General tuning question - fuel economy

[Mike Rolica]

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 at xlvision.com]
		Sent:	Tuesday, June 13, 2000 3:09 PM
		To:	gmecm at 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 at lists.diy-efi.org
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/ms-tnef
Size: 4515 bytes
Desc: not available
URL: <http://lists.diy-efi.org/pipermail/gmecm/attachments/20000613/50321389/attachment.bin>