I think if you take the time to learn what is involved you could get the whole injection package out of a wrecked Mustang and put it in yourself for a reasonable amount of money.

I am in the process of trying this myself, I am trying to get to the local Pick-and-pull next time a wrecked FI car comes in.

I disagree. Fuel injection systems employing narrow-band O2 sensors
(the vast majority) need to operate around stoichiometric (approximately
14.7:1 for pump gas) but fuel efficiency is best when on the lean side
of stoich. Running lean can be potentially worth an 8 to 10% boost in
fuel economy. Also, once there's a little velocity, a carb venturi is
an efficient device, providing good atomization with relatively little
pressure drop. A (former) Ford engineer told me they could get nearly
30 MPG on the highway out of a 5.0L Mustang with a lean-calibrated
Holley 4180 on an Edelbrock Performer intake manifold but a similar 5.0L
Mustang with SEFI was around 28 MPG. This ignores the cold start and
around town mileage where the SEFI is typically better.

It doesn't take very much power to maintain a steady speed, maybe only
25 HP at 60 MPH. Making changes that reduce required horsepower by just
2.5 means 10% less power required which translates into (roughly) a 10%
fuel savings. Small reductions in aerodynamic drag, internal friction,
rolling resistance, and engine efficiency can mean significant fuel
economy savings. A lot of little things add up. Compare a 1967 Mustang
to a 1987 Mustang 5.0L. The 8.8" differential in a late model Mustang
has less friction than an 8" or 9" differential. The late model engine
has less fricition due to low tension oil rings and hydraulic roller
lifters. The late model Mustang has better aerodynamics with flush
headlights, bumpers, and side glass, no rain gutters, a smaller radiator
opening, etc. A manual transmission in an early Mustang is filled with
a heavy weight lube, while the T5 in a late model Mustang is filled with
much lighter ATF. Comparing automatic transmissions, an AOD has a lock-up
clutch to eliminate torque converter slippage. C4, FMX, and C6 trannys
do not.

A big part of the fuel economy difference is due to overdrive transmissions.
Standard gears in a T5-equipped 1987 Mustang were 2.73:1 which combined with
a T5's 0.68:1 5th gear to yield a top gear ratio of approximately 1.86:1.
Compare that to an old Mustang with 3.50:1 and a top gear of 1:1 and you'll
see the early Mustang has to turn nearly twice the RPM at cruise to maintain
the same speed. That means higher friction losses but more importantly,
greater throttling losses. A throttle (the butterfly valve in the carb or
throttle body) is a restriction to incoming airflow and results in a pressure
drop that is maximum at closed throttle and minimum at wide open throttle.
If you ignore any enrichment circuitry, an engine is most fuel efficient at
wide open throttle since the throttling losses are least. This is the main
reason a tall final drive ratio gets better fuel economy. A taller gear
requires a larger throttle opening to maintain a given speed which translates
into lower throttling loss and better MPG. It doesn't take any more power to
maintain 60 MPH at 3000 RPM than it does at 1500 RPM but it does take more
fuel.

Mustangs Plus or NPD can fix you up with the handling and disc brakes.

------------------
Stuart
MCA #48902
M&M #1091
67 stang 5 speed, 351W,
Edelbrock Performer RPM package

I'm not surprosed that the Ford engineers can get great mileage out of a specially modified carburetor but I bet it is hard to buy one of those.

A few years back I was on a team that entered a emissions and fuel economy rally. We were using a new Escort donated by Ford for our use. We went to the emissions facility that Ford had here and the engineers gave us a carburetor to use. Our mileage was better than production escorts and our emissions were very low. They placed two conditions on us for the loan of the carburetor. Don't open it, and give it back.

We finished second in the competition to the factory Mercedes team.

As I understand it, the Extender only alters air-fuel ratio during wide-open
throttle which is handled via an open loop table. By open loop, I mean the
mode does not use the O2 sensors as a feedback (does not measure the air-fuel
ratio). The Mustang's EEC-IV operates in closed loop mode during cruise and
attempts to hold stoichiometric. The output voltage verus air-fuel ratio
curve of the OEM narrow-band 02 sensors is too steep to use directly to hold
a target air-fuel ratio. Instead, it is used to toggle between rich and lean.
There are some lean burn strategies using narrow-band O2 sensors under
development but, as far as I know, none are yet in production. The only
production EFI lean burn vehicle that I know of is the 1992 to 1995 1.5L VTEC
Honda Civic, a special high fuel economy model which used an expensive wide-
band 02 sensor.

> I also believe that the manifold design on the fuel injected cars provides
> a fatter torque curve allowing the cars to accelerate with less throttle
> opening.

This provides better WOT torque but does not help fuel economy during
cruise since less throttle opening means greater throttling loss.

> I also noticed you comparison ignores around town mileage where most
> driving is done.

Yes. I'm not sure how much different EFI is than carb around town.
The main difference in around town fuel economy is transient enrichment
(accelerator pump shot). Some carbs control enrichement fairly well
(others require a big pump shot... much of it comes down to manifolding)
while some EFI systems (GM's cross-fire) do it poorly. On average, I
would think port EFI has the potential to be better than carbs (no wall
wetting problems).

> I'm not surprised that the Ford engineers can get great mileage out of
> a specially modified carburetor but I bet it is hard to buy one of those.

