When the latest Evo model Mitsubishi Lancer came out I looked with interest at the rear fins stuck all over the trailing edge of the roof.

Mitsubishi calls them vortex generators, a term I was already familiar with from aircraft. Some aircraft use vortex generators placed on the upper surface of the wings to delay flow separation and so reduce the speed at which wing stall occurs. But the Mitsubishi isn’t an aircraft flying along, so what do they do on that car? A tech paper from Mitsubishi soon revealed that they improve the flow of air down the rear glass, so getting more air to the wing and probably also reducing the size of the wake.

I was inspired enough by the design to make a bunch of my own (using the alternative shape shown in the tech paper) and stick them over the trailing edge of the roof of my NHW10 Prius. However, on-road testing showed that the reduction in drag (for that was what I was after) wasn’t enough to make a dramatic difference to fuel economy, as I had already achieved with my frontal undertray.

So I put the idea to one side, perhaps for later revisiting with different shaped vortex generators or another car.

But when I came across a discussion group post that talked about an Australian company selling vortex generators with the aim of reducing fuel consumption, my interest was again aroused. The company, VG Fuelsavers, had recently featured on local TV as an invention worth watching. The website http://www.fuelsavers.com.au showed some pics of the vortex generators, which are made of sheet aluminium and look much more like aircraft designs than the shape of the ones used on the Evo Lancer. A kit of nine vortex generators with fitting instructions, cleaning wipes, double sided tape and a template cost AUD$110, including delivery. Which seems fine by me.

From: Julian Edgar

To: info@fuelsavers.com.au

Sent: Thursday, April 27, 2006 7:03 AM

Subject: media test request

I note your website at http://www.fuelsavers.com.au/ and the vortex generating fuel savers.

I’d like to do a test on the product for www.autospeed.com, the world’s largest fast car website. We produce a daily article for our readers and have been doing so for nearly 7 years.

I’d considered developing vortex generators as a modification story but clearly if the off the shelf ones work well then this would be an easier way of readers achieving the outcome.

The aerodynamic undertray stories we did (see Modifying Under-Car Airflow, Part 1 and Modifying Under-Car Airflow, Part 2) attracted considerable reader interest.

We would test the vortex generators on a NHW10 Toyota Prius sedan, for which I have detailed constant speed fuel economy test results.

Julian Edgar, B.Ed, Dip T (Sec), Grad Dip Journ, AFSAE

An email duly came back from Mike Chadwick, one of the contacts listed on the website. He said he’d be happy to send AutoSpeed some for some independent testing. He also asked for my phone number as he wished to chat. I sent the number and a day or so later he phoned.

It eventuated that Mr Chadwick is an aircraft maintenance engineer and had spent some time developing the vortex generators. He’d tried them on his son’s car, a Vectra hatch, and had video of this car wool-tufted, with and without the vortex generators. Some trucking companies were also using them, he said. I requested a copy of the video footage, the contact names and details of the trucking companies he said were getting good fuel consumption gains. I also pointed out that the reduction in aero drag would need to be very great to achieve the fuel savings of “up to 11 per cent” being claimed on the website. (Well, they would if the fuel consumption savings were going to be anywhere near 11 per cent!)

I also made the point that when we test goods, we will publish what we find, whether that’s good or bad. In the phone call I expressed a little scepticism as to whether the vortex generators would work well on hatches with vertical tails (the website shows pics of a Hyundai Getz equipped with the devices) but Mr Chadwick blithely dismissed these concerns.

I got the feeling that Mr Chadwick had not talked with anyone who expressed scepticism based on a knowledge of car aerodynamics (as opposed to just a scepticism about any fuel saving gadgets!) but near the end of the call he casually mentioned that he thought we’d find them as interesting as General Motors Holden, who were (apparently) happily testing them. He also said he had patented the concept.

After the call I emailed, requesting the patent number(s) – a patent has to reveal nearly all the details of the device, so that would be good background.

Back came Mr Chadwick’s email, but this time with the tone rather markedly changed. Could we supply details of the tests we would conduct, he asked. When were we going to conduct the tests because Fuelsavers would be interested in viewing the test and assessing the results, he wrote. He also supplied a patent number but not the country in which it was issued. (A search reveals it’s an Australian patent.)

After the debacle of testing the Davies Craig Electric Water Pump, something we spend a great deal of effort doing (see Testing the Davies Craig Electric Water Pump – Part 1) , I like to make things as crystal clear (although I thought I already had)…

Mike,

As a matter of editorial policy we do not show articles to those supplying goods for review.

The test would involve fitting the devices to an NHW10 Toyota Prius and comparing fuel consumption with that already being achieved in a variety of conditions. It may also involve comparative wool-tuft and/or surface pressure testing.

If you have any problems whatsoever with any of the above, I urge that you reconsider the supply of the goods.

In what country is the patent issued?

Julian Edgar

And I never heard from Mike again….

Footnote: I have since found another source of vortex generators – so stay tuned for more on this topic!