Ford Escort ZX2 Aerodynamics

[freebeard]

Gotcha freebeard!

What purpose do they serve other than directing the air to flow in a longitudinal manner in stead of tumbling?

That's pretty much it, but if you make them from titanium they would throw lots of sparks when you ground them.

[aerohead]

*The 'lowered' ground clearance is a component of the low drag.It affects frontal area,reconfigures the entire belly as a diffuser, alters all the pressure/velocity distributions,cooling system airflow,forward vision/rearward vision,dials in wheel fairing performance,and effective fineness ratio.
*The 'cruise' body inclination of lowest drag would have to be optimized in a wind tunnel or corporate level CFD environment.You couldn't just arbitrarily lower the nose and hope for good results.The body shape is designed only for this particular 'raked' condition.
*You'd lose your SAE Approach/Ramp/Break-over clearances at the nose,tail,and in between the wheels without the active suspension and be tearing off parts of the car every time you drove.
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It's a real issue for us modders.You might study air suspensions that are around and see if anything would lend itself to the Escort suspension.
Tesla and Mercedes-Benz are using active suspension just to get to Cd 0.24-0.22 in a street-able road car.

[freebeard]

Let it grind!

http://www.cardomain.com/makemodel/ford/zx2/page-29/

[BabyDiesel]

Originally Posted by aerohead

*The 'lowered' ground clearance is a component of the low drag.It affects frontal area,reconfigures the entire belly as a diffuser, alters all the pressure/velocity distributions,cooling system airflow,forward vision/rearward vision,dials in wheel fairing performance,and effective fineness ratio.
*The 'cruise' body inclination of lowest drag would have to be optimized in a wind tunnel or corporate level CFD environment.You couldn't just arbitrarily lower the nose and hope for good results.The body shape is designed only for this particular 'raked' condition.
*You'd lose your SAE Approach/Ramp/Break-over clearances at the nose,tail,and in between the wheels without the active suspension and be tearing off parts of the car every time you drove.
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It's a real issue for us modders.You might study air suspensions that are around and see if anything would lend itself to the Escort suspension.
Tesla and Mercedes-Benz are using active suspension just to get to Cd 0.24-0.22 in a street-able road car.

I have seen the effects of lowering on Cd with the Bonnevile Fusion. IIRC, the drag coefficient dropped 0.08, which is huge. That same thread was the one with the decreasing finesse ration of the Porsche.

It appears that an air suspension will cost anywhere from $1000-$2000
ZX2 Air Suspension Kits to customize your Ford

I understand what you mean about trying to imitate the Probe IV rake. It seemed to me that if I could do the math and science with suspension and geometry, sans wind tunnel, that I may be able to get close to optimal.

The last thing I want to do is to tear off any mods! Especially front and rear tire boattails!

I'm just not understanding fully, aerohead sir. If basjoos can achieve a Cd of 0.17 with all his work, what is stopping me from getting my Cd down two lousy hundredths more on a tight budget that desires a moderate ROI, like him?

[BabyDiesel]

Originally Posted by freebeard

Let it grind!

http://www.cardomain.com/makemodel/ford/zx2/page-29/

Originally Posted by freebeard

That's pretty much it, but if you make them from titanium they would throw lots of sparks when you ground them.

You're going to get me in trouble with these ideas, Mr. Wandering Facial Hair

[aerohead]

Originally Posted by BabyDiesel

I have seen the effects of lowering on Cd with the Bonnevile Fusion. IIRC, the drag coefficient dropped 0.08, which is huge. That same thread was the one with the decreasing finesse ration of the Porsche.

It appears that an air suspension will cost anywhere from $1000-$2000
ZX2 Air Suspension Kits to customize your Ford

I understand what you mean about trying to imitate the Probe IV rake. It seemed to me that if I could do the math and science with suspension and geometry, sans wind tunnel, that I may be able to get close to optimal.

The last thing I want to do is to tear off any mods! Especially front and rear tire boattails!

I'm just not understanding fully, aerohead sir. If basjoos can achieve a Cd of 0.17 with all his work, what is stopping me from getting my Cd down two lousy hundredths more on a tight budget that desires a moderate ROI, like him?