The Holley 4180 was standard issue on the 1983 through 1985 Ford Mustang
5.0L V8's. It was a Ford-developed version of the Holley 4 barrel, similar
to a standard 4160 but with emissions calibration, a dashpot for throttle
control during deceleration, vapor vent equipped fuel bowls, "close limit"
jets (tighter tolerancing for emissions purposes), annular discharger
boosters and a specific fuel inlet. The 4180 was able to meet emissions
standards without electronic aids.

------------------
Neal

1. Could the TPS be locked into the WOT position causing the extender to control A/F ratio all of the time and the O2 sensors be deleted from the car?

2. Was the 83-85 carburetor the one used to get 30 mph in a 5.0?

The most straightforward thing to do would be a ring and pinion swap
to the tallest gear you can find. I think gears as tall as 2.33:1 were
available (in 1970). Not sure if that was in a 8" or 9". 2.80:1 was
alot more common. Cost will vary but can be cheap if you get used parts
and do the work yourself. Could be very cheap if you find someone swapping
out an 8" or 9" third member with tall gears for something more performance
oriented. I would have given my 2.80:1 3rd member away when I installed
the 9". New parts and paying someone else to do the work gets expensive.
Tall gears will hurt acceleration though. An overdrive transmission is
a better approach for performance and economy. Speaking of performance
and economy, you might want to pick up a copy of David Vizard's book on
Performance with Economy. It was written many years ago but is still
relevent to old Mustangs and the like.

> A T5 conversion isn't as expensive as you would think if you can find a
> donor car. Something's got to give somewhere.

Good point. Old 5.0L Mustangs aren't worth much. If you can find one
with rusty body but sound drivetrain, you might consider buying one as
a donor. Pull the engine, injection, computer, and transmission and
part out the rest.

> 1. Could the TPS be locked into the WOT position causing the extender to
> control A/F ratio all of the time and the O2 sensors be deleted from the
> car?

The TPS tells it your throttle position. Locking it at WOT would
mean it would try to run at wide open throttle. Also, IIRC, the Extender
only takes control above 4000 RPM, though there are probably ways around
that.

> 2. Was the 83-85 carburetor the one used to get 30 mpg in a 5.0?

Yes, plus a 2.73:1 final drive and T5 with 0.68:1 5th gear. Engine
was a stock 1985 5.0L HO with hydraulic roller cam.

The best I've pulled out of my 1987 Mustang (EFI 5.0L HO) is 28 MPG.
The longblock is stock but the car has a few modifications which aid
fuel economy (or air performance without hurting fuel economy):
underdrive pulleys, bumped timing, no intake silencer or air pump,
off road H-pipe, shorty headers, Magnaflow exhaust, synthetic lubricants
in engine and rear end, and is lowered (lower drag). Other stuff
that might help a bit would be roller rockers and a windage tray.
Adjusting the fuel pressure a bit low might lean it out some too.

Thinking about this a bit, I may have this wrong. Smaller throttle
angles do mean larger throttling losses but that assumes all other
relevent parameters are help constant. In this case, they weren't,
since the resonant RPM of the intake tract was altered. The long runner
intake would work better at low RPM so perhaps there would be a fuel
economy benfit as well as the torque benefit.

Another random thought. Once upon a time, small port single plane intakes
like the Edelbrock SP2P and Holley Street Dominator were touted as fuel
economy boosting intakes. Offenhauser took this a step further with their
"Dual Port" intake manifolds. The dual port design has the runners split
into top and bottom sections with the plenum split fore-and-aft (rather
than the usual side-to-side). It's essentially two single planes of small
cross-sectional area, stacked on top of each other with the primaries feeding
the longer path lower runners and the secondaries feeding the shorter path
upper runners. It's an interesting approach but the packaging required to
fit within a carb intake envelope does compromise the design. By reputation,
it's a good fuel economy, low end response type intake and Offy even made
spreadbore versions of the intake. Many years ago, David Vizard did a big
intake comparison on a 350 Chevy but I think the trends should apply. The
Dual Port was near the bottom of the list when comparing peak horsepower but
had the best BSFC (brake specific fuel consumption) and throttle response.
They aren't good horsepower intakes but do make good towing and fuel economy
intakes. I've only had experience with them on big port Clevelands (2V and
4V) where the approach should work best. On a small port Windsor, I wouldn't
expect the effect to be as pronounced. Come to think of it I did have a Dual
Port for a Buick 215 V8 which has ports even smaller than a Windsor (stock 215
valve sizes are 1.5"/1.3") but I never used it. I sold it to a guy with a
Triumph TR8 (which used the Rover vesion of the aluminum Buick V8) and he
loved it but he was comparing it against a Huffaker single plane race intake
that did not port match very well to his cylinder heads. Dyno tests I've seen
of the Buick/Rover Dual Port shows they give up 10 to 20 HP against an
Edelbrock Performer on a 200 to 220 HP Buick 215 V8.

pthornton, what specifically is an EEC-tuner or a Tweecer? And where can these be purchased?

quote:

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Originally posted by JCQuinn@work:
... where can these be purchased?

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see http://www.tweecer.com/

quote:

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Originally posted by streetstang67:
I have 2.79:1 rear gears now, but I was planning to swap to 3.50:1. How much will this hurt my gas mileage?

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Add ~2 in town and subtract ~3 on the highway. My 70 Boss 302 got mid teens on the highway with 3.50 gears and the original 780 Holley, IF I stayed out of the secondaries.