General tuning question - fuel economy

[Marteney, Steven J.]

Dual pattern - 208 I, 221 E @ 050, Lift is 474 I, 510 E with 112 LSA.

Your mileage figures are obviously a testament to your a) heads, b) personal
tuning, c) well flowing exhaust, d) others.  Those numbers rival factory LS1
F-body specs.  If it's in the 4x4, then I'm doubly impressed.

My average WAS about 19.1, is now about 16.3.  The mods were the cam, 10.2:1
flat-top pistons, balanced rotating assembly, 3-angle valve job.  My biggest
problems are the stock manifolds, heads, TPI, single cat, and no tuning yet.

Steve

> -----Original Message-----
> From:	Mike Rolica [mailto:mrolica at meridian-mag.com]
> Sent:	Tuesday, June 13, 2000 4:00 PM
> To:	'gmecm at diy-efi.org'
> Subject:	RE: General tuning question - fuel economy
> 
> 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
> 
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