Geoff
-
Posts
211 -
Joined
-
Last visited
Content Type
Profiles
Forums
Events
Posts posted by Geoff
-
-
As I was perusing through some files I stumbled across a .pdf of the owners manual for the Escort GT2, a personal accelerometer device. I never had Escort's device though I did have one from a competing company. I don't believe the GT2 is made any longer but the Escort website still hosts the literature and may be found here under Vehicle Performance Meter Owner's Manuals.
Pages 21 - 23 of the owner's manual discuss CDA. The owner's manual also gives a method for finding your car's CDA, posted in screen captures below:
If you know or can find your car's weight, and if you have access to a straight, flat road where "slightly above 60 MPH" is not dangerous and/or illegal, it is possible to find CDA following the directions written above.
-
Gross horsepower and net horsepower are both flywheel rated. Net takes into account the engine driven accessories with an "as-shipped" exhaust system attached. Gross is an engine without accessories and an open exhaust system. Neither rating takes drive train losses into account. On a dynojet, a stock ZR1 shows 535 horsepower to the road. 638 to 535 is ≈16% loss of power, in the range I've heard to account for drive train losses.
I completely agree about the ZR1, it's an amazing creation. Isn't technology wonderful? These are the only aspects I was comparing: 0.36 Cd for the ZR1, 638 horsepower, and a 205 mile per hour top speed. As in, the Corvette ZR1's design took 638 net horsepower (along with its 6 speed gear box, lightweight driveshaft, air conditioning, 1.10 lateral-G rating, etc.) to attain 205 miles per hour.
I also have read the Due Cento engine made 638 horsepower. Since this is grossly rated then it is not equal to the ZR1's 638 horsepower and would be less power in reality. Maybe that's where the 575 figure originates, as somebody's guess converting to net? Even that would be high compared to what the tires put to the ground, so now R5 is down to the 490 horsepower range.
If the Avanti is not even in the same aerodynamic ballpark as the C6 ZR1 (which is 0.36), how could an Avanti body be approaching 200 miles per hour? Especially with only 638 gross horsepower, which we agree is less than the C6 ZR1's 638? Keeping in mind a Bonneville rating is a two-way average, so a 196 average means equal time spent at 192 as 200 or 190 as 202.…Driven by Joe and Andy Granatelli, the Due Cento reached speeds well over 200 mph according to the tach, but was not getting traction due to the wet salt and the best official run was 196.58 mph … -
It's 21.1 square feet according to http://www.theavanti...dimensions.html. I am finding that frontal area is not the whole picture when it comes to drag, it plays a role though using it alone is a rudimentary way of discussing drag. There's more to the equation. We really need an Avanti in a wind tunnel for a solid answer.Andy Granatelli took the Avanti to Bonneville and easily set a slew of international speed records. Mickey Thompson was after the same ones with a hot 421 tri-power Pontiac that probably had some 100 hp on the Avanti. But what gave the Avanti the advantage was its drastically more aerodynamic body, estimated to have a Cd of “in the high 0.30s”, as well as a much smaller frontal area.
-http://www.curbsideclassic.com/curbside-classics-american/curbside-classic-1963-studebaker-avanti-flawed-brilliance/
"There is a lot to drag than meets the eye. What happens underneath, how the radiator air is let in and out. How the rear of the car is shaped all have a big input on the drag."
above quote from busman, here: http://www.planet-9.com/987-cayman-boxster-service-tech/8956-drag-coefficient-cd.html. They're discussing select Porsche models though their conversation gets into Cd. One of the members even has a '63 R2 Avanti.
Who would look at an Impreza and think aero? Bingo! It attains 0.36 Cd and yet to some people it wouldn't appear so. Could Avanti be 0.38 and yet to some people not appear so?
Here's a comparison to think about:
The C6 Corvette ZR1 can reach a speed of 205 MPH. It does so with 638 peak horsepower and a Cd of 0.36 [which is higher than other C6 packages because ZR1 adds ground effects].
How much power did the R5 produce … circa 575? An Avanti with R5 could peak at 196 MPH.
-
I thought it was more widely known Raymond Loewy had a good handle on aerodynamic design.… Andy Granatelli, President of Studebaker's Paxton Division, prepared several cars to make USAC-sanctioned record attempts at Bonneville late last winter and although most of the trials were frozen out by bad weather, he did manage to make some official two-way averages with a Lark, a Hawk and an Avanti, all equipped with R2 engines and four-speed transmissions. The cars were completely stock including exhausts. Naturally, they were tuned to the highest degree. The Lark averaged 132.04 mph. The Hawk, with its sleeker body lines, averaged 140.24 mph. The Avanti, a real slippery customer in the aerodynamics department, averaged 158.14 mph through the flying mile. With everything else equal, it proves how important body shape can be …
I used this quote as my basis though I don't know who arrived at that estimate or by which method. I am curious and would like to know a solid answer, primarily for the Studebaker but then also for the Newman/Altman, Blake, and Kelly/Cafaro generations.It's a fact: The Avanti drag coefficient was estimated in the high 0.30's when most stock American cars were in the 0.50's.Let's compare three vehicles: 1969 Opel GT, 2010 Subaru Impreza WRX, and 1999 Mustang. All achieve a Cd of 0.36 via different sizes, shapes, profiles, and stature.
