Honda K20A & Toyota 2ZZ-GE

 

The K20A has cemented it's status as a legendary four cylinder platform. For all out naturally aspirated power screaming to stratospheric redlines, there is nothing better quantitatively. However, there is a quiet gem born of Toyota's collaboration with Yamaha in the 90's, which in my opinion was designed to take on Honda's dominance of naturally aspirated small displacement motors.

 

The 2ZZ-GE was launched in some Toyota models like the Celica, but really found a home in the Lotus Elise and Exige platforms. An often overlooked factor was that this engine was approximately 12-15% lighter than the equivalent K20A. In addition, the bore size was 8% smaller as well, leading to more compact packaging. 

Looking at one of the heaviest components of a car, the 2ZZ-GE's engineers worked extremely hard to make a lightweight yet powerful engine. This was demonstrated in a study that was published on the 2ZZ below: 

 

 

 

 

 

If there are any Toyota engineers who have access to the raw data above, please contact me or publish it online for the world :) Clearly we can see that the 2ZZ is a wonderful compromise of power to weight ratio. 

While the Suzuki Hayabusa 1.3 Sport Bike engine will have even better numbers in this regard, we have to remember that absolute power from lightweight engines come at the cost of high RPM's and a reduced power area under the curve. 

We can see that the ground that the 2ZZ loses to the K20A is in torque due to the 200cc reduction in displacement, and a powerband that is 38% smaller. This means that the 2ZZ needs a skilled driver to keep it the right RPM range to extract maximum potential from the engine, unlike the more forgiving K20A. 

The 2ZZ head employs the  VVT-i system uses engine speed, intake air volume, throttle position and water temperature to calculate optimal cam timing. They then added a changeover mechanism that utilises 8 lobes and a linked rocker arm assembly to move to the different profile. 

 

This is in contrast to the Honda VTEC system which required 16 lobes that each activates one valve to perform the switch over, reducing overall weight in the valve-train.

 

In addition, The Honda VTEC system uses 2 low-speed, 1 high-speed roller followers, while the Toyota 2ZZ uses rollers for the low-speed lobe and fingers for the high-speed which means less friction on the K20 valve-train.

The 86mm bore of the K20 allows for larger valves than the 82mm in the 2zz:

K20 in= 35mm, 2ZZ in= 34mm
K20 ex=30mm, 2ZZ ex=29mm

More airflow, more power. 

While it's rod ratio is not as optimal for high rpm performance, tuners have been pushing the engine to about 240hp, by solving it's main problem - oiling.

The 2ZZ’s stock oil pump gears can fail if the engine is over-reved or even sometimes for no reason at all. For this reason, upgrading the oil pump, adding oil cooling or even a dry sump system is advisable for performance use.  

Looking at the last two lines of the analysis, I'm certain that the 2ZZ engine is a star when it comes to how hard it punches for it's weight. With the right gearing and in a lightweight car, it's virtues will speak for itself.