With strength and high-rpm performance being two of the K24’s primary strong suits, turbochargers naturally fit into the equation. Historically, turbocharged K24 TSXs, Accords, and other wild swaps have shown that you can push the Honda 2.4L extremely far with stellar reliability. 300 horsepower is a breeze for a Turbo K24, with power figures in the mid-400s being jogging pace.
In this guide, we cover K24 turbo kits and upgrades, engine power limits, and some of the necessary considerations that should go into a turbo upgrade.
K24 Turbo Power Limits
One of the defining characteristics of the K42 engine is its ability to handle an absurd amount of power using stock internals. Despite the only forged internal component being the crankshaft, the cast pistons, rods, and other internal components hold up extremely well to the added boost.
It isn’t uncommon to see a turbocharged K24 run in the 400-horsepower range without opening up the engine. That is a relatively safe and attainable horsepower figure for a turbo build. Once you pass the 400 horsepower threshold, reliability can certainly decline if you aren’t taking proper precautions with your tune.
Pushing Beyond 400whp
For turbo builds extending beyond 450-500 horsepower, it would be a good idea to consider a race gas conversion kit. Running a turbo K24 on E85, which has a high ethanol concentration, reduces internal temperatures. This allows for higher peak horsepower numbers and a safer environment for high boost levels. We’ll go into fueling modifications in more detail in a later section.
While many Honda enthusiasts claim that a turbo K24 can produce power in the 600 horsepower ballpark without opening the engine, that is stretching the boundaries a bit too far for comfort on stock internals. If you plan on making that much power, you’ll want to start thinking about forged internals. Pistons and rods are the main components that you’ll want to think about upgrading once you reach 600 horsepower.
Best Variants to Turbocharge
In total, there are four unique variants of the Honda K24 engine, each split into even more subvariants. The four main variants are the K24A, K24W, K24Y, and K24Z. While all of the engines share many of the same characteristics and specifications, some variants of the are better for forced induction than others.
A2 Variant – Performance Option
The K24A2 is -without a doubt – the best engine option to turbocharge. There are a few key reasons for that. As a catch-all answer, the K24A2 is the best variant in factory form. It has the highest redline of any variant that we received here in the US. That translates to high RPM performance once VTEC engages. On the subject of VTEC, the A2 has true performance VTEC on both the intake and exhaust sides. It is also has one of the highest-flowing cylinder heads out of all variants. That said, cylinder head flow figures can be easily improved by swapping on a K20Z1 head from an RSX Type-S. Quite a few parts are interchangeable, leading to increased performance from a Frankenstein K-series engine.
Overall, the K24A2 is one of the best variants available and is ready for boost straight out of the gate. While the news is almost entirely positive, there are a couple of limiting factors that plague even one of the best variants as far as forced induction is concerned. In factory form, the K24A2 has an extremely high 10.5:1 compression ratio, which is somewhat high for the addition of a turbocharger. Lower compression is generally preferred for turbocharging, as it increases the safety of the engine’s internal components. For that reason, People looking to squeeze big power out of a turbo generally swap to low compression pistons. That isn’t to dissuade you from using the K24A2 as a foundation. It is still able to handle moderate amounts of boost without issue.
A1/A4/A8 Variants – Budget Option
These variants were used in a ton of vehicles making them extremely inexpensive and easy to find. If you are on a budget, any of these three variants is your best bet, as you’ll likely be able to find one on Craigslist for less than $500. While the three variants are slightly unique, they share a very similar construction that makes their differences negligible.
In comparison to the K24A2 engine that we previously discussed, the A1, A4, and A8 have slightly less desirable characteristics. For instance, the three all have a diluted VTEC system that only applies to the intake side of the engine. For that reason, you won’t get the same high RPM performance that you’d get from an A2 with full-performance VTEC. Additionally, their cylinder heads are not ideal from an airflow perspective. Comparatively, the three A variants have restrictive heads that can benefit to a certain degree from a port and polish. Like the K24A2, the three listed A variants also benefit from a cylinder head swap.
