The H22A is an incredibly popular and in-demand engine for Honda owners worldwide. Why is it so popular and how does it stack up against the H22A4? This article gets into all of that and more. Given how popular the idea of turbocharging these particular engines is we will even cover which is best when equipped with a turbo booster!
What Is The H22A Engine?
The H22A is one of the most reliable and powerful engines in the Honda H series engine line. Its power and reliability have made it quite coveted around the world and over time it has developed a pretty respectable reputation. The H series is one of the larger performance engines coming out of Honda in the late 90s and early 2000s. It is very similar to its predecessor the F engine though slightly more powerful and just a little lighter. Many Honda drivers using the F series engines elected to swap to the H22A series before turbocharging as the compression levels were also a lot more suitable.
Where Is The H22A Engine Used?
The H22A engine is what is known as a JDM. Which means it is an engine that was purely intended to be used domestically within Japan. While you can still find the H22A all over the world they are exceedingly rare compared to the H22 A4.
You can easily identify which H22A was built and sold within Japan because its serial Engine ID will be on the engine block itself (unless it happened to be decked off by a clumsy mechanic). The H22A engine was used in every Japanese model of the Honda Prelude and is quite popular due to its rarity overseas (in North America).
Where Is The H22A4 Engine Used?
While the H22A engine was used exclusively in Japan the H22A4 was used exclusively in North America in all Honda Preludes manufactured between 1997 and 2001. It is not uncommon for Honda, and other car manufacturers, to have slightly different versions of the same engine to comply with domestic rules. However, it doesn’t appear like that was the case for the American market.
More interestingly, it seemed as if Honda had tried to improve in some areas and cut back in others. For many people the differences are negligible and actually, it is simply a matter of personal preference whether they prefer the H22A or the H22A4 (we will cover the differences in just a moment)
What Variants Of The H22 A4 Engine Are There?
The H22 A4 Engine actually has two sub-variants that you might come across. The base model and the SH block model. The SH block should be the only model you are interested in if you are looking to make an SH swap. And maybe because it is the only one that allows the Active Torque Transfer System to be installed.
What Are The Differences Between The H22A And The H22A4?
There are several differences between the H22A and the H22A4 that you should be aware of before you pull the trigger on purchasing either of these two engines. While they are very similar, they both excel in slightly different areas. Here are the differences:
- Compression Rate – The H22A Engine has a compression rate average of about 10.8:1 whereas the H22A4 has a compression rate of about 10:1.
- Deck Design – The H22A has a closed-engine deck design which means its aluminum frame is around the cylinders and coolant port compared to the H22A4 which has an open-engine deck design without this frame and the cylinders are instead attached at the bottom of the block. This allows the H22A4 engine to cool much faster.
- Oil Pump Sensors – The oil pump sensors required in the H22A are not all needed in the H22A4 because the A4 makes use of the second-gen OBD2 scanners.
- Intake Manifold – The H22A series engine uses an older intake manifold design that is a little less efficient. Additionally, the H22A4 intake manifold is polished down as standard improving airflow dramatically.
- Crankshaft Harmonic Balancer – A minor difference, but one that should still be mentioned, is the crankshaft harmonic balancer is smaller on the H22A engine which means it’s slightly less efficient.
- Thermostat Housing – The thermostat housing on the older H22A engines is slightly different. Which doesn’t have an effect on performance but is something to consider in terms of customizability. The H22A4 thermostat housing is much more conveniently positioned.
- Piston Types – While the H22A uses type A pistons the H22A4 uses type B pistons. The type B pistons are smaller tolerance but there is only 0.1mm in it so it’s nothing to write home about for most people.
Does Every 5th Gen Prelude Come With A H22 Engine?
Yes, 5th gen preludes exclusively come with an H22 engine. Whether it’s the H22A in Japan or the H22A4 in the United States. Interestingly, the 4th gen Preludes come with an H23 engine which is quite funny considering the H22 came first and the 4th gen naturally came before the 5th.
Which Engine Is Best For Turbo Charging – H22 A4 vs H22A
If it comes down to how suitable each engine is for turbocharging then you will want to go with the H22 A4. The reason is that the A4 is a slightly lower engine compression than the Japanese H22A. Turbocharging requires lower engine compression meaning the gap between the A4 and a turbocharged engine pressure is much smaller and therefore the engine is far more tolerable of being turbocharged.
As you can see while there are a few key differences between the H22A and the H22A4 engines they are very similar. Whether you prefer the SH block H22A or the more flexible H22A4 is a matter of personal preference. Regardless, if you are anywhere outside of Japan the H22A4 is going to be the better option purely because it is far more readily available! The Honda H engine series is pretty robust and despite being an afterthought for Honda all these years later has remained incredibly popular among enthusiastic Prelude owners.