# Weather Effects on Turbo



## dhpnet (Mar 2, 2014)

I have never owned a turbo before. I understand the general idea - a fan that blows air into the engine, and there is some lag time while the turbo spools. But that's about it. 

This week we had some warm, dry weather. Temps were in the 80s - 90s with lower humidity. The weather in San Francisco is cool, often foggy, usually around 50-60 degrees with 60-70% humidity - all year round. With the warm, dry, sunny weather, it seemed like I was getting more turbo boost and more torque this week. Yesterday the fog rolled back in off the ocean. The temps went back down and humidity went back up. It seems like there is now less boost and torque. Maybe this is just in my head. Is this normal for turbos? What causes this?

It also seems like the turbo has more power after the car has been driven on the freeway for a few miles as opposed to just driving around the city for a few miles. Is it just my imagination, or is this the case? 

I couldn't really find any good threads about how the weather affects the turbo, but I did learn a few new things. For example, I had never heard of an intercooler before. After learning about these, it made me wonder if there is water condensation in the intake during the compression and cooling of the air. If so, does the humidity affect condensation in the intake, and does this affect engine power? 

I am sure there are a lot of new Cruze owners who have no real-world experience with turbos. They seem cool, but a lot more complicated.


----------



## Eddy Cruze (Jan 10, 2014)

I honestly think that is all in your head? Turbo cars can run very hot, today its 110 and the A/C was blasting Ice cold air as the CRUZE displayed cool engine temps, very encouraging! As far as power differences I can hardly notice this Turbo at all, and I most certainly don't hear it or feel it like my previous two turbo cars, one being a 1.6 Dodge Colt with 110 HP!


----------



## tracepk (Aug 20, 2013)

Eddy Cruze said:


> As far as power differences I can hardly notice this Turbo at all, and I most certainly don't hear it or feel it like my previous two turbo cars, one being a 1.6 Dodge Colt with 110 HP!


The turbo in the cruze is very very small, small compressor wheel means less exhaust and less inertia is required to get them spooled so that spot when you feel the boost take effect comes on very early. so early most people dont notice it. get a rolling start in first gear, about 2 mph, then stomp on it. you'll notice around 1800-2500rpm power will increase pretty drastically.


----------



## obermd (Mar 3, 2012)

What octane are you running? Yes, the Cruze can run on 87 but the engine was designed for 91. Temperature and humidity can really impact how the Cruze responds to the throttle and 89 or higher octane can make a noticeable difference.


----------



## Eddy Cruze (Jan 10, 2014)

obermd said:


> What octane are you running. Yes, the Cruze can run on 87 but the engine was designed for 91. Temperature and humidity can really impact how the Cruze responds to the throttle and 89 or higher octane can make a noticeable difference.


 Yes but this was more of an ambient temperature question and not the engine itself. My previous V6 loved the hot weather and got its best mpg, but the power was always the same Spring or Fall? Oh and it loved 87!


----------



## stamas (Mar 7, 2014)

I think the humidity has got a small roll to play , i do defiantly know you will feel more boost on a cool night as a-posed to a hot day , when your driving on the free way the wind resistance will cause the car to feel much more underpowered so when you come to a stop and drive of again in a lower gear it gives the feeling of more power I suppose .


----------



## sx sonic (Nov 25, 2013)

Conventionally (and w/o computer intervention) turbo cars produce more power in cooler weather. Cool air is more dense, thus more oxygen per given volume; at a given boost pressure this means more air is ingested into the engine and more air= more fuel= moar powwa (not necessarily to be confused with more fuel consumption... Unless you're WOT.


However our platform is heavily computer controlled and will adjust boost pressure based on atmospheric temps/conditions to maintain a preset torque value. So for instance a 0F day in death valley (how likely ) might result in 10psi of boost and a 100f day in Denver might be 16 psi, in both instances power at the wheels is the same.

GM used this "torque based" control strategy to keep power and driving feel consistent regardless of where in the world you are and what the temps are.


The only caveat is that high temps are pro knock and if the ECM detects knock it will scale back power. So you may not be able to meet the max torque values on hot days, 91+ octane fuel will combat this.


So to answer youre question, it's in your head or there are unforseen variables.


----------



## dhpnet (Mar 2, 2014)

obermd said:


> What octane are you running. Yes, the Cruze can run on 87 but the engine was designed for 91. Temperature and humidity can really impact how the Cruze responds to the throttle and 89 or higher octane can make a noticeable difference.


