986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post

Lil bastard · 08-19-2011, 08:31 AM

The typical parasitic draw from a car AC compressor is 10-15 crank HP.

Add to this, an additional 1-2 HP is drawn from crank HP by the alternator (which basically 'free wheels' unless a load is put on it) to power the blower, and you're getting dangerously close to a 10% reduction in usuable output on the 2.5L motor.

If that 2.5L motor is well used, and no longer putting out the 218 ponies it originally came with (or you're not driving at peak HP on the rev curve), the total reduction of usable output could easily approach 15%.

Those are numbers you're likely to feel.

Cheers!

08-19-2011, 08:31 AM	#2
Lil bastard Registered User Join Date: Feb 2008 Location: Du Monde Posts: 2,199	The typical parasitic draw from a car AC compressor is 10-15 crank HP. Add to this, an additional 1-2 HP is drawn from crank HP by the alternator (which basically 'free wheels' unless a load is put on it) to power the blower, and you're getting dangerously close to a 10% reduction in usuable output on the 2.5L motor. If that 2.5L motor is well used, and no longer putting out the 218 ponies it originally came with (or you're not driving at peak HP on the rev curve), the total reduction of usable output could easily approach 15%. Those are numbers you're likely to feel. Cheers! __________________ 1990 Porsche 964 Carrera 4 Cabriolet 1976 BMW 2002 1990 BMW 325is 1999 Porsche Boxster (gone, but not forgotten) http://i933.photobucket.com/albums/a...smiley-003.gif Never drive faster than your Guardian Angel can fly! Last edited by Lil bastard; 08-19-2011 at 08:35 AM.