1999 Acura EL or Civic EX sedan - dropping Cd from 0.33 to below 0,20

[ACEL]

I have been looking at Tesla model 3 for sometimes and scratching my head about the shape of its nose. Some newer Ford Mustang also rode my street. These cars have something in common! The upper front facia profile!







First pic is borrowed from "Tesla Model 3 aerodynamics!" :

https://www.youtube.com/watch?v=yKWl_4EYaKo

Second picture is borrowed from "Tesla M3 DIY Wind Tunnel Testing - Front End Aerodynamics" :

https://www.youtube.com/watch?v=x1X0x3SGxP4

Tesla Model Y shares the same "filtrum" in front fascia. Also, the most recent Ford models like the Fiesta, Focus, Fusion and even the Escape share that convex pointed nose. See attached pictures for proof.

Hypothesis: Since the Ford models horizontal upper edge is located over the upper front grille, when the grille shutters are closed, the boundary layer thickens and the air flows pretty much the same way as for a solid obstacle (Tesla). With a blocked upper grille, the air may be flowing as with the grille shuttered. Then the only cooling air enters the engine compartment from the lower mouth. Could a massive bumper cover be modified to increase the air flow to the bottom air intake mouth and reduce some drag from the top part of the car?

So, I thought 2 things.

1. Tesla and Ford may be onto something aerodynamically beneficial;

2. If this fascia type is good for some cars, could it bring some good to my car?

Guess what! It is in some way for my old 1999 Acura EL.

Pictures, description and results in my next post!

Cheers!

[ACEL]

From my hypothesis and observation of recent cars, the convex front may be adapted to some older cars.

Why what is good for newer cars could not be used on older cars?

So, here is a mock-up built with plastic quarter round and some tape.





The air pressure was measured in front of the mouth air intake with a digital air pressure meter that is generally used for building ventilation systems.





Simultaneously, the top speed reached at a given throttle stop was monitored and recorded with the Android Torque App through a ELM327 OBD2 Bluetooth adapter.

The mocked-up modification allows for a light increase of 0,1 inch of water in air pressure at the air intake mouth. At the same time, the car speed increased about 1% at 104-105 Km/h and 17,65 % throttle opening. There was no measurable fuel economy realized. Still, there seems to be some improvement worth pursuing the experiment.

A second series of test was conducted with a more elegant "lip" acquired from the commerce.





The results are better. Pressure at the air intake mouth was about the same as with the mock-up. Speed increase at a given throttle opening varied between 2 (104 km/h reached) and 6 Km/h (114 Km/h reached) while fuel consumption reduced by 0,1 L/100 km (during the tests at 5,6 L/100 instead of 5,7 baseline before the mock-up mod).

This modification is beneficial and becomes permanent.

Cheers!

[ACEL]

This 2020 summer is great for aero mods. It seldom rains, climate is warm. Not too much work to do around the house, so lots of time to work on the car.

I picked the idea of a rear diffuser extension from a SAE publication about a movable extension that could increase fuel economy.
See:
Kang, S., Cho, J., Jun, S., Park, H. and Song, K., "A Study of an Active Rear Diffuser Device for Aerodynamics Drag Reduction of Automobiles", SAE International. 2012-01-0173, 2012, doi: 10.4271/2012-01-0173

This work is also cited with details in:
Umut Aktas Christian Abdallah, 2017, Aerodynamics Concept Study
of Electric Vehicles, Drag Reduction and Range Increase, Master thesis, Chalmers University of Technology, Gothenburg, Sweden, 2017

A movable diffuser extension relative to vehicle speed is probably not doable on a production car. Neither, is it practicable on an older car. So, I decided to try a fixed diffuser extension. What the heck, when I have to reach for something in the trunk, my legs never touch or come close to the bumper cover. So, there is room for some appendage at the back of the car that extends from the diffuser and under the bumper cover. Picking some stuff in the trunk, I measured that my knees were at least at 20 centimeters (8 inches) from the bumper cover. Kang et Al, 2012, obtained drag reductions of 5,8 % and 5,9 % at 80 and 100 Km/h respectively. Over than 1 or even 2 % drag reduction by a passive mean is worth an inquiry. The best diffuser extension was the whole rear bumper cover width and having rounded corners.

The extension I fabricated is made of 3/16 in (4 mm) choroplast. To make sure the extension would not bend down and sag, 6 little ¾ in (18 mm) plastic corner moldings 4 in. long (100 mm) were glued perpendicular to the material creases at 8 inches center apart (200 mm). The plastic corners are not angled but about perpendicular to the rear extension line. The extension is 48 in. long and centered on the car width. It also falls nicely between the rear wheels "boat tails" as I did not want the extension to interfere.