K24 Turbo Upgrade Considerations
Okay, we’ve already briefly covered why a turbo K-series is a solid engine choice, so now let’s talk about what goes into turbocharging a Honda K24 engine. As with adding forced induction to any previously naturally aspirated engine, there are quite a few factors to consider. In comparison to a lot of other engines, however, the K24 is a relatively straightforward engine to turbocharge. I mean that in the sense that internal work, auxiliary fuel management systems, E85 conversions, and other supporting modifications required for some engines to even get off the ground with forced induction aren’t immediately necessary for a moderate turbo K24-powered car.
While there is a pretty well-outlined formula as far as turbo K-series go, turbocharging a car is never easy.
Turbo sizing is an important consideration when throwing together a K24 turbo build. Sizing determines both how much horsepower can be generated from forced induction as well as how that power is delivered. There is quite a discrepancy in the amount of power a T3 and T70 size turbo, for instance, is able to produce. While a larger turbo might be able to produce more power and run higher boost levels, there’s more to consider.
Generally speaking, Honda engines tend to do the best with smaller, faster-spooling turbos. T3 and T3/T4 hybrid turbos are the most common size for turbo K-series applications. Small turbos are best for street/daily driven cars, as they benefit the mid-rpm range the most. While it might be fun to have a K24 top-end VTEC, large-turbo monster, it won’t really be usable power on the street. With a small, quick spooling turbo, power will be on demand immediately.
With that being said, you won’t be able to achieve the same power figures with a small turbo as you would with a large one. Larger turbos, such as a Garret GTX3584RS or a turbo from Garret’s GT40 series, have the potential to make more horsepower at the same PSI than a smaller turbo. Since larger turbos take longer to spool, they are good for racing applications where you want your power to come on high in the rev range. These turbos are for K24 owners shooting for the 600-horsepower range.
A good rule of thumb is to find the smallest turbo possible for your power goals with a bit of breathing room for future plans. T3 and T3/T4 turbo hybrids are thoroughly capable of close to 400 horsepower.
Engine Management System and Tuning
One of the most crucial aspects of any turbo setup is the accompanying tune. Not only will a proper tune squeeze the most performance out of your K24 turbo setup, but it is also the first and last line of defense from potential damage. Working with a qualified Honda tuner to develop a safe and conservative tune is the best way to ensure that your turbo build stays in one piece.
While there are flash/piggyback tuning options available for the K24 engine, modified ECUs -like the Hondata KPro- are far more common. Almost every turbo K-series owner vouches for the Hondata KPro as their ECU of choice for their turbo build. Not only is the KPro one of the most customizable options out there for the K-series platform, but it is also one of the easiest to install and use. The KPro allows you – or a qualified tuner – to make adjustments to engine characteristics, adjust fuel and ignition tables, and essentially anything else you could possibly want to alter. It is a one-stop shop for K24 tuning and is the go-to for almost every turbo build.
As we briefly hinted at earlier, if you’ve never tuned a car before, this isn’t the time to experiment. For the safety and reliability of your K24 engine, adjustments to engine management characteristics should be left to the professionals. They’ll likely be able to guide you to your target goal while making sure that the chances of anything critical going wrong are minimal.
Proper fueling is a critical component of the turbo K24 equation that needs to be considered as well. Since your engine will be taking in a higher amount of compressed air, your engine needs fueling to match. The two most important components in need of an upgrade are the fuel pump and injectors. A high-flow fuel pump is critical to your engine’s ability to supply the injectors with enough fuel. By extension, you’ll also need higher flow injectors to keep up.
Walbro fuel pumps are typically the go-to for an ungraded option. While there are a number of fuel pumps that will be able to supply enough fuel flow, a 450LPH pump is a good bet for K24 turbo applications pushing up to 600 horsepower. Walbro pumps work with both pump gas and E85, so if you are planning on upgrading to race gas in the future, Walbro has you covered.
