hypothetical fuel economy / power build ideas

[gadget73]

OK, totally hypothetical build thoughts here. What would it take to make a panther thats both good on fuel (20+ mpg highway) and capable of 300hp or better at the rear wheels? Only restrictions are as follows:

EFI, mass air OK but prefer to stay Ford EFI
Windsor based engine
automatic trans
fits under a stock hood
must retain AC
Cats present, able to pass idle sniffer test. Visual inspection not important
car remains visually unmodified to any significant extent
not so loud that the neighbors ears will bleed when I start the car
exhaust ends at the rear bumper

budget isn't a huge concern, but lets keep it in the realm of lesser mortals

I'm thinking maybe start with something like this
351 roller block
afr 185 or 205 heads
custom cam or maybe something like an XE264
edelbrock 351 efi intake
wide ratio aod or 4R70w with controller
higher stall converter, whatever is appropriate for the cam, 2000-2500ish stall?
3.08 or 3.27 rear
whatever tuning to the EFI is appropriate, assuming larger injectors and fuel/timing curve tweaks will be needed
shorty headers, 2 1/2 exhaust of some form TBD


I know that motor ought to run, but will it be a fuel hog? Would there be any economy benefits with a small super or turbocharger? I know those would give me more power but will there be any gains at 75 on the highway for long periods?

[Pesty351]

[Southern_Pride]

I can tell you this. I'm not sure how much power my car has but it will blow the doors off an aero or whale. Even with the 4 barrel if it is 75 degrees or less outside I can get better than 20 on the highway. Maybe this helps maybe it doesn't. But is it possible, yes. It really boils down to gearing. With the gear you want to run, no. On stock tires you will need at least a 3.73, 4.10 would be better. If you dog these bigger cams like a stock one your mpg goes to shit. Even with my 4.10 gears if I'm in od at less than 2000 rpm my engine bogs.

[1980c10]

It can be done with the combo you said above. If you have the ability to tune it you can lean out the cruise a/f ratio to like 16:1 then 20 mpg on the highway should be now problem. Just build a nice free flowing 351w and start tuning, also go with a little more gear like southern pride said. I don't think it would be a problem.

[gadget73]

The idea with the gearing is the wide ratio. A WR trans with a 3.27 has an effective first gear lower than a stock AOD with a 3.73. The tall gearing is purely for highway reasons. My thoughts were lower rpm = less air and fuel moving through the engine.

[Pesty351]

F the auto go 5-speed.

[Southern_Pride]

The tall gear is what will kill the mpg. Rpm doesn't matter so much as being in the powerband does.

[johnunit]

should go without saying, but lighter/more aerodynamic wheels (alloy or aluminum), the police/taxi front spoiler, and other weight and aero mods might be a good idea.

Maybe try something like the cover/deflector that some whales use going from the trunk pan to rear bumper, which could be made easily out of plexiglas.

I've heard claims of looser cam, rod, and main bearing tolerances resulting in significant gains in mileage. I have no idea what the specs you'd ask for would be though.

[gadget73]

well, the gearing is certainly flexible. Just keep in mind the OD ratio on a WR trans is 0.70:1 where a standard AOD is 0.67:1, so on the highway given the same rear gears, a WR trans will tach a little higher. The WR trans thought is also flexible. basically anything is on the table other than my initial restrictions. I'm not hard set on anything, other than my initial must-have list. This is also a 2-5 year down the pike project so its not like I have a deadline in mind here.

[jayh]

347
afr 185 or tfs 170
edelbrock rpm I
probably custom cam
tight 3000stall l/u converter
3.73

with steeper gear it wont have to work as hard, if rpm doesnt get out of hand, mpg will improve
347 will make more power than 351 and use less fuel, lighter rotating assembly
no need to limit stall, city mpg is always gonna be not so good no matter what, better off to keep motor in its powerband at WOT, part htrottle will only be a few hundred rpm difference, motor doesnt have to work as hard, doesnt need as much throttle input, converter locks up on the freeway

heres an experiment for you, hook up a noid light or 194 bulb to an injector, put it under the wiper blade and go drive around, monitor the light and note throttle position, when it gets bright, shes drinking, when it dim, she is sippin. so less throttle input(from less load) will save mpg

also, think about it this way, injector pulse isnt a faster blink, like on off on off on off etc.; it is pulse width modulated, when the light gets brighter, its on more. for example at cruise- just as an example- 10%on 90% off 10%on 90% off; 1/2 throttle- 50%on 50%off 50%on 50%off, 3/4 throttle- 75%on 25%off 75%on 25%off; this is general theory, your long and short term fuel trims fine tune these numbers

[jayh]

I think you need to be a member/10posts to read this, I dunno-
http://sbftech.com/index.php/topic,5081.0.html

360rwhp 27mpg @ somewhere around 3400lbs

306
ported edelbrock heads
tfs R
90mm tb
1 3/4 longtubes
custom cam

[hemihotrod402]

Gadget the setup you posted above is almost virtually identical to the build I am planning, except I'm going with TFS 190 heads and the TFS Intake (I haven't tried it yet, but I'm 99.9% sure it will fit). I'm also running steeper gears.

Anyway I would think that it could be done like that, but again you are pushing the hood space limits. The 306/347 setup that jay posted I'm sure would be able to do it no prob, but I'm guessing it would cost a little more, although budget really isn't that much of an issue.

I'm assuming with the eddy intake you are referring to the TB elbow setup?

[1987cp]

I think you need to be a member/10posts to read this, I dunno-
http://sbftech.com/index.php/topic,5081.0.html

360rwhp 27mpg @ somewhere around 3400lbs

306
ported edelbrock heads
tfs R
90mm tb
1 3/4 longtubes
custom cam

I was going to say, I seemed remember David Clafin reporting 28mpg with a 351. This is apparently either a different build or I'm remembering it wrong.

Either way, I want to do what he's been doing. Making ~200hp and getting 15mpg max really sucks (gas).

[jayh]

yeah I think it is actually 368rwhp and 28mpg. its a 306 though

when I say rpm I, Im talking about the first rpm EFI that professional products ripped of the design for(typhoon). I actually prefer the holley systemax][ but you cant flip the upper

btw the tfs351 intake has the same runners as the tfsR for 8.2 deck

[1990LTD]

How much can realistically be done to these cars to save weight before you start getting ridiculous (ie pulling out seats)