This post will serve as a complete guide to N54 stock fueling limitations and upgrades available. What are the limits of the stock N54 fueling system? At what power do N54 LPFP's, HPFP's, or port injection become necessary? How does E85 factor into all of this? We plan to answer all of these questions and then some. Additionally, we will discuss a few of the best options on the market for all N54 fueling mods.
N54 Stock Fueling Limitations
Before diving into any upgrades let's discuss the limits of the stock fueling system. This will be a quick overview, and we'll add to it throughout the post as we discuss each of the mods individually. A quick note before:
*Fueling limitations will vary from N54 to N54 even with the same mods, boost, fuel, etc. Some of it comes down to the health of your stock LPFP, HPFP, and injectors. Data-logging is an important and valuable method to keep an eye on fuel flow. If you intend to push the stock fueling limits keep an eye on HPFP and LPFP pressures, fuel trims, and AFR's.
That said, let's lay out the fueling limitations of the stock N54 system:
- Pump gas: 450-500whp
- E30: 425-450whp
Running much more than E30 or E40 fueling is going to cap the stock LPFP quickly. Pump gas will be a bit easier on fueling, however stock turbos can't make over 425whp on pump gas. It's also important to note meth injection will play a role as it acts as supplemental fueling. Anyways, in general a FBO N54 running E30 or E40 fuel will just about cap out the LPFP. This will be the first fueling mod most N54 owners will want to knock out.
Leaving Some Headroom
We always like to throw in these reminders. Not only for our readers, but also for ourselves. It's kind of a follow up note to the above. We'll reference power numbers as best we can but we cannot stress the importance of data-logging and paying attention to fuel flow and AFR's. A lot of the numbers we mention in this post are nearly maxing out the fueling system.
However, we believe it's a good idea to build in some headroom. This applies to everything from fueling, to turbos, to engine limits. If your goal is 800whp you don't build out the motor to handle 800whp. You likely build it to handle 900-1000whp. If you want the same 800whp you don't buy a turbo that's absolutely caked at 800whp. You opt for a turbo that's within its efficiency range at that power.
The same should apply to fueling. E85 mixes are a great way to improve peak boost, timing, and overall engine safety. However, it puts a lot of stress on any fuel system. Full E85 requires somewhere in the ballpark of 30-40% more fuel flow than 91/93 octane at the same power. That's beside the fact you're likely running E85 to run more power. If you're running your fuel system at 99% of its maximum capacity and something goes wrong at 500+whp, then what? The chances of a blown motor if you lean out become very real at that power. Ultimately, accept the risk or play it safe up-front and build in some headroom.
1) N54 Upgraded Low Pressure Fuel Pump (LPFP)
First off, this is the most common N54 fueling mod and there are a lot of options out there. We'll give an overview, but may expand this into its own post in the future. It's really the only fueling mod required to completely max the stock turbos. A stage 2 or 3 LPFP should support low-mid 500whp on an otherwise stock system with E50 fuel. Therefore, a modest upgraded turbo setup can likely get by with an upgraded LPFP alone.
Also, for those NOT running E85 mixtures you'll likely hit an octane limit before you max out the N54 fueling system with a LPFP only. Really the point we're getting at is that most N54's will only need a LPFP upgrade. The fueling mods in the next sections are primarily reserved for those looking to push 500+whp on heavy E85 blends.
N54 LPFP Upgrade Options
You're going to run across stage 1, 2, 3, and 4 low-pressure fuel pumps for the N54. Additionally, bucketless fuel pumps are available. For anyone who frequently runs their cars under 1/8 tank we would advise avoiding the bucketless options. The same can be said for those tracking their cars or frequently cornering at high speeds under a 1/2 tank of fuel. Again, we'll write a post in the near future and link to it here. There are a ton of different options out there so this is by no means an exhaustive list.
1. N54 Stage 1 LPFP Upgrade
This kit is available from Fuel-It as are most of the upgrades we will recommend in this post. They have a ton of fueling solutions for the N54. The stage 1 LPFP uses a Walbro 255LPH pump. It's an inline LPFP upgrade meaning it's installed alongside the stock fuel pump. Therefore, it may not be the best or cheapest solution for those wanting to replace their factory LPFP.
The Stage 1 Walbro pump will flow roughly 50% more fuel compared to the stock pump on its own. This is a well priced solution for those with a healthy stock LPFP simply looking for a bit more flow. To note - this Walbro pump is NOT certified to be run with E85. It will run E85 and likely won't have any issues. However, you may consider opting for a stage 2+ pump if you intend to run heavy E85 mixtures. This stage 1 LPFP kit is not recommend for those running upgraded turbos or who plan to do so in the future.
