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How to drive a VVT-i and other modern engine to save fuel

Not all engines are designed the same.  The more advanced the engine, the more power the engine can deliver while maintaining lower emission and lower fuel consumption.  However some people did not understand what a modern car's engine can do.  On this article, I'll use Toyota's VVT-i engine to represent modern engine, since VVT-i is the most commonly used valve timing stechnology.

Most people just think that the word VVT-i is just a marketing gimmick, they are wrong.  As my test has shown, by using VVT-i correctly, the driver could save up to 30% fuel compared to non VVT-i engine!  However using VVT-i incorrectly could waste 30% of fuel compared to non VVT-i engine.  So it is a double edged sword.  Why do I write this?  I write this to help other drivers, especially VVT-i engine drivers to save some petrol.

  • Here I share my experience on driving VVT-i engine.  I've been using VVT-i enabled car since 2003 and very satisfied with it.  My experience shows that - when used correctly - a 2AZ-FE on ACV 36 Toyota Camry engine could deliver close to 14 km/L (32 MPG), that is the fuel consumption of 1.6 L non VVT-i engine.  I've tested this on a trip with my friend from Bunbury to Albany.  At that time I drove ACV 36 Toyota Camry and my friend droves 1.6 L VW Golf 4. 

  • On Bunbury both of us filled up our car with RON 98 BP Ultimate then when we arrived on Albany, we fill up the car again and I found that it is amazing we fill the same amount of petrol! 

  • My other experience with VVT-i happens when I drive a Daihatsu Xenia from Magelang to Bandung, while my driver droves a 8 years old Suzuki Carry.  Both car has 1.0L engine, the Xenia is VVT-i enabled and driven swiftly at much higher speed compared to Suzuki Carry that is driven moderately.  I could manage to get 18 km/L (42 MPG) while the Suzuki Carry only manages to get 13 km/L (30 MPG)!  When driven carefully the Xenia manages to get 22 km/L (52 MPG).  FYI, when the driver of Suzuki Carry is driving Xenia, the Xenia could only deliver 10 km/L (23 MPG).

  • Before continuing on how to drive car with VVT-i, I believe I will need to give a short explanation on VVT-i.  VVT-i is a sophisticated valve timing control mechanism developed by Toyota, other manufacturers has similar technologies such as Honda's VTEC, BMW's Vanos.  I have not tried this technique on other brand of car, but I believe this technique can be used on other brands. 

  • Compared to conventional engine, VVT-i engine is capable to deliver more torque at lower RPM range and more horsepower at higher RPM while maintaining fuel efficiency and lower emission.  However as other systems, VVT-i has disadvantages.  Using VVT-i requires learning, which took me almost 1 year.  Here I write you my learning VVT-i experience so you will be able to minimise your car's fuel consumption immediately. 

    • First thing is you will need to study your engine's characteristic.  Usually VVT-i engine will change its timing between low engine speed and high engine speed at around 3000 RPM.  Try to find the difference between low speed timing and high speed timing.  Usually you will feel that the car's acceleration goes faster at that RPM. 

    • You will then need to check the lowest RPM that your engine can work to move your car on straight and level road.  Check it on each gear.  Usually it will be near 2000 RPM.  This is where VVT-i plays, it could deliver 90% of its torque from RPM as low as 2000.

    • Then you will need to change your driving habit.  To drive quickly you will need to press the throttle quickly but then shift up just under the engine's timing change RPM.  So, if your engine's timing change RPM is at 3000, you will need to shift at 2950.  Usually the engine and transmission is designed to work together so the RPM could drop to just above the lowest RPM to move the car comfortably (e.g. from 2950 to 1900). 

    • This will preserve the car's swiftness and safe some fuel.  Contrary to popular believe to press the throttle softly to higher RPM (3500 - 4000 RPM), my theory says that we should press the throttle quickly to low RPM.  This comes from of high school physic theory:

      • E=P*T or Energy = Power * Time or watt (horse power) * second

    • The higher the RPM the more horse power your engine deliver.  The longer you stay at high RPM the more energy you waste.

    • The quicker you press the throttle the quicker you reach desired RPM and this results in quicker you shift to the next gear.  This will reduce the time required to reach the desired speed, so the 'T' variable will be small.  Then by using lower RPM means lower average power output from the engine, therefore reducing the 'P' variable.  With 'P' and 'T' small the 'E' will be small as well, while 'E' is the factor that directly related to fuel consumption.

  • How about inefficiency?  Old carburettors engine tends to waste fuel when accelerating quickly, VVT-i with injection engine will only use the needed fuel, in millilitre precision!  This is not an issue.  Hopefully this trick helps you that is in trouble with increasing fuel price.

  • How if VVT-i engine is used incorrectly?  Well, it will waste more fuel, a lot of fuel.  Because VVT-i engine deliver more power compared to conventional engine at higher RPM's, which means larger 'P' variable, and larger 'E' variable, which wastes a lot more fuel!

Is driving VVT-i slow?

I drive using this technique from Bandung to Serpong (somewhere near Jakarta) using a tollway (a paid freeway) for 180 km and clocked for 2 hours, which means average speed of 90 km/h, quite fast.

Ok, it might not be that fast.  However for your illustration, there are thousands of vehicle drives on that highway and only 5 of them overtook me.  That means less than one percent of the vehicle on the street is faster than me.  Compare it to your driving style!

Moreover with this technique, I could maintain 14.2 km per litre figure on RON 92 Total fuel which is not bad.

If you think driving this style is slow, you are wrong!

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