For good measure, the extension is painted black as the car is that colour. The extension was then affixed under the bumper cover with self taping screws on two rows where feasible to strengthen against a possible bend. See pics.



The results are presented in the pictured table. The average speed increase measured with the “throttle stop” method is 3 Km/h in the speed range of 105 to 115 Km/h. The fuel economy is almost in average 0,1 L/100 km (0.6 mpg). The drag reduction being proportional to the before-after speed squared is averaging at 5,34 % which is lower than the Kang et al, 2012, results but not by far for speeds that are superior to 100 Km/h (62 mph). For a speed of 120 Km/h (75 mph), Kang et al, 2012, got a 4,5 % drag reduction.



If this diffuser extension resists the wear and tear of weathering by wind and rain and other physical damages, it will remain on the car. Some damage is already done to it by the exhaust pipe hot gases. The extension opening facing the tail pipe will be enlarged hoping that the damage can be limited.

[ACEL]

For 2-3 years the 4 original struts replacement was postponed on the 1999 Acura EL aka Honda Civic EX with more than 237 000 Km life now. The shocks (or dampers) were looking good and doing their job but the coil springs were fatigued. The car was lower at the front, on the driver side. It did not show much. The ride was OK but could have been better.

In the 2020 Spring, cheap coil spring spacers were added to the front left and to both rear springs. The spacers were of the 2 bolts adjustable type reputed for braking the springs. The spacers did not damage the small diameter springs spires but scratched the shocks tubes and caused annoying noises. But for the benefit of evening the front car heights, there was the “rake” improvement gotten from raising the back of the car. Improving the “rake” may also improve the aerodynamics performance.

So from May through August, the car rode with the coil spring spacers and some “funky” noises. The car wheels were balanced and aligned and the ride was OK. The cost of the fix was low. Then, wifey got tired of the noises and demanded a real “professional type” fix. Then, the adventure of struts replacement with new ones on a 21 year old car with many winters under the belts with eastern Canada harsh weather effect on suspension parts and bolts launched.

Youtube and Civic forums helped define the work to do and the various difficulties that were on the road to replacement.

The rear struts replacement was the highest challenge. The Lower Control Arm (LCA) bolts could be seized in the bushings requiring cutting the bolts to start. From there, the bolts, the link kits and LCA would have to be replaced plus the strut and spring assembly. Knowing all that, the LCA rear pair (Mevotech), the link kits (Mevotech) and the strut assemblies (Unity Automotive) were ordered online. The bolts were first looked for online and acquired locally cheaper as a kit of 6 bolts and nuts (Dorman 13508). The bolts are the same “grade 10” as the Honda bolts but the Dorman kit sells for little more than the price of one Honda LCA bolt. The Dorman bolts do not look the same as the Honda but I suppose they can still be trusted.

The work of cleaning the bolts end threads and putting penetrating oil daily started a week ahead of the parts delivery. Still, at first attempt of removal the first bolt head broke off. Then trying to turn the welded nut from the other side yielded no movement from the bolt shaft seized in the bushing and resulted in braking again. The impact driver turning both ways yielded no better results. Then the “sawsall” came as the best solution to limit time and useless suffering. The bolts and bushings were cut between the fork legs. Still some bolts shafts and heads remained “welded” solid and had to be worn down with a sharpening stone on a rotary tool (aka Dremel) to clear the bolts holes. The same operation was required for the link kits. One the bolts were removed and cleared. The rear strut installation was a breeze. The bolts under the car were installed covered of copper antiseize grease and tightened at the specified torque. Then “Rust Check – Coat and Protect” spray mixture was applied to all threads protruding from nuts and on nuts and heads in contact with any steel part.

The front struts replacement went much easier. All bolts were removed starting with penetrating oil 2 days ahead and the impact driver alternating tightening and unscrewing until the bolt gave sign of moving. Again, “Unity Automotive” strut and spring assemblies were used. The only difficulty arising was the “pointer index” needing to be rotated to fit in its place in the strut fork.

The car being more than 237,000 Km, big name struts with big price tag were out of consideration. On Carid.com “Unity” struts received a 4.8/5 satisfaction rating from 217 reviewers. So I thought, I could trust these China made struts. After all, big names struts are, as most now also made in China (i.e. Moog). The price tag has something to do with the longer the name is been in the market and the amount invested in publicity of the brand. Let see how long the “Unity Automotive” last on a car driven about 10,000 Km a year.

As ETCG says "stay dirty"!

[California98Civic]

Stay dirty!