Regarding my tire choice: I'll accept the drag and rolling resistance hits because I'm in the American minority; I prefer road course racing where higher lateral grip is desired. If I were to build the car for a sustained top speed run I would select narrow tires and cover the exterior of the wheel wells as much as reasonable. In both cases I would fit an air dam spanning the whole front width, tires included. True, an air dam increases frontal area which increases drag. Also true, an air dam reduces air traveling under the car which decreases drag. I had a conversation with a friend who took fluid dynamics courses and he told me air is easier to displace horizontally than it is to displace vertically; the part of the air dam in front of the tires works to displace air horizontally.
-
Aero then is what it is and aero now is a continuously evolving science.
That ties in to my thinking. Apply what has been learned to a car that could benefit from time's lessons. The Avanti has a problem with the rear window getting vacuumed out, and air under any car is bad. These can be rectified using knowledge gained between when the car was first drawn on paper and today.
Avanti, even with its near vertical windshield, is estimated to have a Cd in the high 0.3 range. A number respectable even today. New pony cars like 1999 Mustang (0.36) and 1995 Camaro (0.338) are better though not by as wide a margin as one might expect. That tells me the Avanti's body does a very good job of displacing air since we know the windshield isn't helping matters. Under that closed hood I bet there are turbulent regions at the firewall and under the passenger compartment.
Lowering an Avanti isn't difficult. I would fit an '84 or '85 with 275/40-17 wheels & tires and would lower it on stiffer springs in a coilover setup. I couldn't get it 4th gen. F-body low though it would be lower than stock and that would be an improvement. I would also custom design a hood to reduce the quantity of air in the engine bay, and would glass-in some fender extractors to keep the air that does get in from going under the car.
As with many things, research and development would have to be undertaken to maximize the effectiveness of any change made to a car's body but it's not impossible. What if the culmination of aerodynamic tweaks: lowering the car, an air dam feeding an air extracting hood, fender air extractors, a belly pan, vortex generators, and a rear diffuser, could take Avanti's Cd from [let's use 0.38 for simplicity's sake] to 0.35 Cd or less? That takes the car to first gen. Viper GTS (0.35) and C6 ZO6 (0.34) levels. It would be interesting to see further research into this, even if it is in a CAD program and computer aerodynamic simulations to start.
-
Air can be considered our frienemy. It’s an enemy when we desire to punch through it to travel faster though it’s extremely necessary to have. Luckily for us we can manipulate it; we can coerce it to go places and do the things we want it to do while it puts up a fight. I am curious about some aspects of Avanti’s aerodynamics.
First, pertaining to the rear window being sucked out. What about vortex generators as seen along the rear roofline of some Mitsubishi Lancer Evolution models? They’re not specific to the Lancer and are more often found on aircraft.
Vortex generators redirect the boundary air layer so as to keep it from abruptly separating and causing a turbulent region. In the Lancer’s case they redirect the airflow downward along the rear window. Without them, the air detaches from the roof and tumbles over the car’s rear. They also happen to increase the air velocity over the Lancer’s rear wing, an item Avanti doesn’t have. As a side, the TVR Sagaris has a clear spoiler affixed to its very curvaceous rear. I wonder if Avanti would benefit from a similar design?
Some research and development would need to be undertaken to design and install vortex generators on an Avanti. I have heard their design and how they are mounted angles the air various degrees. In short, the ones designed for Lancer wouldn’t be as effective as on other cars. If an Avanti were to have vortex generators, would the redirected air flowing closer to the rear window help keep a turbulent low pressure zone from sucking it out?
Next, air flow management under the car. Sporty cars rake the radiator, some push the top forward others recline the top. I understand this is primarily to increase the radiator’s surface area relative to air flow, though a side benefit is a lower hood line. Some cars like the Cobra Daytona [coupe] utilize an isolation box and hood design to suck air through the radiator. Then the airflow is directed over the car rather than allowing the air to remain under the hood and causing an eddy at the firewall or continuing to travel beneath the body.
Avanti slopes its radiator forward, I would use that and borrow a page from Cobra Daytona. On an Avanti being prepared for sustained speed, I would: remove the engine driven fan and stock fan shroud, install an electric fan in front of the radiator, redesign a hood that starts to "waterfall" as soon as it clears the front of the engine and accessories, create an isolation box in place of the stock fan shroud and be sure it contacts the hood. The idea is to not let air remain under the car, to force air through the radiator and out over the top of the car.
The new Z/28 and other cars use a rectangular opening with louvers in place whereas some, like ALMS race cars, the new Viper, and the Shelby Series 1 have design elements built into the hood for the same purpose.
