BMW S55 M2, M3, M4 Water Methanol Injection (WMI) Guide

Finally, we're getting around to writing about water methanol injection for the S55 M2, M3, and M4. WMI acts as additional fueling for the BMW S55, and also offers cooler intake temps. There are several other benefits to WMI that we'll jump into in this guide. However, there are also a few risks when running methanol injection. In this article, we discuss the benefits, risks, and performance of S55 M2, M3, & M4 WMI kits. We also list a few of the best methanol kits on the market.

S55 BMS WMI KitPin

S55 Water Methanol Injection Benefits

Some benefits of running water methanol injection on the S55 engine include:

  • Power gains
  • Cooling effects
  • Knock suppression
  • Source of fueling

The last 3 bullet points are what allow WMI to offer the benefit most people are interested in - horsepower gains. Exact power gains for the S55 depend on many different factors. What other mods are you running, how much boost, and how heavily are you leaning on the WMI kit? Those are just a few of the factors that affect how much power each BMW S55 will gain from a WMI kit.

That said, gains can be as low as 10-20whp on stock turbos with a low methanol mix and a conservative tune. However, water methanol injection can show staggering power gains of 50-100+whp with upgraded turbos and aggressive tuning.

WMI also offers colder intake and internal engine temperatures. This partially helps reduce the chance of the S55 M2, M3, and M4 engine knocking. Methanol also acts as additional fueling which can provide further knock suppression. It also may save you from needing expensive port fuel injection to keep up with fuel demand. A lot of benefits to S55 methanol injection are similar to those of E85 fueling. However, E85 increases demand on the fuel system while WMI has the opposite effect.

BMW S55 E85 vs WMI

For those that have access to E85 we still believe this is the better long-term fueling solution. As with most modern BMW turbo engines the S55 is handicapped without high octane fuel. However, not everyone has access to E85 or high octane race fuels. That's where S55 WMI comes into play. Methanol is considered a high octane fuel. The S55 loves octane which is why the performance benefits with E85 and/or methanol are excellent.

Even for those who have access to E85 can choose to run that along with methanol injection. That will help offer the ultimate cooling, power, and knock suppression for the BMW S55 engine. On stock turbos the S55 fuel system can handle very heavy E85 mixtures without any fueling mods. Add in some methanol injection and you reduce the demand on the fueling system. It's a good way to effectively build in a safety net and a little margin for error.

In essence, we believe E85 is the superior fueling solution for the S55 engine. However, there's no reason you can't run E85 and methanol injection for the ultimate setup. WMI is also great for those who do not have easy access to E85.

S55 M2, M3, M4 WMI Risks

Water methanol injection has plenty of benefits on the BMW S55 engine. However, it does come with a few risks that should be taken into account. There is good news, though. As with just about anything - there are ways to mitigate the risks of S55 WMI kits. We'll quickly discuss the following risks and how you can avoid them:

  • Loss of WMI flow
  • Uneven flow

Loss of Water-Methanol Flow

WMI kits rely on a pump to move the water-methanol mix to the injectors or nozzles. There are then of course the nozzles themselves and the lines. Though it's rare, there is room for any of those parts to clog or fail. If the WMI mix suddenly stops flowing then the cylinders are starved of that mix that's acting as fuel and knock suppression. In this case, the chance of pre-detonation increases which isn't good if you're relying heavily on WMI and pushing the S55 to the limit.

Using a proper fail-safe system, such as JB4 integration, will greatly help reduce this risk. The JB4 will quickly notice the loss of methanol flow and pull boost to avoid damage. There are plenty of other fail-safe methods that we don't have time to cover. Another way of reducing this risk is to not lean too heavily on S55 WMI setups.

Uneven WMI Flow

This is similar to the above in that specific cylinders may be starved of water methanol flow. Basic S55 M2, M3, M4 WMI kits inject the mix into the chargepipe - before the intake manifold or ports. It's common for cylinders 1 and 6 to receive a little less flow than the others. If you're relying too heavily on WMI then this may cause issues.

Direct port methanol injection is the best way to avoid this problem. We'll discuss CP vs port WMI in a few moments. The basic idea is that you're injecting the water/meth mix in the intake ports. This ensures all BMW S55 cylinders are receiving equal flow.

What is the Best S55 WMI Mix?

A 50/50 mix is a common choice for many BMW owners running water methanol injection. We tend to agree with this being a good option. Methanol acts as fueling while water helps absorb heat and cool intake temps. The M4 GTS powered by the S55 engine runs 100% water injection straight from the factory. Point is - even just injecting straight distilled water has benefits.