*AEROCIVIC might get in trouble in many states due to the mirror delete.If so,with the restoration of the driver's mirror,the Cd might be 0.177.(fabulous still!).
*To get to Cd 0.15,or below,Hucho is going to tell you to do more elongation and perhaps do an active diffuser which can be lowered on the highway.
*An inflated tail would be one approach,as it's only deployed for the highway.
Here's a pictorial thought experiment with one

*If you'll do everything to the Escort as AEROCIVIC,and then push a little harder,then you've got a shot at it.
*'Fix' your suspension at some attitude,then design the bodywork close to the template at that inclination.Mockups of body parts can be tuft-tested as you go to check for separation.When they show 'clean' flow,you can commit to that part knowing it will perform.

[BabyDiesel]

The fact that you used "two lousy hundredths" as the title cracked me up

Originally Posted by aerohead

*AEROCIVIC might get in trouble in many states due to the mirror delete.If so,with the restoration of the driver's mirror,the Cd might be 0.177.(fabulous still!).

ECOSCORT might get in trouble as well, since I have no side mirrors I am legal as far as the state of NC is concerned. And wow, I did not realize how much side mirrors affected the Cd!

*To get to Cd 0.15,or below,Hucho is going to tell you to do more elongation and perhaps do an active diffuser which can be lowered on the highway.
*An inflated tail would be one approach,as it's only deployed for the highway.
Here's a pictorial thought experiment with one

I recall that if the template was followed exactly on my car, the total length would reach between 20-21 feet! That is longer than an extended cab long bed Chevrolet Silverado, but it is still shorter than this -



How is that for elongation??

An active diffuser, hmm... what is wrong with a set height diffuser that is low enough for good aero,flexible enough to withstand city driving and rigid enough to survive 60 mph?

The inflatable boattail is a wonderful thought! I am unsure how to implement it in the real world. I'll think on it and weigh between it and the rigid tail.

*If you'll do everything to the Escort as AEROCIVIC,and then push a little harder,then you've got a shot at it.
*'Fix' your suspension at some attitude,then design the bodywork close to the template at that inclination.Mockups of body parts can be tuft-tested as you go to check for separation.When they show 'clean' flow,you can commit to that part knowing it will perform.

That is what I love to hear

I am planning on a 2" suspension drop front and rear, keeping the car as level as possible. I MAY try to drop it a little less in the rear so my belly pan acts as a diffuser. It will work out the geometry when that time is closer.

I actually have access to a smoke machine at my church so I am tempted to borrow it and do a mock-up wind tunnel test! This will have to be on a super calm day, or even indoors. First thing I will have to do is see if the fog can even get thick enough to see and if I can get a fan to generate 50+ mph winds. I could make scale models and test them out easier.

Right know, I am trying to figure out how to attach tire boat tails to my car along with outer and inner side skirts, and it is more difficult than it first appeared. Then I want to redesign the rear fender skirts along with designing the front fender skirts!

...Gotta take it one day at a time...

[freebeard]

The fan would need to have about as much power as your car's motor. Like a propeller airplane. And you would need a duct. Like a coin-op car wash bay.

With scale models you could use a water tunnel/channel. See http://ecomodder.com/forum/showthrea...ies-31047.html

[aerohead]

Originally Posted by BabyDiesel

The fact that you used "two lousy hundredths" as the title cracked me up



ECOSCORT might get in trouble as well, since I have no side mirrors I am legal as far as the state of NC is concerned. And wow, I did not realize how much side mirrors affected the Cd!



I recall that if the template was followed exactly on my car, the total length would reach between 20-21 feet! That is longer than an extended cab long bed Chevrolet Silverado, but it is still shorter than this -



How is that for elongation??

An active diffuser, hmm... what is wrong with a set height diffuser that is low enough for good aero,flexible enough to withstand city driving and rigid enough to survive 60 mph?

The inflatable boattail is a wonderful thought! I am unsure how to implement it in the real world. I'll think on it and weigh between it and the rigid tail.



That is what I love to hear

I am planning on a 2" suspension drop front and rear, keeping the car as level as possible. I MAY try to drop it a little less in the rear so my belly pan acts as a diffuser. It will work out the geometry when that time is closer.

