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Old 09-05-2013, 05:49 PM   #71 (permalink)
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improbable CRX figure

7 horsepower to go 55 mph.
typical internal combustion engine numbers 1/2 gallon per hour per HONEST horsepower
7 HP then equates to 3.5 pounds of fuel per hour Or .583 gallons per hour at 55
55 miles / .583 gallons = 94.3396 miles per gallon

Horsepower ranges mostly below the 1 HP per .5 gallon range, and very slightly above it........ There is a lot of lying done about horsepower and about fuel consumption per horsepower. If it varies much from that number for an internal combustion gas engine, someone's not telling the truth. Dynomometers are infamous for producing bogus numbers.

Anybody ever get 94 MPG from their CRX except momentarily on the scangage........ strongly doubt it!

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Old 09-05-2013, 06:35 PM   #72 (permalink)
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Most decent engines without powertrain losses will do about 10-16 HP per gallon per hour. This diesel is rated at 180 grams per hour per HP. My Insight would go 40 MPH on .5GPH. 1 horsepower per hour on .5 gallon of fuel sounds very low. A V8 burns .5 GPH idling same as my Insight did going 40 MPH. I guarantee you the Insight did not got 40 MPH on one horsepower.

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Old 09-05-2013, 06:36 PM   #73 (permalink)
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7 hp

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Originally Posted by owly View Post
7 horsepower to go 55 mph.
typical internal combustion engine numbers 1/2 gallon per hour per HONEST horsepower
7 HP then equates to 3.5 pounds of fuel per hour Or .583 gallons per hour at 55
55 miles / .583 gallons = 94.3396 miles per gallon

Horsepower ranges mostly below the 1 HP per .5 gallon range, and very slightly above it........ There is a lot of lying done about horsepower and about fuel consumption per horsepower. If it varies much from that number for an internal combustion gas engine, someone's not telling the truth. Dynomometers are infamous for producing bogus numbers.

Anybody ever get 94 MPG from their CRX except momentarily on the scangage........ strongly doubt it!
I suspect that the 7-hp figure is for only the aerodynamic road load at 55 mph.
I believe that the entire road load horsepower for the CRX at 50-mph was 11-horsepower,including the friction and tire losses.I have the numbers at home.I'll get them.
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Old 09-05-2013, 06:49 PM   #74 (permalink)
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94 mpg

I averaged 52 mpg at the 55-mph speed limit over 365,000 miles.
With the streamliner package it went to 60.8 mpg in 1990.
On three occasions,the 'naked' car achieved its EPA HWY 62-mpg at 55-mph.
On one occasion,from Cloudcroft,New Mexico,to Denton,Texas,with a beautiful S-W quartering tailwind I got 82-mpg.I went back to the same station,same pump the next day and attempted to top-off the tank.It wouldn't accept any fuel at all with 6-miles on the trip odo.
I have the high-altitude gearing and turn a couple hundred extra rpm than the 49-state CRX 1.3-liter.
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Old 09-06-2013, 04:42 PM   #75 (permalink)
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1984 CRX values

*The 1.3 is reported @ Cd0.32-33,18.5 sq-ft frontal area,and 93 mph in 3rd gear with 60 bhp.
*The 1.5 is Cd 0.35,with passenger side mirror and wider tires,and does 105 mph with 76 bhp.
*Road Horsepower for the 1.5 at 50 mph,new 10.5 hp (4.0 R-R,6.5 Aero)
*Road Horsepower for R-R on my 1.3:
---------- @ 30 mph = 1.76 hp
---------- @ 50 mph = 2.94 hp
---------- @ 70 mph = 4.12 hp
@ 1926-lbs + 150-lb driver + 30 lbs test gear,@ Chrysler Proving Grounds,Chelsea,Michigan,10/16/1991,by Donald Schroeder,CAR and DRIVER,Ann Arbor,Michigan,42 F DB,49 F WB
--------------------------------------------------------------------------
United States Auto Club published findings from their 4-car transcontinental mpg run and was available at HONDA showrooms in 1984.
The four CRXs returned between 54.0 mpg and 86.3 mpg for a 32.3 mpg scatter.
They averaged 71.627 mpg.These were 49-state low altitude cars.
-------------------------------------------------------------------------
In the April,1984 Motor Trend,they reported:
*51.9 mpg for the 1.3 high-altitude CRX
*59.3 mpg for the California-spec CRX
*64.76 mpg for the Federal-spec CRX

