While no additional mods are necessary for building a 3.8T, there are some components that can help you improve your vehicle’s traction, performance, engine thermal management, or handling. The below components are a good example of what you could consider as you grow your car’s capabilities. But let’s be very clear: you do not need any additional mods that the Remnant Performance turbo kit doesn’t provide. You do not need to build your motor. You do not need water/meth. You do not need risers. You do not need a new radiator. A bone stock GC 3.8 is ready.
What is a good exhaust?
The Remnant Performance turbo kit is sized for Magnaflow and Solo Performance catbacks, which use the OEM distance between the 3.8 downpipes (note: you will no longer use your OEM downpipes with this kit). Because the OEM downpipes also support lateral movement with a flex joint, other exhausts are often sized differently expecting the adjustable downpipes you will no longer have. That means kits other than Solo and Magnaflow may not bolt straight up. An exhaust shop will need to heat your catback at the downpipe connection and expand or contract the distance between the first set of flanges to correct this, and should cost not more than $100 for an hour of shop time.
More broadly, it’s important that your exhaust provides sufficient airflow to move air out of the turbo. This will maximize your performance. Dual exhausts should be at least 2.5” from the downpipes back, and single exits should be at least 3.5” from the downpipes back. Exhausts with lesser airflow (e.g. 3” single exit) will reduce performance by up to 30 HP.
For more info on proper exhaust design for the Genesis Coupe 3.8, please visit this knowledgebase article.
Can I run headers?
All of the headers on the market are designed for the naturally aspirated Genesis Coupe, meaning the tubing is longer than it needs to be and will introduce turbo lag. Also, most of the models are too long or too short for proper fitment with a turbo kit, which can make for frustrating installation and/or a leaky exhaust. But now there is one perfect option: the Remnant Performance 3.8L Turbo Kit Headers!
The Remnant Performance headers are the perfect length for interfacing with the Remnant Performance turbo kit. They also replicate the size and shape of the OEM headers, which will aid with ease of installation and maximize performance after install.
In truth, the OEM headers are pretty good except for the unfortunate fact that they come attached to the primary catalytic converters. So moving to an OEM-like design--a design called the “log style”--without the catalytic converters will improve spool times by 200-300 RPM and improve power by 15-20 WHP. This is probably the best bang-for-the-buck upgrade you can make.
Before purchase: Please be certain that you can pass emissions testing (if any) in your state without primary catalytic converters. Installation of these headers will automatically result in check engine line (CEL) code P0420 and P0430 indicating primary catalytic converter failure or unreadiness. It is your responsibility to investigate your state or county requirements before proceeding.
What is a good radiator upgrade?
The CSF 7038 and Koyo koyVH13059 have confirmed fitment with both BK1 and BK2 Genesis Coupes running the Remnant Performance Turbo Kit. If you have an automatic transmission, you will also need to add a standalone transmission cooler. This radiator will improve your engine’s thermal management, as it is thicker than the OEM option. However, you should not feel like a new rad is a required component. Coolant temperatures are not the weak point of the engine, but every little bit can help if you're looking to maximize your platform.
I have an automatic transmission. Do I need a cooler?
Automatic Transmissions should seriously consider an external transmission cooler to ensure your AT’s performance and reliability. Remnant Performance customers can purchase one for $125.
What wheels and tires should I run?
This is a big topic in the Gen community, and this FAQ will not give you guidance on slammed fitments. Slammed fitments reduce your ability to put power to the ground, and negatively impact handling of the vehicle. The below fitments are strictly designed to balanced fitments for maximum traction. Some of them may require fender rolling if you want to get low. Please ask.
We recommend our customers run the following wheel/tire configuration:
19” Setup (Example Image)
- Front: 19x9.5+20 wheel and 245/35R19 tire
- Rear: 19x10.5+25 wheel and 305/30R19 tire (or 295/35R19 tire)
18” Setup
- Front: 18x9.5+20 wheel and 245/40R18 tire
- Rear: 18x10.5+25 wheel and 305/35R18 tire
Other Options (YMMV)
REAR Tire Options
An ultra-high performance (UHP) tire is recommended for traction, with Summer > All Season if your climate allows. Good options include:
- Federal 595 RS-RR
- Federal 595 RS-PRO
- Toyo Proxes R888R
- Continental Extreme Contact
- Michelin Pilot Sport 4S
- Michelin Pilot Sport Cup 2
FRONT Tire Options
You can easily consider a less expensive front tire option, as your traction is less dependent on these tires. Good options include:
- Ohtsu FP8000
- Achilles ATR Sport 2
- Firestone Firehawk Indy 500
- BFGoodrich g-Force Sport COMP-2
- Nitto NT555 G2
- Hankook Ventus V12 EVO2
What are some good coilover/suspension upgrades?
