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Old 08-20-2012, 01:38 PM
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Maximize Gas Mileage

Hello: I have a 1935 Ford two door sedan that weights 3400 lbs. I have been running for years a stock 1980 Buick V6 with Turbo 350 trans, Holly 490 cfm four barrel, 3:55 rear gears, P 95/75 14 front and P225/75 15 rear. I was getting 20 to 22 MPG.

Attempting to maximize mileage I added a stock 2004R trans with no lockup, changed the rear to 3:35 and installed 500 cfm Edlebrock four barrel carb. I bored out engine 30 thou., polished and ported heads and mileage went to 13 mpg. Drives wonderful at 80. My tach doesn't work but I could hook one up.

I'm told I'm out of the power band of the V6 and lugging engine.

I want to get up towards 30 mpg. Ha Ha but I'm going to try. TA Performance can build me a V6 with aluminum heads and 330 hp. How do I determine the best build for the 2004R, what rear ratio to use and any other tricks. I don't mind considering EFI if I can do for under $1000.

I don't want to change the architecture of the engine bay by changing to V8. Not sure if 3800 or 4.1 V6 has the same motor mounts.

Any ideas. Thanks Steve

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Old 08-20-2012, 01:59 PM
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put your car on a chassis dyno,make sure the facility can measure sfc9specific fuel consumption) It will tell you how many pounds of fuel is burned per horse power produced. This will also tell you the rpm that the engine is most efficient. .38 pounds of fuel /hp is a good start,,,,determine how much power it will take to get your ride at the speed you want to travel,,,

wheel alignment,tire pressures,aerodynamics especially over 47 mph makes a very big difference.
I see no reason to get less than 30/gal when all is working well.
I managed 28/gal in the wifes 1980 camaro with a 350.
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Old 08-20-2012, 02:40 PM
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You went the wrong way with the gears. That 200 trans has a .67 OD and your poor motor is working overtime to keep that thing at speed. A 3.90 or 4.10 gear would be about right. If you're using a 28" tire, 3.35 gears and a .67 OD you're turning a mere 1700 RPM @ 60 mph. Correct me if I'm wrong, but those v6s are really stout in the low end torque department. I would think that V6 wants about 2400 to 2500 rpm at cruise.
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Old 08-20-2012, 05:12 PM
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Quote:
Originally Posted by Stephen Dellinger View Post
Hello: I have a 1935 Ford two door sedan that weights 3400 lbs. I have been running for years a stock 1980 Buick V6 with Turbo 350 trans, Holly 490 cfm four barrel, 3:55 rear gears, P 95/75 14 front and P225/75 15 rear. I was getting 20 to 22 MPG.

Attempting to maximize mileage I added a stock 2004R trans with no lockup, changed the rear to 3:35 and installed 500 cfm Edlebrock four barrel carb. I bored out engine 30 thou., polished and ported heads and mileage went to 13 mpg. Drives wonderful at 80. My tach doesn't work but I could hook one up.

I'm told I'm out of the power band of the V6 and lugging engine.

I want to get up towards 30 mpg. Ha Ha but I'm going to try. TA Performance can build me a V6 with aluminum heads and 330 hp. How do I determine the best build for the 2004R, what rear ratio to use and any other tricks. I don't mind considering EFI if I can do for under $1000.

I don't want to change the architecture of the engine bay by changing to V8. Not sure if 3800 or 4.1 V6 has the same motor mounts.

Any ideas. Thanks Steve
EFI and a lock up converter would help. EFI, especially port injected, does a lot to eliminate the cylinder to cylinder fuel deficiencies of a carb and to some extent TBI as well, but even TBI does better than a carb because of the precise fuel schedule for RPMs and power extraction. The over-under shoot of the carb on throttle changes is eliminated as is the often quirky on-off-on again relationship between main metering and the power system. The pulsing air flow through the ventures causes this shaky metering especially at lower RPMs. EFI, even TBI, doesnít respond to the pulsing air flow itís concerned with the weight of air passing into the engine not the volume and as freshman chemistry class taught us, chemical reactions occur by weight not volume. Because of these features EFI will let you run the engine in what is often described as the lugging zone, where a carb has a very hard time and is inconsistent moment to moment in this range of low RPMs with high crank loading and quite an open throttle.

