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Old 10-23-2011, 08:59 PM   #21 (permalink)
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I hope the upside down one is set up right.



Great work here by the way. I could definitely see strakes/wheel fairings on it, as well as that kammback becoming radiused as it goes back. Just make a section for the rear edge of it and then score some of the flutes until it bends to fit the section.

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Old 10-23-2011, 10:16 PM   #22 (permalink)
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Quote:
Originally Posted by Reloadwin View Post
Looks great could you please take pictures of the inside bottom of you front grille. How do you keep it sturdy from the wind hitting it?
Do you mean the lower grill area under the bumper?


I peeled the tape off to show you. The front of it is simply bent upwards and screwed into the choroplast cover of the front bumper cover. The other end overlaps the choroplast belly pan and is also secured with sheet metal screws backed up with hand cut sheet metal tabs.
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Old 10-23-2011, 10:41 PM   #23 (permalink)
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By the way a few of us went back out yesterday and drove our 120.9 mile loop through the southern Adirondacks in an attempt to set new personal bests. Let me start by saying the weather men were wrong as they were calling for no rain and temps in the upper 50's. But up in the mountains we had a wet mist requiring wipers at times. We were driving through wet roads with standing water, and trying to dodge the bigger puddles. It was quite cool up there as well, only in the upper 40's.



I was really hoping to break 80 mpg, but in the end I waited too long for this second attempt. It was almost 40 deg. cooler than it was at the Tri-State Fuel Economy Challenge event almost 6 weeks ago and it was wet. So the benefits of having ethanol free fuel this time out and using a more "fuel mileage friendly" course were in my estimation nullified by the wet roads and cool temps. I improved just a bit from 76.04 to 76.90 mpg.

Here are a few more pics I took yesterday:





It's hard to see in this picture, but the fuel level is right to the top of the flapper. This is the fill and refill point I use. The others were using the clicking off method which I believe is less accurate. I like to be able to "see" the fuel level during the before and after fills, and am glad I have an older car and can top off like this without causing any problems.

On my way home I decided to see what I could get driving the car "normally", or what some would call "real world" driving. So without any engine off coasting or pulsing and gliding, I simply cruised at a steady 50 mph on the NY Thruway for 30 miles.



I was able to get 50 mpg. Not bad for a two liter Sentra.
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Old 10-24-2011, 05:36 PM   #24 (permalink)
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template alignment

Quote:
Originally Posted by Sven7 View Post
I hope the upside down one is set up right.



Great work here by the way. I could definitely see strakes/wheel fairings on it, as well as that kammback becoming radiused as it goes back. Just make a section for the rear edge of it and then score some of the flutes until it bends to fit the section.
Sven7,your primary alignment for the Sentra looks right on the money,revealing that the roofline is a tad too fast.
With respect to the inverted template,it's not designed to address diffuser angles.
The latest 'Template' is drawn to incorporate a 2.5-degree diffuser which begins just aft of the rear axle.
These can be as steep as 4-degrees or so,according to research published in Hucho's book and elsewhere.It all depends on the diffusers point of origin.
The clincher will be departure ground clearance,as Mike rolls straight down a driveway,across the gutter and onto the street.
The diffuser may have to remain 'steep',so as not be torn to shreds on the pavement.
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Old 10-28-2011, 05:40 PM   #25 (permalink)
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Sentra/Template

I photo-enlarged your photo and did a Template overlay.
From a 1993 Sentra road test,it looks like your car is 53.9-inches in height(unladen),and 170.3-inches length.
To get the roof extension to the Template would require raising it around 4.6-inches at the top trailing edge.
Also,it looks like the valence/diffuser could drop about 2.6-inches ( unless that would risk a ground-strike).
With your extension,you're at 33% aft-body,same as Prius II @ Cd 0.26.
The Daimler-Benz "bionic","boxfish",@ 32% aft-body is Cd 0.19.
Kamm's best car,@ Cd 0.25 had 38% aft-body.
So you're scratching at some tasty Cds now.
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Old 10-28-2011, 08:19 PM   #26 (permalink)
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That's terrific aerohead.

Thanks for taking the time to research the Sentra's body specs further. Your findings are very encouraging!

I did very little with the front of the car. It's rounded but the surfaces are basically verticle. It doesn't seem very efficient to me. Is there anything you might recommend?

Mike
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Old 10-29-2011, 04:12 PM   #27 (permalink)
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Quote:
Originally Posted by blownb310 View Post
That's terrific aerohead.

Thanks for taking the time to research the Sentra's body specs further. Your findings are very encouraging!

I did very little with the front of the car. It's rounded but the surfaces are basically verticle. It doesn't seem very efficient to me. Is there anything you might recommend?

Mike
Everything I'm going to say needs to be weighed against AeroCivic and what basjoos has achieved.
90-mpg from a car which originally returned 55-mpg with the VTEC engine ( I've witnessed this first hand with John Gilkison's Civic VX) is nothing to sneeze at.
Conventional wisdom has it that once flow is attached,that any further softening of forward leading edges will result in no mpg benefit.
So the PhD is going to say to forget the front end,it's good enough,go after the rear end.
The Ford Probe-IV violates this dogma and returns Cd 0.154.With a 'conventional' cooling system that Cd might rise to 0.172 (basjoos territory!)
The Probe-IV has only 28% of a full boat tail.
There was an Italian concept car,the 'APOLLON' which achieved Cd 0.13 with very little aft-body.There is very little published for that car.
The Renault Vesta II has 28.5% of a full boat tail and achieves Cd 0.19,with a blunt nose,but 'PERFECT' windshield.If Renault were to move the Vesta's cooling system to the rear it might see sub-Cd 0.17.Don't know.
Klemperer's 'minivan' model of 1921 achieved Cd 0.16 with very little tail at all.It was a 1/10th-scale,no details,just a smooth model.It's aft-body does not exceed Mair's magic 22-degrees,although it gets there very aggressively!
My opinion is ,that since we know so little about fore-body mods/mpg,and that the 'experts' tell us to focus on the aft-body,that we SHOULD focus on the aft-body.
I tried some tricks at Bonneville and saw little from massaging the front,but when I went after the tail I got big gains for speed and mpg (I averaged 60.6 mpg from the Salt Flats to Los Angeles,and back to Texas.
I recommend you try the 'Template',push it to any length you're willing to live with.Do as much plan-taper on the sides as well.
You shouldn't see any separation at all.Empirical studies have shown that it's impossible to have separation.
From tuft testing by members,it looks like we can 'cheat; a little,but I wouldn't go too far afield.
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Old 12-18-2011, 10:55 PM   #28 (permalink)
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what kind of weight reductions have you done to your sentra?
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Old 12-19-2011, 08:31 AM   #29 (permalink)
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what kind of weight reductions have you done to your sentra?
There is no interior, other than a single aluminum race seat. No radio or speakers, no sound deadener, no spare tire or jack, etc. The hood is choroplast, 3.5 lbs.

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Old 03-14-2012, 04:32 PM   #30 (permalink)
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that's some wicked cool mpg you've got there. Any idea how many pounds that weight reduction netted you?

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