Good coilovers can improve traction and keep your car level in the corner. Good options include: PartsShopMax (“PBM”) Competition, KW Variant 3, Bilstein B14, Stance Pro Comp 3, BC Racing BR Type. Beyond coilovers, there are additional options that can improve your ability to create traction and stability. These are hardly required, but are interesting options for someone looking to take their gen to the next level.
Genesis Sedan Subframe Swap: The rear subframe from the 4.6L Genesis Sedan (model years 2009 through 4/6/2011) is compatible with the Genesis Coupe. It is significantly stronger, with tubular steel and gusseted steel reinforcements in the corners. Genesis Coupes pushing substantial power, or drag racing, can sometimes crack or warp the stock subframe. The Genesis Sedan subrame is a ~$300 replacement option, if you can find one at a junkyard, but it does bolt right up to the Genesis Coupe.
PartsShopMax Multi-Link Rear Arm kit: Significant reinforcement and rigidity in the rear suspension, plus extensive adjustability for perfect alignment. There's a lot more to know about this kit, and rear arms are complicated. Please see this Genesis Coupe Rear Suspension PDF for more detailed info.
PartsShopMax Solid Subframe Risers: corrects the rear suspension geometry if the vehicle is lowered.
Exceladyne Polyurethane Differential Bushings: eliminates the flimsy rubber bushings that can dry rot and/or induce wheel hop through deformation.
Upgraded Sway Bars: There are many options, but Whiteline-brand sway bars are proven solutions for the Genesis Coupe that serve this car well.
Can I make my car lighter?
Shedding weight is an easy way to improve your performance, with every 50 pounds being equal to another ~10 HP. The Remnant Performance Seraph CF Trunk and Remnant Performance Seraph CF Hood can shave those precious pounds and improve your vehicle’s performance. Don’t forget to remove your spare tire and have a tow truck on speed dial if you get a flat! ;)
As an added bonus, the Seraph CF Hood has functional heat extractors that can improve heat removal from the engine bay. Turbos are hot!
Do I need to upgrade the clutch in my manual transmission?
The stock clutch can handle the increased power of 3.8T... if you’re careful. Several 3.8T customers have put significant mileage on their clutch, while more aggressive drivers have burned theirs in a few thousand miles. It’s not required that you upgrade the clutch, but any significant increase in power on a car suggests that you should upgrade the clutch.
- Good: Competition Clutch Stage II with Valeo Slave Cylinder
- Better: SPEC Stage 3+ or Competition Clutch Stage 3 with Valeo Slave Cylinder
- Best: MT Motorsports Dual Clutch and Slave Cylinder package (for built 3.8T)
Additional nice-to-haves include the Exceladyne Shifter or CoolerworX Shifter, plus a Megan transmission mount.
Can I use e85 fuel? Other platforms use it with turbo!
Short answer: Sort of.
Longer answer: Fuels with higher-than-gasoline ethanol content (e.g. e85 @ 85% ethanol) are prized for their ability to:
- Reduce engine intake temperatures (cooler intake charge)
- Add more oxygen to the engine (ethanol has a higher O2 content than petrol)
- Advance engine timing (more performance)
- And clean the engine
It’s no surprise why many other platforms use e85 alongside turbo! However, e85 has less energy per molecule than petrol, so it requires 30% higher fuel consumption for the same horsepower. This puts an additional load on the vehicle’s injectors. We can overcome this limitation on BK1 with larger replaceable injectors, but we presently have limited control over the BK2 direct injectors and they cannot be replaced.
This is what leads to comments about “running out of fuel.” The 1.3X fuel requirements of e85 may cause the injectors (under our current understanding) to reach 100% capacity too soon to match e85’s higher power potential with a corresponding fuel supply.
To put it another way: our current best understanding is that the engine will attempt to provide XXX performance to you, but the injectors will need to work 30% harder to keep up with the demand. Because our ability to control the injectors is limited, we may be unable to make them perform at the level demanded by the engine. If that happens, the injectors cannot push any more fuel and the performance of the engine becomes artificially limited. So even if e85's benefits could theoretically allow you to run the engine harder, there's not enough fuel to do the work.
There is ongoing work in the AlphaSpeed tuning network to improve our understanding and control of e85+turbo to overcome this situation.
The current state of R&D is this: one Remnant Performance customer is running e85 + 70mm turbo. It is fair to say this configuration is largely untested, but not impossible to run. Our best guess suggests that we may be able to improve WHP by ~35 with e85 (on the 72mm turbo kit), provided that we don’t run into the aforementioned injector fueling limits. Going beyond the stock Remnant Performance 6 PSI on e85 is not possible at this time on BK2; but is doable on BK1 with an aftermarket ECU (Haltech).
