A simple Volvo Airbox Thermostat Mod to the N/A (non-turbo) 850 will increase your power, decrease your gas usage, and is actually better for the environment.
“If you own an N/A (N/A = non-turbo) 850 or S70 (and maybe others), you may wish to check your airbox thermostat. What I discovered three weeks ago about my 850 shocked me.
For the 18 months I’ve owned my 850, I’ve been trying to figure out why I’ve been getting only 15-16 mpg city and highway combined (mostly city stop-and-go). After a while, I gave up and just thought “this is normal.”
I’ve done all the stage 0 maintenance items over at volvospeed and somehow I can’t even drag another 1 mpg out of the car. Auto-Rx and everything, just can’t get more for some reason.
About three weeks ago I opened up my airbox to check the filter. Something was bothering me. After 12,000 miles, the air filter is still surprisingly clean.”
That’s when I did some research and learned about this Volvo Airbox Thermostat Mod.
When the thermostat fails, it sticks the airbox in a state where it is taking in hot air from the exhaust manifold. That bypasses the air filter, and your air filter is likely quite clean as a result.