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| MPG's Challenge https://slantsix.org/forum/viewtopic.php?t=28382 |
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| Author: | MichaelS [ Sat May 03, 2008 3:02 pm ] |
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My '74 Dart was given to me back in 1985 with about 30,000 miles on it. I drove it till it had 70,000 and then stored it. I looked back at my fuel log and it got a worst of about 13 mpg and a best of 20 mpg. This was while i was in college and didnt drive economicaly, the car was in good shape though. Roads were a combination of city and highway, 50/50. Just wanted to share what a 225 got when it was closer to new with low mileage. I have it back out after its 18yr nap and would like a little better mileage, I think I've come to the right place. |
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| Author: | Aggressive Ted [ Sat May 03, 2008 6:30 pm ] |
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Micheals, My stock set up varied almost as much on my 74 Dart with the 1945 Holley. I switched to 1920 Holley's from 68 to 1972 and started tuning them and the mileage became more consistent over time and much better overall. It is an easy carb to tune and make perform. 
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| Author: | Dan Townsend [ Sat May 03, 2008 6:31 pm ] |
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Since our cars have the aerodynamics of a brick, keep in mind ( according to some experts, 40% of the work of the engine is moving through the air. Sea level pressure of almost 15 pound per square inch. So, a good polishing of the car will help. Any one up to quantifying the theory? |
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| Author: | kipamore [ Sat May 03, 2008 7:23 pm ] |
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I'm no expert, but I have read that waxes, polishes, etc are bunk as far as aero is concerned. There is a boundry layer of air that clings to the car, making this unnecessary. To the best of my knowledge, there is little you can do short of very drastic changes, other than to lower the car, block excess air from getting in the grille, and block air from going underneath the car. I don't think the percentage you quoted is quite right, but I do know that drag increases exponentially with speed. Slowing from 70 to 60 will make a big diff. And as I understand it, aero improvements below 40mph are pretty much not worth pursuing. Kip on Truckin' |
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| Author: | CrAlt [ Sun May 04, 2008 3:48 pm ] |
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Well with the bumped timing the car did 25mpg from CT to VT. Running at 60-70mph. When i hit the hills i'ed let it slow to 60 then on the down side i'ed let it creep up to 70 and stay there until another hill. This is strait up highway. About 240miles. On my way home i was tired to i just wanted to get home. Did my normal 75ish. I'll compare those numbers when i get some gas. I think they will come out closer to the normal ~22. On a side note. I was messing around some in the mudd wile trying to get the car up to the site. My 1st WOT wack blew the dang flange gasket out again. This one didnt even last a whole day. I know something is going on with that exst system now. The pipe is so small and i think the muffler is way to restrictive. At WOT the night before I put a new gasket in, on the highway the vacuum gauge wouldnt go to zero. 5 is the lowest it will go. So im thinking to little carb and to little exst. |
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| Author: | Joshie225 [ Sun May 04, 2008 5:08 pm ] |
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If the exhaust was really restrictive the vacuum gauge would go to zero early rather than late. Less vacuum is more pressure. Where is the vacuum gauge connected? The exhaust pipe to manifold gasket blowing out is usually due to a warped pipe flange. I've had luck getting them to last longer by gluing two gaskets together with Permatex Ultra Copper and a little Ultra Copper on the manifold and pipe flanges themselves. If you are going to step up in exhaust size 2 1/4" works well. Plenty of posts on this if you search. |
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| Author: | CrAlt [ Sun May 04, 2008 5:21 pm ] |
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Ya i am going to step up to 2.25 ASAP. Im guessing 170's use a different headpipe since they have a shorter deck. I may have to wait until after i get that setup. |
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| Author: | Aggressive Ted [ Sun May 04, 2008 9:05 pm ] |
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Use a Remflex gasket at that joint PN 6006. It solved my problems. I bought extra thick flanges and they still blew out until I switched to the RemFlex. End of story......
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| Author: | ValiantOne [ Mon May 05, 2008 8:40 am ] |
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Quote: Quote: None of this will help economy. It is a case of power based on time (amp hours). It will take the same amount of fuel to charge 10 amps for 10 minutes, as charging 5 amps for 20 minutes.
