Getting in from Bonneville trip

[aerohead]

I've ground out some additional numbers and posted them at #1 permalink under their respective headings.
Streamlining seems to look better and better!
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Heroes of the future bragging,"Mine's smaller than your's."

[aerohead]

I've had hundreds of hours to mess around on the calculator and have some new quanta.Al's gonna close in a few minutes and I'll finish next week:
*The stock T-100 is capable of 111 mph at sea level with modified gearing.
*With a 'Template' body it would do 157 mph at sea level.
*Adjusting the values from the trip,as 'raced' in 2012,the truck had Cd 0.208.
*Due to the density altitude the mpg reflected Cd 0.169.
Gotta go!

[aerohead]

Truck's still dead so I continue crunching numbers.
*The 2,949 miles at maximum 75-mph netted an average 31.894 mpg,a 36.844% fuel economy improvement over baseline.
*Using 6.33% delta-mpg/10% delta CdA (extrapolated from Kelly & Holcombe's SAE Paper)this 36.844% difference suggests a 58.268% reduction in CdA,retaining only 41.732% of the original drag,or 0.41732 X 0.44= Cd 0.1836.
*Since these values were basically generated at 'altitude',with air density at only 0.00193 slugs per cubic foot,the drag coefficient can be down-graded to Cd 0.208 for 'standard air.'
*With the belly pan missing,and airdam mitigating some of the belly's performance,I might estimate a 0.025 benefit if restored.
*With the full-coverage ventilated wheel covers restored I might expect 0.018 (Pontiac's value).
*Completing the driver's side front wheel skirt may provide 0.0088.
*Together,these mods could drop the Cd from 0.208,to Cd 0.155.
*This is with attached flow down to the 9.743 sq-ft transom of the present 30-inch boat tail.
*From Hoerner's reporting of the fuselage truncation vs drag coefficient,by adding the new 18-inch 'stinger' boat tail extension,which reduces the body wake and base pressure area down to 6.02 sq-ft; the T-100 should have a shot at Cd 0.13.
*Comprehensive wheel/tire fairing integration could push the Cd even lower.
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If things work out I'll have these mods ready for North Carolina,late August/early September,and if I can just get it to Moorseville I'll get some hard numbers.
It's been an interesting project,it would be nice to complete it.
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A closing thought:
I located a CAR and DRIVER TEST RESULTS for a 1989 Peugeot 405 Mi16.It is the fastest car in my records which shares the same horsepower as the T-100 (150 bhp)
*Cd 0.28
*Af 21.5 sq-ft (1.998 m-sq)
*CdA 6.02 sq-ft (0.5594 m-sq)
*2,691 pounds curb weight
*0.76:1 5th-gear
*4.43:1 axle ratio
*Michelin MXV 195/60 VR-14 tires @ 32/32 psi
*131 mph,6,600rpm
*29 mpg at 75 mph
I would not be able to match the frontal area or light weight of the Peugeot with the T-100,but I could attack the Cd.And even compensating for the thin air on the trip,the streamlined T-100 gets better fuel economy than the smaller,lighter car,mountain passes and all.(This was the premise of Don Sherman's 'Crisis-Fighter Pinto' project of 1974)
Conversely,if the Peugeot were to receive the body off the 1993 HONDA Dream-2 it's 150 horsepower would be able to push it to 171 mph according to Hucho's Figure 3.11'Influence of aerodynamic drag on top speed.'
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From the Salt Flats:
*Jeff Mcvey's normally-aspirated Maxda 3 dropped from 130 mph,to 113 mph.I'm blaming the damp salt for the 13% loss.
*Sarah Curtis' Mini Cooper fell from 139 mph,to barely over 130 mph and her car is turbocharged and electronically-limited to 139 mph.And she only made 130 mph after packing the inter-cooler with ice.(a trick which can get the inlet temps down to 58-degrees F and almost a 6% increase in charge-density.Her 6.4% velocity loss I also attribute to the damp salt.
The normally-aspirated T-100 'gained' over it's sea-level and on-pavement top speed of 96 mph.And this is in consideration of the fact that a 'stock' Cd 0.44 T-100 might have seen only 83 mph due to the salt conditions.That would make a 26% velocity improvement without actually achieving terminal velocity.And with a 300-pound weight liability!
So it looks like all the body modifications helped both mpg and speed potential,which Hucho reports will always favorably impact mpg.
The trip was worth the trouble.Now it's time to see what the wind tunnel says.

[aerohead]