Cars built on Studebaker frames have an integrated x-brace and the exhaust pipes route through the cross. This means the exhaust piping does not hang lower than the frame and a belly pan could be fitted, at least from the firewall, back. Ceramic coating and/or insulation wrapping of the exhaust pipes would be recommended to prevent exhaust heat from becoming trapped between the cabin floor and the belly pan. Once a belly pan is fitted another idea would be to add a rear diffuser.
Lastly, air trapped in the engine bay. Some cars use air extractors placed along the front fender. Many examples I’ve seen are low and behind the front wheel well, exemplified on Corvette and front engine Ferraris, while others are up high on the fender such as on Plymouth ‘Cuda and 1970s Firebird. I don’t know exactly where it would make sense to alleviate any trapped air under an Avanti hood, though once some research was done (GoPro camera and yarn affixed under hood), it could be found out.
Most of what I discussed makes sense for a racing Avanti, whether it is one set up for Bonneville top speed or one suited to road course racing like the Mid-Ohio car, and some of the ideas could be implemented on a daily driven Avanti. I would apply these to a blended bumper Blake car, as he was pretty focused on putting Avanti back in racing. Now I just need some money bundled with space and time to make it all happen.
In the below game graphics, generally speaking red lines represent air surrounding the car while blue and green lines represent air passing through various car orifices. Dashed lines represent air that has come through an orifice. In the case of the Mitsubishi pictures, red line / blue line rules don't apply. The red line more accurately portrays how the air would flow without vortex generators.
Mitsubishi related material:
PDF written about Lancer's vortex generators [top of fifth page has good comparison graphics]
Motor Trend vortex generators picture
Mitsubishi Lancer Evolution vortex generators, elevated rear side view
Mitsubishi Lancer Evolution vortex generators side rear view
Air Tab [different than vortex generators though they also manipulate air flow]
TVR Sagaris picture:
Sagaris' rear view
Cobra Daytona coupe pictures:
Front 3/4 view, hood up
Shelby Cobra Daytona Coupe front aerodynamics, forward roof view
Shelby Cobra Daytona Coupe aerodynamics, elevated forward 4/5 view
Examples of hood air extractors:
2014 Z/28 hood extractor shown in action
SRT Viper forward roof view, bonnet/hood closed
SRT Viper forward roof view, bonnet/hood erased [to display where air extractors are "vacuuming" air]
Corvette C5R front aerodynamics, forward roof view
Corvette C5R front aerodynamics, front view
Corvette C6R front aerodynamics, front view
Shelby Series 1 front aerodynamics, front view
Examples of fender air extractors:
Firebird Trans Am side aerodynamics, rearward front side view
Firebird Trans Am side aerodynamics, forward rear side view
Plymouth 'Cuda side aerodynamics, forward rear side view
Plymouth 'Cuda side aerodynamics, rearward front side view
Examples showing both extractors:
Corvette C5R aerodynamics, side 4/5 view
Corvette C6R aerodynamics, elevated side view
Shelby Series 1 aerodynamics, front side view -
I know this particular thread is from 2007 though I also know it's important to keep on topic and post where applicable.
I admire the Mid-Ohio car too so I scoured the Internet for pictures and information. Interesting tidbits I learned: It was considered a 1985 1/2 car, it had a Borg-Warner T-5, 'coilovers', double wishbone A-arms at each corner, a Dana 44 independent rear, and its fenders were flared. Those sound like a fun combination to me. It sounds to me like the race car was considered a 1985 1/2 because Blake wanted to use it to test build changes he was planning for the street cars. Had the paint debacle never occurred, I bet a 1986 Blake Avanti would have been über cool.
While the actual Escort Avanti GT may or may not physically be long-gone, its build is not a giant secret. I would love to duplicate this while keeping it street-able and update with new advancements. The factory 1984 and 1985 Avanti track is 57.4" front and 56.6" rear. The factory 1984 (through 1991) Corvette track is 59.6" front and 60.4" rear, both are differences where flares of 1.2" front and 2" rear [each side] on an Avanti would conceal additional track width. M/T Corvettes from 1985 - 1996 had Dana 44 IRS (all 1984s, and every A/T C4 'Vette had Dana 36 IRS). I'd like to find a way to adapt C4 suspension to a blended bumper Blake car; both the front, and the 5-link rear complete with IRS. Aforementioned fender flares would be required to accommodate.
I'd post pictures directly though some of them are huge and they'd stretch the screen, so here are links to the pictures.
If the Tiny Pic website also loads, click on the picture and it should somewhat 'pop out'. Then click in the lower left corner where it says "View Raw Image."
http://oi42.tinypic.com/wb5fo5.jpg
http://oi41.tinypic.com/2j5yrfb.jpg
http://oi44.tinypic.com/2mchmkp.jpg
NOS Avanti Body Parts for Sale
in 1963-64 Avanti
Posted
Oh, yes! Thank you for posting. I need some body parts for 1025 and I would rather not use SMC fiberglass for originality's sake. E-mail going to Don, promptly.