As an aside: if you want to live experimentally and tune for e85 fueling, please see this Q&A for the required steps and components.
Can I use water/meth with the Remnant Performance Turbo Kit?
Please read this answer thoroughly: water/methanol (W/M) injection is a powerful tool, but carries its own risks. You should proceed with extreme care and caution.
Yes, it is possible to tune for W/M and turbo. A Snow Performance Stage III kit is advised for this application--the standalone controller is good and doesn’t require a gauge pod.
Running W/M can:
- significantly reduce your intake air temp ("intake charge temp");
- raise fuel octane levels;
- clean the GDi valves on BK2;
- reduce exhaust gas temperature (EGT)
These benefits can enable more aggressive tuning ("advanced engine timing") and inhibit the untimely fuel ignition ("knock" or "pre-ignition") that kills motors. In short: W/M is a very potent performance enhancer if the correct safety precautions are used. Don't get excited, yet.
Customers installing a W/M configuration should use multi-port injection, rather than throttle body injection, to ensure even distribution to the cylinders. The 3point8performance manifold riser with NPT ports, for meth injection, is ideal for this application.
HOWEVER… tuning for W/M will make your engine depend on a steady supply of W/M for proper operation (AFR). Should you have a clog in your line(s), pump failure, solenoid failure, dry tank, or another event that interrupts W/M supply, your engine could easily run lean and cause catastrophic damage. It is highly advised to use a W/M controller that can cut boost in the event of W/M loss or lean AFR. The author of this FAQ personally recommends that you tune without meth, then add the meth solution ontop for additional cooling and safety.
W/M is also not a magic bullet. It will not magically solve for the mechanical weaknesses in your motor that prevent pushing higher boost levels. It is to be used judiciously, to be used wisely, but it is not a one-way ticket to more performance.
If you intend to go water/meth, a good setup for the GC would be:
Snow Performance Stage 2.5 meth kit (steel lines, 4AN fittings)
Snow Performance trunk relocation kit (steel lines, 4AN fittings)
DevilsOwn 6-Cylinder Distribution Block (steel lines, 4AN fittings)
6x ProMeth 75CC nozzles (⅛” NPT fitting)
JRC or 3point8performance manifold riser (with ⅛” NPT taps)
- NOTE: Not all carbon fiber hoods will fit once your intake manifold has been elevated with a riser. Please verify fitment.
I want to build my Genesis Coupe 3.8 motor. Who should I talk to?
You should contact Travis Buechler of MT Motorsports in Las Vegas, NV. MT Motorsports is the premiere engine specialist for the Hyundai Genesis Coupe and other KDM platforms.
Travis has many performance-enhancing options for your engine, including: custom pistons, rods, sleeves, stronger head studs, stronger main studs, dry sump oiling, and more. Very little of this is DIY at this time. There is no builder in all of North America that has more expertise with Hyundai engines. These engines have bizarre quirks, unusual weaknesses, and tricks only learned through working on hundreds of motors. You should not trust your Gen's motor to a build shop that does not specialize in them, no matter how good the price sounds. You've been warned.
Will I benefit from a manifold riser?
A manifold riser improves volume in the intake runners and, more importantly, increases the length of the runners for air to reach optimal velocity for natural aspiration. However, a turbo essentially replicates these benefits by forcing air into the engine at high velocity via above-atmospheric pressure. Therefore adding a manifold riser does not contribute anything additive on top of your turbo. And while there is no performance benefit to the turbo, the risers drilled with 1/8" NPT ports are required for direct cylinder W/M installs. Please also note that the riser + manifold height may be too tall for some carbon fiber hoods!
Can I use an engine leash?
Maybe. The engine leash runs through the area recommended for the Remnant Performance windshield wiper reservoir. You can eliminate this tank or find a new spot for it if you wish to use the leash. In place of the leash, you could purchase polyurethane-filled motor mounts.
Should I use a grounding kit?
Maybe. There is evidence to suggest that some Genesis Coupes have poor electrical grounding from the factory, which reduces battery voltage delivered to the vehicle. While sagging voltage is not generally harmful, it can limit the performance of devices like the fuel pump when they are being pushed harder than the OEM engine would demand. In the fuel pump example, the vehicle would demonstrate "top-end breakup" or inconsistent performance at the top end of its power band. This is because the fuel pump cannot keep up with the fueling demands requested by the tune/ECU. A ground kit would definitely help in these cases, and we have seen 2.0T and 3.8T cars push more power and behave more consistently with a better ground. It certainly can't hurt, and it's not expensive.