Monday, Sep 02, 2013 at 15:22
There's a lot of sneering about Hiclones as being as useless as all the other "
fuel-saving" gimmicks that have no basis in scientific fact.
However, I installed a Hiclone in my turbodiesel auto HZJ80 Cruiser way back in 1992, and I measured an average of around 2-3% improvement in
fuel economy. It's not huge, but it was measurable.
The Hiclone website claims 10-20% gains. This is just pure marketing BS. The gain is only small.
The principle of adding swirl to intake air in diesels is
well known, and I came across this principle in 1962, when Allis Chalmers advertised the improved
fuel efficiency of their newly-redesigned "Thousand Series" direct injection engines.
The new A-C diesels had a projection, termed a "mask" in A-C literature, on the back of the head of the intake valve.
This projection was specifically designed to add swirl to incoming intake air, to ensure a fine and even distribution of the diesel droplets in the combustion chamber.
Diesels
fuel efficiency relies on even and very fine distribution of the
fuel droplets with the incoming air. Large droplets of diesel unevenly dispersed in the
fuel-air mix result in incomplete combustion. Incoming air swirl produces better results at higher RPM (2000 RPM and upwards).
As to the Hiclone results with petrol engines, the claims are somewhat spurious. A petrol engine does not rely on very fine
fuel droplet distribution with the air, as diesel
fuel does. Diesel
fuel is a relatively slow-burning
fuel, and trying to say the results are the same with petrol and diesel engines is marketing BS at its best.
The Hiclones used to be very high priced (I seem to recall about $160 or $180 in the early 1990's), but no doubt they're more reasonably priced today. For the investment of a few dollars, the Hiclone will probably gain you a few extra dollars in a diesel over a lengthy period of time - but as to major
fuel savings - definitely, No.
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Follow Up By: Notso - Monday, Sep 02, 2013 at 15:29
Monday, Sep 02, 2013 at 15:29
An interesting sidelight, but my Triton 3.2 litre diesel has what they call a "Swirl Control Valve" obviously designed to give some sort of turbulence to the air but it's pretty hard to understand how the air can still be "Swirling" after its been compressed something like 16 to 1 before the
fuel is injected.
I sort of thought it may be to thoroughly mix the Air and gas recirculated from the exhaust?
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Follow Up By: Ross M - Monday, Sep 02, 2013 at 19:02
Monday, Sep 02, 2013 at 19:02
All diesels have a combustion chamber and piston head features to cause an extremely high degree of swirl as the piston rises and gets to TDC. The idea of having a masked valve isn't real good as it may swirl the air a bit but also restricts flow into the cylinder and it is the cylinder which you are trying to fill. The design then does the swirl and thus mixes the incoming injected
fuel.
A hiclone can only swirl before the airflow branches out into 6 and that makes the swirl somewhat altered and not happening anymore.
A petrol engine DOES rely on the same mixing of
fuel and air for good flame propagation within the cylinder and it is also chamber swirled by the design. Hiclone will also restrict a petrol engine intake airflow.
2 stroke engines have a squish band design of head to induce intense turbulence so all is mixed for burning. Anything in their intakes restrict induction and power will suffer.
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Follow Up By: Ron N - Monday, Sep 02, 2013 at 19:41
Monday, Sep 02, 2013 at 19:41
Hmmm .. interesting article here ..
http://en.wikipedia.org/wiki/Swirl_flap
There's a lot at play in induction aerodynamics - nothing is ever as simple as it seems, because of the large number of factors involved in the IC engine induction and compression processes. It really keeps a lot of engineers busy over a long period of time.
Engine design has also altered in many subtle ways over the last 40 years - extremely high pressure common rail injection, piezo-electric injectors, staggered injection, developments in intake manifold design, lighter and stiffer valve trains that are more responsive, variable valve timing .. as the engineers play with one area of design, so it affects the other areas.
In the 1960's direct injection and masked valves were cutting edge - now they regarded as just stepping stones along the path of modern engine development.
Some really fascinating information in this highly technical engineering paper, below.
High-tech computational programs now play a very big part in determining optimal choices in design. Check out "3: Modelling Methodology". The complexity involved in the examination of combustion dynamics is mind-boggling.
http://www.ltnt.ethz.ch/people/sharmac/Chander_d.pdf
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