Best Turbo for 12v Cummins: Unlocking Your Diesel's True Potential
Alright, let's cut to the chase. You've got a 12-valve Cummins, and you're probably like me – absolutely love the mechanical simplicity and raw power these engines offer. They're legendary for a reason, right? But if you're reading this, chances are you're also thinking, "How can I make it even better?" And usually, that path leads straight to one of the most impactful upgrades you can make: a new turbocharger.
The quest for the best turbo for 12v Cummins is a journey many of us embark on. It's not just about more horsepower; it's about improved drivability, better EGT (Exhaust Gas Temperature) control, quicker spool-up, and honestly, a more satisfying driving experience. Whether you're towing heavy loads, tearing up the drag strip on weekends, or just want a more responsive daily driver, the right turbo can completely transform your truck.
But here's the thing, and I'll say it upfront: there isn't one magical "best" turbo that fits every single 12v Cummins owner out there. It really, truly depends on your specific goals, your budget, and what other modifications you're running (or planning to run). It's a bit like trying to find the "best" pair of shoes – are we talking running shoes, work boots, or fancy dress shoes? See what I mean?
Don't worry though, we're going to break it all down. We'll explore the popular options, what they're good for, and what you need to consider before shelling out your hard-earned cash. Think of this as a chat with a buddy who's been down this road a few times.
Understanding Your 12v Cummins: What Are We Working With?
Before we dive into specific turbos, let's just briefly touch on our platform. The 12-valve Cummins, particularly from '94-'98, came stock with an HX35 turbo. It's a decent unit for what it is – reliable and capable of around 200-220 horsepower, depending on the year. But it's also a choking point for anything beyond mild fueling upgrades. Boost levels are often limited, and EGTs can quickly climb if you push it.
Your 12-valve is a workhorse, a cruiser, or maybe even a beast waiting to be unleashed. Identifying its primary role is super important for turbo selection. Are you looking to keep it as a stock-ish daily driver with a little more pep? Do you regularly tow trailers that weigh more than a small house? Or are you aiming for big power numbers, maybe 500hp, 600hp, or even more, turning heads wherever you go? Knowing this upfront helps narrow down the choices dramatically.
Oh, and a quick word of caution: a turbo upgrade isn't always a standalone fix. These engines are incredibly robust, but if you're chasing serious power, you'll need to think about supporting mods like injectors, a beefier fuel system, head studs, and a transmission that can handle the extra grunt. We'll touch on those more in a bit.
The "Best Turbo" Depends on Your Goals: Let's Talk Scenarios
Since there's no one-size-fits-all answer, let's look at turbos through the lens of common usage scenarios.
Scenario 1: The Daily Driver/Light Towing Warrior (Reliability & Efficiency)
If your truck is your trusty daily companion, maybe hauling a boat or small camper on weekends, you're probably looking for something that offers a noticeable bump in power and responsiveness without sacrificing drivability. You want quick spool-up, good EGT control, and minimal lag. You're likely aiming for the 300-400 horsepower range, maybe pushing 450hp with other mods.
- Upgraded Stock Turbos (HX35/HY35 variants): For those on a tight budget or wanting minimal fuss, a modified stock turbo can be a good entry point. Swapping to a Wicked Wheel 2 compressor wheel in your HX35 can help with surge and slightly improve airflow. Some folks also run upgraded billet compressor wheels, like a 60mm, to get a little more out of the stock housing. It's a cost-effective way to get some improvement, but it has its limits.
- Small S300 Series (e.g., S362 or S363): This is where things start to get really good for daily drivers. Turbos like Industrial Injection's PhatShaft 62/65/12 (a 62mm compressor, 65mm turbine with a 12cm exhaust housing) are hugely popular. They offer significantly better airflow than a stock HX35, keep EGTs in check, and spool incredibly well. You get a solid boost in power and a much more responsive truck without crazy lag. They're a fantastic all-around upgrade for 350-450hp trucks. A 14cm exhaust housing option is available for slightly better top-end flow, but with a tiny bit more lag.
Scenario 2: The Heavy Hauler/Work Truck (Towing & Mid-Range Power)
When your truck's primary job involves pulling serious weight, your turbo choice shifts towards sustained EGT control and dependable mid-range power. You need a turbo that can hold its own up long grades without making your pyrometer scream for mercy. We're talking 450-550 horsepower here, where the truck can still work hard without feeling overly stressed.
- Mid-sized S300 Series (e.g., S363 or S364.5 FMW): Stepping up from the smaller S300s, options like an S363 FMW (Forged Milled Wheel) or a S364.5 FMW with a larger exhaust housing (say, 14cm or even 16cm) become your best friend. These turbos excel at maintaining lower EGTs under heavy load. The FMW wheels are more durable and efficient, helping with both spool and overall performance. BD Diesel's Super B Special (64/71/14) is another excellent contender in this category, known for its balanced performance and excellent towing characteristics.
- S366: While often found in performance builds, a well-matched S366 with a 14cm exhaust housing can also be a viable option for a heavy hauler, provided you have adequate fueling and supporting modifications. It offers excellent top-end flow for sustained power and EGT control, but you'll need to accept a slight increase in spool time compared to the smaller S300s.
