Float like a Butterfly, Sting like a Kia? - Performance Intercooler R&D, Part 6 - Blow-Off Valve Adapter
Kia is just the latest manufacturer to add the symphony turbocharging to their line of vehicles with the whirring and hissing duo attached to the Lambda II GDI engine powering the 2018+ Stinger GT. With the addition of these mechanical snails to Kia's repertoire, it's not much of a surprise that enthusiasts want to crank up the boost. And while it's imperative to improve the capacity of the intercooling system when tuning the Stinger, it's just as important to ensure it can handle the extra PSI. Specifically, the recirculation valve system needs to be up to snuff.
Luckily, the engineers here at Mishimoto have already been cooking up the means to adapt a more robust blow-off or recirculation valve of your choosing, but before we dive into that, let's take a quick look at why bypass valves are so important. For a more in-depth look, make sure you head to our technical post on blow-off valves.
Reduce, ReUse, Re-PSSSHT
If you've ever peeked under the hood of your Stinger GT, you might have taken notice of the twin recirculation valves perched on top of the intercooler merger pipe. These valves utilize a pneumatic piston to recycle unused boost pressure back into the intake when off-throttle to protect the compressor wheels on the turbos from compressor surge.
I'm sure you've heard it before on highly modified turbocharged vehicles, the characteristic "STUSTUSTU" coming off of hard throttle. That sound is known as closed throttle compressor surge. When the plate in the throttle body snaps closed, the turbos are still spinning, and sending boost pressure through the system. Since that compressed air has nowhere to go, it bounces off the closed throttle plate, and heads straight back for the turbos. Once it reaches the turbo compressor housing, the compressor wheel begins to stall and can no longer push air out of the turbo. The air forces its way back into the intake until the pressure ahead of the turbo drops and the compressor can force the air forward again. This cycle repeats as the pressure ahead of the turbo builds and falls, causing the tell-tale chuckle sound.
The negative effects of compressor surge aren't immediately detrimental to the longevity of the turbos equipped on your vehicle. In small doses, it can cause a slight lag in the spool-up once you're back on throttle; but prolonged surge places a lot of stress on the compressor wheel and bearings and can mean replacing a turbo sooner than expected.
To combat compressor surge and premature turbo failure, a blow-off or recirculation valve needs to be placed between the turbo and the throttle plate. Essentially, these valves house a pneumatic piston that allows the unused boost to be vented from the system. When the throttle plate closes, vacuum is applied to the blow-off-valve piston, and combined with the pressure in the system, opens the valve allowing the excess boost to vent into the atmosphere, or recycle back into the intake tract.
When it comes to the Stinger's recirculation valves, Kia added a few more pieces to the system for quicker response. First, you might have noticed a large square growth stemming from the intake plenum. This is a vacuum chamber designed specifically for actuating the Stinger's recirculation valves. The chamber is controlled by a check valve (to ensure that it's always in vacuum) and an electronic solenoid that activates the valves.
The idea behind a bigger BOV is to keep up with the extra boost that needs to be evacuated from the system as the vehicle is tuned. Simply put, the more boost you command from your turbos, the bigger the BOV needs to be in order to properly protect against compressor surge (the added soundtrack is a bonus). For that reason, we did some research on the popular choices of blow-off valves for the Stinger and got to work on creating our adapter.
We started with the mount. Given the popularity of Tial's 50mm Q valve, we worked with them directly and initially used this valve as the inspiration. We opted for a 2" opening, which works perfectly for not only Tial's Q valve but a wide variety of other aftermarket blow-off valves as well. To ensure a wide range of fitments, as well as a perfect seal, we opted for a V-band clamp mount. This method of mounting will hold up to just about any amount of pressure running through the system, without the need to weld anything to your intercooler piping.
After the mount came the legs for our adapter. Seemingly modeled after a body builder, these legs match up perfectly with the mount we carved out on our merger pipe. In order to minimize the potential for boost leaks, we opted for a cast-aluminum construction, followed by CNC machining to perfectly shape the mount and feet. To further ensure the boost stays in the system, the feet are secured with a pair of Viton O-rings.
One Step Further
Now, we couldn't spend all this time on an adapter for aftermarket blow-off valves and then leave you without a tasty sound bite of the mighty twin-turbo V6 having a hissy fit. Well, we tried, but the Kia's power plant turned out to have a fit in a different sense, which lead us down quite the rabbit hole.
The Stinger might now hold the Mishi record for most consecutive dyno pulls. After installing our Tial 50mm Q blow-off valve, the Stinger was silent. Not a single "fun" sound made its way out of the blow-off valve, and Dan wanted to find out why. After two days on the dyno, and plenty of data crunching later, we got to the bottom of it.
Remember just a few paragraphs up when we mentioned that the Stinger had a vacuum chamber actuated by a solenoid specifically for the factory recirculation valves? Well, if you did your homework, and took notes on our blow-off valve tech post, you might already be putting the pieces together. That chamber is sized to pull just enough vacuum to actuate the stock recirculation valves, whereas with the Tial's Q equipped in the softest spring configuration, the Stinger's build in vacuum chamber still couldn't move the piston effectively.
Even with our stage 1 tune loaded on the Stinger, when we were able to actuate the valve it was on a slight delay. The simple explanation: while this is a serious BOV, it's overkill for the Stinger. Tial specifically designed this valve for 1800 horsepower dragsters, which even the most powerful Stingers are still a few hundred HP behind.
When it comes to running aftermarket blow-off valves on your Stinger, there are other options. First, if you're dead set on the mega Q valve, there is a means of bypassing the vacuum chamber, taking the electronics out of the equation, and tapping directly into the manifold. We still noted a slight delay in the performance, but we were able to have the valve operate as intended.
The second option is to opt for a more appropriately sized blow-off valve. Per suggestion from our contacts at Tial, we installed the tamer, 900HP rated, QRJ valve. The horizontal orientation, as well as the tapered piston design, means much less vacuum is required to actuate the valve giving you that satisfying sound every time you lift off the gas pedal and, more importantly, keeping your turbos safe.
When modifying any vehicle, going with the biggest option is typically the name of the game, but in some cases, it's going with just the right size. That's especially true when it comes to the blow-off valve options for your Stinger. With our 2018+ Kia Stinger GT Blow-Off Valve Adapter, you have the option to pick the best valve to suit your build.
Thanks for Reading!