Buy Here: Fuel-It N54 Stage 1 LPFP
2. N54 Stage 2 LPFP Upgrade
Cost: $405 ($480 with optional upgrade to Walbro 525 pump)
The stage 2 LPFP kit from Fuel-It runs a Walbro 450 pump that provides up to 100% more flow than stock. There's also the option to upgrade to the Walbro 525 pump. Both are E85 compatible and these are likely the most cost effective fuel pumps for N54's targeting under 600whp. In essence, this pump will be able to take your N54 to the next fuel limit - the HPFP. The stage 3 and 4 pumps coming up next are really for those who want 600+whp.
Of course, while this pump will support upwards of 600whp on full E85 the HPFP will be capped well before then. You'll be looking at HPFP upgrades, charge pipe injection, or port injection.
Buy Here: Fuel-It N54 Stage 2 LPFP
3. N54 Stage 3 LPFP Upgrade
Stage 3 LPFP kits are venturing into the territory of extreme fueling demands. Fuel-It's stage 3 kit features dual Walbro 450 or 525 pumps (option to upgrade one or both pumps for $75 each). The kit is a complete plug and play offering, however the secondary pump will require a second wiring harness. The wiring harness is included but installation is an additional factor to consider.
This is a great solution for those wanting to make serious power on E50+ fueling with the addition of port injection. These pumps flow about 300% more fuel than the stock N54 LPFP.
Buy Here: Fuel-It N54 Stage 3 LPFP
4. N54 Stage 4 LPFP Upgrade
Stage 4 LPFP kits are similar to stage 3, however it requires the use of port injection. The dual pump set up is the same as with the stage 3 kit. However, stage 4 kits include a custom E85 compatible filter, along with all the fuel lines to complete the LPFP + port injection upgrade.
If you don't already have the port injection kit then you may consider purchasing Fuel-It's complete upgrade. This includes the stage 4 LPFP kit, port injection kit with injectors, and a port injection controller.
Buy Here: Fuel-It N54 Stage 4 LPFP
N54 LPFP Summary
LPFP upgrades are typically the first fueling mod for N54 owners. Those planning to run lower or no E85 mixtures on stock turbos may find the stage 1 upgrade the most cost effective option. However, since inline pumps still rely on the stock LPFP it may not be a good option for those with weakening or faulty stock pumps. Stage 2 LPFP's are recommended for E40+ on stock turbos or upgraded turbos below 550-600whp. Stage 3 and 4 options run dual pumps and are highly recommended if you're planning to run port injection.
2) N54 Upgraded High Pressure Fuel Pump (HPFP)
We're going to keep the HPFP mods section pretty short. Following the LPFP upgrade the N54 stock HPFP is the next bottleneck on fuel flow. However, it does not need to be upgraded. There are ways around that such as port injection or charge pipe injection. Both of those options will essentially bypass the HPFP limit. That's due to the fact the HPFP is intended to support the incredibly high pressures required for direct injection. Port injection and charge pipe injection don't need high pressures to operate. As such, they're driven by the LPFP.
Anyways, HPFP upgrades are a promising option for those who don't want to add a second fuel rail utilizing port injection. The two primary options are HPFP overdrive kits or adding a second HPFP.
1. N54 VTT HPFP Upgrade - Shotgun Single Barrel Kit
Vargas Turbo Tech's single barrel shotgun HPFP kit is an overdrive option for the stock high pressure pump. It actually relocates the HPFP to be driven by the serpentine belt. The kit includes the HPFP drive housing, a new belt, and all other hardware required for installation. However, you do "re-use" your OEM HPFP unit. If you're in need of a new high pressure fuel pump then expect to tack on an extra $800.
In essence, the belt is able to help overdrive the HPFP. That basically means the pump is being driven faster than it was designed to do. It might not seem like a great idea on HPFP's that are already known to be problematic. However, most HPFP failures are caused by modes unrelated to over-spinning the pump.
Vargas states this pump relocation and overdrive is good for up to 550whp on 100% E85. Upwards of or beyond 600whp may be possible on lower E50 or E60 mixes. Pretty solid with a price tag of $799.
2. N54 VTT HPFP Upgrade - Shotgun Double Barrel Kit
This kit is similar to the previous option from Vargas Turbo Tech, but adds a second HPFP. Your OEM pump stays in it's same location and the second pump is added in and driven by the belt (as with the single barrel kit). The base kit starts at $1,299 which includes everything needed to add the second HPFP. However, it does not include the second N54 HPFP. A new one is going to run $800 from Vargas bringing this kit up to $2,098+.
