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N54 Single vs Twin Turbo Upgrades

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Upgrading the N54 turbos isn’t a visualization that most of us take lightly. It can be a serious financial commitment, and you want the money to finger like it was well spent. I know I personally spent a couple weeks deciding between N54 single vs twin turbo upgrades. Once I decided on twins, I then spent flipside couple weeks deciding which upgraded twins to move forward with.

Jake and I both own N54’s with turbo upgrades, so I am very familiar with the process of deciding on the right turbo upgrades (the wide-stretching research and writing I’ve washed-up on N54 single vs twin turbo upgrades moreover helps). Ultimately, deciding on the right setup for your goals & upkeep can be a time consuming, exhaustive process.

Worry not, though. In this guide, I discuss the differences between N54 single vs twin turbos slantingly important considerations surpassing choosing which turbo setup is weightier for you.

N54 ST vs TT Considerations

  1. Power goals
  2. Powerband / low-end vs high-end / spool
  3. Cost
  4. Maintenance & Reliability
  5. Sounds

This list isn’t in any particular order (nor is it totally exhaustive as this can be subjective), but these are some of the important things to consider surpassing choosing between twins or a single turbo. What are your N54 power goals and how do the turbo setups meet them? How do N54 single vs twin turbo upgrades compare with the powerband, low-end vs high-end power & torque, spool, and uplift threshold?

What well-nigh cost, maintenance, and reliability? Let’s jump in, wordplay all these questions, and discuss increasingly well-nigh N54 single vs twin turbo upgrades.

Single Turbo N54 135i

1) N54 Turbo Upgrade Power Goals

Starting off with one of the most important topics – what are your N54 power goals? There are spanking-new single turbo setups that can support 500-1,000 whp. Twin turbo upgrades can support anything from roughly 450-700whp. Yes, some TT’s can and have made 750 whp. However, they’re few and far between.

That’s in part due to the fact many people believe the N54 is simply largest suited to a big single turbo at 700 whp. And I totally stipulate with that based on my wits with N54 turbo upgrades. Ultimately, if your goals are 700 whp I would recommend just crossing twin turbos off the list right away.

At the end, I’ll whirligig when with recommendations on which setup to segregate based on power goals. It may fit in this section, but it’s easier to discuss once we move thru the rest of the ST vs TT considerations.

2) ST vs TT Powerband, Lag, Spool, Etc.

This is flipside major topic when it comes to single turbo vs twin turbo setups, and there are a lot of individual pieces to swoop into here. A couple factors to consider include:

  • Twin turbos offer largest spool, a lower uplift threshold, and increasingly low-end torque
  • Single turbos unhook largest mid-range and top-end power
  • Single turbos are easier on the engine at a given power level

Now, these are generalities and don’t necessarily wield to every single vs twin turbo setup. For example, a small single turbo like a PT5558 will likely unhook similar spool to RB Game Finishers (or any other true TD-04 twin setup). Meanwhile, the RB Game Finisher’s will unhook largest largest peak and top-end power.

Nonetheless, these unstipulated rules wield to most setups. TD-03 twin turbos built for 550whp are going to spool faster and unhook increasingly low-end torque than any single turbo. TD-04’s will spool largest than most single turbos, but won’t unhook as much peak or top-end power.

Ultimately, the main takeaway is that larger, increasingly capable turbos are going to have increasingly lag, a higher uplift threshold, and less low-end torque. You’re trading off those factors for largest peak and top-end power. 

If you want an OEM-like finger then TD-03 stock frame turbos are going to be your weightier bet, but they’re capped virtually 550-575whp. If you want big power then TD-04 twins or a big single will deliver, but you’re sacrificing some spool and low-end. Now, the most important topic is for those planning to run stock engines without any internal upgrades.

A Single Turbo is Easier on the Engine

Larger turbos shift the power lines to the right. Again, you have less low-end torque, increasingly lag, and a higher uplift threshold. Let’s squint at a couple dynos quickly.

N54 ST vs TT Upgrades - Single turbo dyno

*Image from this forum thread (also trammels out Jake Spence on YT; he has some unconfined content)

This is a Precision 6266 (PT6266) turbo making 749whp at 29psi. A closer squint shows roughly 300wtq at 3,000rpm, 420wtq at 3,500, and 540wtq at 4k. Peak power occurs at the very top-end of the dyno run. Now, let’s squint at a twin turbo dyno (true TD-04’s for a somewhat similar example).

