groar's 1997 Megane Modding Thread

[groar]

Originally Posted by Piwoslaw

Hi Groar, good to see you back

Thanks

Is the trunk cover a new piece of coroplast or is the uglyback reincarnated?

Another piece of coroplast, but as the one used for the uglyback it's a used one which has defaults, this one has a folding. I rapidly added two inner pieces of expanded polystyrene to prevent the cover to become concave.

Was there a noticible difference in coasting/handling right after removing the uglyback?

From my butt-o-meter the uglyback was effective, but rear view was so reduced that I considered that it lowered my safety. The fact the coast down test was a failure was only caused by the fact the road I used (another one from the one used to test the rear wheel skirts) was too short, not flat enough and too busy.

Did the wheelskirts stay on all winter?

Yes, and they will stay a long time... I think, or at least my butt-o-meter, that they are currently the most effective mod on my car.

Denis.

[groar]

As the uglyback was sacrificed and there is a lot of place between the C pillar and the trunk cover, I used a free quarter of hour this evening... I got a small piece of coroplast and taped it at the end of the roof (c-pillar), with a smaller piece put vertically to give the primary one a "good" angle.

Here are three pictures :




I'll have to work on the visibility but I think it will be better than with the ugglyback, I won't hesitate to shorten the miniback if I can't improve visibility enough only by working on the vertical piece.

Hope this will improve the aero. As tomorrow is a day off, I'll be able to test it only Monday morning when I'll go to work...

Denis.

[Piwoslaw]

On the second picture (whole car) I can see some black lines on the windows. Are those tufts for tuft testing your airflow?

[groar]

Originally Posted by Piwoslaw

On the second picture (whole car) I can see some black lines on the windows. Are those tufts for tuft testing your airflow?

Great observation, that's it. Now they are used to entertain my son

My TODO contains a few films including one about these tufts.

I have been very surprised to see by how much the tuft is going up on passenger window, the angle is up to 45°.
I have some on the rear windshield and the more surprising is the lower center which is turning around like a clock needle... which I interpret as a detachment of the air flow. This is certainly due to the fact the upper part of the rear windshield is around 20° with horizon, while the lower part is around 30°.

From that same picture I tried to measure the angle between horizon and the lines from the C-pillar. The following data are the measures plus 0.68° which is the angle between the horizon and the picture (measured between the lower part of the circle which is drawn on the hubcaps).

• rear of the miniback : 11.99°
• front of the cover : 17.78°
• rear of the cover : 12.27°
• rear of trunk extension : 16.68°
• rear of the trunk : 19.43°

And the trunk cover has itself an angle of 7.26°

The fact these measures to the rear of the miniback and the cover being both closed to 12° give me hope to feel a real improvement

Denis.

[groar]

Got a quarter of hour today... so here is the front wheel deflector :

• From the front :

Picture taken with both right wheels aligned.

• From the side :

You can compare both pictures with the ones of the uglyteeth a few posts backward. You can see that more wheel is hidden and a safe ground clearance has been used : 5.3in instead of 2.4in for the teeth. Also the front side of the deflector has been cut to push forward the lower part of the grill block and the uglyteeth.

"Sadly" I built only one deflector and decided to focus on another quarter of hour project...

Denis.

[groar]

so here is the mini tail :

• From the side :

I couldn't bend the chloroplast, so I cut two lines to permit it to fold and permit me to tape it correctly.

• From the front :

It certainly add some frontal area, but should permit a better and longer air flow...

• From the rear :

Isn't this one funny ?

Denis.

[groar]

Originally Posted by groar

so here is the mini tail [...]

Built the left one today, as well as the left front wheel deflector. Here is megane from the rear :


And tried some CoastDownTesting from 110 to 80 km/h (68 to 50 mph). As I didn't found the perfect flat straight road, I used one near home. The 1st run was with the minitail, while the 2nd was without it.
I traveled around 20 km (12 mi) before to heat the drive train a minimum. Even if this distance isn't enough (iirc 30 km (20 mi) is better), I hoped the improvement between 1st and 2nd run from the better heated drive train wouldn't erase the un-improvement of disappearing minitail.

I got my notebook and an USB GPS to record the coordinates.

As every time I get the car with new mods, I feel it more powerful, but weather has been much more hot during last days compared to last weeks. On several parts of the heating travel I found the car coasting longer. At two FAS I have been able to wait longer before bump start and on both cases I passed the usual bump start line with 2 more km/h (1-1.5 mph).

I don't have yet look at the results because it takes time to calculate the different times... I can say that :

• the east-ward coasting have been much more disturbed than west-ward ones and I don't know if I will have conclusive east-ward data.
• during all west-ward coasting with the minitail I passed the 80km/h after I got into the exit, while without the minitail I passed this speed before the exit line. IIRC the length difference was around 2-3 seconds (55 m = 180 feet).

Hope I'll be able to sort data soon and they will be consistent to show how much improvement the minitail permits.

Denis.

During the heating travel and the test I got even more abnormal behavior from cars passing me... I do have to free time to paint all the addons that are visible from rear.

[groar]

Originally Posted by groar

And tried some CoastDownTesting from 110 to 80 km/h (68 to 50 mph). As I didn't found the perfect flat straight road, I used one near home. The 1st run was with the minitail, while the 2nd was without it.
[...]
Hope I'll be able to sort data soon and they will be consistent to show how much improvement the minitail permits.

The analysis confirmed that the east-ward data were not consistent enough
Here are the results for the west-ward data :

With MiniTail : avg = 31.35 , stdev = 0.75
Without MiniTail : avg = 30.79 , stdev = 0.51

I'm not very satisfied as it seams that the lower traffic was too much disturbing... and the average difference (31.35-30.79 = 0.56) is between the greatest and the smallest stdev

A simple calculation gives a small 1.8% (31.35/30.79-1) average improvement in power needed from 110 to 80 km/h (68 to 50 mph).
A dump calculation would translate this to a 1.2 mpg if it could be applied asis to my best tank (69 mpg)... but my average speed is certainly under 70 km/h (44 mph).

Denis.

[Piwoslaw]

Good job
I was expecting slightly better results, but as you said, the interfering traffic probably messed things up. Hopefully you'll get another chance.

[groar]

Originally Posted by Piwoslaw

I was expecting slightly better results, but as you said, the interfering traffic probably messed things up. Hopefully you'll get another chance.

They are called minitail as they are far from being as long as a boat tail should be, so they can only have a small efficiency if they have some. They are also behind the rear wheel skirts which are effective.

On both configurations I had from front to rear : the uglyteethes, the front wheel deflectors, the rear wheel skirts, the roof extension and the trunk cover; the first three being in front of them. With all these improvements (at least I hope that none have a negative effect) it must be harder to prove the efficiency of another improvement.

I may try to do some coast down testing where I did my first one to compare the results obtained with the stock car and only with grill block and rear wheel skirts, with the current "package". Of course I don't remember tires pressure, atmospheric pressure, temperature and wind... but it could permit a rough comparison with my stock car.
As I severely "killed" my current tank with this test (I estimate I lost 50 km = 31 mi) and as I have the feeling that I can beat my longest tank with this tank I want to keep my chances to do so.

Denis.