Increased Fuel Efficiency (gearing/transmissions)

[LJS30]

You know I've noticed many of us have done mods in order to make our Mark 7's faster, especially mods such as rear gears, intakes, cams, etc........ However has anyone on here done any mods with the intent of making the car more fuel efficient? Has anyone put in some even lower rear gears or possibly a more fuel efficient tranny? Is the T-5 more fuel efficient?

[Bluegrass]

First thing you would have to do is reverse your throught process and driving style.
The basis of ecomomy is moving weight with the least amount of power for the fuel consumed.
Then how efficiently the power is generated.
This can get very indepth when looking at the individual items that goes into it.
From what point do we look at this?
The engine design is the place it all starts. The lower the rpm the less air has to be combusted therefore the less fuel consumed.
Optimizing this process is the key.
With supporting design that uses less power to get the driving force to the wheels is all important to be sure. A manuel trans is more efficient than an automatic.
Other items are tire design and operating pressure.
In the engine, an increase in compression ratio automaticly make more efficient use of the fuel as well as making more power.
Elements such as the exhaust system flow losses also account for some portion of fuel economy. It is not generally done or known but a larger exhaust valve size help in this quest.
How much exhaust left behind to contaminate the new drawn air is a factor. Exhaust tuning for max cylinder scavanging at the cruise rpm is another good way to accomplish better fuel milage.
At what pont do we spend resources on optimizing all these things?
Working with an existing design only brings so much reward for accomplishing a milage considered very good.
High tire pressure, efficient exhaust, ignition in first class shape, engine seal up to OEM standards, ignition timing optimized, EGR operational, low numerical ratio gearing and a light foot are the best we have to work with without getting deep into making specific changes for just that end.

[gadget73]

All the above I agree with except for the numericly lower gearing. This isn't the best in all situations. The key here is making the engine work less to accomplish the same goal. For stop and go low speed driving, often a numericly higher (rear) gear will give you this since the engine has a greater mechanical atvantage to get a heavy car up to speed. Its once you are under way that the higher gear becomes a good thing. Our stock 4 speed transmissions are a huge improvement over previous 3 speed and 2 speed transmissions in this area, but modern cars have 5 and 6 speed transmissions now. Short of a 5 or 6 speed swap, we can do a wide ratio automatic 4 speed and get some extra atvantage down low, and still keep the low gearing for highway economy.

[Bluegrass]

Your right but we can't tear down into all the small things that will affect the fuel mileage without it becoming book sized.
A sterling example of this is the late pickup trucks that have quite high weights.
The engines are 281 and 330 cu/in displacments.
The 281 (4.6L) is quite small and down on torque to move well over 5000 lbs. My F50 dry weight is 5400 without a driver.
The factory uses a 4r70wide automatic with a lower first gear. Couple this with a 3.55 rear and it begins to make up for the low torque output of the 281 engine size when moving from a stop or pulling a trailer from a stop.
In top gear the 3.55 x .77 OD. gives a 2.73 final ratio to try and get some better mileage from a heavy truck with a small engine.
On the road, speeds and engine rpm in the higher torque producing ranges are needed to effect any decent throttle response without a kickdown into third gear, a 1 to 1 ratio through the 3.55 rear.
It is important to consider where the engine torque begins to really build. In the 5L HO engine that point is above the 2600 rpm. For the 4.6L up to 03, this is well above the 2800 rpm range with peaking in the 3200 area.
At 60 mph in the truck the engine rpm is less than 1600 well below any reasonable torque output for the load.
You hit a point where compromise is in effect of either running the engine rpm up to get some torque using more fuel at lower road speeds of running faster road speeds to keep the engine in OD with enough torque to pull the weight.
With this peticular combination, which I own, a road speed of 55 to 65 seems to be the optium travel speed range to effect the best fuel milage and keep the engine making enough torque to pull without down shift and still begin the have some throttle response without down shifting occurring due to low torque.
The use of Cruise Control with this situation is a disaster unless moving beyond 65 mph. I found it better to foot control the throttle and accept a greater variation in road speed to keep the trans from down shifting.

The oppisite of this situation, which I also have on the Mark VII, is a K.B. blower that goes the other way.
More than enough torque to ever cause the trans down shift at any speed above it's normal drop out controlled by the trans govenor.
Use of Cruise Control is so well accepted by the engine that there is never a down shift out of OD even at speed less than 55 mph with speed corrections for going up hills. The boost gauge just goes into a couple pounds positive pressure and the engine just pulls to delight. Of course there is some extra fuel consumption to pay for this but i's not all that much on this setup.
IMO the bottom line is to cause the vehichle to move how desired with the least amount of throttle opening.

[John Dancy]

I drove a 1988 Lincoln Mark VII Bill Blass for like 400 highway miles at about 55 - 65 mph and got a manually calculated 26.4 mpg.

A 3.08 rear for long hauls is what I'd like.

[LJS30]

This is an excellent discussion, some very well informed, very intellectual responses to a complicated topic.

