The Top 5 Acura RSX Mods. From 2002 to 2006, the Acura RSX and its performance variant, the Type-S, were two of the most fun cars money could buy. Acura powered the RSX and Type-S with various iterations of the Honda K20 engine, which was reasonably priced and provided adequate performance. Honda/Acura enthusiasts have long praised the K20 engine for its ease of modification and ability to handle power reliably. Acura rated the standard RSX at 160 horsepower and 142 lb-ft of torque, while the RSX Type-S was rated at 200-210 horsepower and 142-143 lb-ft of torque.
While the RSX and Type-S perform admirably stock, they excel with a few minor engine and suspension modifications. With the cars approaching two decades old, a few performance RSX mods are almost required to keep up with more modern cars. Adding bolt-ons to the engine and suspension is a low-cost way to improve performance while remaining dependable on the RSX.
This guide will go over the top 5 best Acura RSX mods for both standard and Type-S models. Before we get into the best RSX mods for your build, we’ll go over the basics of the suspension and engine differences between the two. Let’s start with the basics of the RSX and Type-S in the United States.
History of the Acura RSX
Acura introduced the RSX and Type-S to the United States market in 2002 as the replacement for the outgoing third generation DC5 Acura Integra. Even though Acura badged it differently, the RSX is considered the Integra’s fourth generation (DC5). It was sold as the Honda Integra in the Japanese and Australian markets.
The RSX was available in three different configurations: standard, Type-S, and Type-R. Only the standard and Type-S models were available in the USDM market. Acura used the K20A3 inline-four engine, rated at 160 horsepower and 142 lb-ft of torque, in the base RSX from 2002 to 2006. Acura fitted the Type-S with the K20A2 engine, which produced 200 horsepower and 142 lb-ft of torque between 2002 and 2004.
The Acura RSX Type-S used the upgraded K20Z1 engine from 2005 to 2006. Acura rated the engine at 210 horsepower and 143 lb-ft of torque in 2005, but advertised power dropped to 201 horsepower in 2006. While some may believe that this means the 2006 Type-S is less powerful, this is not the case. Acura adopted the SAE’s new horsepower rating regulations in 2006, resulting in a drop on paper to 201 horsepower for the K20Z1. According to the new SAE method, the 2005 Type-S would have produced 201 horsepower as well.
Acura discontinued the Integra/RSX line worldwide after the 2006 model year. It was only recently resurrected for the 2023 model year, with a completely new engine and chassis.
Acura RSX Engines
Before we get into the best RSX mods, let’s take a look at the various engines found inside the standard and Type-S models. For its entire run, the base RSX used the K20A3, the 2002-2004 Type-S used the K20A2, and the 2005-2006 Type-S used the K20Z1. All of these engines are naturally aspirated and part of the K20 engine series. Internally, they are all quite similar.
Engines K20A3 vs K20A2
All K20 motors have a 2.0 L (1,998 cc) displacement and an inline-four configuration. The K20 series engine has a bore and stroke of 86 mm x 86 mm, making it a perfectly square engine. Both the RSX and Type-S engines are DOHC and feature VTEC, Honda’s well-known proprietary VVT system. Honda rated the K20A3 at 160 horsepower and 142 lb-ft of torque, the K20A2 at 200 horsepower and 142 lb-ft of torque, and the K20Z1 at 201-210 horsepower and 143 lb-ft of torque.
The K20A2 is essentially a performance version of the K20A3. It has a higher compression ratio of 11.0:1 than 9.8:1 due to a new cylinder head and higher compression pistons. Honda equipped the K20A2 with a balanced crankshaft as well as dual valve springs for the upgraded i-VTEC system. The K20A2 also has a higher red line (7,900 RPM vs 6,800 RPM), more aggressive camshafts, and a higher flowing PRB intake manifold.
