Should I Fit a Hiclone to Save Fuel?

QUESTION: Hi John, I have a question about in line air filter for my daughter's Subaru Forester (2012). She's very happy with it, but recently changed jobs, and now she's worried about the cost of petrol.  I have found a company called Hiclone Air Management Systems. They saying by fitting one or two of their products she could save 10-20 percent on fuel and a boost in performance. Have you heard of this company or products and if yes your thoughts please. They cost around $230 each so are not cheap.  Thanks, Peter.


Peter, these things are a joke - they do not work because they cannot work. As in: It’s physically impossible. All of these miracle fuel savers prey on people who didn’t pay attention during physics and chemistry at school. Issac Newton, Bernoulli, Einstein all have a good giggle over it in heaven, I’m sure.

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Selling this fuel saver stuff really is predatory. I actually studied physics, thermofluids, aerodynamics, etc., at uni. I’ve interviewed full-on combustion engineering experts about these alleged fuel savers. Guaranteed if you stick one of these things in the Forester consumption will increase and performance will decline. They’re a complete fraud; the ACCC has been onto miracle fuel saver sellers a million times. They are never endorsed by a reputable academic or institution - with good reason; they're always marketed by mug punter endorsement, and I’m not sure how much of that is written in house...

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From Hiclone:

“Hiclone simply changes the flow of air through the air induction system. Hiclones special fins create a swirling effect, this optimises flow through the air intake system and improves fuel-air mixing to allow near-complete combustion.” 

Why statements like these are a load of bullshit - 

  • It does change the flow. It makes it worse. It can only restrict flow. Thermodynamics 101. You can't put something in the path of inlet air and expect the airflow to improve. You can't spin a fan using the energy of inlet airflow without absorbing some of the energy and reducing the inlet air mass/speed.
  • There’s already plenty of swirling near the combustion chamber. Injectors squirt the fuel basically just before the inlet valve - the air is already tumbling violently in that location. Swirling (or not) at the location of the Hiclone (a long way upstream) can have no meaningful effect on the tumbling of the inlet air past the inlet valve.
  • Fuel-air mixing is already optimised in a bespoke way per engine during R&D. This is extensively tested.
  • Combustion is already complete - modern engines run stoiciometric air-fuel ratios. There’s a feedback loop in the exhaust (oxygen sensor…)

Injection and combustion is computer-controlled. The software that determines how much fuel to inject under what operating conditions is fixed - and it is optimised for the precise configuration of engine hardware. You can’t just dick with the plumbing in this arbitrary way, and expect the software to cope.

More info (you want to review myth #8)

And (a story I wrote for Wheels magazine years ago)

Diesels save about 30 per cent on fuel. Is a diesel car right for you? Find out here >>

How to save money on fuel

If your daughter wants to save 10-15 per cent on fuel, tell her to pump up her tyres to placard +20 per cent, make sure the air filter is in good shape, and drive more gently. (Your right foot is connected to a tap. It empties the fuel tank… If you want to save money, don't open the tap as aggressively.) Fuel costs only about $1.50 for every 10km in a Forester. It’s cheap. If she drives like a self-obsessed Gen-Y, consumption will go up as much as 50 per cent. Tell her to drive gently. Spend the $230 on something worthwhile.

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