Scenario 3: The Weekend Warrior/Performance Build (Power & Fun)
Now we're talking about making some serious grunt! If you're building a truck for drag racing, sled pulling, or just want a monster under the hood for pure exhilaration, you're likely aiming for 550+ horsepower. Here, you're willing to trade a little low-end responsiveness for a significant kick in the pants once the turbo spools.
- S366/S369SX-E: The S366 is a very popular choice for this power level. It's often seen as the sweet spot for a single turbo pushing 550-650hp. It spools decently for its size and really comes alive in the mid-to-upper RPM range. However, for maximum street performance and a better balance of spool and power, the BorgWarner S369SX-E has become a true fan favorite. It uses cutting-edge compressor wheel technology to spool incredibly fast for a turbo of its size, making 650-750hp (with the right fueling) very streetable. It's often considered one of the best turbo for 12v Cummins for high-performance single-turbo applications.
- S400 Series (e.g., S467.7, S472): If you're pushing past 700hp with a single turbo, you're likely looking at the larger S400 series. Turbos like the S467.7SX-E or an S472SX-E can deliver huge power, but they will have more lag. These are serious turbos for serious builds, and require extensive fueling, head studs, stronger valve springs, and often upgraded piston cooling nozzles. They're usually seen in dedicated competition trucks, or as the "atmosphere" turbo in a compound setup.
Key Factors to Consider When Choosing
Alright, so you've got an idea of the categories. Now, let's nail down some critical considerations that will guide your final decision.
1. Horsepower Goals
Be realistic here. Do you really need 700hp, or would 450hp make you perfectly happy? Over-turboing a truck can lead to excessive lag and an unhappy driving experience, especially if you haven't matched it with the right fuel.
2. Intended Use
We've covered this, but it bears repeating. Daily driver, tow rig, race truck – your primary use case is paramount.
3. Budget
Turbos can range from a few hundred dollars for a basic upgrade kit to several thousand for a high-performance unit. Don't forget to factor in installation costs if you're not doing it yourself, and most importantly, the supporting modifications.
4. Supporting Modifications (Crucial!)
This is where many people get tripped up. A big turbo without the fuel to back it up is just a paperweight. * Fuel System: You'll need bigger injectors (often 5x12, 5x14, or larger), a capable lift pump (like an FASS or AirDog), and potentially modifications to your P7100 injection pump (e.g., governor spring kit, delivery valves, rack plug, custom fuel plate). The more air your turbo shoves in, the more fuel you need to burn to make power. * Air Intake & Intercooler: Make sure you have a free-flowing air filter system and consider an upgraded intercooler, especially with higher boost levels, to keep intake air temperatures down. * Exhaust System: A 4-inch or 5-inch straight pipe system is practically mandatory to let that exhaust flow freely and reduce backpressure. * Transmission: Stock 47RH/RE automatics or NV4500 manuals generally start to complain around 400-450hp. If you go beyond that, plan for a built transmission (new clutches, valve body, input/output shafts, etc.). * Head Studs: Absolutely critical if you're pushing past 450-500hp. ARP head studs prevent the cylinder head from lifting under high boost, saving your head gasket and potentially your engine. Don't skimp here! * Valve Springs: If you plan on spinning the engine higher RPMs or running high boost, stronger valve springs can prevent valve float.
5. Spool-Up & Lag
This is the balance you're always chasing. Smaller turbos spool fast but choke at higher RPMs. Larger turbos offer huge top-end power but take longer to build boost. Find your happy medium.
6. EGT Control
Keeping EGTs in check is vital for engine longevity. A well-matched turbo will help you maintain safe temperatures, especially when working the truck hard.
Popular Brands and Series to Look Out For
When you're shopping around, you'll hear these names come up a lot: * BorgWarner: Their S300 and S400 series turbos, especially the SX-E line, are incredibly popular and well-regarded for their performance and durability. * Holset: The OEM turbos, but also offer upgraded versions of the HX35 and HX40. * Industrial Injection: Known for their PhatShaft and Silver Bullet turbos, which are often highly customized BorgWarner units. * BD Diesel: Their Super B series are solid choices, particularly for towing and street applications.
Installation and Tuning Considerations
Once you've picked your turbo, remember that installation involves more than just bolting it on. You'll need new gaskets, potentially different oil feed and drain lines. You'll likely need to adjust your AFC (air-fuel control) on the injection pump to properly match the increased airflow. If your new turbo has a wastegate, you might need to adjust boost pressure. If it doesn't, ensure your setup can handle higher boost. Sometimes, professional installation and tuning by a reputable diesel shop are the best ways to ensure everything works together safely and efficiently.
Conclusion: Your Dream Turbo Awaits!
So, what's the best turbo for 12v Cummins? As you can see, it's not a simple answer. It's the turbo that best aligns with your specific needs, your driving style, and your budget, all while being supported by the right fuel and other mods.
Take your time, do your research, and be honest with yourself about your goals. Talk to experienced friends, hit up some forums, and don't be afraid to reach out to reputable diesel performance shops for advice. They've seen it all and can steer you in the right direction.
The 12-valve Cummins is an amazing platform, and with the right turbo, you can truly unlock its full potential. Happy wrenching, and enjoy that newfound power!