The K20A3 has VTEC-E, but only for the intake cams, and it is primarily used to improve fuel efficiency and emissions rather than horsepower. The K20A2 has Honda’s i-VTEC system, which uses both intake and exhaust cams to increase horsepower. Here’s a good breakdown of the VTEC-E vs i-VTEC systems.
The K20Z1 Engine
The K20Z1 engine has the same displacement and size block as the K20A3/2. It has the same PRB intake manifold as the K20A2, as well as the same 11.0:1 compression ratio, but it has a new exhaust manifold and even more aggressive camshafts. Honda raised the red line on the K20Z1 even higher than on the A2, to 8,100 RPM with an 8,300 RPM rev limiter. The K20Z1 i-VTEC engages at 5,800 RPM, as it does on the K20A2.
Top 5 Acura RSX Mods
The top five best Acura RSX mods (including Type-S) are:
- Cold Air Intake
- Exhaust Header and Cat-back Exhaust
- ECU Tuning
- Sway Bar
- Forced Induction
Now, let’s look at the top five Acura RSX and RSX Type-S mods. To keep costs down, we limited the list to basic bolt-on engine and suspension upgrades. This is not an exhaustive list of RSX mods, but it is a good starting point for your K20A/Z build.
Unfortunately, the RSX has become less popular over time, and as a result, there isn’t nearly as large an aftermarket community as there once was. By 2022, most of the popular and well-reviewed manufacturers from the RSX’s early-2000s heyday, such as Comptech, Greddy, and Cybernation Motorsports, will no longer be producing parts for the car.
Nonetheless, there is a decent RSX mods community out there building and racing K20 powered DC5 Integras. Depending on which RSX engine you start with, full bolt-ons can add 20-35 wheel-horsepower. While we won’t go into detail, swapping on a Type-S intake manifold and cylinder head to a standard RSX is another popular mod that results in decent gains.
1) Acura RSX Mod : Cold Air Intake
A cold air intake is by far the most popular mod for the Acura RSX and Type-S. They are not only inexpensive, but they also provide a reasonable performance boost on a naturally aspirated engine. Short ram and cold air intakes are the two types of RSX intakes. We strongly recommend the cold air over the short ram.
The short ram RSX intakes barely relocate the filter from where the stock airbox is, and they are prone to heat soak. In contrast, RSX cold air intakes relocate the filter very low in the engine bay. Instead of taking air from the top of the bay, which is extremely hot, the filter is routed to take air from behind the fog light grill area on the driver’s side. It is one of the few true cold air intakes for modern vehicles.
The following are the primary advantages of cold air intake:
- +5-15 horsepower
- improved throttle responsiveness
- Increased engine noise
- improved fuel economy
After installing a cold air intake, you should see 5-15 horsepower gains and the car will feel more responsive on the throttle. Moving the filter brings in cooler air, which increases oxygen content and thus horsepower. The tubing is also less restrictive and optimized for maximum flow.
In addition to the increased power, you will definitely hear your intake much louder than before. The whooshing sound of air being sucked in will be much more audible, indicating that your intake is working.
Finally, though it will be minor, there will be a slight improvement in fuel economy. The colder air allows the engine to work more efficiently, allowing it to produce the same amount of power while using less fuel. The difference is probably only 0.5-1.5 MPG, but it adds up over time.
Concerns Regarding the RSX Intake Hydrolock
When upgrading to a cold air intake, keep hydrolocking in mind. Hydrolocking occurs when the air filter becomes so saturated that it sucks water into the combustion chamber. Once water enters the engine, it will fail to compress and spark properly, which can have serious consequences for your internals.
Some argue that most upgraded RSX cold air intakes sit too low and risk hydrolock, while others argue that it’s not a big deal. In general, unless you completely submerge the air filter in water, such as driving through a flooded area, you should not be concerned. However, if you frequently drive in flooded or extremely wet areas, you may want to consider a short ram.
Top RSX Intakes
The AEM, Injen, and Comptech IceBox intakes are by far the most popular in the RSX community. The Comptech IceBox was one of the most popular intakes, but it has been discontinued for several years.
