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Old 03-09-2014, 02:31 PM   #11 (permalink)
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Quote:
Originally Posted by Mista Bone View Post
I do NOT prefer the longer geared transmissions.

53 MPG in my 93 DX HB with aero/performance upgrades using a stock geared DX transmission.
What Old Mech said in the previous post. And also, a 1992-1995 vx/cx transmission would essentially shift your current rpms in 5th to 4th, and 4th to 3rd (almost exactly). Downshift and you'll get the same acceleration characteristics, but then you have 5th gear down near 2000 rpms at 60mph for cruising. This is my setup right now in my DX civic. At times I cruise at 60 mph getting over 70 mpg, but on average in mild weather I top 60mpg at steady 60 mph without even trying. I should run a test, using my current 4th gear and 5th gear in an ABA pattern experiment to show the difference in mpg the gearing makes.

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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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Old 03-09-2014, 05:35 PM   #12 (permalink)
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You will likely find out that your mileage is LOWER from lugging the car in too tall of a gear, keeping the engine out of the range it is most efficient in.

The 16 valve DX motor likes a higher cruising rpm, say 2800-3200 rpm, over the lower rpms the HF/CX or VX/HX on low cam to keep intake port velocities up. This helps with even fuel atomization and dispersion in the cylinder.Just look at the throttle body diameter.

Now with better aero than I had 10 years ago it might be possible to lower the cruising rpm without lugging the motor.
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Old 03-09-2014, 08:05 PM   #13 (permalink)
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My VX pulled fine from 30 MPH and 1000 RPM. If you want faster acceleration choose anyone of 3 lower gears , and on one 64 MPH jaunt, I managed 68 MPG for 300 miles.

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Mech
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Old 03-09-2014, 09:19 PM   #14 (permalink)
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Quote:
Originally Posted by Mista Bone View Post
You will likely find out that your mileage is LOWER from lugging the car in too tall of a gear, keeping the engine out of the range it is most efficient in.
Not true. I just described to you the experience I have had. My point about testing was to make it plain as day. But I have watched the difference more times than I can count because all it takes for me to see the MPG numbers go up is a gear shift from 4th to 5th while observing my instant mpg gauge on the dash. These lower rpm ranges are not "lugging" in the negative way you seem to understand it, they are actually closer to the most fuel efficient BSFC ranges. Ask yourself why all the automakers always gear for taller gearing in their more efficient models? And ask yourself why, for example, the 2012 Civic LX manual with shorter gearing gets 36 mpg in the highway EPA test while its taller geared auto trans sister LX gets 39 mpg highway? The two cars are indentical except for the gearing.

TESTED: just did some quick-n-dirty testing to show you what I see... posted results: check my modding thread linked in my signature file below.
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.


Last edited by California98Civic; 03-11-2014 at 02:36 PM.. Reason: "rpm" not "mpg"
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Old 03-10-2014, 05:33 AM   #15 (permalink)
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EPA rated vs. real world testing.

Also I prefer averaging a test change over a few fill ups to looking at an instant readout which can be misleading at times. Works great if you drive on flat lands all the time but in real world driving, the lugging on hills or the downshift kills most gains for a net average of about the same.

I did all the real world mileage testing years ago. If fact I'll bet you are using some of my info when looking into tranmission gearing options.

"D" tranny guru.
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Old 03-10-2014, 09:02 AM   #16 (permalink)
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Quote:
Originally Posted by Mista Bone View Post
EPA rated vs. real world testing.

Also I prefer averaging a test change over a few fill ups to looking at an instant readout which can be misleading at times. Works great if you drive on flat lands all the time but in real world driving, the lugging on hills or the downshift kills most gains for a net average of about the same.

I did all the real world mileage testing years ago. If fact I'll bet you are using some of my info when looking into tranmission gearing options.

"D" tranny guru.
Well thanks for your interest in this forum. There are a lot of people on this site with decades of mechanical and/or engineering experience. Some amazing professional aero people. I'm just a devoted hobbyist. But I can tell you that I observe mpg improvements on my gauges while climbing high, long hills. At 1500-2200 rpms at 80% engine load, my 5th gear will show 30-32 mpg and my 4thgear will show 25-27 mpg (at the same speeds). These are observations I make everyday, precisely, because that's how to hypermile for the 60+mpg tank-to-tank averages I've been reaching for a couple years now. A key idea is where you are on that BSFC chart.
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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Old 03-10-2014, 07:47 PM   #17 (permalink)
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Quote:
Originally Posted by Mista Bone View Post
"D" tranny guru.
He's not exaggerating about that, either. He is very well-known and well-respected in the Civic (and Civic-derivatives) worlds for his knowledge of the D-series transmissions.

He and I have had discussions in the past about gearing and fuel economy multiple times. I still disagree with his assertion that 3000 RPM is more efficient than 2000 RPM. If you dig deeper, you can see that his testing was not A-B-A testing--though that is pretty difficult to set up when talking about transmission swaps...

-soD
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Old 03-10-2014, 08:12 PM   #18 (permalink)
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550-600 mile round trips to Detroit and back while noting the ambient temperature differences make for a very consistent test loop. 90% of the driving was at night. Less traffic and rules out any differences because of alternator draw.

I will reprove all my test data before going forward. While some will agree I do things a bit different, the MPG numbers are still there AND the car is more fun to drive. The sweet spot is just a bit wider.

Everyone laughed at Smokey because he did things differently. I still have the original Popular Science magazine about the Fiero Motor...
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Old 03-10-2014, 09:31 PM   #19 (permalink)
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Black and Green - '98 Honda Civic DX Coupe
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Looking forward to your presence here, Mista Bone!
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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Old 03-11-2014, 08:25 AM   #20 (permalink)
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Quote:
Originally Posted by Mista Bone View Post
EPA rated vs. real world testing.

Also I prefer averaging a test change over a few fill ups to looking at an instant readout which can be misleading at times. Works great if you drive on flat lands all the time but in real world driving, the lugging on hills or the downshift kills most gains for a net average of about the same.

I did all the real world mileage testing years ago. If fact I'll bet you are using some of my info when looking into tranmission gearing options.

"D" tranny guru.
Why would the downshifts kill the gains? To the average driver, maybe, but to an ecomodder who knows how to handle hills? I am not sure I agree with this. For example, if the ecomodder is driving with load and already knows how to drive up hills to save fuel, I think in the end the VX/CX geared transmissions would still come out ahead in mileage because of the lower rpm benefit.

Do you have some of this real world mileage testing for us to look at? It'd be great to see.

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