Generally speaking at the track they say that you can take off .1 second per every 100 lbs shed on 12-15 second et cars.
The BMW listed curb weight of a 330i/330ci manual is 3285 lbs. The stated US HPis 215 (non-m, non-zhp). that's a power to weight ratio of 15.28 lbs (roughly) per horsepower. M3's are 10.25 lbs per HP. Every pound helps and it's cheaper to loose weight (to a point and generally speaking) than adding horsepower to our NA engines.
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