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. One of the principal sources of information is a report titled "Development of the High Speed 2ZZ-GE Engine" published by Toyota in March 2000. 

The date of this report tells a story. The K20 engine was launched in 2001, and it is highly likely that the 2ZZ engine was benchmarked against the Honda B18C. In a way, this whole article is kind of redundant because they were designed in different eras, but I think this comparison allows us to understand each engine in comparison to each other. 

 

The Toyota engineers worked extremely hard to make a lightweight yet powerful engine. However evidence I found suggests that the K20 and the 2ZZ engine and transmission packages have a  10-20kg  weight difference with the 2ZZ being lighter.


I found this compelling post by Fluffyninja on S2Ki to back up this research: 
 

"Just for some background I was the engineer responsible for our ZZ assembly line from September 2000~End of 2004, I look after engine testing of all engine types we build, I made all the engine test standards (including engine weights all the major varients) upto the end of ZZ production.

 

I was responsible for Cylinder block machining, cylinder head machining, block/head casting and periodically assisted with cam, rod and crank machining. You might say I know a thing or two about this engine family. Now I will admit we didn't deal with 2ZZ (we built 1ZZ, 3ZZ and 4ZZ) but I do happen to know that a fully dressed 1ZZ engine was approx 105Kgs.

 

The main difference in this engine was the lift system and had a marginally larger cylinder head. That marginally larger cylinder head is not 30Kgs worth! (a full cylinder block weighs less than 20) for that 30kg's you could have a second cylinder head mounted on there. 

 

I would say a far more realistic figure for the engine weight would be 110kgs. At that his comparison to the K-series is only about 15kgs. Not a massive amount of difference. I could take a good healthy dump and save that weight."

This was demonstrated in a study that was published on the 2ZZ below: 

ratio.jpg
2zzk20.png

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 an engine like 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. 

Speaking of area under the curve, let's study torque per litre (lbft per liter). This will give us an idea of how the 2ZZ and the K20 stack up against other engines, particularly the bottom end.  

Honda S2000 AP1 
153 / 1.997 = 76.6 lbft/l

Honda S2000 AP2
162 / 2.157 = 75.1 lbft/l

 

BMW E46 M3 
262 / 3.246 = 80.7 lbft/l

Ferrari F430 
343 / 4.308 = 79.6 lbft/l

Toyota 2ZZ 

133/1.796 = 75.1 lbft/l

Honda K20

152/1.997 = 76.6 lbft/l

In terms of torque per litre, they are comparable, with a slight advantage to the K20. The additional torque produced by the displacement difference is only the beginning of why Honda produced a superior engine. 

Let's get into the top end of the engine. 


The bore size of of the K20 is 4mm larger than the 2ZZ (86mm vs 82mm). The bigger bore in the Honda allows for larger valves to be fitted to the cylinder head of the K20. The shorter stroke also allows an engine to rev higher, which creates more horsepower. 

Valve Sizes: 

K20 in= 35mm, 2ZZ in= 34mm

K20 ex=30mm, 2ZZ ex=29mm

If you imagine air flowing through a wide angle port of a cylinder head, the more horizontal it is, the closer to a 90 degree angle it has to turn to go into the vertical inline combustion chamber. A narrow angle port design allows the air to flow more naturally into the engine, as it moves along the straighter path. 

 

As the revs rise, the K20 uses roller followers for all 3 of its cam lobes (two low-speed, one high-speed). The 2ZZ uses rollers for the low-speed lobe and fingers for the high-speed. While the 2ZZ is an incredible engine, it is outgunned by the K20 at the higher RPMs from a design point of view. 

2ZZK20A.png

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.

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.  

While the torque potential of the cars per liter is somewhat comparable, the significant advantages of the cylinder head design of the K20A leaves the 2ZZ in the dust, which is clear since it was designed in an era where the Honda B18C was it's competition. It would have been amazing if Toyota continued development of the 2ZZ and perhaps produced a response to the K20, but even Honda moved onto forced induction engines, so we are likely left with the swansong to naturally aspirated 4 cylinder engine. .  

References: 

 

Toyota ZZ: Everything You Need to Know

Development of the High Speed 2ZZ-GE Engine 

DOI: https://doi.org/10.4271/2000-01-0671

Citation: Shikida, T., Nakamura, Y., Nakakubo, T., and Kawase, H., "Development of the High Speed 2ZZ-GE Engine," SAE Technical Paper 2000-01-0671, 2000, https://doi.org/10.4271/2000-01-0671.