Since its debut in 2018, the Kia Stinger has made a name for itself as one of the premiere sports sedans of the modern age. When equipped with the GT2 package, the Stinger puts down 368 horsepower and 376 lb-ft of torque through a twin-turbocharged 3.3 liter V6. While that is already good for a zero to 60 mph time of just 4.7 seconds, the Lambda II engine is just begging to be unleashed with more power.
Enter Kia Stinger downpipes upgrades. Upgrading from the restrictive OEM Stinger downpipes is one of the best ways to improve turbo spool and increase horsepower and torque.
What are Downpipes?
The Kia Stinger is a relatively new sedan, with Kia just introducing it for the 2018 model year. Since its debut, Kia has opted to use the Lambda II 3.3 liter twin-turbocharged V6 engine in the higher performance GT2 trim. As of 2023, it produces 368 horsepower and 376 lb-ft of torque. This is the same engine that Hyundai uses in their high-performance G70, G80, and G90 Genesis. Previously, when we looked at the top Kia Stinger performance mods, we listed downpipes as one of them.
Downpipes are the part of the exhaust system that connect directly to the twin-turbochargers. The purpose of the downpipe is to collect the spent exhaust gasses exiting the turbochargers and direct them through the rest of the exhaust system For the Stinger, there are two downpipes, one for each turbocharger. In addition, the downpipes themselves consist of two parts, the primary downpipe and the secondary downpipe. Sometimes, people refer to the secondary downpipes as the midpipe, but it’s the same thing.
The purpose of upgrading the Stinger downpipe is to reduce the amount of back pressure in the exhaust. This is done by increasing the diameter and/or replacing the OEM catalytic converters. By using larger diameter piping, the exhaust gasses are able to exit the engine with greater velocity. This allows for more horsepower and torque, as the engine can replenish itself with cleaner air more quickly. In addition, upgrading the cats also reduces restrictions and allows for better flow.
Kia Stinger Primary vs Secondary Downpipes
As we mentioned, the Stinger is somewhat unique in that they split the downpipe into two parts, the primary and secondary downpipes. Both the primary and secondaries have catalytic converters in them, but of the two, the primaries are much more restrictive. This is because of their location, being literally inches from the turbochargers themselves. This creates a ton of restriction and back pressure, which really harms power output and prolongs turbo spool.
The real performance gains from Kia Stinger downpipe upgrades are from swapping out the primary downpipes. The primary downpipes can net as much as 50 horsepower, even with high-flow cats, when paired with catless secondary downpipes. In comparison, catless secondary downpipes by themselves will only net about 5-10 horsepower. As of now, there are no HFC secondary downpipes available for the Stinger, so catless is the only option.
For the most part, people upgrading the secondary downpipes will notice an improvement in exhaust tone, as well as a healthy bump in noise level. They really deepen the exhaust note and make it sound very aggressive and mean, but will not add much in terms of performance.
409 vs 304 Stainless Steel
When purchasing a Kia Stinger downpipe, typically there are two options: Either 409 stainless steel or 304 stainless steel. For the most part, high performance exhaust systems are made largely out of 409, because it presents a good balance of cost and corrosion resistance. It also polishes nicely, and is much cheaper than the next step up, 304.
304 is the top dog for mass produced performance exhaust material without using titanium. It looks sleek, polishes very nicely, and is even more corrosion resistant than 409 – hence the increased cost. Compared with 409, 304 has double the amount of chromium, and more than 20x the amount of nickel, which is what makes it so corrosion resistant. It’s often referred to as marine steel because it even holds up to repeated use in saltwater. 304 can turn gold after repeatedly being subjected to high heat.
For most people, a 409 exhaust will be a good compromise of price and performance/longevity. In most climates, 409 will be more than fine for lasting several years without succumbing to any corrosion or rust.
Kia Stinger Downpipe Upgrade Benefits
- +15-50 horsepower
- +15-50 lb-ft of torque
- Improved turbocharger spool
- Decreased back pressure
- Increased turbocharger efficiency
Upgrading the downpipes on the Kia Stinger is one of the biggest bangs for your buck on the Lambda II equipped GT2s. While tuning is required, you can pick up an astonishing 50 horsepower and 50 lb-ft of torque with downpipes and tuning. That even includes high-flow cat versions and not just catless.
The factory downpipes on the Stinger are incredibly restrictive, and have a tiny 1.25” exhaust port opening to go with a subpar 2.0” diameter. Most aftermarket downpipes are at least 2.5” in diameter, which allows for a serious reduction in back pressure. As we explained earlier, reducing back pressure is paramount when increasing performance through a downpipe.
The decrease in restriction will also allow for the turbochargers to work more efficiently, as well as to spool quicker and reach peak boost earlier. This means a widely improved power band and not just better peak numbers. You’ll instantly notice an improved throttle response from upgraded Stinger downpipes.
