Our Assessment of the "Active Shutter System"

[freebeard]

I'm thinking of adding a forward splitter to offset this nose up.

Else add overload springs to raise the rear a little?

low profile shark fins...

Air Tabs?

The claim of top speed going from 80 to 110 is likely to rile up one of our curmudgeons. https://en.wikipedia.org/wiki/Drag_equation. there is an inverse square involved. 80->110 would require 1.89X the horsepower. Did that come from removing the slats? Prepare yourself for some incoming...

[LostinTransit]

@freebeard thanks for the suggestions and I've been looking into the airtabs or diffusers. The airtabs are a bit unattractive but we may opt for the smaller roof top diffusers.

As for the speed issues, Yes for 3 years the van struggles to go 80MPH through a 75MPGH zone. But after remove 10 of the 14 slats and for the first time, the van reached a top speed of 110MPH. Nothing's change and driving on a flat straightway.

1 weeks has now passed and the van MPG's is holding steady at 24.0

[redpoint5]

From an aerodynamic standpoint (the most important one for fuel efficiency), you're going to want whatever angle was original to the vehicle. Adjusting height on one end without doing the same adjustment to the other is going to deviate from the engineered aerodynamic profile.

[LostinTransit]

Speaking of airtabs.. yesterday we stopped at RedRobins for a salad and the Ford raptor pulled up with the airtabs on the rear cap. I asked the fellow if he's notice any difference in fuel economy. he told me that there's no fuel difference, but he did notice that the these airtabs helps reduce cross winds as he said this truck seem to be more stable. I may place at least one airtab in the front fender as out hood has bene flutters. Would this device reduce the hood flutter which is very similar to the pocket on the newer Jeep wranglers? Not convinced we'll try these on the van, but data shows these are more effective between 50-70 MPH. If we do decide to use these, I'll get the shop to 3D print a few of these for us.

[aerohead]

The model year 2024, Transit 'Connect' BEV van in on sale in Europe today.
It's a complete redesign. AUTOCAR and other websites are reporting:
* 15mm lower.
* A 13% lower drag coefficient, @ Cd 0.319.
* It's height is under 2-meters.
* Above 30-mpg equivalency.
* 200mm added length.
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1) If we accept the published Cd 0.319, and a delta- 13% drag, then the outgoing model must have had Cd 0.3666.
2) If the OEM top speed was 80-mph, a 13% drag reduction ( according to Dr. Wolf-Heinrich Hucho's math, would be good for 83.46-mph top speed.
3) By the same metrics, achieving a top speed of 110-mph, from 80-mph would require Cd 0.2153.
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A) Just for ----- & giggles, if we allowed a cooling system drag delete of Cd 0.025, that would get us to Cd 0.3416.
B) If the 2024 Connect's front air curtains were a 'new' modification, we might allow a delta-Cd 0.010 ( BMW ), which could get us to Cd 0.3316.
C) And then the difference of delta-Cd 0.0226, for a complete flat underbody of an electric van might explain the remaining drag discrepancy, down to the reported Cd 0.319 ( which would not be unreasonable, as a diffuser by itself can deliver a delta-Cd 0.020 ).
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The arbitrary change of the Transit's front and rear height is problematic as far as attributing differences in performance. Historically, even, what would seem to be very small changes to a vehicles 'inclination', can result in dramatic changes to drag.
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Removing 10 out of 14 slats from a radiator shutter system is not sufficient to explain the top speed difference experienced. It's scientifically impossible.
We need to look elsewhere for the actual attribution.

[aerohead]

I'd pop the hood open, and look to see that the adhesive bonding between the pressed-steel superstructure underneath the hood hasn't separated from it's metal outer skin. ( I have this condition on my truck )
The engineers try to create a small high-pressure separation bubble at the cowl area, in order to provide passive airflow into the cabin ventilation/ heating/ air conditioning system ductwork.
If the skin is properly 'glued down' you'll never know the turbulent bubble is out there.

[redpoint5]

This doesn't belong in aerodynamics, but the unicorn corral.

We're to believe that active shutters are not just a little inefficient, but very inefficient based on 1 uncontrolled observation. Manufacturers are wasting tons of money installing these to get worse efficiency. This is absurdity upon absurdity.

[LostinTransit]

[3D Printed] Testing "AirTabs" for Better Fuel Economy, Reducing Hood Flutter & Reducing Cross Winds?

Although I'm not hip to the idea of running a line of these across the roof or down the sides of the rear of the van, I am willing to test at least 2 of these airtabs while mounted in front of the driver's and passenger doors. The van's hood has developed a flutter in the middle of the hood back towards the windshield. I'm hoping these two small low profile airtabs will help solve this hood flutter issues. We've contacted our shop to see if they can print at least 2 of these airtabs for us. If successful, we may opt to print more.

[freebeard]

Compare the cost of two one-off pieces to the cost of your own 3D printer. It might run to 1/3rd.

Did you follow aerohead's advice?

[LostinTransit]

@freebeard when the company has it's own 3D printer setup they've already done several projects for us. This isn't the first nor will it be the last, This issue is, the tech running the printed is not fluent in how to resize the print. So it's unclear as to how big these airtabs are. Prob about the size of the palm of your hand. I may opt to see if I can get the designed to shrink it down a tad.

As for what aerohead may or may not have said it went through one ear and out the others.. language of this kind is far beyond my skills.