Anyone Build 302's for MPG? And General Wagon Economy

[t65neon5]

"more efficient air management....more cool air in with less restriction,more air(exhaust) out with less restriction,possibly a cold air intake,some porting,then less restrictive exhaust manifolds..."

In reading on engine theory, I do know this can be taken too far... there's tuning involved, deliberately restrictive intakes and exhausts so that the reciprocating "shock wave" of air pressure can help to cram fresh air into cylinders, and help to scavenge exhaust gas out of cylinders. As I understand it, when the the intake valve opens, air rushes in, when it slams shut, that moving air hits the valve, and the pressure front/wave bounces away, hits the next obstacle (throttle plate?) and then bounces again... and you want to time it so that pressure wave arrives at an intake stroke again right when it opens.
Hence different length runners for different applications, both on the intake manifold past the throttle and on the exhaust runners before the collector: a lopo intake, an HO intake, a truck intake, all designed for different rpms. And variable length intake runners on many modern cars (so, like variable timing, you can be efficient at some lower rpm range, AND switch runner length to develop efficient power at some higher rpm range).
So don't throw on long tube headers unless the rest of the engine is designed around the very high rpms those give you benefits at.

I'm wondering if the stock lopo isn't a very well engineered engine, even the best for its intended purpose of low-rpm torque and fuel economy, and to just leave the engine bit alone: I like the idea of instead having enough gears in the transmission to just ride the peak torque (and therefore peak fuel econ) curve of the stock lopo all the way.

yup...the whole shock wave thing is correct....i was referring more towars smoothing out the flow more that opening up for more volume(you start adding to much air,then you need to put in more fuel to keep it from leaning out)....more can be had for the money by lowering the back pressure by changing the exhaust to a dual setup.less restrictive manifolds would probably help too.....all this was said based totally on improving fuel mileage without any concern for any real power gains(a more efficient engine should produce a lil more power,but nothing major,I.E.,the slight gain in HP when going from single to dual exhaust.....)

[t65neon5]

Honestly, the lopo isn't as terrible as many make it out to be. My winter wagon, with it's 250k mile lopo with very basic mods (HO upper, TB, EGR spacer, 1.7 rr's, factory stang headers, 2.5" exhaust, a/c and smog delete, and a full tune-up), runs really well. It still pulls 22mpg with 3.55's out back and a very shitty AOD.

Agreed....the stock setup(stock LOPO with SEFI) is actually pretty good considering everything(federal emisson standards,driveability,fuel mileage,durability etc....) however ,EVERYTHING needs to be in good to great shape to get good fuel numbers(good,even compression,no vacuum leaks,good cooling etc)....basically,without spending gobs of money,a good hot ignition,and a less restrictive exhaust is money spent wisely,a "cold air" kit may help some also. there may also may be a minimal gain by using a "lighter" oil,5w20 instead of 10w30 for example.

[Rassel90]

cruise control uses more gas never touch mine

[Grand Marquis GT]

Holy zombie thread there, guy!

[sly]

at least it was only 3 years old. Always fun when someone posts to a thread that's a decade old.

[knucklehead0202]

I'd call him a boner but I've done the same thing. Lol

[JeffBoudah]

I got 20-21 Highway at 70mph with a Phead lopo longblock, HO cam, HO upper/tb combo with a AOD and 4.10's. In town I got about 17... 8-10 if I drove that thing like an ahole. (which was often)

[sxcpotatoes]

You want to hypermile these biatches, get an '88-91 (my first car was '88 LTD), I did true-duals with no crossover, glasspacks etc, 2.73 or 2.83 single-wheel-peel rear end, and set the cruise control at 55-60. I did so back in the day, and starting out the trip with 19 miles on the trip odometer, had 420 on it from Northeast Ohio all the way down through the back roads of Charleston, WV and BACK 1 tank trip. 28.5 mpg (@55mph pissing off all the truckers on the way). Oh, and I also had 4-12" subs in a box and a 1000w amp running the entire time.

Of course the '98-'02 I had blew this out of the water, on the flat roads in NE Ohio the 70 mile trip to Cleveland routinely showed 32.5 (to 33.0 if you could draft a Semi, not on his ass, just run behind one a safe distance) with the cruise control set at 60-62 mph. Same crappy highway gears 2.73 or 2.83s whichever. This is with 212k on the driveline when we got it! 30 mpg at 70, my dad just chimed in.

[johnunit]

Low speed really is the trick. 50-55mph is the butter zone with 2.73's. Our speed limits on major highways are 62mph. Find a truck or bus that's driving predictability and just below the speed limit, then just concentrate on smoothly keeping a reasonable distance behind them. My two real long runs doing mostly that were over 23-27 mpg in a badly tuned somewhat heavily filled 351w car.

[gadget73]

My car just feels so much more solid at 70 though. Its out of the exhaust drone RPM range, and the motor is at a speed where its making power. It would do better if I could stand being nearly run over at 55.

[GM_Guy]

My '89 didn't show any significant mileage difference between 55 or 70mph (3.08 gears) doing steady state interstate cruising. Once you are up to speed, it is just loafing along anyway.

Alex.

[gadget73]

3.55 for me, so I'm already at an RPM disadvantage. Its a car utterly lacking in aerodynamics so I really don't expect miracles. Maybe someday I'll see about putting a splash pan underneath to help smooth out the underside, but only if I can do so without making it a cumbersome PITA to actually work on the car.

[pantera77]

My '89 didn't show any significant mileage difference between 55 or 70mph (3.08 gears) doing steady state interstate cruising. Once you are up to speed, it is just loafing along anyway.

Alex.

Same here.
The Battle wagon with it's tired lopo and 3.55's got 24mpg on the way back from Detroit with the cruise @ 75. These cars excel in the 70-80mph range.
The new wagon with a HO and 3.08's got 22.1 on the way back from Scott's @ 70.

[gadget73]

I've never broken 18 with any consistency. The stock motor managed 14 at it's best. Its not just my driving habits either, other people have driven it to the same shite fuel economy.

[sly]

my 88 gets 21 on the highway with the 3.55 gears. In town, it's 15 though.