N54 Single vs Twin Turbo Upgrades

The whilom dyno shows RB Game Finisher High-Flow 19T turbos at 27psi. These are true TD-04 twin turbos, so this isn’t an lattermost comparison with the previous PT6266. Here, we see roughly 375wtq at 3k rpm, 525wtq at 3,500, and 590wtq at 4k. The dyno moreover starts at 2,600rpm (vs well-nigh 2,100 for the 6266 single), so the torque numbers would maybe plane be a tad higher given flipside 500 rpm to start spooling.

Why is the ST easier on the engine?

Torque – that’s the simple one word answer. However, there are really a few things at play here. A large single turbo can make higher peak power with less uplift and less torque. Uplift and torque put increasingly stress on the engine than horsepower. 

Torque is the worthiness to do work while power is simply the rate at which work is done. In essence, torque tells you how forcefully the pistons are driven downwards in order to create the twisting force. But isn’t the single turbo whilom making increasingly torque?

Yes, but let’s squint at 6,500rpm. The single turbo is making 749whp at just over 600wtq. On the other hand, the twins are rapidly dropping torque by that point. They dip to 600wtq virtually 5,900rpm where they’re making well-nigh 670whp. If you tuned both of these to make 600wtq peak, then the ST is making well-nigh 740whp whereas the twins would be making virtually 670whp. That’s 70whp uneaten at similar uplift and torque.

More importantly is the rate at which the twin turbos pour on torque and uplift on the lower-end. Lower engine speed ways the pistons are moving slower and the cylinders are firing slower. That subjects the cylinders to upper pressures and heat for longer periods, which increases the endangerment of engine knock.

Ultimately, shifting the power lines right leads to increasingly power with less peak torque. It moreover helps stave the danger of making too much torque too quickly in the lower RPM’s. I should moreover note – both the whilom dynos are on stock engines and pushing vastitude the limits for longevity and reliability. On a stock engine, the max recommended power levels recommended are:

  • TD-03 twins: 550-600whp
  • TD-04 twins: 600-650whp
  • Single turbo: 650-700whp (for a 6266, 6466, or equivalent size)

3) N54 Single vs Twin Turbo Costs

Alright, that portion took a little bit to cover, but I promise these next topics are much quicker. Twin turbos are less expensive than single turbo conversions. Financing for turbo kits – not including bolt-ons or other recommended supporting mods – are often about:

  • Singles: $3,500 to $7,000
  • Twins: $1,500 to $3,500

The starting price of single turbo conversions is well-nigh the top-end of what you’ll pay for twin turbos. However, single turbos include a downpipe, filter, and don’t require inlets or outlets. Twin turbos don’t include those items by default as they’re OEM fitment. 

Inlets & outlets may not be required, but they are highly recommended. This is a moot point if you once have the bolt-ons anyway. However, if you’re starting with a wipe slate then it’s well-nigh $1,000 in uneaten mods for twin turbos. That can bring the prices pretty tropical if you’re looking at something like a SpeedTech PT Gen2 top-mount kit (~$3,800-4,500) versus RB GF Upper Flow (~$4,200-4,500 once factoring inlets, outlets, intakes, and downpipes).

That said, there are moreover some spare factors with single turbos like the PCV system, MAC solenoid, etc. that can add some uneaten financing too. Additionally, you can get quality twin turbo kits for under $2,000 – much cheaper than you’re going to find any quality ST kit. Ultimately, twin turbo upgrades are the cheaper route.

N54 RB Twos Plus Upgraded Turbos

4) Maintenance & Reliability

Back in the day, N54 twin turbo upgrades weren’t unchangingly reliable. It makes sense since a lot of the turbo upgrades were from newer companies. There were kinks to work out, lessons to learn, etc. However, the twin turbos now days (from companies like RB, Vargas, Pure, etc.) offer good reliability.

Single turbos are every bit as reliable – if not increasingly so – than twin turbos. Most single turbos come from major manufacturers like Precision, Garrett, and BorgWarner. Turbo reliability isn’t the only point here, though.