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The 7 hp figure must be for only aero power absorption at 55 mph.
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Old 09-06-2013, 05:21 PM   #76 (permalink)
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Some rough numbers on tadpole

I scratched out some numbers:
*I took the 64" width and resolved it into a semicircle of 32" radius for the greenhouse.
*From the beltline down to the belly,just a 64" by 18" rectangle.
*Then using 145mm tires,at 8" exposure X 3 for the three wheels
*This gets me a projected frontal area of 20.121 sq-ft.
*At Cd 0.15 we'd have a drag factor of CdA 3.018 sq-ft (0.28 sq-m)
*At 1,300-lb,with 170-lb driver,the test weight would be 1,470 lbs.
*With 9.0 bhp,and a powertrain mechanical efficiency of 94% we'd have 8.46 hp available for propulsion,which would also be its road load at top speed.
--------------------------------------------------------------------------
Using Honda R&D Co.,Ltd's R-R power curve for a 1996 Accord I did some iterations to dial in the velocity at which 8.46 hp would be consumed.This is with a Coefficient of rolling friction of Cf= 0.0134 lbs drag/pound vehicle weight.
*I came up with 63 mph for the top speed.
*With an enthalpy efficiency of 42% and 129,900 Btu/gallon diesel,we have 54,558 Btu's per gallon of useable energy.
*At 2544.433 Btu/horsepower-hour it gives 0.4197 gallons/hour= 150 mpg at 63 mph.
If I use a BSFC of 0.38 lbs/bhp-hr,at 9 bhp I get 3.42-lbs,or 0.4858 gallons/hour,for 129.6 mpg at 63 mph.
-------------------------------------------------------------------------
A Lilliputian turbocharger would be handy for hills,but on the flat,the tadpole won't have much competition for mpg.
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Old 09-06-2013, 05:31 PM   #77 (permalink)
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I'm still thinking it would be nice to keep the curb weight close to 1000 pounds and I weigh just over 200. I was hoping it would get to 65 MPH which is probably close to your calculations. Looking at the pictures, the Fiesta is 58 inches high and it looks like the R.I.D.E. is slightly lower. I know it is tight inside for my 6 feet. Thanks for the time and effort aerohead.

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Old 09-06-2013, 06:27 PM   #78 (permalink)
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65 m ph

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Originally Posted by Old Mechanic View Post
I'm still thinking it would be nice to keep the curb weight close to 1000 pounds and I weigh just over 200. I was hoping it would get to 65 MPH which is probably close to your calculations. Looking at the pictures, the Fiesta is 58 inches high and it looks like the R.I.D.E. is slightly lower. I know it is tight inside for my 6 feet. Thanks for the time and effort aerohead.

regards
Mech
I think that the hoops for the greenhouse are not full semicircles,so your actual frontal area is probably such that 65 mph is already in the bag.If she's a tad lower in height,then she's golden.
Neil thought he'd be able to use a software-based tool to get an accurate measure with some true-length photos.That would be the hot ticket!
Yeah,the lower weight is always a nice gift.
I enjoyed the thought-experiment of testing the car on paper.It helps me focus on predictive capabilities,which can save a whole lotta man-hours.And I don't have as many of those left.
We've got to tip our hat to you for undertaking the project.She's really a pure form.
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Old 09-09-2013, 01:49 PM   #79 (permalink)
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Brilliant mate!

I've been dreaming about doing this kind of build for a long time, now I get to do it vicariously through you!
Nice clean shop, a man after my own heart. Although I admire people who can create cool stuff in pigsties, it'll never be for me.
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Old 09-09-2013, 01:54 PM   #80 (permalink)
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I've been dreaming about doing this kind of build for a long time, now I get to do it vicariously through you!
Yah, what you said. I always figured I'd use a ninja250 motor, or something similar, maybe a 400 single, but the diesel will be cool.

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