High-Flow Cats vs Catless
Generally, catless downpipes will give you better power potential then catted downpipes, but it’s important to keep in mind that in most areas catless downpipes run afoul of local emissions regulations. High-flow catted downpipes allow for almost the same amount of performance while staying street legal. In addition, catless downpipes are known for smelling absolutely terrible, something catted units mostly eliminate. This is due to the raw emissions flowing from the engine, which have very minimal filtering without the cats.
Even though both the primary and secondary downpipes have catalytic converters, 90% of the gains come from swapping out the primary cats. The secondary cats are much further downstream in the exhaust, and while they do offer some performance benefits, it’s very tame compared with upgrading the primaries. As of now, there are both HFC and catless primary downpipe options, but only catless secondary downpipes.
It’s important to keep in mind that upgrading the downpipes, primary OR secondary, will require some form of tuning solution. Without a tune, your turbochargers will likely start to overboost. This will cause lean conditions and may also cause the ECU to overcorrect itself, resulting in lower boost pressure and uneven performance. You can check out our top 5 Kia Stinger performance mods guide for more info on Kia Stinger tuning.
Top Kia Stinger Downpipes
- Ultimate Performance
- ARK Performance Secondary Downpipes
There are a ton of different downpipes for the Kia Stinger available, and we have narrowed them down to the top 3. The Ultimate Performance, IMR, and ARK Performance Kia Stinger downpipes are the consensus for the best downpipes on the market. They combine excellent welding with solid engineering to deliver outstanding products. These are not the only downpipes available, but they are definitely the most reliable.
1. Ultimate Performance Downpipe and Midpipe Set
First up, we have the Ultimate Performance Kia Stinger HFC downpipes and catless midpipes set. For many people, the Ultimate Performance downpipes and midpipes (primary and secondary downpipes) are the best option. They use 304 stainless steel and are 2.5” in diameter with a 2.4” exhaust flange. UP back-purged the TIG welded the units, and they look outstanding.
These downpipes come with Magnaflow high-flow catalytic converters in the primary downpipes and the secondary downpipes are catless. They deliver a solid 46whp and 62wtq gains according to the manufacturer. They are direct bolt-on fits and offer serious performance gains. You can’t go wrong with UP downpipes and midpipes, and they look, perform, and sound outstanding.
2. IMR Kia 3.3T Downpipes
Next up we have IMR’s Kia Stinger primary and secondary downpipes. IMR has two flavors of downpipes for the Lambda II: IMG Kia Stinger catless downpipes and IMR Stinger HFC downpipes. In addition, they also have catless secondary downpipes that are available separately for a complete kit. The IMR downpipes are the same diameter as the Ultimate Performance downpipes, and they also use 304 stainless steel with backpurged TIG welding.
Though it is not as popular, the IMR primary and secondary downpipes will perform just as well as the UP downpipes. They are basically the same, and the cats are only 200 cells, which are not very powerful (but better for flow). Price wise, the difference between a HFC IMR set and a Ultimate Performance HFC set is pretty minimal, so it’s really a complete toss up between the two.
3. ARK Performance Secondary Downpipes
Our last recommendation is for the ARK Performance Kia Stinger catless secondary downpipes. These downpipes only replace the secondary downpipes and leave the primaries in place. Since the primary downpipes are by far the most restrictive of the two, gains are somewhat muted with just secondary downpipes. Still, they will add some performance and improve turbo spool. The ARK secondary downpipes are 304 stainless steel and full 2.5” like the Ultimate Performance and IMR units.
For most Kia Stinger owners, replacing the secondary downpipes is more about improving the tone and less about horsepower and torque gains. Dyno comparisons have only shown repeatable gains in the 5-10 horsepower range, though they do make the torque line more consistent. There are two main secondary downpipe manufacturers, ARK and Jun BL, and of the two the ARK are priced much cheaper while still performing the same.
Kia Stinger Downpipe Upgrade FAQ
Kia Stinger downpipes collect the exhaust gasses from the turbo and direct them through the exhaust. Upgrading to aftermarket Kia Stinger downpipes will increase horsepower and torque while improving turbo spool.
With high-flow Kia Stinger downpipes, gains can be as much as 50 horsepower and 50 lb-ft of torque.
Upgrading the Kia Stinger downpipes will add horsepower and torque and improve turbocharger spool. You can gain as much as 50 horsepower and 50 lb-ft of torque from upgrading the downpipes.
The Kia Stinger uses two sets of downpipes, an initial set of primary downpipes and set of secondary downpipes attached to them. The primary downpipes connect to the turbochargers, and both sets of downpipes have catalytic converters in them.