Good luck, CS. I tried pointing this out and got called a "naysayer" by those who think that if they just believe hard enough, the laws of physics will politely step aside for them.  Make the engine do less work = more energy to drive the rear wheels. agrees with the laws of physics, and is relevant to this thread. Dan, while you are obviously VERY smart, your comments come across as very rude at times. "naysayer" was not meant as a personal attack. If you took it that way, I certainly apologize. C |
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| Author: | tlrol [ Mon May 05, 2008 9:41 am ] |
| Post subject: | Alternator tweaks |
In its stock configuration an alternator performs unneeded charging and maintains the battery at a higher voltage than is needed for the operation of a 12 volt electrical system. While SlantSixDan is correct about the laws of physics in regards to energy in=energy out + losses, he is skirting the issue of holistic design. In my EE graduate school days we used a vacuum controlled clutch on an alternator (among other things) as part of a heavily funded research project to do a couple of things: 1. Look at >12 VDC power systems in automobiles, and 2. Look at improvements to internal combustion engines. Guess what, we found many possibility for improvements. We noted that many of these were deemed not cost effective as long as fuel remained at less than $3 a gallon--this was based on the notion of comparing an equivalent return in an investment market and all that. What we found was this: 1. Alternators are not terribly efficient at what they do, they have excess windage losses, they tend to run at a constant load regardless of what the engine is doing, and they represent perhaps a 1 HP load (i.e. 746 watts= 1 HP). If you are willing to pay more you can get a rather efficient machine, better than what is in most cars today. Of course, this requires a capital investment program that simply does not pencil out if you are a automobile manufacturer. This is where the market place needs nudges from the government from time to time. 2. We found that the use of a high vacuum triggered clutch helped apply the alternator during periods when the engine's output was not required (i.e. high vacuum during braking, coasting, etc). This type of control could also be used to interrupt the field to the alternator as well. We took advantage of the battery's inherent storage capacity to "brake and bank" using the alternator, and we withdrew energy from the battery when we needed it. 3, You can gain some improvement in mileage by doing this--anyone who says you can not simply has never done this. We are NOT creating energy out of nothing, we are merely scheduling power generation activities at the appropriate times--please note that the amp-hour charge rate will increase during the high vacuum periods of motor operation. Ironically, we specified a larger alternator in order to gain more efficiencies through its higher amp output so we could quickly charge the battery--think of it as a brake. 4. A better fix for short haul trips could be to do away with the alternator and just use battery power. Electricity is cheaper than gasoline and there is NO alternator within this galaxy that is more efficient than a battery charger. If you drive 10 or so miles round trip this is an easy thing to do, provided that your water pump, etc still functions. You car will work fine and you WILL save money. Bottomline: Think about what you want to do, and give it a whirl. You best set your expectations fairly low though. Otto Cycle heat engines (i.e. Slant Sixes, Hemis, Chevy 350s, etc) have some pretty low efficiencies. A car has a bunch of moving parts as well (think losses). Get your rig in a good state of tune, check your tire pressures and all that, and then play the marginal mileage tweaking game. Best have a light foot too. Keep in mind that there is a bit of slop in measuring mpg increases as well. At the end of the day, however, if you can eak out a 1 to 3 mpg increase that looks like $$$ at $3.50 a gallon. FYI, electric cars show an equivalent cost at the gasoline pump at around $1.00 a gallon, depends on electricity prices, motor efficiency, etc. Note that an electric motor used in a car is better than 80% efficient. Also, the blended efficiencies involved in electricity production exceed 50% (60% for combined cycle CT, >80% for hydro power, etc, etc). Interestingly enough wind power is NOT terribly efficient, it is in the higher 30%--but the fuel is free so it works. Anyway, short of using Seebeck thermo-electric generators on the hot parts of your engine your tweaks to the car's electrical system are somewhat limited. If you want to chase down every little thing you could replace your lighting with LEDs, etc. Don't count on a pay back any time soon--although not replacing bulbs might be worth it depending on where the bulb is, what it costs, etc. My view is that if you want really good mileage a Slant Six might not be the best choice--but you can make them get better mileage. Keep an open mind, don't buy "magnetic fuel savers" etc, and bring up things in places like this--people will surely tear them up if they are dubious. I remember one thing my an instructor once told me that puts this all in perspective though. He asked us all how much energy a gallon of gasoline had--we guessed, used analogies, etc. His answer was "enough to move 4000 pounds twenty miles." Never forgot that statement--there is plenty of work that we already extract from gasoline, and it beats walking in the snow. |
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| Author: | kipamore [ Mon May 05, 2008 4:00 pm ] |
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Geez. When I went to college, all we did was read Beowulf. No wonder I dropped out. Kip on Truckin' |
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