Well, do you have any cam specs??? With my single pattern, 208 @0.050" 278adv and .555 lift with 112 deg lobe center on a l98 (350tpi) I get 30mpg. 300miles out of 10impgal Or for you us guys 27 mpg.@ 85 mpg, 2500rpm Mike Rolica Plant A, Magnesium Products Division Strathroy (519)-245-4040 Ext. 265 -----Original Message----- From: Marteney, Steven J. [SMTP:smarteney@xlvision.com] Sent: Tuesday, June 13, 2000 3:09 PM To: gmecm@diy-efi.org Subject: General tuning question - fuel economy Not having really any engine "tuning" experience I stumble on some of the basic concepts (such as when to add spark advance). My rebuilt 350 TPI F-body gets about 20% less highway gas mileage with its bigger cam (GM ZZ3) and stock computer. I figure more air in at X rpm requires more fuel to appease the O2 sensor, hence gas mileage goes down. How do I compensate, or can I? I noticed there are some Hiway mode parameters, such as Hiway spark add (?), in the 165 ECM that I could take advantage of. Or, is the only way to get better mileage mean changing the target AFR? However, I also thought that this engine cruises at about 2200 rpm on the highway at 75 mph. I'm wondering if the different cam (and valve timing) has defeated the ram tuning effect of the runners and made the engine less efficient on the highway. Any thoughts? I'd appreciate a little basic help. Since this car is my daily driver (70+ per day) I'd like to keep fuel economy in mind when tuning. Thanks, Steve Marteney ---------------------------------------------------------------------------- To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes) in the body of a message (not the subject) to majordomo@lists.diy-efi.org
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