Here's an interesting test of a corvette and a VW with no accessories and with AC + headlights + rear defroster on:
http://www.motivemag.com/pub/feature...tic_Loss.shtml
Bottom line is they lost 10hp on the VW and more than 15 on the vette. We haven't talked about electrical loads but they sap power too. I would guess the AC alone is at least half the hp loss. Our ACs seem small to me but it would seem we are losing at least 5hp and possibly 10hp when we run the AC.
The comments about ambient temperature are also correct IMHO. My SUV will ping in hot weather when the plug gap gets a little big on 87 octane. The car computer cannot retard the spark enough to compensate. The AC also makes the car run hotter which compounds the issue. High ambient temperature = less spark advance + AC on both of which reduce power.
Jim
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128i Convertible, MT, Alpine White, Black Top, Taupe Leatherette, Walnut, Sport
Ordered 5/22/09, Completed 6/4/09, At Port 6/9/09, On the Georgia Highway 6/13/09, Ship Arrived Charleston 6/24/09 at 10pm, PCD 7/21/09