That means the real competition is between the AEM and Injen cold air intakes. Both offer short ram versions, but as we previously stated, we strongly recommend the cold air versions. We recommend the AEM RSX intake over the other two. It has dyno-proven performance and is very simple to install.
One thing to keep in mind is that when you install the AEM cold air intake, you will need to relocate the stock windshield wiper reservoir. This is because the filter is located where the stock reservoir is, allowing it to get as much cool air as possible. It’s not difficult to relocate, and AEM includes a new reservoir, but it’s something to keep in mind.
2) Best Acura RSX Mods : Header and Exhaust
After upgrading to a cold air intake, the next step for most RSX builds is to upgrade the header and exhaust. For the RSX, there are two types of headers: race headers and shorty headers. Because race headers do not use catalytic converters, they produce more power than shorty headers.
Because race headers are not street legal in most places because they lack a cat, shorty headers are often the only option for many people. After upgrading the header, the cat-back section of the exhaust is also ready for an upgrade.
Top RSX Header and Exhaust Benefits:
- +15-25 horsepower (race header)
- increased exhaust flow
- increased exhaust noise
- Back pain relief
On the K20-powered RSX and Type-S, upgrading the header will result in an increase of 15-25 horsepower. An upgraded header will have larger diameter piping, which means more exhaust flow, less back pressure, and more exhaust scavenging. With upgraded headers, your engine will be able to breathe easier and expel exhaust faster.
A larger cat-back exhaust will not have the same effect on power as a header, but it will definitely increase exhaust volume and improve the tone. Most race headers will not connect to the stock exhaust, necessitating the purchase of a new cat-back or adaptor.
Related : The Nissan 240Z vs 280Z Comparison
Best RSX Header and Exhausts
There are several options for upgrading the K20 header. We recommend the Private Label Manufacturing RSX race header. Their header is catless, 2.5″ in diameter, made of 304SS, and has a CNC machined flange. It is the best RSX header on the market right now.
Previously, the DC Sports Race header was the top of the line, but they now only make a shorty version. However, their shorty version is CARB compliant, making emissions legal in all 50 states.
The header we would recommend is from CompTech, but it is no longer in production. We recommend avoiding the Skunk 2 Alpha header due to known fitment and quality issues.
In terms of exhaust, the DC Sports cat-back and HKS cat-back are considered RSX standards. They both produce excellent volume and tone and are known for their good fitment and ease of installation.
3) ECU Tuning is one of the best Acura RSX mods.
After you’ve upgraded the intake, header, and exhaust, the next step is to investigate RSX ECU tuning. The ECU controls almost every aspect of the RSX engine’s operation, including its performance. You can add horsepower, torque, improve the power band, and optimize your mods by upgrading the RSX’s stock ECU tuning.
The upgraded intake and exhaust are designed to push more air into and out of your engine at the highest possible velocity. Tuning maximizes the benefits of these upgrades by optimizing parameters such as ignition timing, cam timing, and air-to-fuel ratios. After ECU tuning, you can expect your mods to increase performance by 15-20%.
ECU Tuning Options for the RSX
For basic tuning on the RSX, there are only two options: the Hondata KPro and the KTuner. They both do the same thing and have very similar characteristics. The KTuner allows for a little more customization than the KPro, but the KPro is more well-known among tuners in general.
For most people, the decision comes down to price. The KPro is less expensive to use on the 2002-2004 RSX and Type-S. The KTuner is the less expensive option for the 2005-2006 RSX and Type-S. This is due to the KPro’s ability to work with the ’02-’04 ECU without modification, but not with the ’05-’06 ECU. In comparison, the KTuner works without modification with the ’05-’06 ECU but not with the ’02-’04 ECU.
A complete standalone system, such as a Haltech or AEM EMS, is another option for RSX tuning. However, these are significant and much more expensive upgrades. A KPro or KTuner will suffice for almost all moderate builds.