I have only been running 91 Chevron. I am not sure how different the gas is here in California. The manual says that the gas in other states could cause problems with the California emission system that wouldn't be covered by the warranty.


----------



## dhpnet (Mar 2, 2014)

sx sonic said:


> Conventionally (and w/o computer intervention) turbo cars produce more power in cooler weather. Cool air is more dense, thus more oxygen per given volume;


How does humidity affect air density. Is dryer air more dense than humid air?


----------



## spacedout (Dec 7, 2010)

dhpnet said:


> Temps were in the 80s - 90s with lower humidity. It also seems like the turbo has more power after the car has been driven on the freeway for a few miles as opposed to just driving around the city for a few miles. Is it just my imagination, or is this the case?


With anything over 80F outside driving in a city environment(especially with hills) will build allot more heat in the turbo. The now heated air charge travels though the intercooler which is suppose to cool it back down before it enters the engine, however because of the high outside temperatures the intercooler becomes much less efficient and itself starts to heat up. When this happens its known as heatsoak.

Now the air entering the engine is much hotter than usual once this happens, the engine will likely detune itself. This is especially true if your not running premium gas as your more likely to experience knock with lower octane & high air intake temperatures. Only thing you can do once the car gets this way is to go drive on the freeway and get the air moving through the intercooler.


----------



## Merc6 (Jun 8, 2013)

dhpnet said:


> ...It also seems like the turbo has more power after the car has been driven on the freeway for a few miles as opposed to just driving around the city for a few miles. Is it just my imagination, or is this the case?...


In the city the intercololer is heat soaked. On the freeway you have moving air to transfer heat away.


----------



## dhpnet (Mar 2, 2014)

spacedout said:


> With anything over 80F outside driving in a city environment(especially with hills) will build allot more heat in the turbo. The now heated air charge travels though the intercooler which is suppose to cool it back down before it enters the engine, however because of the high outside temperatures the intercooler because much less efficient and itself starts to heat up. When this happens its known as heatsoak.
> 
> Now the air entering the engine is much hotter than usual once this happens, the engine will likely detune itself. This is especially true if your not running premium gas as your more likely to experience knock with lower octane & high air intake temperatures. Only thing you can do once the car gets this way is to go drive on the freeway and get the air moving through the intercooler.





Merc6 said:


> In the city the intercololer is heat soaked. On the freeway you have moving air to transfer heat away.


Ahh, that makes a lot of sense. So I am not crazy. Learning a lot of new things about how turbos work. Thanks.


----------



## dhpnet (Mar 2, 2014)

dhpnet said:


> This week we had some warm, dry weather. Temps were in the 80s - 90s with lower humidity. The weather in San Francisco is cool, often foggy, usually around 50-60 degrees with 60-70% humidity - all year round. With the warm, dry, sunny weather, it seemed like I was getting more turbo boost and more torque this week. Yesterday the fog rolled back in off the ocean. The temps went back down and humidity went back up. It seems like there is now less boost and torque. Maybe this is just in my head. Is this normal for turbos? What causes this?


I know I am answering part of my own question here, but I thought others might be interested in what I discovered. I did some searching on the web about humidity effects on turbos and I found that humid air is less dense than dry air. This article has a good explanation including the history of how this was discovered. 

USATODAY.com 

The next article I found shows dyno testing on a turbo Subaru at different temps and humidity. It is interesting to see that warm, dry air performs better than cool, humid air. 

Fine Line Imports

The graph I found most interesting was this one: 

View attachment 81914


This shows that the car had more HP and Torque with with warmer, dryer air, using a top mount intercooler, and less HP and torque with cooler, humid air using a front mount intercooler. 

The end of the article also has in interesting quote: "Next time you read a dyno sheet from one of your friends, ask them if they know what the temperature and humidity was in the dyno room at the time of their dyno run for a better baseline of comparison."

When the fog rolls out here in San Francisco, the temps rise, but the humidity drops, which could relate to why I thought I had more power this last week. When the fog rolls back in, the temps drop and the humidity climbs, which could relate to why I thought I had less power after the fog rolled back in. Again, this could be all in my head because it wasn't a very dramatic change, but the data from these sites seem to agree with what I noticed. 

Maybe this will be interesting to anyone else living in cool coastal areas.


----------