[88LSCinSW-FL]

I don't know that it'll increase gas mileage any, but my more radical possible plan (that I mentioned in the KB thread) was to build a supercharged 300 I6 to put into my '89 LSC, and try to build the car toward being the ultimate highway cruiser. (ultimate by my definition, anyway) I6s are torquey lil' monsters, plus they're naturally balanced (as is a V12) and quite smooth. I would probably mate that with a 4R70W (300 uses the 5.0 bellhousing bolt pattern) and a Baumann computer to control the transmission. We've had some long discussions over at Fox T-bird/Cougar about putting I6s in Fox bodies, and there's enough evidence to show it's possible.

Some people think I'm crazy for wanting to replace a V8 with an I6, but I'm one of those weirdo fans of I6s.. plus, my V6 '86 T-bird will probably be getting my 351W at some point in the next year or two.. so it's not like I'm hurting for V8s or anything. (also a 318 in my truck)

300s aren't the most efficient stock engines fuel-wise, but I'm thinking with maybe some gearing tweaks and such, that I can make that LSC pull along all day under 2000 RPM at 70 mph without breaking a sweat. Plus it will be mostly unique.. it'll definitely be "my" car.

[gadget73]

The problem you might have with the 300 is that its just so stinking tall. Shame its not canted over like the Chrysler slant six. EFI 300s are a very strong motor, with gobs of low end torque. You could couple this with some fairly steep gearing, like a 3.08 or 2.73 and it should still have plenty of oomph to cruise on down the road efficiently in top gear. It would be interesting for sure.

[88LSCinSW-FL]

I've had a few reports come back to me about people successfully putting 300s in Fox bodies. One in a T-bird, one in a Capri, off the top of my head. We also have someone over at Fox T-bird/Cougar who's putting a 250 small-block I6 (but still taller than the 200 of the same family) in his Fox 'Bird. Major issue with the 300 is the oil pan.. gotta make something custom, even if you use the Fox I6 K-member.

The boost is a question.. but I'm thinking about asking Kenne Bell if they could adapt one of their 4.0 I6 Jeep kits to the 300. If not, I'd probably consider a mild turbo setup. Gearing won't be a problem. 4R70W plus a sedate rear gear should be a good efficient combo with still a little better get-up-and-go than using an AOD. EFI is another concern, since I gather the stock 300 is very inefficient even as bank fire setups go.. but there's always stuff like Megasquirt.

Yeah, it's a rough plan.. initially meant for my 4-eyed T-bird, but now I want to make that the local monster and make the Mark the all-day long-distance cruiser. But I seem to have sparked off a small wave of I6 mania over at the other forum (the T-bird/Cougar one) since several people are now looking into it.. so I'm guessing there's something to it.

When I think of it, I think of the old phrase "runs like a sewing machine". That's something I think the big-block I6 (240/300) can do even better than the 302/351W can. (not to take anything away from the Windsors.. I own four of them and I'm not displeased with them in the least)

[LJS30]

Man that would be a crazy modification that's for sure. What vehicles is that I-6 in at this time?

[88LSCinSW-FL]

The 300 I6 is a truck engine. Can get them as new as mid-to-late-90s, if I recall.

[Desert Stallion]

As has been said, a 300 I6 is pretty tough to get into a Fox.

That being said, the older 250 I6 is a direct fit, more or less. It's a cousin of the 200 I6, which as we all know was installed in the Fairmont's and early Mustang's.

Using that k-member, the 250 I5 is a direct bolt in, physically speaking.

Check out Clifford's Performance for some other groovey inline 6 performance ideas. I know there are a handful of fuelie inline 6's running around, mostly in vintage Mustang's, but they utilize FAST setups to do it. Combine that with forced induction... could be a cool peppy little car.

[NYC LS8]

I had an I6 in my old '78 Fairmont, and I couldn't kill that thing - and I tried!! :D

[Nick]

The problem you might have with the 300 is that its just so stinking tall. Shame its not canted over like the Chrysler slant six. EFI 300s are a very strong motor, with gobs of low end torque. You could couple this with some fairly steep gearing, like a 3.08 or 2.73 and it should still have plenty of oomph to cruise on down the road efficiently in top gear. It would be interesting for sure.

Why can't you slant the thing and then use dry sump lube? Not easy, but it'd be surely interesting for bragging rights.

[88LSCinSW-FL]

So we're not re-inventing the wheel here, I'll include a link back to my original thread on using a 300 in a Fox body. The original intent was to put it in my '86 T-bird.. but that was before I got this '89 LSC. Now I am thinking the T-bird will be the around-town toy, and the LSC would be the one built for long trips:

http://www.foxtbirdcougarforums.com/showthread.php?t=1938

[Bluegrass]

If you don't have to have an I6 then consider a 260/289 SBF as a drop in custom built with fuel mileage in mind, then there are no fitment issues.
Torque is a matter of min. flow losses, high chamber swirl, high compression all in the engine's mid rpm range.
If one looks at a hp/tq curve it is seen that the most linear rising part of the hp curve equates to the best torque range most all the time unless there are other circumstances that influence this.
A camshaft profile can be used to favor torque at the expense of some hi end hp.
So the engine can be built to effect a specific result.
This is what the factory tries to do for the average buying customer, then we come along and try to change it for more power.
Notice there are a lot of small engines with turbos trying to get economy as well as hp but in a lght weight package.

