Ford Escort ZX2 Aerodynamics

[JohnAh]

Oops, I just realised that I've kept making the same conversion error from L100 to mpg for a long time. The converter I've used was set to imperial gallon, not to US.

My driving last month gives an mpg average of about 50 US mpg, not 60, but that's still 4,6 litres per 100 kilometers and quite impressive for a 40 year old piece of junk.

[BabyDiesel]

50 mpg in your car is doing awesome I get right around 60 mpg on the instant readout doing a 45-55-45 Pulse/Burn & Glide. I do have an automatic transmission, so I do not do EOC unless I am heading towards a planned stop and it is relatively safe to do so. I try to limit my P&G now after finding out that the ZX2's torque converter has paper in it, which equals weak!

Brakes are evil, this I know, this eco crowd, they tell me so... I have learned this very quickly and use it as much as possible when I am out driving. Conserving momentum is crucial to good mpg.

Thank you for the helpful tips, JohnAh

[BabyDiesel]

Freebeard - The air dam got an unexpected test recently. I pulled into a parking space at Starbucks and went to far up. Got out and looked, the entire dam was buckled backwards. I jumped backed in and coasted in N, EOC of course when I looked again, it was back to its original shape. The bars were bent slightly, but they bent back with no trouble.

[BabyDiesel]

It has been almost a month since I updated this thread! Wow, does time fly by.

My focus has shifted away from aerodynamics the past month or so. Not that I wanted to, but it was a necessity. It became apparent to me that I was hitting a "road block" when it came to lowering my Cd. My engine's load was dropping out of it's efficient area, so any more work could have been counter-productive!

However, I will be installing lean burn on the Ecoscort soon This will increase the load on my motor so it can run in a more efficient BSFC zone. I should go from 45-50% load to 55-60% load in a steady state cruise setting.

Having LB will mean that more radical aero mods will have a greater positive effect, and I will be able to better utilize the effects by not losing engine efficiency. So I am open to suggestion as to what I should attempt first. I have not added anything to the car beyond what is written in my threads BTW.

I am thinking:

- Rear diffuser at appropriate angle

- Mid section belly pan

- Tire splats and boattails

- Kammback

- Boattail

[aerohead]

This is awkward for DIY's.
An automaker knows the road load and BSFC for their vehicle.If they plan to modify it,they can predict it's performance numerically.
If you had intentions to fully trick out the Focus aerodynamically at some point,there would be a practical issue of going ahead with all that,and then modify your gearing to control the BSFC.Altering the engine isn't necessarily required.Just gear-matching. So says the automakers.

[BabyDiesel]

Originally Posted by aerohead

This is awkward for DIY's.
An automaker knows the road load and BSFC for their vehicle.If they plan to modify it,they can predict it's performance numerically.
If you had intentions to fully trick out the Focus aerodynamically at some point,there would be a practical issue of going ahead with all that,and then modify your gearing to control the BSFC.Altering the engine isn't necessarily required.Just gear-matching. So says the automakers.

The automakers gave my car the highest gearing possible from the factory, which is why I have not mentioned it Mr. Phil. Thanks for that one, Ford

Now, the sedan manual transmission I plan to swap in has very similar gearing to my auto. It will make the engine turn 75-125 rpm more at my usual speeds. What the manual does offer is the option for a custom 5th gear with an ultra-deep OD.

Here is the link to someone who did it several years ago.

I think what I was trying to say in my previous post is I have too much engine/power. Also, the powerband is too high for the best performance down on the low-end. So I have to either reduce displacement or reduce the power of the engine through shifting the powerband downward. Hence why to go with LB to make the engine more efficient below 2500 rpm, and to simulate having a less powerful engine.

I also am planning to go from 16 valve (2I, 2E) to 12 valve (1I, 2E) which in theory will reduce the total amount of power the enine can make, increased swirl in the combustion chamber and have better low-end performance. The idea is comes from the VTEC-E engine in the VXs.

