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Old 11-20-2010, 03:49 PM   #1 (permalink)
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HONDA P-100 hybrid----------- 173 mpg



The October 1992 issue of AUTOMOBILE Magazine carried a photo and caption for the 1972 HONDA P-100 hybrid,photographed by Ronald Ahrens at the Kruse Auto Auction,May,1992,at Auburn,Indiana,USA.

The owner of the car refused a bid of $3,500 for the car.

From the image,the cars graphics report "173 mpg Documented".This is the year before the 1st Arab oil embargo,the EPA and CAFE did not exist yet,so it's hard to gain any insight as to what the mpg numbers actually mean or the context in which they are presented.

Digging through my records,this is what I've been able to put together regarding the car:

* the base vehicle is a 1972 HONDA 600
* width = 52.4"
* height = 52.4"
* length = approx. 158.6" ( scaled from photo )
* Frontal area = approx. 16.238 ft-sq ( estimated @ 85% of gross due to low tumblehome of greenhouse )
* L/D = 3.026
* D/H = 1.513
* Coefficient of aerodynamic drag,Cd approx. 0.15
* TRW patented 1970 hybrid system ( used today by Toyota ) may have been employed
* HONDA's CVCC engine likely employed ( went into production for 1973 model year )
* full suite of aerodynamic streamlining features as set out in R.G.S.White's recipe for a Cd 0.24 automobile,MIRA,1969,plus full front spats and compound windshield.Full bellypan is presumed
* Dunlop steel-belted radial tires ( available at the time )

------------------------------------------------------------------------

A website for this car existed at one time although I have been able to relocate it.They did not have any images for the car.The photo by Ahrens may be the only extant photo which survives.
------------------------------------------------------------------------

I've taken the photo,de-cluttered it and reversed it as I like to do and fitted it along with the HONDA 600 under the 'Template.'
The car bears a striking resemblance to a certain HONDA CIVIC in South Carolina.Can you guess?


------------------------------------------------------------------------ photos to follow soon

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Last edited by aerohead; 11-22-2010 at 01:49 PM.. Reason: add photos publication dates correction
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Old 11-20-2010, 06:34 PM   #2 (permalink)
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I think the curb weight of the N600 is about 1,200 pounds so that helps a little as well, stock mileage of that car was 70mpg at 40mph and around 40mpg and 70mph, my parents tend to get 45mpg or so with theirs even with the leaky gas tank and other minor issues.
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Old 11-21-2010, 08:37 AM   #3 (permalink)
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The angle of the back end is really steep - about the same as a new Beetle.
How did he get such a good Cd with all that flow separation ? ( and where were these results tested at )
Thanks for posting Phil.
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Old 11-21-2010, 11:31 AM   #4 (permalink)
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Aero-tyro weighs in:

To my eye, the high point on the modified car is at the top
of the B-pillar. Loaded rear suspension due mods at rear?



Doesn't that mean the template should be positioned there,
vice at the after end of the roof?

It appears that there would then be a closer match between
car and template, with some small portion of the rear window
above the template. Aero speaking, how bad would that be?

Is the rear window tapered side to side to a central ridge or
is it smoothly curved?
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Old 11-22-2010, 02:05 PM   #5 (permalink)
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good Cd

Quote:
Originally Posted by Cd View Post
The angle of the back end is really steep - about the same as a new Beetle.
How did he get such a good Cd with all that flow separation ? ( and where were these results tested at )
Thanks for posting Phil.
Cd,the Cd I posted is a SWAG on my part,it's probably too low.I was considering basjoos AeroCivic with Cd 0.17,the P-100 has a more GTP type windshield so I cut it some slack.
Automobile Magazine offers no additional data.Honda Motor Company offers nothing at GOOGLE to help us.
All we have is a 50-mm photo and a caption.
With respect to the roofline,it is too steep although there is evidence going back to Jaray,Kamm,Fachsenfeld,Lay,Carl Breer,etc.,that whenever you stuff the wake, it shows up positive at the gas pump.The 40+% aft-body,even if mediocre,is still producing a streamlining function.
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Old 11-22-2010, 02:19 PM   #6 (permalink)
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high point

Quote:
Originally Posted by Rokeby View Post
Aero-tyro weighs in:

To my eye, the high point on the modified car is at the top
of the B-pillar. Loaded rear suspension due mods at rear?



Doesn't that mean the template should be positioned there,
vice at the after end of the roof?

It appears that there would then be a closer match between
car and template, with some small portion of the rear window
above the template. Aero speaking, how bad would that be?

Is the rear window tapered side to side to a central ridge or
is it smoothly curved?
Rokeby,I enlarged the photos to 11"X 17" and used my drafting instruments to locate the position of max roof camber as indicated in the two images.
If I've erred there and the high point is as you mention,having the roofline go outside the template wouldn't be a big deal.The M-B C-111 III does it,also GM Sunraycer,MG Ex-181,and others.
As far as the backlight,there's no other views of the car,especially in plan view.Looking at the highlights reflected off the glass I would presume that the backlight is of compound form.There would be some pretty serious vortices coming off there.
There's no way to know if the cars were ballasted or not.
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Old 11-22-2010, 10:31 PM   #7 (permalink)
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The rocker panels are sloped up on the stock car, and closer to level on the modded car, so I think you are correct that the 'B' pillar is the new high point -- which helps the curve a lot I think? It hopefully has lots of side taper, too? The 600 is a narrow and small car, so the side taper might help the air close in cleanly?

The wheels are tiny -- 10-12" if I recall correctly, and they may have redone the gearing, too.

Hey -- they seem to have lengthened the wheelbase? The front wheels look farther forward.... and the windshield is slightly more raked, and it has a lot more curve to it. The sides curve back more to the 'A' pillars.
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Old 11-23-2010, 02:35 PM   #8 (permalink)
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another tyro weighs in

Quote:
Originally Posted by Cd View Post
The angle of the back end is really steep - about the same as a new Beetle.
How did he get such a good Cd with all that flow separation ?
The Honda 600 is a very narrow car (just over 3 feet wide IIRC?) and to my eye it looks like the back window is a compound curved polycarbonate. It does appear to be too steep from a side view but there is probably a lot of taper from the sides. The New Beetle C pillar has sharp edges and minimal plan taper. I believe this creates two big trailing vortexes and increased drag (I have seen a fastback diagram from the Hucho book somewhere that shows this). The smooth compound curves on the P-100 would help fill the wake and reduce drag. The back end of Honda reminds me of the front of the Bullet Train I rode in 1979. It also looks like there is a 4 upslope on the rear diffuser. I wish we had more photos and info on this car. Thanks Phil, good find!
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Old 11-23-2010, 06:39 PM   #9 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
Hey -- they seem to have lengthened the wheelbase? The front wheels look
farther forward.... and the windshield is slightly more raked, and it has a lot
more curve to it. The sides curve back more to the 'A' pillars.
Right you are! (How'd I miss that?!)

To my mind, the change in wheelbase downgrades this to a P-100 based car...

But still a great find by aerohead.
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Old 07-27-2011, 11:46 AM   #10 (permalink)
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173 MPG Honda

Hello! I am the (new) owner of the Honda, and have VERY little info on its history. Any idea who built it, when and why? Once I determine how to post pictures, I will attach some current images!

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