[Bluegrass]

The 200/250 sixes were also used right up to at least 77 in the Comets and Mavericks.
A few have been turboed a lot have been modified and a some replaced with the 300 truck engines.
Some years back I was at Englishtown all Ford weekend showing my 73 GT. There was a Mav from N.Y. state called the MAD FRENCHMEN.
This car had the 300 six engine but could have been larger.
Three Weber 2 barrels, cam and who knows what else.
Can you say low 11 sec 1/4 miles times.
About a year ago I was discussing this car on another board and come to find out it was built right under my nose less that 5 miles away back in 1972. The original builder now lives in Mass and contacted me about the car because I have photos he wanted, of it.

On using the 300 six, the combustion chamber efficiency should be a high consideration.
This engine is also fuel injected in the later 80s trucks and could be integrated in a Mark as such.

The term combustion chamber efficiency needs some definition.
The amount of spark advance required to allow peak cylinder pressures to occurr within that 12 to 15 degree range, after piston top center, is the prime indicator.
I have first hand experience of this on a 351w Ford all out race engine. The heads we use are away more efficient than most other heads used and even the GM heads at this point to the tune of needing an average ignition advance some 8 degrees (less).
This means the power loss from the time the charge is ignited (before top center) is less and mean more power is left from the previous cycles of all the other cylinders. This can be some substantial power from the reduced losses to crank inertia during that part of the cycle.

[gadget73]

Why can't you slant the thing and then use dry sump lube? Not easy, but it'd be surely interesting for bragging rights.


Well, you'd need an adapter plate of some form to keep the transmission level for one thing, but it could be done I suppose. Its an interesting idea. Would also need to either be EFI or have a custom intake made up to keep a carb level. Exhaust header would need a little modification as well.

[eVole420]

now that would be interesting, I think a slant would definetaly get the ladies. If anyone ever did do this and someone got a pic post it!

[88LSCinSW-FL]

Although I've already had more than one person tell me they've witnessed or heard of a 300 fitting in a Fox body even with a stock hood, I think it would just be easier to do a cowl hood if for some reason the engine did not fit under the stock hood. I'll leave the "leaning tower of power" thing for the Mopar car guys. :p

[macx]

Just to throw this on the table for guys interested in turbos -

www.ststurbo.com

I've emailed them and they said they would work with
someone on a custom setup.

I've been dreaming Factory Five Cobra in my retirement
for years, and now have the basic powertrain for it,
although much too mild as it is currently built to haul a
7 down the freeway with decent mileage.

All along I'd been thinking 393 with much better HCI.

This system has me intrigued as it would allow me to
basically allow me to keep my shortblock with just
some upgrades such as main studs, a girdle, prep
the stock football rods, and MAYBE even keep the
hyper pistons.

One thing it would do would help keep the mileage
penalty to a minimum while still having the GO
when I want it.

(AND not really showing up under the hood!)

So, set up properly, might work with either an I-6
or a really small V8, or how about a turbo V6?

Also, and this is a totally different direction, I know
the AOD in all versions takes quite a bit of power
to turn.

It may be blasphemy in a sport/luxury car, but how
about converting to a 5 speed just to cut parasitic
power losses? As far as that goes, BMW does that a lot.

[Bluegrass]

Macx, we have one Factory Five in the family, built in my shop.
5L with World heads, B cam, 4 barrel and 5 speeds.
Can you say a lot of power right now even with the small motor.:)
Photos if you like to your e-mail add.
The other car is a 351w all out sprinter at 500 + on alky.
Take care.

[macx]

That's one thing about those FFR cars,
they're so lightweight that even using
stock Mustang power they're really quick!

Actually, I've been considering their Ferrari
look-alike roadster as it has a little longer
wheelbase and their info says they're
developing an all weather top for it.

Even though it would add some weight,
I'd thought of A/C, cruise, and maybe
even some Mk7 seats if they can be
squeezed in - make more of a daily driver /
longer haul road car out of it (and then
FINALLY go on the Power Tour). With my
351 beefed either to 393 or with a Squires
turbo, the power to weight ratio would
still be there in spades.

[Bluegrass]

It may be unusual to say, but building so much power into a light car becomes a problem of how much is enough when the throttle just burns the tires and the car gets away if prudence is not used.
Then the investment become highly damaged.
The thread has gone a bit off subject but is nice to have the exchange.;)
Talking about efficiency, the sprinter has the N351 heads. We found that these heads are so efficient as compaired to more triditional designs that spark advance required is an average of 8 degrees less even with pure meth alky as the fuel. Found out the hard way from blown gaskets then analysis of all the tell tail signs inside the engine.
We were lucky not to blow the engine in a lot of pieces due to the forged rotating assembly and race block.