You think to yourself one night while scrolling through youtube videos and ricers on Tik-Tok “the Japanese build one hell of a car, but are JDM engines good too?”
You’ve got a tuner car. Particularly a Japanese one. You want to upgrade your mill under the hood for some more power (because there’s never enough), or maybe you blew your old engine and just need a new one.
Sourcing an engine from Japan is actually a great idea. Not only are JDM engines good, they are a better option than most other engines for many different reasons including their reliability, condition, and availability.
Japanese Domestic Market vs Others
I guess the first question is what’s the difference between JDM engines and other markets, say the United States domestic market (USDM)? The answer is very little.
The market makes pretty much no difference on how the engine is manufactured, the differences lie in the designs and more importantly their usage.
The Japanese market has very different standards of emissions than we do in the United States. Tied with the European market, Japan has the strictest standards for vehicle emissions in the world.
This affects what vehicles and engines are created. Off of an assembly line a JDM engine is not particularly better than a USDM, one just different.
Some vehicles were offered in Japan only, making that particular engine unique and sought after like the performance engines enthusiasts look for.
Check out the table below to see what some of the common differences are between JDM and USDM.
You wondered why the Japanese are so good at making small efficient engines. Now you know that fuel taxes and incentives to build smaller pushed this into creation, it’s market forces!
JDM Low Mileage Engines
JDM engines generally come in two flavors. Some are beaten to hell, but the majority are cherry low mileage engines. These are the ones you want.
As with everything, the condition all depends on what engines you’re looking at and from which cars, but more on that later.
To understand how the engines come about in these two vastly different conditions, we first need to understand Japanese car buying culture and their laws surrounding them.
See in Japan people buy cars often, usually replacing cars between 4 and 5 years. The tax regulations and inspections in Japan make it prohibitively expensive to keep and maintain an older vehicle on the road.
Combine that with strict fuel efficiency standards, you get a unique situation in which vehicles are only economically viable to own for short periods of time.
Most vehicles are changed often, creating a supply of good quality low mileage vehicles as well as a thriving used auto parts industry. That’s where we get the low mileage engines that the JDM market is so readily known for.
The occasional vehicle that has been on the road for longer (generally an enthusiast car), will be more liberally used as the owners would have paid substantially just to keep it registered (also known as Shaken). These cars would probably be heavily modified, tracked or even raced.
Japanese Domestic Market
Jidōsha Kensa Tōrokuseido, better referred to as Shaken, is the inspection registration system in Japan designed for all vehicles over 250cc in size. It is one of the most stringent inspection systems in the world.
It was invented to insure compliance and safety of all vehicles on the road as well as to prevent illegal modifications. The process to pass a Shaken inspection has many steps.
First cars are registered by appointment and vehicles are required to have mandatory insurance. Premiums can be as much as 10 times higher than the U.S.
A required recycling fee is also applied depending on make, model, and displacement. Intended use also affects the fee; commercial vehicles are levied much higher.
Vehicles with engines greater than 600cc pay substantially more as prices increase in each category. That’s why a special vehicle class in Japan called the KEI Car was invented and popularized.
KEI cars avoid paying higher fees as well as being more suitable for Japan’s narrow and dense city streets. The Kei cars have engines smaller than 660cc, and are limited to 78.74 inches in height, 58.26 inches in width, 133.85 inches in length, and have no more than 64 horsepower.
For all vehicles the inspection revolves around 7 different segments of the car from exterior to interior as well as emissions. You can find out more of what goes exactly into the Shaken inspection here on it’s Wikipedia page.
After the initial Shaken and first three years of car ownership you are required to get one every two years after that. Each time you renew your Shaken it increases with the car’s age.
You can imagine how fast the costs can add up and outweigh the benefit of keeping an old car. It’s significantly cheaper just to get a new vehicle, which is exactly what most Japanese do. This is what makes the JDM engines so good and reliable as replacements.
JDM Engine Reliability
Engine reliability of Japanese domestic market engines isn’t particularly better than the reliability of other market Japanese engines. The dependability isn’t specific to the geographical region it came from but more a testament to Japanese engineering and quality control standards.
Yes, the engines from low mileage vehicles surely impacts how long things will last. Things that haven’t been used as much will have more longevity especially if they don’t have much age.
This is what makes the JDM engines unique as they are so young, and used so little. However, it isn’t all equal across the board.
Searching through Japanese auction sites you will notice the older vehicles will have much higher mileage and more modifications. It’s the nature of enthusiast vehicles, we love them so we drive them.
Like I mentioned earlier, enthusiast cars are subject to much more abuse and wear. These are the popular tuner cars we know and love. Toyota Supra MKIV, Nissan Skyline GT-R, Mazda FD Rx-7, and on it goes.
Even though Japanese cars are known for meticulous attention to detail and superb reliability, enthusiast vehicles will have substantial use.
The whole car industry is designed so you’re disincentivized from buying large, powerful vehicles and also from keeping them very long. So imagine when you do, you’re going to use it.
Japanese enthusiasts have to pay a lot more to keep their cars. It’s a pay to play situation, and since they pay more they play more.
If you’re looking for JDM high performance engines for your project like a Toyota 2JZGTE, or Nissan SR20DET you definitely want to inspect the motor for wear. It’s good practice to inspect everything you purchase especially when used, but more so.
Remember people change cars every 4 to 5 years in Japan. Some of these performance engines are pushing upwards of 20+ years old. Double check everything!
Check the oil, look for signs indicating head gasket failures, or fouled spark plugs. Drop the oil pan. Check the heads. Do everything you have to do and more to make sure what you’re getting will work before you buy.
Commuter cars that have much less mileage and haven’t had much drive time (4 to 5 years) are much less likely to be worn. These are engines that carry over across the model lineup like Toyota’s 2GR FE or Nissan’s VQ35DE.
Engines like that are plentiful and cheap, but like with everything else in life, even JDM engines have their pros and cons, nothing is 100% assured.
Pros And Cons Of JDM Engines
|Generally Less Wear and Tear||Performance Engines are more abused|
|Lower Mileage||Smaller Displacements|
|Ample Supply of engines||Not a direct swap always/ Small differences in manufacturing/Ecu|
|More efficient||Emissions equipment is missing for regulations requirements in USA|
|Costs less than the equivalent mileage USDM engine||Customs/Taxes/Shipping|
Where To Buy JDM Engines
There are tons of sites where you can get engines imported from Japan. Ebay is a big one and it appeals to a lot of people because of the ease of use.
Unless you know exactly what you’re buying, I wouldn’t order an engine online. Instead do a thorough search on google to try and find a location near you that sells JDM engines.
Then you want to call those people up, ask about the engine you’re interested in. Make sure to get all the details, history, mileage, where it came from, how long they had it, and what has been done to it.
A lot of websites use generic photos of one engine as a mock up. You want to see the exact engine you’re going to purchase. You’ll be surprised how different they can be.
Once you have all the info, go out and inspect it in person. Check everything you can from top to bottom inside and out. Check out this great video from Corey Hosford below of how to inspect a JDM engine.
If you can’t go out to inspect it (I highly recommend you do) get as many photographs and videos of the engine you can from the seller. The more you know the better it is.
Make sure you know how much power per dollar you’re getting out of your swap by using our horsepower per dollar calculator here. You’ll know exactly how much value you’re getting and if a swap is even worth it!
Many things make Jdm engines good, but your ability to match it to a good donor is what makes it great.
May the tuning gods bless you on your journey and let the horsepower flow!