VW ID3 aerodynamics

[Vekke]

Cannot test windows down.Its so cold it will start to heat the cabin and it will ruin results. Should have +20 celsius outside temp and it would give accurate results. Lowest temp request goes is 16 celsius.

Cool report on the wheels and grill shudder. There was measurable difference with grill block in place...

Did more pressure testing. Test was correct yesterday(it was sunny today cloudy so tarmac colder today which is seen in results). Testing method is still accurate and valid the optimum pressure is between 2,4-2,6 bar. In the end did two runs with 2,3 bar and results were 0,24% difference to each other ( in the end of measurements there started to be more wind (tuulta) In EV you hear it clearly. Consumption starts to go higher after under 2,4 bar and over 2,6 bar.

There is noticeable difference in grip with low 2,4 bar pressures the slip ligth is not coming on in dry tarmac but with 3,5 bar is on up to 100km/h speeds.

[JulianEdgar]

Interesting.

But I really don't think any on-road measurement is going to be remotely accurate to a resolution of 0.24%.

[Vekke]

I would agree on petrol or diesel cars, but this ev keeps the speed much steadier and on downhills it recharges battery so energy is not "lost". I had to build the constant iq method for the diesel to get good steady results on the same route. Cruise control varied the speed too much on this hilly route. With this car the results are leveled to each other after car is warm, which takes about 20km with the grill block in place.

How many times same results would prove test method to be accurate?

[JulianEdgar]

Originally Posted by Vekke

How many times same results would prove test method to be accurate?

If you are quoting changes to 0.01 per cent (as you have), then I'd expect the repeatability of the car in one condition to be far better than 0.01 per cent.

But I would suggest that no car on any road route will be remotely near that.

[Isaac Zachary]

Originally Posted by Vekke

I would agree on petrol or diesel cars, but this ev keeps the speed much steadier and on downhills it recharges battery so energy is not "lost".

That depends on a lot of factors, mainly the driver.

Diesels and gassers are more efficient near full load. I find I get better fuel mileage going over certain hilly areas than non-hilly areas (unless I pulse and glide on purpose). The trick is to slow down towards the top and coast down the other side. As long as the hill isn't too steep or too long you don't have to brake. I had one friend that lived some 15 miles out of town with some hills that were just perfect for this kind of driving. It was easy to get +50mpg in the full sized Avalon on that road to her house.

On the other hand you can do that with an electric, but there's no advantage. Actually running closer to full load is probably less efficient as far as the battery is concerned. Of course at least you get the regen if it is too long and steep. This is why I'd love to increase the HV battery size on the Avalon and Prius for those mountain passes we have here in Colorado.

[Vekke]

Here are the pictures of mods:
This much blocking works at least in +7 celsius if you are charging with one phase 16A. If you use fast chargers or outside temp is higher you need to verify how much grill can be open. Propably the upper block need to be removed. There is active grill block in this ID3 but still that mechanical block gives you 1,3% better energy consumption

Bigger Front tire deflectors 0,5%
In this picture wheels the ones from Audi A8 project. Those 195 are wider and the flap covers that. Shape is not yet final should make more versions to find even better shape. This shape gives you 0,5% better energy consumption

Shape is still rough as its not final. Its made from 2mm polycarbonate

Fixing is under the 3 fender bolts. In tests I only use the 2 bolts as its faster to change it on and off.

Front suspension arms are covered with 3mm thick abs plastic. Rear part of the cover need to be bend downwards to create smooth passing towards rear. Rear edge is also bend tight towards ground. This gives you 0,6% better energy consumption


Rear a arms were hugely open in my mind. They wer easy to cover with 3mm abs sheet. In this the rear edge need to be bent up starting from tire centerline again making nice passing towards rear. At the moment the arm is too high and the lowering will fix that a lot and give much better overall results. Still at the moment this gives you 1,3% better energy consumption



All parts are fixed with cable ties and no holes is needed to be drilled. This in not ready and small improvements will come after car is lowered. At the moment Ground clearance is 165mm(factory setup is 150mm but the 4% taller tires make in sit higher)

[Vekke]

Ordered H&R 40/30mm lowering springs estimation is that the drag coefficient will drop 0,01 to 0,014. That would mean car is already at 0,23 to 0,226 range. If Cd drops 0,014 units it would mean 3,2% better energy consumption. Total improvements would be close to 10% compared to stock car. In range that means you will get 42km more range in this version. I think 15% better consumption is possibly even without kammback extension.

[JulianEdgar]

It's nice that you are modifying a modern electric car, but the accuracy of your data seems very open to question.

If I understand correctly, you are using road testing to purportedly measure the outcome of changes to a resolution of 0.1%.

I just can't see how that is possible, when I would think that there will be a greater variation than this is in back-to-back testing, with the car unchanged.

Surely the starting point would be to do, say, 10 runs with the car identically configured and show us the scatter in the measurements?

(And before people say that I rely on road testing to assess aero changes - yes I do, but to an accuracy of about 2 per cent...so a factor of 20 times lower resolution.)

[freebeard]

First aerohead and now Vekke? You've made your point.

Just round down until your happy.

[Isaac Zachary]

If someone is happy with their measuring... Good!
Usually whatever you don't won't make someone else happy anyway, si as long as you're happy.

I do agree with @JulianEdgar though. Fine measurements are hard to do with just test driving. Even barometric pressure can have an effect on the results.