Beyond a fuel pump upgrade, you’ll also need upgraded injectors with a higher flow rate than stock. Of course, the flow rate that you go with entirely depends on how much power you intend on making. In the 300-450 horsepower range, 550cc injectors should be sufficient. For boosted power figures approaching the 600+ mark, 1,000cc injectors might be best. In addition to upgrading the injectors, some K24 owners also opt to upgrade their fuel rail at the same time. While a stock rail will work just fine for most mild turbo K-series applications, it might be a necessary upgrade for those aiming for high triple-digit power figures.
Acura RSX Type-S Oil Pump Swap
One of the biggest factory faults with the 2.4L K24 engine is the oil pump design. The K24 pump utilizes balancing shafts that Honda claims improve idle quality. Most Honda enthusiasts have a problem with the design as the balancing shafts zap a few horsepower from the engine and lower the redline. Beyond the performance handicap, the factory K24 oil pump is known to cavitate at higher RPMs. That is especially troublesome for turbo applications where revs climb high and do so quickly.
Luckily, there’s a very straightforward solution to that problem – swap the factory oil pump with one from a 2.0L K20Z1. The new pump will allow your engine to rev sky-high without any of the downsides of the factory pump. In addition to the pump itself, you’ll also need to swap the oil chain guide, tensioner, and chain. All of which can be acquired from the same engine.
Custom Turbo Setup vs Turbo Kit
Generally speaking, there are two routes that you can take when turbocharging your Honda K24 engine. You can either choose to piece together all of the individual components needed for a full K24 turbo setup, or you can purchase a preassembled kit. There are pros and cons for each of these routes and no definitive answer as to which is the best.
When it comes to a custom, piecemeal, K24 turbo setup, you’ll have to rely on heavy research and diligent organization to make sure that you have all of the necessary components that you need in the end. Also, you’ll need to source all of the individual components which can get pricey. However, with this route, you have the ability to source used parts from forums, craigslist, and other secondhand sites. While you’ll likely need additional odds and ends as well, the components that you’ll need for a custom K24 turbo setup are as follows:
- Turbo manifold
- Turbocharger of your choice (T3 or T4 recommended)
- Large and quality intercooler
- Intercooler piping/fittings
- Blow-off valve and wastegate
- Turbo downpipe
- High flow injectors
- Hondata K-Pro
If you aren’t willing to hunt down all of the individual components for a K24 turbo setup, you can always go for a turbo kit. With a kit, all of the needed components are assembled for you. While you won’t have the same level of customization when it comes to the individual parts, you’ll know that you have everything that you need with a kit. K-series turbo kits tend to either be extremely affordable or extremely expensive with few options in between. We’ll cover a couple of kits in detail in the following section.
K24 Turbo Kits
Turbo kits are the easiest way to acquire all of the necessary parts to turbocharge your Honda K24 engine. Unlike a custom turbo setup, a turbo kit is comprised of components arranged by a supplier or manufacturer. Here are a couple worth checking out:
- CX Racing 2004-2008 Acura TSX K24A2 Turbo Kit with Intercooler
- Full Race ProStreet K24 Turbo Kit
Just Drop a K-Series In and Boost It
The 2.4L Honda K24 is an extremely solid platform to turbocharge. Historically, Honda 4-cylinders have responded extremely well to forced induction and have a reputation of being reliable as well. A 400 horsepower power goal is very attainable with a mild K24 turbo setup, and the stock internals can hold up to that threshold too. Once you extend too far beyond that, you’ll want to think about some safety upgrades like an E85 conversion and forged pistons.
While there is certainly a lot to consider when putting together a K24 turbo setup, the process is not as difficult as it is with many other engines. Of course, you’ll have to consider turbo sizing, engine management, and fueling upgrades, but that is the majority of the job. Of course, it will be a bit more involved if you choose to piece together a custom setup. A turbo kit would alleviate the pressure of collectivizing all of the individual parts at the cost of customization. Either route can yield impressive results from a 2.4L K24.
If you liked this guide and are interested in more K-series content, check out our Honda K20 vs K24 Engine Guide. As always, safe driving!