I actually have access to a smoke machine at my church so I am tempted to borrow it and do a mock-up wind tunnel test! This will have to be on a super calm day, or even indoors. First thing I will have to do is see if the fog can even get thick enough to see and if I can get a fan to generate 50+ mph winds. I could make scale models and test them out easier.

Right know, I am trying to figure out how to attach tire boat tails to my car along with outer and inner side skirts, and it is more difficult than it first appeared. Then I want to redesign the rear fender skirts along with designing the front fender skirts!

...Gotta take it one day at a time...

*It's great that you can do the inside mirrors.
*Hucho and others will have you figure on a final length equal to about 4X body height to get a slick fineness ratio.Here you can see Jaray's length to get Cd 0.13.

*The 'active' tail provides a 'practical' length for parking and driveway ramps.
*The active diffuser allows the 2.5-degree angle of lowest drag,which will get knocked off if you drive it around town.
*My 1st inflatable was a bean bag chair envelope stapled to a wooden box and 12-V inflation fan.A later,Naughahyde envelope saw road duty

*If you do models,you've got to watch your dynamic similarity,verisimilitude.In full-scale you need at least 20-mph for critical Reynolds number.
*At 1/2-scale you need 40-mph
* 1/4-scale 80-mph
*so on.
*It's actually easier and cheaper to do full-scale.
*The template works as far as drag reduction,although we can't control how your engine's BSFC will react.MetroMPG proved this to us in his latest CIVIC testing.
*For the wheel boat tails your minimum contour would be the center form in the table below,but actually the better the longer as the SAE Ecomarathonners and solar teams have found.

*As to the boat tails themselves,if you had access to a sewing machine;the fairings can be foam rubber cut with an electric carving knife,inside a leatherette envelope (made exactly like a seat cover),attached to an aluminum plate,which has Velcro taped on.The units are Velcro'd onto the belly.Very light.Relatively fast build.Low tech.
*For the wheel skirts,have you been to the AEROCIVIC thread where Mike illustrates how he did his.It's kinda how I did mine on the T-100,although my rollers are inferior to Basjoos' setup.

[BabyDiesel]

I read the entire Aerocivic thread yesterday I saw how he did his front fender skirts. I was unable to track down conveyor belt rollers, so I will build ones with a slight bulge outward. I hate to do this due to increasing frontal area. I am going to try and shape the bulge in the likeness of the Aerodynamic Template.

The stock height for a Escort ZX2 is 52.3 inches, from Wikipedia. For easier math, I am going to assume that I have a 2" drop along with 1" smaller tires(0.5" drop from stock), giving me a ride height of ~50". So I need to shoot for 200" or 16' 8". The car is already 175.2" long (14' 7"). According to Hucho, I need to add only 25" of boattail! The full length boattail puts me closer to 5X.

I think I am going to shoot for a 4-7* diffuser angle. This is enough angle to keep a majority of the flow attached to the bottom, yet allow me to go to Wal-Mart without fear This will also reduce the length of my boattail to ~18'. Much better than 21'!

With only 20-mph wind speed needed, the full scale smoke testing seems to be my best and easiest bet. I will have to figure out a way to "inject" the smoke into the air stream. When we use it at church, it is sucked through the fan and it disperse rather quickly.

I have many answers to the BSFC problem With drag reduction, I am going to be in the same boat as Darin was with the Civic. Here is the BSFC graph for my 2.0 ZETEC -



BSFC is around 270 at cruise now (50% load at ~2000 rpm). Decreasing drag will only make that number go towards 295 from decreasing the load. No no, it is going up!

I have a plan through deleting an intake valve through a custom intake cam to create a VTEC-e effect (1I, 2E creates high swirl, improves torque, possibly higher load through more throttle angle), retarding the intake cam to reduce pumping losses and have a more open throttle, and I will be utilizing lean burn to increase the load even farther. I really want to tune for variable leanness on the fly, so the engine will behave more like a diesel. I plan to add turbo with small boost (3 psi. max) to go even leaner. I know that this work will change the BSFC graph, but it should get me closer to ideal

I'm soon going to work on aero mods and should get some work done today! I will update the thread with pictures and commentary as work is completed!

Thank all of y'all for your support, direction and wisdom. It means a lot to this aerodynamic greenhorn