Btw, the plan is still to max out the aero Mr. Phil. I'm trying to get to 0.15 Cd, remember?

[aerohead]

Originally Posted by BabyDiesel

The automakers gave my car the highest gearing possible from the factory, which is why I have not mentioned it Mr. Phil. Thanks for that one, Ford

Now, the sedan manual transmission I plan to swap in has very similar gearing to my auto. It will make the engine turn 75-125 rpm more at my usual speeds. What the manual does offer is the option for a custom 5th gear with an ultra-deep OD.

Here is the link to someone who did it several years ago.

I think what I was trying to say in my previous post is I have too much engine/power. Also, the powerband is too high for the best performance down on the low-end. So I have to either reduce displacement or reduce the power of the engine through shifting the powerband downward. Hence why to go with LB to make the engine more efficient below 2500 rpm, and to simulate having a less powerful engine.

I also am planning to go from 16 valve (2I, 2E) to 12 valve (1I, 2E) which in theory will reduce the total amount of power the enine can make, increased swirl in the combustion chamber and have better low-end performance. The idea is comes from the VTEC-E engine in the VXs.

Btw, the plan is still to max out the aero Mr. Phil. I'm trying to get to 0.15 Cd, remember?

Of course,you're the boss of this project.However,it is my opinion that you shouldn't introduce simultaneous variables.
Chrysler Corp. and GM Research Labs have been down this road and their recommendation is to do all the load reduction FIRST,then alter the powerplant/powertrain from there.
You're working with unknown quantities,and unless you can dyno your car,you're just throwing stuff at the wall hoping something will stick.
I'm just playing the Devil's advocate here.
And from a safety point of view,I would recommend that you maintain whatever horsepower bias you already have.That power reserve could save your life one day.

[BabyDiesel]

Originally Posted by aerohead

I picked up where NASA left off with their 'Shoebox' van streamlining and took it to completion.
Starting from their fully-boat-tailed Cd 0.238 van I:
*added body side camber (Buchheim,Deutenbach,and L'u'ckoff)
*added upper edge radii (Hucho)
*added roof camber (Buchheim,Leie,and L'u'ckoff)
*added wheel skirts (Heltemes,Tremulis,Cogotti,Garrone,and Masoero)
*added MOON-esque wheel covers (Shinella,Tsukada,Sakagami,Arai,and Takahara)
*and full wheel fairings (Tamai),allowing 50% of Tamai's factor allowing for wider tires (SWAG).


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We'd have to add back in some features drag associated with a working cooling system,wipers,and mirrors,but that's not a lot of fruit to put back on the tree considering the GM Precept concept car.
PS these are just estimates but should fall close to the tree.

Aerohead, your work on NASA's Shoebox has given me a wealth of ideas! It is impressive how adding the side body camber and adding radii the to the upper edge was worth a Cd value of 0.6 That is as much as all of my mods combined, minus the air dam

Could these be replicated on my Escort? I know that the side body camber will be next to impossible. What about the others?

[freebeard]

Your problem would be the roof. Adding that much upper body radius would affect the windshield and door tops. Compare with the bubble-top coupes, like the Mercedes 300SL or 1964 1/2 Mustang.

Not much opportunity for camber in the mid-body, unless you add a boattail.

Underneath could be most similar; the bellypan, wheel spats, engine cooling, etc.

[aerohead]

*From a practical standpoint,I think you're looking at using whatever plan taper Ford put in the Escort and blend from there.
*As to the upper radii,you could do as Jaray did in 1922.Take your more rectangular cross-section,and gently morph it into a more organic half-body cross-section as the body proceeds rearward.HVAC sheetmetal shops do this all the time in commercial/industrial ductwork when the dust must enter a chase or wall for part of the run.You can't do it with plumbing due to the pressure balooning the flat walls,but with air,it's a snap!
*The tumblehome can progressively increase as Honda does with their FIT,and the edge radii can also grow incrementally as she goes further rearwards.I worked this into the flying buttresses on the CRX to pretty good effect.