However, methanol is the part of the mixture that actually acts as high octane fueling. As such, the methanol injection is going to offer the biggest power gains. Methanol is, of course, highly flammable. That's part of the reason it's important to mix in some water. If you're primarily after knock resistance and cooling benefits then anywhere from 60-100% water and 0-40% methanol is a good choice. Those looking for more performance may consider going up to 50-75% methanol.

Charge Pipe vs Direct Port Methanol Injection

We'll be fairly short and straight to the point to keep things moving. Charge pipe (CP) methanol injection is the cheaper option for the S55 engine. It gets the job done for those who just want a bit more performance and knock suppression. We recommend S55 CP water methanol injection kits if you're not planning to heavily lean on methanol.

If you're running pump gas and want to push 600-700+whp then direct port S55 WMI is the right way to go. It's a safer setup that utilizes 6 injectors for precise flow. The overall flow capacity of direct port methanol is also higher. It's similar in price to port fuel injection, so it's not a cheap route. However, for those that plan on relying heavily on S55 WMI then direct port meth will be the best setup from a performance and safety standpoint.

Best M2, M3, M4 S55 WMI Kits

Alright. We're finally here. In this section, we'll mention a few of the best S55 water methanol injection kits on the market. There are plenty of great options out there that we don't dive into specifically. Some options include AEM, Snow Performance, etc. Anyways, below are a few of our favorite options that we believe offer a great balance of price, quality, performance, and safety. Additionally, we highly recommend running the S55 JB4 tune for the simple WMI integration and good safety features.

1) BMS S55 Water Methanol Injection Kit

Price: $459 - $717

Burger Motorsports (BMS) is well known in the BMW world for their popular JB4 piggyback tunes. They also offer some other awesome products including a chargepipe WMI kit for the S55 M2, M3, and M4. The full kit starts at $459 including a one gallon tank. There are then options to upgrade to the 2 or 3 gallon tanks, and a billet cap with a safety check valve. This can bring the price of the kit up to $717, but the convenient mounting for the 3-gallon tank does look great.

Anyways, BMS water methanol injection kits are highly proven with tons of them in use. The one catch is that it relies on the JB4 for integration. We love the JB4 and recommend it anyways, but some don't like the idea of piggyback tunes (which is why we recommend stacking with a back-end flash). The JB4 does offer simple integration and precise control of the water-methanol flow.

The S55 WMI kit from BMS is an excellent option, in our opinion. It's a proven kit from a reputable company that's experienced in the aftermarket turbo BMW world. All for a fair price with simple JB4 integration.

Buy Here: BMS S55 Water Methanol Injection Kit

2) Fuel-It! S55 Direct Port WMI Kit

Price: $1,538 - $1,768

S55 Direct Port WMIPin

Fuel-It! is a well known company in the world of BMW fueling solutions. They make some awesome kits for other fueling upgrades, such as port fuel injection, LPFP's, etc. Additionally, Fuel-It offers an awesome, highly versatile direct port methanol kit for the BMW S55 engine. With JB4 integration and the base 550cc injectors this kit starts at $1,538. That can run up a couple hundred extra if you want to upgrade to 750cc or 950cc injectors.

This S55 direct port WMI also offers two additional ports on the methanol rail for CP injection. It's optional but it means you can flow even more methanol via two chargepipe meth bungs. Point is - this kit has some serious flow potential and will support incredible power on pump gas and methanol injection only.

Pricing comes in a bit high compared to chargepipe kits. It's similar to if you were planning to run port fuel injection. However, this Fuel-It kit is the ultimate solution for those wanting to make big power on WMI only.

Buy Here: BMW S55 Fuel-It! Direct Port WMI Kit

S55 M2, M3, M4 Water Methanol Injection Summary

There are many benefits to running a WMI kit on the BMW S55 engine. Impressive power gains likely top the list of reasons to run water methanol injection. However, the benefits run even further. WMI offers similar pros to E85 or race gas since methanol acts as high octane fuel. However, unlike E85, meth injection actually reduces demand on the S55 fueling system. There are also a few risks to methanol, but those can be mitigated with a proper setup.

Charge pipe methanol injection is a proven and cost-friendly option, but isn't quite as precise as direct port meth. We recommend CP kits for S55 owners who don't plan on leaning too heavily on WMI. If you demand the most out of a water methanol injection kit then direct port is the way to go. They offer superior flow and performance potential while being a little safer.

What's your experience with M2, M3, or M4 S55 WMI kits? Are you considering one?

Drop a comment and let us know!

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