosting doesn't throw a code so the dealer won't find anything.

What does an ECU tune cost?

 

[StingerMG]

What does an ECU tune cost?

That depends on the tuner you go with but ECU tunes can range from $400 to $2000. I was able to get a 2nd hand Lap3 ECU for $350 and sent it back to Lap3 for a VIN unlock and a reflash. Ultimately I was able to get a $1850 tune for $1000. If you do decide to go with a ECU tune over a piggyback tune, do your research and ask owners their experience.

 

[rtv900]

From what I understand, the cold air can cause overboosting because it is more dense.

The ecu would only see actual PSI of boost, so colder denser air would make it "see" overboost.
Generally ECU's in turbo cars calculate down max boost as it gets colder to account for the denser air so as to not fry the motor.
So 10psi will do the same as 12 psi in warmer weather. I haven't noticed that much in mine this winter, but the gauge also is not the greatest.

In my STI the ECU would go from about 18psi in summer to maybe 14 max in single digit or teen temps

 

[cwfl]

23 GT2 here, weather is around 25 Fahrenheit, it will go into limp mode occasionally, and turn the engine off and on will make it disappear. Seems like a common issue, maybe it is just protecting the engine from not reaching operating temperature even if I drove it like 5 miles to warm up. Don't worry, I don't think it's going to do any damage to the car, it just a bit annoying.

 

[Thomby]

Generally ECU's in turbo cars calculate down max boost as it gets colder to account for the denser air so as to not fry the motor.
So 10psi will do the same as 12 psi in warmer weather.

I don't think it's to not fry the motor so much as it is to let it keep consistent power over a variety of conditions. So you don't notice a dropoff in power under worse conditions (higher altitude, hotter air), but the tradeoff is you have unused potential under good ones.

I believe the B8 S4 opens its supercharger bypass valve from 4-5000 rpm and boost flattens out, so in poorer conditions the ECU can hold it closed longer and keep you near stock power. A tune will hold it closed most/all of the time and give you a few dozen extra horsepower in good conditions.

 

[rtv900]

I don't think it's to not fry the motor so much as it is to let them keep consistent power over a variety of conditions. So you don't notice a dropoff in power under worse conditions (higher altitude, hotter air), but the tradeoff is you have unused potential under good ones.

I believe the B8 S4 opens its supercharger bypass valve from 4-5000 rpm and boost flattens out, so in poorer conditions the ECU can hold it closed longer and keep you near stock power. A tune will hold it closed most/all of the time and give you a few dozen extra horsepower in good conditions.

it's definitely to not fry the motor.
Air at 0F is 75% denser than air at 100F, and both of those temps are totally plausible in America. That has an identical effect to just increasing your peak boost by 75%.
It would be the same as taking a car designed for 12psi in summer and just ramping it up to 21psi without making any other mods, which of course would blow the thing up pretty quick.
I agree it would feel great briefly, but no chance the motor would hold up to that much of a power boost

 

[Thomby]

Air at 0F is 75% denser than air at 100F, and both of those temps are totally plausible in America. That has an identical effect to just increasing your peak boost by 75%.

I don't think that's quite right...you sure it's not that air at 100F is 75% the density of 0F air? Meaning about 30% more air molecules at 0F

 

[rtv900]

I don't think that's quite right...you sure it's not that air at 100F is 75% the density of 0F air? Meaning about 30% more air molecules at 0F

yeah you're right, I used a calculator and messed it up. But it's about 25% denser at 0 than 100.
I mean 25% more air is still quite a bit of difference. That should translate pretty directly to 25% more power between those two temps all other things being equal. So our 375 hp car in summer would become 470 hp.
I'm not saying it actually makes 375 at 100 degrees, just making the point.

 

[Snicklefritz]

maybe it is just protecting the engine from not reaching operating temperature even if I drove it like 5 miles to warm up.

Five miles is nowhere near enough to reach operating temperature. If your trim doesn't come with the "gauges", which show oil temperature, you can be sure that when the coolant temperature gauge reaches full - approximately the needle pointing at eleven o'clock - it will take quite a few minutes longer before the oil reaches c. 200F, at least twice as long as it takes to get to max coolant operating temperature. In warmer weather the oil temperature reaches 200F a lot faster than that.

 

[cwfl]

Five miles is nowhere near enough to reach operating temperature. If your trim doesn't come with the "gauges", which show oil temperature, you can be sure that when the coolant temperature gauge reaches full - approximately the needle pointing at eleven o'clock - it will take quite a few minutes longer before the oil reaches c. 200F, at least twice as long as it takes to get to max coolant operating temperature. In warmer weather the oil temperature reaches 200F a lot faster than that.

Frankly I don't really press the gas pedal at all in winter, but it is always safe to warm up