The lock up converter will really let you take advantage of this zone by dropping the RPMs by virtue of the slip loss that is inherent to a torque converter or other hydraulic couplings. This runs in the range of loosing from 7to 10 percent of road speed for the RPMs the engine is turning.

I rather doubt there is 30 mpg hiding in any of this, that kind of mileage really takes a detail systems engineering approach to the vehicle. While current production is in this range under certain conditions, for a 1980 Buick V6 it would take just for the engine a major rebuild around using more modern components, if this stuff is even available, for this motor. That would include the super accurate machining of these modern engines. These are things that are hard to come by at the corner parts store. This is the reason why crate engines are so popular as the accuracy and tolerances they hold are difficult and expensive to do without the investment at the corner shop in very costly machinery and tools.

What you're looking at is a lot easier to accomplish with a modern Chevrolet, Chrysler or Ford V8 or V6 for that matter than what can be gotten to with these older engines. As far as that goes the Chevy Gen III LS series or the Ford Modular will run rings around their 1960 early 70's era muscle cars and get well over 20, and some engines over 30 mpg doing it. I say this because if you're really hung up on great mileage figures getting a late model donor car from the wrecking yard will prove to be the least costly way of getting all the modern stuff designed for the whole car as system which is a position that really doesn't exist prior to 1996. Yeah, you start seeing this concept coming in the mid 1980's but it takes nearly 10 more years to solidify the concept, another 5 to get into the early 2000 period where it really comes together with new point designed hardware as a completely integrated and optimized package, instead of trying to force old, dated designs into a new mold.

You can't do this simply by using a smaller engine than you have because at the most basic point it takes X amount of power to move your 3400 pound vehicle. That X amount takes a certain amount of fuel energy, it doesn't matter if that's 250 inch six working its guts out at 80 mph or a 400 inch V8 loafing along at that speed. Inside the details of what you have to do to extract that power is where differences in fuel burn come in, for the small 6 working higher on its power curve, more fuel is put into it both to maximize the mixture ratio for power and to put in extra fuel to cool the cylinder below the detonation/preignition limit. This is a place where port injection shines as the fuel is puddled behind the valve then mixed and evaporated in the cylinder where it absorbs excess heat without the need for excess fuel. The problem is compared to your 1980 engine, this also requires a highly active combustion chamber hence the Chevy Vortec which under other names is the Ricardo chamber with all its frills that everybody uses these days. This comes to the piston whose shape is the bottom of the combustion chamber so it needs to be carefully considered also. Additionally, the materials of the piston have changed to high silicon alloys often referred to as hyper-eutectics. Whether as castings or forgings, this is a very strong and thermally stable material which will take more abuse. It run's tighter wall and ring clearances which keeps the rins square to the wall and stable so compression isn't lost to blow-by and the effort of the burning fuel is used to push the crankshaft around rather than pressurize the crankcase. This lets the designers use a thinner lighter ring that absorbs less power as the piston moves in the bore and allows a lighter weight oil to be used to reduce pumping and windage loses. This leads to synthetic oils which are molecularly stronger than mineral oils so they will carry more loads in the bearings and other rubbing parts with less friction and without having to use so much power to pump heavier oil at higher pressure.

I know this is a long way around the bush, but this is an example of how these modern technologies play together to make high mileage motors both in fuel economy, reliability and longevity. It's hard to close this gap with older engines simply because of how all these changes integrate and the lack of any one in a rebuild of an older engine skunks the whole deal with less than optimum results.

Bogie
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Old 08-21-2012, 05:07 AM
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At low rpms, the engine isn't getting enough timing advance to get good mpg.
So, if you get an efi system, make sure to get one that also has ignition timing control.

The ignition timing curve is very important for good mpg. Look into that.

Drive the car around in 3rd gear and see if the mpg is the same. Maybe you have too much trans pressure dialed in on the TV cable?
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Old 08-21-2012, 10:26 AM
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Quote:
Originally Posted by 454C10 View Post
At low rpms, the engine isn't getting enough timing advance to get good mpg.
So, if you get an efi system, make sure to get one that also has ignition timing control.

The ignition timing curve is very important for good mpg. Look into that.

Drive the car around in 3rd gear and see if the mpg is the same. Maybe you have too much trans pressure dialed in on the TV cable?
You point out a big problem with an undersized engine using conventional timing management methods of centrifugal and vacuum advance.