4) Best Acura RSX Mods : Rear Sway Bar Upgrade
After we’ve looked at some basic engine upgrades, your next concern should be the car’s handling. The RSX is notorious for having a woefully inadequate suspension setup from the factory. While many people start with lowering springs or coilovers, we recommend starting with a larger rear sway bar.
The sway bar, also known as an anti-roll bar, is used to connect the left and right sides of the suspension. When a car turns, the weight shifts from both wheels to the outside wheel. The sway bar’s purpose is to clamp down on the springs on the inside wheel, keeping the car level and preventing body-roll.
When you start adding more power, the stock sway bar and rubber bushings are completely outmatched. Body roll can be reduced by using a stiffer and stronger sway bar with better bushings. A larger size improves overall stability.
Best Rear Sway Bars for RSX
The factory RSX sway bars are 18-21 mm thick, but most people upgrade to something 22-24 mm thick. There are numerous sway bar options available, and the majority of them perform similarly. Although top brand names such as Eibach, Whiteline, and Cusco are available, we recommend the Progress rear sway bar.
The Progress rear sway bar is 24 mm in diameter and features a brace, adjustable end links, and strong polyurethane bushings. It will definitely provide more traction when turning, and it is also known for its quietness.
Many sway bars, particularly adjustable ones, will pop and bang after installation, but the Progress is very gentle. If you’ve already upgraded some bolt-ons, a stiffer rear sway bar is a must before adding anything else.
5) Best Acura RSX Modifications: Forced Induction
For our final suggestion, we’re going with the big one: forced induction. To be clear, a turbo or supercharger is not the first modification you should consider. However, the K20A/Z engines found in the RSX are fairly limited in terms of power output with only bolt-ons. With natural aspiration, the K20 motors can only do so much. If you want decent power, you’ll need to add a blower.
There is some disagreement about how much power the stock engine can handle, but the general consensus is that it can handle quite a bit. Some supposedly stock K20A/Z motors are producing over 500 wheel horsepower with stock internals and a stock block. For us, 450 horsepower is probably closer to the limit before adding forged pistons, rods, and head studs for reliability.
Best RSX Turbo Kits
Greddy, Cybernation, HKS, RevHard, and Full Race, the most popular turbo kits from the RSX’s heyday in the early 2000s, are now all long discontinued and out of production. Instead, we recommend CX Racing’s turbo kit or a custom-made turbo kit from Full Race.
The GT35 turbo in the CX Racing RSX turbo kit is housed in a T3 housing. It can produce up to 450 horsepower and includes a bar and plate intercooler, as well as all intercooler piping and a downpipe.
For the K20 series engine, Full Race offers turbos, intercooler piping (charge pipes), intercoolers, exhaust manifolds, and more. Building your own kit through Full Race will undoubtedly be more expensive, but the quality will be far superior to the CX Racing kit. Furthermore, you can combine parts from the Full Race kit with custom fabricated parts to save money.
Keep in mind that the compression ratios of the K20s in the various RSX models and years vary. The K20Z1 has the most horsepower but also the highest compression ratio (along with the A2 at 11.0:1). The K20A3 9.8:1 ratio is much better for boosted motors, but it is also the least powerful out of the box.
The K20Z1/A2 still performs admirably, but it’s worth noting. Obtaining pistons with different compression ratios is one option that may be beneficial.
Summary of the Best Acura RSX Mods
While the Acura RSX and RSX Type-S are not performance vehicles out of the box, a few tasteful engine and suspension upgrades can really wake it up and make it perform on par with much newer vehicles. The K20 engine is one of the best Honda engines ever built, and all three RSX iterations respond to bolt-ons.
Whether you want a few extra horsepower to make getting on the interstate and merging easier, or a full-fledged 450 horsepower monster RSX terrorizing the streets, this guide can help you get there. Don’t forget to upgrade the suspension as well, or your newly powerful RSX will be difficult to control.