Top-mount single turbo kits are the real topic, and it’s a well-spoken win for them. If a top-mount ST fails, it’s a few bolts and you can waif a new turbo on in a matter of minutes. Twin turbos or marrow mount singles? You’re dropping the subframe and spending flipside 8-15 hours for replacement.

Plus, if you overly decide you want to upgrade turbos then the single is, once again, as easy as a few bolts. With the twins, you have to factor in your own time or the $800-1,500 a repair shop is going to tuition for install.

5) N54 Single vs Twin Turbo Sounds

Of course, sounds are very subjective so I’ll be equally as quick. In my opinion – and I believe most will stipulate – single turbo N54’s sound better. I think my twin turbo N54 sounds great, and I personally don’t superintendency well-nigh sounds too much (so it wasn’t really a factor in my decision). However, I have to requite it to single turbo N54’s; they sound pretty badass.

Ultimate Recommendation By Power Goals

With all that out of the way here’s my ultimate recommendation on turbo setups by power goals:

  • Under 550whp: Twins
  • 550-650whp: Either
  • Over 650whp: Single

In my opinion, the N54 is weightier suited to twin turbos under the 550whp mark. Stock-frame turbos can hit these numbers with relative ease while retaining an OEM-like feel. 550whp is plenty for most and this is a very realistic and obtainable goal.

Moving to 550-650whp it really just comes lanugo to personal preference (& the whilom factors). Skip the TD-03’s and opt for TD-04 if you go with twins, though. Ultimately, there are plenty of twin and single turbo options that can hit 550-650whp with ease.

At 650 whp I recommend ignoring twin turbo upgrades. Again, there are some setups that can reach these goals (as did the 680whp example from above). However, singles are a bit easier on the engine, and at 650 whp it becomes increasingly well-nigh the top-end rather than low-end torque and spool.

Our Personal Setups

Jake and I followed the same unstipulated guidelines in deciding on our N54 turbo setups. I opted for RB Twos Plus turbos for my 335i since my goal was ~550whp. Jake went with a Precision 6266 single turbo conversion as his goal was 650-700whp. We both believe they’re the perfect setups for each of our goals.

We moreover both stipulate that Jake’s single turbo 135i looks and sounds better. As such, if you really value those factors then you may prefer a ST conversion plane if you only want 550whp. Anyway, as one last piece of information on our setups let’s quickly talk well-nigh cost.

I am ignoring spare financing here like our fuel pumps, port injection setups, etc. Instead, I simply want to squint at the numbers for the turbos themselves and any mods veritably required for one setup but not the other:

My N54 335i

  • RB Twos Plus Twins: $2,200
  • Inlets outlets: $400
  • Downpipes: $200

This brings the forfeit of my N54 twin turbo upgrade to $2,800. I did have inlets & outlets prior to the upgraded turbos, but I’m including the financing since ST conversions don’t require these mods. Well, a ST requires a downpipe but it’s included with N54 single turbo kits.

Jake’s Single Turbo 135i

  • SpeedTech PT6266 Gen2: $4,250
  • Mac solenoid: $50
  • PCV setup: $200

The total forfeit of Jake’s N54 single turbo conversion comes out to $4,500 – or $1,700 increasingly than my twin turbo N54. It’s a good price for a single turbo, but still highlights the fact that twin turbo upgrades are often less expensive.

N54 Single vs Twin Turbo Summary

N54 turbo upgrades are a big financial commitment, and if you’re spending the money you want it to finger well spent, right? I know from personal wits it can be challenging and time consuming to decide on N54 single vs twin turbo upgrades.

Big single turbo conversions offer largest top-end power and higher peak horsepower. The trade-off is a higher uplift threshold, increasingly lag, and less low-end torque. N54 ST setups are moreover increasingly expensive than twin turbos. However, single turbos can make future life easier and cheaper as the top-mount turbos are simple to maintain or replace.

Ultimately, I recommend sticking with twin turbos virtually or under 550whp. Twins and singles can both be unconfined options for 550-650whp goals. At 650 whp it’s likely weightier to navigate N54 twin turbos off the list and opt for a single turbo conversion.

I hope this vendible offers a unconfined starting point for N54 owners looking to upgrade their turbochargers. Once you’re set on the N54 single vs twin turbo debate trammels out our holistic, in-depth guides for single turbo kits and twin turbo upgrades.

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