T-100's still dead so I continue to grind on the calculator:
*I've down-graded the trucks 'high-altitude' 31.894 mpg down to 28.484 mpg at 'standard' air density.
*Working with some weight-penalty curves from RICARDO (Consulting Engineers,Ltd.,England)INC.(online)I've adjusted for the 820-pound travel weight liability,adding back 0.523 mpg,for 29.007 mpg.
*Then,from TABLE 2.10,'Excess Gasoline Consumed per Stop or Slowdown Speed Change Cycle-Automobiles,' by Paul J.Claffey,National Cooperative Highway Research Program,Highway Research Board,Washington,D.C.,1971,and adjusting their 'composite vehicle' values to dovetail the T-100's,@ 0.012518 gallons/stop cycle X 8-stops for the Salt Flats-Carson City-Salt Flats segment;I pick up a 1/10th of a gallon dividend,pushing mileage to 29.189 mpg.
*This mpg reflects a 40.275% Delta MPG.
*Which (extrapolating from Kelley&Holcombe) yields 63.626% drag reduction.
*Or,36.374% of original drag remaining,yielding Cd 0.160.
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Segregating the body from the wheels gives:
*Body frontal area= 27.795 sq-ft (2.688 sq-m)
*Wheel and tire frontal area (allowing for front and rear track)= 1.129 sq-ft
*Total frontal area = 28.925 sq-ft.
*The original turbulent wake of the truck is essentially equal to its frontal area.
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If I begin to 'shrink' the body without changing its shape,while maintaining the wheels as a constant,when I get to the configuration with the 30" boat tail,the wake of the transom and wheels is 10.872 sq-ft,or 37.58% of the original.
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From the drag force and power formulas,by reducing the T-100s 'signature' from 28.925,to 10.872 sq-ft is the same as reducing the Cd from 0.44,down to 0.165.
*This Cd 0.165 is in close agreement with the Cd 0.160 we get from General Motors CdA/mpg relationship.
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Technically,to do a full accounting I'd need to include 'curve-resistance' and 'grade-resistance',calculate losses from cold-restarts in Winnemucca and Carson,City and a myriad of meteorological affects which are just completely beyond the realm of a simpleton like myself.Same goes for coastdowns.
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It does appear that we can use some of the simple relationships to 'rough-in' predictions before we begin mods.
And it looks like some of the 'vintage' numbers,published so long ago acquit themselves quite nicely even by today's metrics.Especially Klemperer's, which turn out lower than when initially published in 1922.
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Cd 0.13-0.12 looks real 'do-able'.
It's going to come down to a corollary of the old racing adage of Q-'how fast can you make my car go?
A-'how much money do you have?,to:
Q-'how many miles per gallon can you add to my car?
A-'how long of a tail can you tolerate?

[slowmover]

From the drag force and power formulas,by reducing the T-100s 'signature' from 28.925,to 10.872 sq-ft is the same as reducing the Cd from 0.44,down to 0.165.
*This Cd 0.165 is in close agreement with the Cd 0.160 we get from General Motors CdA/mpg relationship.
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It does appear that we can use some of the simple relationships to 'rough-in' predictions before we begin mods.

And it looks like some of the 'vintage' numbers,published so long ago acquit themselves quite nicely even by today's metrics.Especially Klemperer's, which turn out lower than when initially published in 1922.

Thank, you, sir!

.

[aerohead]

I'm still dead in the water and thinking things to death.
I brought a HIGHWAY ENGINEERING textbook in the backpack and have enlarged some tables for grade and curve resistance to work with.
Short of allowances for these effects,I ran out a Road Horsepower curve for the T-100,and using a power-train mechanical efficiency of 92%,the useable 138-horsepower balances aero and R-R absorption at a little over 134-mph,as configured at Bonneville.
To reach this speed would require a long,level,smoothly-paved stretch of highway,say at Daytona Beach;on a calm,dry,60-degree F day.
And the truck would have to be geared for 4,900-5,000 rpm in 5th-gear,as well as redo the whole aero kit in carbon-fiber epoxy pre-preg.
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The 131 mph Peugeot 405 Mi16 is lighter by 600- pounds,but its CdA is 6.02 sq-ft,compared to 4.628 sq-ft for the T-100,and as drag varies almost arithmetically with weight,but varies geometrically with CdA, the truck edges out the notchback for an overall advantage of both speed and fuel economy.
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From the Road Load curve I got the brake-horsepower,and by dividing that into the fuel mass (gallons X 6.00894 LB/Gallon) per distance ended up with 0.39516 LB/HP-HR BSFC,which at 116,000 Btu/gallon net heating value gives a thermal efficiency of 33.3% which is in close agreement for other engines produced by Toyota.
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With the 33.3% thermal efficiency,and absorbing 1/3rd of the heat flux coming off of the brake-horsepower at 75 mph cruising,the cooling system is over-sized by a factor of 2.68X which explains why the severe grille-block accomplished at Bonneville never really impacted the cooling system.(Which again,goes way back to "Crisis-Fighter Pinto" of March,1974)
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I like Hucho's CdA/Top-Speed table.I have high confidence in it.The caveat for those of us in the United States and maybe Canada,is that we've got to ascertain our vehicles actual top speed in stock form to use Hucho's table.
Engineers are using gearing as a governor to limit top speed,and it's mandatory that we know true terminal velocities before we can use the 30%/10% benchmark.
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I'll spend some time with the 'new' 1971 tables and see where they go.
With the enormous radii of interstate highway curves,and 'as flat as possible' gradients,I may not have suffered too much a penalty through the mountains.Don't know.
So far,the drag seems close to what the 'Template' would predict.
It will be interesting to see if the 'stinger' shows up on the radar screen.I think I could finally break over 40 mpg on the 'easy' road portions.That would be a hoot!

[freebeard]

And the truck would have to be geared for 4,900-5,000 rpm in 5th-gear,as well as redo the whole aero kit in carbon-fiber epoxy pre-preg.

If you went to the expense of redoing the whole thing, would you consider narrowing the rear axle a few inches first?

[aerohead]

Originally Posted by freebeard

If you went to the expense of redoing the whole thing, would you consider narrowing the rear axle a few inches first?

Absolutely!
Something from the pre-Tacoma,or S-15/S-10,Ranger pickup,would allow greater plan-view body taper for overall,better drag reduction potential.
If these types of rear axles posed a gearing problem,then a 'shortened' rear end would allow more infinite ring and pinion selections.
I'd like to maintain about 49-inches clearance between the wheel wells to handle drywall and plywood on the bed floor,so I'd have to be mindful.

[freebeard]

The Ultimate would be:
Speedway Engineering's IRS Quick Changes

[aerohead]

Originally Posted by freebeard

The Ultimate would be:
Speedway Engineering's IRS Quick Changes

That's plenty delicious! I'm already squirming though,thinking about the price.
'suppose I'll have to stay close to shore along with the other little boats.