I seem to feel like there are days when my 930 runs better than others. Is it just me? What could cause this?

 

I agree- I could swear mine does too. I think the humidity and temperature and maybe even the barometer reading may play a big role in this.

 

I think what you are experiencing is the variations in air pressure/density. The barometric pressure of our atmosphere is affected by temperature/dewpoint and altitude, the variations are more noticable in our car because they are turbo applications. Most will note that our cars feel like they have gained power on colder days when the air is more dense and optimal for combustion. My 2 cents recollection from basic physics.

 

It is odd... sometimes it feels like she just isn't breathing as well as on other days... I could swear the tach needle can be just a tad bit more sluggish. Probably just weather factors as discussed.

 

It's the weather, the cooler it is the better the turbo breathes, the car will definately run better in colder weather.

Christian

 

But water injection can help in hotter temps right?

 

It'll help protect against predetonation if you’re running a lot of boost. A good solid intercooler is a much better fix for that and for smoother throttle response.

The amount of air brought in will be denser as noted above but don't forget as these cars are air cooled the overall engine efficiency will be increased when the air’s colder. The cylinders cool better and the oil does as well.

 

Guys this is VERY common for Turbo cars, even brand new ones....here is some supporting evidence:

Car and Driver Recent Test
2005 Volvo S60 AWD R - 295hp, 300hp - 6speed stock (inline 5cyl Turbo)

Ambient Temp 70F: 0-60mp/h = 5.9secs

New Ambient Temp (same car) 108F: 0-60mp/h = 6.6secs

Yasin

 

I guess sometimes I feel like I get different running conditions in seemingly similar weather conditions... probably just my over active imagination.