VW ID3 aerodynamics

[Vekke]

I would say only variation in results came from temperature increase and more road also came off from shadow which increase more tarmac temperatures. If there is little wind that still does not effect the results in my route. Little wind is that leaves start to move in trees, the branches still stay put.

And the effect of windows up vs down in my test was 3,9%

[JulianEdgar]

You make your own decisions, but I would never use data with spread like you are showing here.

Are these all instantaneous readings? (I thought I'd already addressed the deficiencies of that approach...)

I think you'll learn nothing without doing proper averages over decent distances.

[IRONICK]

Originally Posted by Vekke

spats are in that about 60mm in that iX and car has air suspension which I guess will lower the car to reach that 0,25 drag coefficient. That is about the correct heigth for front spats if they are shaped like they are on that car.

Did you design the ID3 aerodynamics?

All off-road BMWs have something like that, it's not just the iX. Many brands has started using them even higher ground clearance.

Although I do not share what JulianEdgar says in general, this time I agree with what he says. You are on the wrong way ...

[JulianEdgar]

Originally Posted by IRONICK

All off-road BMWs have something like that, it's not just the iX. Many brands has started using them even higher ground clearance.

Although I do not share what JulianEdgar says in general, this time I agree with what he says. You are on the wrong way ...

I don't think Vekke is necessarily going the wrong way with the deflectors. I just doubt any change will be measurable on the road without running many kilometres.

[Vekke]

Test method is still same. Average measured from start to A B directions. Results are in same order of magnitude already at the middle of test leg. If you calculate results from 4th measuring point you would get up 17.68kWh vs 18,3 kWh and thats 3,4% difference.

If you calculate results from second point up would be 14,38 vs down14,91-->3,5%

Again if you just measure the end point average consumption you dont see what migth cause the changes in results if there is any. Thats why in formulas you measure speeds all around the course to see more.

Outside temperature have been more stable in the past days from 12-17, but still the tarmac gets hotter and wind conditions change. Just by testing with this short about 5km long route testing took total of 1.5 hours. How do you keep the tests variables constant in longer tests if I am able to see changes when temperatures change 0,5 celsius?. When I end the test I could see wind is already much more than in the start when it was dead still. If you plan to do testing with electric car same setup in this car 3+3 AB test runs max test legth would be around 20 km to one direction which is 350km in range. When you test with longer distances the other cars will ruin some of your results. Here we don`t have 2 lane roads to pass other cars and if they pass you they still ruin your results as cruise control will brake to keep safety distances to obstacles in front.

I really don`t see any benefits to test on longer routes than is necessary to see the differences. At the moment this length seem to work fine. Target of these tests is to see if new aero parts work better or not. If better you keep them if not you take them out. Same principle as with business fail fast and more results you will get. yesterday evening best results compared to 2 month old results in the +5 celsius weather was 10,3%. Temperature raise effect +15 celsius is 2,7% of that.

Wheel angles will be checked and adjusted today afternoon.

Next is coming again some tire testing. I am currently running the oem tires. Will test the same winter tires in 195/55r20 which were better on previous test, but i also have same wheel set coming with summer tires. The cooling holes will be blocked in the best tire setup.

[JulianEdgar]

Originally Posted by Vekke

Test method is still same. Average measured from start to A B directions. Results are in same order of magnitude already at the middle of test leg. If you calculate results from 4th measuring point you would get up 17.68kWh vs 18,3 kWh and thats 3,4% difference.

Ok, you obviously didn't understand my points last time.

The data is valueless - you have (off hand) something like a 16 per cent variation in instantaneous measurements in ostensibly the same configuration - and you're trying to calculate 3 per cent changes.

It's really easy to do crap measurements fast.

What actually is your reasoning for not doing (say) 20km average energy consumptions at 100 km/h, one each way?

[Vekke]

You just dont understand all things, thats fine by me. There is not 16% variation in the results used for the results. Its not flat road so A and B direction results cannot be the same if start point of the other direction is not at the same level. Thats just physics. I did 3 runs to see if the temperature trend is constant for each 0,5 celsius change and its seems to be stable. Only thing making the last measurements double the effect was more tarmac came to sunligth. That is good information for future test I will do so I can take that into account better when interpreting future results.

Windows up vs windows down test does not lower my cars energy consumption at all. I really don`t see any benefits doing that long testing. My results is that 3,9% I havent found any reliable data that proves the result should be 6% like you claim. You havent showed your raw measurement data so why bother. I did not find any other data either that would prove that claim. I publish the hard measurements so someone with more time can play with the numbers more.

For other mods testing if I am able to see the results with shorter driving that is enough for me. If I would have straighter and more level roads close to me I would ofcourse use them. 2 days ago I drove 50km for "flat" 2km long test straigth. did few test runs 80,100,120km/h speeds to both directions. Just one of each speed. 2 of the results were screwed by other cars.

On this place where I test its only 10 km away from home. 1.5 hours of testing time today I saw 3 cars and had 0 faults in the tests. One result, I missed due to one of the cars passing by.

0,1kWh change in the energy consumption is 0,6% difference in consumption. Thats the resolution of my results at the moment. I haven`t released any other results, because some people seem to know better how to make tests and I don`t have time to argue as that does not get me closer to my goals for the project...

For me its enough when all ready mods are fastened I will do a test full to empty and let the results do the talking. Anything else is just meaningless talk. Getting to lower consumption figures is not a matter of belief only the results matter. Better is better.

On the way to wheel aligment 54km avg consumption to A and B direction at 100km/h speed was 15,5 kWh. Then I only had 30mm lowering and 3.5 bar tire pressures on. Temperature was +24 celsius.

[JulianEdgar]

Originally Posted by Vekke

Windows up vs windows down test does not lower my cars energy consumption at all.

Then you have some big problems with your measurement of aero drag changes, don't you?

Katz lists changes in drag windows up/down for a variety of car shapes. In all cases, it's pretty major.

[freebeard]

Katz lists changes in drag windows up/down for a variety of car shapes. In all cases, it's pretty major.

Since you have the referent, what does i say about the Subaru Alcyone SVX?

[JulianEdgar]

Originally Posted by freebeard

Since you have the referent, what does i say about the Subaru Alcyone SVX?

Nothing - it's not mentioned.