Volvo 850 Made from 1993 to 1997, this Volvo line was available in both a wagon and a sedan, both with were graced with several trim levels.

850 Poor gas mileage - Tips to improve mpg...

Old 10-15-2018, 12:26 AM
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Join Date: Sep 2015
Posts: 17

Originally Posted by mt6127 View Post
the ECU upgrade kits all work pretty much the same way - they reflash the ECU to modify the boost curve (ie turbo boost level vs RPM) and the spark advance vs RPM. The gain in HP comes from increasing the boost which overcomes the pumping losses in the engine allowing for more mixture to find its way into the cylinders per RPM (same end game as bigger exhausts, free intakes, even bigger displacements). If you advance the spark as well, you are giving the engine more time to burn the mixture- which also gives you more HP, and since this happens even during off boost/highway driving, you can expect some improvements to MPGs. So if you're wondering why cars simply don't ship with more spark advance, the reason is two fold - more advanced spark means a hotter burn, which while reducing HC emissions, it creates more NOx emissions (ie too much advance can fail a smog test). Secondly too hot a burn or too early a spark can lead to pinging (knock) and engine damage (ie valves) over time. That's why when you run upgraded ECUs you MUSt run premium gas (ie 92/93 octane) - otherwise the knock sensors will work overtime trying to retard the spark your new ECU just upped. Assuming your 850T is stock, you have the 15G turbo and this product advances the spark 1 degree and bumps the maximum boost 3.3 PSI which are fairly modest changes IMHO. If you are ok sticking to premium gas, I'd say add a K+N air filter and enjoy the new ride and at least a small bump in MPGs.
K&N filter bad for MAF
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