It's designed to support up to 700whp on full E85. More power may be had with lower mixtures, such as E60. It's a unique kit and cool to see how much fuel the stock direct injectors can actually flow. However, we wouldn't particularly recommend this kit. It rivals the price of a full port injection system. Although, the performance is of course pretty strong and it supports more flow than most N54's will ever need.
3. N54 Helix HPFP Overdrive Unit
The Helix N54 HPFP overdrive unit is a very promising development. Unlike the VTT options above this does not add a second pump or relocate the stock pump. Rather, it uses a gearbox that allows for an increase in HPFP shaft speed. We won't pretend like we fully understand the engineering behind the gearbox. Either way, it's been proven to work with great results.
Standard Helix overdrive units can support 600whp of fueling on full E85. Expect closer to 700-750whp with E50 or E60 mixtures. A Helix Xtreme unit is also in longevity testing but is expected to support 750whp on full E85. This is truly incredible for a slightly modded HPFP and stock injectors to make this kind of power. However, there might be a catch.
The N54 and N20 use a very similar timing chain design. It's nearly flawless on the N54, but highly problematic on the N20. Part of that likely has to do with the nature of inline 6 engines being harmonically balanced. There are concerns that over-driving the pump could cause additional vibrations and lead to an increased chance of timing chain failure. We don't think this will be a serious concern or too likely. However, it's something to pay attention to as more and more N54's opt to run these Helix overdrives.
N54 HPFP Upgrades Summary
High pressure fuel pumps weren't a common thing to upgrade for a long time. It wasn't until the last few years viable solutions started hitting the market. The VTT and Helix options certainly have potential. However, we'd like to see some more long-term results from the Helix units before we would consider them on our own cars. Additionally, the VTT double barrel option supports excellent flow but rivals or exceeds the price of port injection. Finally, the single barrel kit from VTT is a solid option but 550-600whp on heavy E85 mixes may not meet everyone's goals.
3) N54 Charge Pipe Injection (CPI) Kits
Alright, we went a bit deeper on HPFP upgrades than initially planned. We'll speed this section up a bit since it's pretty basic. Charge pipe injection (CPI) is another exciting development in the recent years. However, it's not totally new. CPI is a similar concept to methanol injection. Aftermarket charge pipes are generally fitted with one or two 1/8" NPT bungs. If you can run meth through the CP, why not offer an additional fuel injector and fuel lines, too?
You can technically run an extra injector anywhere you can fit a 1/8" NPT bung. However, we would recommend only running injectors after the FMIC. There could be concerns of detonation if sprayed before the FMIC where air temps can be extremely hot.
As with port injection or meth injection you'll need a controller to actually utilize the injection system. It's also important to note - this likely won't support any more power than a typical N54 meth injection kit. Of course, unless you're running several injectors throughout the intake system. Anyways, it's a great option for those who need a bit more fuel flow and do not want to run meth.
4) N54 Port Injection Fueling
Price: $1,600 - $2,550
Moving onto the highly tested, proven fueling method to make big power on the N54. Port injection adds a new fuel rail along with 6 injectors. The stock direct injection system still remains carries quite a bit of the weight. However, port injection kicks in at a certain point to handle the rest of the fuel flow demands. Port injection with the proper LPFP setup and high flowing injections can support in excess of 800whp. However, port injection is an excellent option for anyone running 500-800+whp on heavy E85 mixtures.
We're just going to focus on the N54 E Series Port Injection kit from Fuel-It. There's quite a bit of customization possible with the kit. Depending on how everything is optioned out you're looking at $1,600-2,550. It's not cheap, however it remains the ultimate fueling solution for the N54. If you're in need of a LPFP too then you might consider the full kit including the stage 4 LPFP.
N54 Fueling Mods Summary
Before diving into this post we didn't realize how much we really had to say about N54 fueling mods. There are a lot of different options out there dependent upon your personal preferences and goals. Again, we'll likely expand a few of these fueling mods into posts of their own. Anyways, hopefully this was a helpful outline of the different N54 fueling possibilities out there.
LPFP's are the first limitation on the N54's stock system. Often, a LPFP upgrade alone will support low-mid 500whp range with roughly E40 or E50 fueling. However, that's highly dependent upon the health and function of your HPFP and injectors. Once you begin pushing beyond 500whp you'll quickly reach the limit of the stock HPFP. There are several options at this point. Charge pipe injection can add a 7th N54 injector to support additional power and E85. Those looking to push 550+whp on E40+ fueling will need to consider HPFP overdrive mods or a full port injection system.
What fueling mods do you have on your N54? What kind of power are you running? Leave a comment and let us know!