I'm sorry to tell you that you.......as the thread starter........have the onerous of providing the hard evidence. You've provided anecdotal stories without a shred of hard evidence concerning a back to back test on a M/B diesel.


And, you've clearly ignored the very good analogy of an architect who would laugh in the face of someone who demanded hard evidence of the fact that a 2" x 4" won't work as a proper header above an 8' garage door.

You do know that this header would be inappropriate.......don't you?? Maybe I'm making some cavalier assumptions regarding your knowledge of building construction??

it just seems that to refute anecdotal storys with other anecdotal stories just doesnt cut the mustard...engineering wise i mean.

and i am not sure you understand what a 2x4 is... or a header. you know, not being an Architect and all.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

...........sorry you didn't understand the analogy.........oh well.........as I mentioned several times in this thread........you can believe what you want.

My goal is to simply present the facts for other members....................

They can make their own judgment of whom to believe.............three engineers............or an architect without good data.

but you really don't have the hard data for a na diesel, do you?

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

i happened to think to look at their web site.

for a dodge they offer three applications:
1. 28.6% od on an older four speed = 25 to 28% better fuel economy.
2. for the five speed trucks they offer a 22% od and say it = 20% better economy.
3. and for a six speed like mine they offer 28% od and claim 20% better fuel economy.

they don't say whether it is for diesel or gas, but they have power graphs for all the recent gas and diesel engines. the 5.9 cummins for example has a torque peak at 1300 rpm and max hp at 2750.

when i am towing with mine i shift at 3000 and it drops the rpm down to about 2000 and thus keeps the boost on pretty well.

i dont know if they have used actual engineers on these figures or not.

you can decide for yourself whether this qualifies as near the same percentage or not.

they also offer them for cars with a lot of pro street and such shown. i didn't look at that though.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Hi Tom,
It would appear from the information posted on their site that Brian may owe you if not an apology, at least a concession that you are right in many instances.
I looked at all the figures for GM, Dodge and Ford trucks, and in most cases, they indicate a mileage percentage increase at or almost at the ratio percentage change. In a few cases where the final drive ratio is already at the low end they also indicate much less of an increase.
It just goes to show that many vehicles are not optimized for best mileage, even in these days of high priced fuel.
I do suspect that vehicles with less surplus horsepower and torque will show less of a gain, and that it would be quite possible to overdo the principle to the point that there would even be a mileage drop.

Regards,

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

I'm reaching back to remember a magazine story on your "double nickel" in the early days... a Volvo wagon consumed more fuel in overdrive than it did in the straight ratio at 55 mph.

My anecdotal architectural contribution here is intended to cast a critical light on the legacies of that profession...

In old England, the Monarchy had identified two lengths of wood for the stoves, and of course the gentry had the longer. The peasants stacked their wood up against the inside walls of their "houses". Thus the basis for the 16 inch pitch in 2 x 4 construction, and 24 inch for 2 x 6.

Now, perhaps the modern architect has a mathematical engineering model which shows the maximum safe pitch of the studs in the wall, eight foot garage door or not.

now bobsterman, you have not insulted me or my profession, so i will respond to your story.

i have never heard that one, but i have heard similar stories about how the width of rail road tracks go all the way back to the roman times and is in fact the width of a two wheel ox cart. (that one i beleive)

i dont know about medieval england but i do know about what i have found in this country. in older structures with wooden lath and plaster, it is dicey business driving a nail in the wall because the stud spacing can be anything from 8" to 33" more or less. you really dont get into precise locations of wood framing until the introduction of standardized sheet goods such as 4 x 8 plywood and drywall. in order to avoid cutting each and every piece of material so that you can nail the ends to a board (and, structurally this is essential) you have to maintain precise spacing that works with the 8' dimension. so 6", 8", 12", 16" and 24" all will work. 16" is by far the most common for floors and walls. 16" and 24" are the most common for roofs.

in older buildigs also, you can find many examples of walls that are not plumb and rooms that are not square (in the corners). i have seen rooms that are nearly a foot longer one side than the other.

folks say "they don't build them like the used to" and in many cases that is a good thing.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

so i went back to my log, which i still have since the buyer of the car didn't care if he had it, and looked again at the info that was there before changing the rear end from 346 (stock for a 300 na) to a 307. my kids were driving the car and there is evidence of at least eight tanks but they were a little sloppy and didnt always record all the info so there were only three tanks that i could decifer. they worked out to 21, 26 and 22 mpg. i can tell that the one at 26 included a trip to colombus oh. so that was pretty much all highway.

so then we changed the rear to 307. i wont put a sharp pencil to it but that is about a 10% change in ratio.

the next twelve tanks i did. the mileage on them was 29.4, 20,26,28,28,25,30,20+,28,20-,22 and 20. the ones near between 28 and 30 were all highway. the others were mostly town driving.

so it is not a double blind test using computers and regisered engineers, but it is sufficient for me anyway, and i think i am more critical than most, to say that the mileage increase was pretty close to the same percentage as the gear change.

in any case it is enough to convince me that if i wanted a mileage increase i would spend good money doing it and expect this kind of results.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

and i found torque and hp max specs on the na engines.

max torque on all the 616 and 617 engines from 74 to 81 is 2,400 rpm.

max hp on the na 617 is always 4000 rpm.

max hp on the 616 is shown to be from 4000 to 4200 to 4400, depending on the year.

there could be some errors because i found that the 79 sd is listed as having 8.7 compression, 217 hp and 235 ft. lb or so of torque. this can't be right, can it?

so the max figures seem pretty close to the 617 turbo curves posted above.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

No...that can't be right. Compression is in the neighborhood of 19:1. Those look like numbers for a 450.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

actually brian, werent you predicting 7% gain in fuel economy on a 20% gear ratio change?

7% gain on a 10% gear ratio change more nearly supports my position.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Average fuel economy with very poor data: 23.0 mpg


Ratio change = 11.3%


Average fuel economy: 24.7 mpg


So, the average fuel economy improvement is 7.4%


As I've told you, you'll never get the the same percentage fuel economy improvement as the axle ratio change.

Even with your widely varying driving conditions, your own data proves my previous statement.

It's time to get off your soapbox and agree that you're not correct.

Tom... much belated answer, but I can't resist...

Railroad track width goes back to the standardized width of Roman chariots, based on the standardized width of two horses arses.

I understand the lathe and plaster thing, as for the past 18 years I have been renovating my great grandfather's farmhouse, built variously in 1908 and 1920. I get lots of leftover drywall. I rebuilt the windows by looking for the most square and plumb corner, and going from there.

Up here (North of North Dakota) a lot more 2x6 in the wall is used to make room for more insulation.

I'm not afraid of used lumber because by the time I'm done, the new stuff looks used anyway. Hooray for screws (Robertson head of course).