An engine that is undersized for the weight and drag it has to move requires that for a given RPM to hold a road speed it is easy to get into a situation where to get cruise power and RPMs for a road speed the throttle is quite open which reduces manifold vacuum and with it the amount of advance while the RPMs are too low to bring in much centrifugal advance. The result being the engine is operating with less than optimum advance and some amount of fuel energy is going out the exhaust instead of pushing on the pistons. An electronic advance system if retaining a carburetor, especially one that features multi-strike spark events in the lower RPM ranges can be quite effective in extracting the energy you're paying for.

Frankly if this was mine I'd jerk the V6 and put in a Buick 350 V8. That should be nearly a bolt in swap, will keep the character of the 90 degree Buick 6 with two more cylinders which will boost up the bottom end torque right where needed for efficient cruising.

The other cold reality is that the cost of modifying the engine and driveline to get mileage in the 30mpg range is so expensive that in practical terms there is no return on the investment through spending less money on gasoline.

Bogie
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Old 08-21-2012, 10:53 AM
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wow,talk about making mountains out of mole hills,lol.work with what you have,my first point is valid and Im not offering 5 more mph,maybe 1 or 2? Lets see what you have first.
examples my mom had a 1980 monza v-6 over 30 mph bone stock,good tires,perfect wheel aligmnment,small advance in ignition timing. In 1992 I bought her a cavalier,v-6,lots of options,a/c (not as common in Canada) all this car got was a KnN air filter,good wheel alignment,max pressure in tires and it was over 30 mpg.
EG3: My cessna 1972 L model as tested by me,averaged 3 mph faster,same day,3 direction test,same power setting,just by waxing the airplane.a lot different than a car,just to prove aero dynamics counts.same plane went 4 mph faster by using wheel pants.
back to your car:
do you run the car with a partially open engine bay,is the car tuned perfectly? refer to chasis dyno. we have not addressed your driving style?
what kind of tires and size,are they radial? does your car have much camber in the alignment? toe? do you have a front chin spoiler?what hangs in the wind? what speed do you travel at? Can the car be lowered?do you have a wind dragging brim over your wind shield. Can you change anything with out ruining the look of the car?
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Old 08-21-2012, 11:06 AM
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Originally Posted by vinniekq2 View Post
wow,talk about making mountains out of mole hills,lol.work with what you have,my first point is valid and Im not offering 5 more mph,maybe 1 or 2? Lets see what you have first.
examples my mom had a 1980 monza v-6 over 30 mph bone stock,good tires,perfect wheel aligmnment,small advance in ignition timing. In 1992 I bought her a cavalier,v-6,lots of options,a/c (not as common in Canada) all this car got was a KnN air filter,good wheel alignment,max pressure in tires and it was over 30 mpg.
EG3: My cessna 1972 L model as tested by me,averaged 3 mph faster,same day,3 direction test,same power setting,just by waxing the airplane.a lot different than a car,just to prove aero dynamics counts.same plane went 4 mph faster by using wheel pants.
back to your car:
do you run the car with a partially open engine bay,is the car tuned perfectly? refer to chasis dyno. we have not addressed your driving style?
what kind of tires and size,are they radial? does your car have much camber in the alignment? toe? do you have a front chin spoiler?what hangs in the wind? what speed do you travel at? Can the car be lowered?do you have a wind dragging brim over your wind shield. Can you change anything with out ruining the look of the car?
Are we talking mileage to the Imperial Gallon which is 20 percent larger than the US gallon; 4.55 liters versus 3.79. So 30 mpg Imperial would be 24 mpg American which sounds a lot more in line with a 1980 Monza with a V6.

Bogie
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Old 08-21-2012, 11:24 AM
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good point bogie,the monza did over 30mpg/canadian gallon and the cavalier did quite a bit better.Still I would re shoe the race horse before I replaced the horse.
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Old 08-21-2012, 11:53 PM
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First step in better mileage is throw the edelbrock to the side and get a Quadrajet. Second is get lower gears, right around the 3.73 range.
Tune it up with the best components out there, spiral core plug wires, brass terminal cap. Replace all the lubes over to Synthetic, including the wheel bearings and rear diff. Use a K and N air filter. Get a set of headers and a dual exhaust system added with a H pipe. Plumb a fresh air induction to the carb. All these will give you a improvement in mileage, but you still won't reach 30.
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