For those who don’t know, about 3 or 4 years ago, Classic Mini DIY introduced their first fuel injection product, the EFI Cable Throttlebody | HIF44 Replacement. This was a product I personally wanted to make and use on my car in my fuel injection journey.

Over those years, our cable throttle bodies helped numerous people convert their legacy carburettor systems to fuel injection. As well as allowing folks who had SPI and MPI systems to easily switch to a more modern and reliable ECU setup.

Despite its short run, I am incredibly proud of the impact this product has made in the Classic Mini space. Offering a more reasonably priced option for Mini owners, while also challenging some existing companies to modernize their setups as well.

After much deliberation, we have decided it’s the right time to retire this product in favor of something more reliable and more versatile…

Retirement and What's Next?

Over the last year of development, working closely with Haltech Engine Management Systems and some other OEMs, we have found incredible versatility and functionality in the next evolution of aftermarket fuel injection, Electronic Throttle Control1, or more commonly called, Drive-By-Wire (DBW).

Drive-by-wire as a concept and technology is nothing new in the automotive world. Almost every modern OEM vehicle produced since the mid to late 2000s has been shifting its systems to drive by wire, and there is an extremely good reason for this. I will be borrowing from a previous post where I break down the differences between DBW and Cable setups.

Pros:

• Safer Operation2

  • Throttle Sensor Redundancy

  • No chance for stuck pedal

  • Configurable Safety cut out (ECU Dependent)

  • Brake and Clutch pedal Safety check (ECU Dependent)

• Considerably more reliable with less points of mechanical failure

• Dramatically better idle and cold start behavior

• Ability to implement custom pedal curves

  • This allows custom configuration of how reactive you want your pedal

• Launch Control (ECU Dependent)

• Cruise Control (ECU Dependent)

Cons:

• Not all ECUs support Drive by Wire

• Requires Drive-by-wire pedal or a modified mini pedal

  • See Info - https://substack.classicminidiy.com/i/141183405/drive-by-wire-pedal

• More complexity in wiring at initial setup

• Can be more expensive depending on ECU

So given these reasons, paired with our vision for what DIY fuel injection should look like in the future. Classic Mini DIY is all in on electronic throttlebodies, and we hope that with our focus solely on these modernized systems, we will be able to provide you with more complete solutions in the future, as well as pioneer some awesome advancements in EFI technology for the Classic Mini.

Questions?

Have questions about our changes? Post them in the comment section below, or consider becoming a Patreon to gain access to our private chat server full of Mini lovers like you!

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Today, I wanted to dive into one of the biggest misconceptions related to fuel injection, as it relates to the Classic Mini, charge robbing!

Notable Terms used in this article:

• EFI - Electronic Fuel Injection

• ECU - Electronic Control Unit

Charge Robbing makes Fuel Injecting Impossible

The phrase I see posted online constantly, even parroted by experts. Thinking about this, I suspect it’s due to some outdated technical write-up from the last 20-30 years that never got revised or updated. As a result, people have been posting this as gospel online for years.

What is charge robbing?

Let’s start with what charge robbing actually is in a practical sense. The mini has a “unique” (see also “bad”) design for its original cylinder heads. They use something called a Siamese Port head.

What this means is that both the intake and exhaust ports are on the same side of the head. Where it gets especially tricky is that each cylinder does not have its own intake manifold branch. Meaning cylinder 1 and 2 use the right side of the intake manifold, while cylinder 3 and 4 use the left side as viewed from the front of the car. This means that as fuel/air is being pulled into the cylinders, there are scenarios where a cylinder can rob/steal that mixture from the other cylinder in its shared port.

This is, at a high level, the reason why Classic Minis always have slightly leaner outer cylinders (1 and 4).

Why does this matter for EFI?

In a traditional carburetted setup, your carb would produce what’s called a “wet manifold” environment, which essentially means, the more air that comes in, the more fuel gets pulled in from the float bowl via the venturi effect. This ensured that there was fuel on the way to cylinders in effectively every engine load scenario.

Even with this setup, though, charge robbing is still happening, though it’s mitigated enough to allow the car to run properly and without failures.

In EFI setups, injectors behave differently. Meaning, instead of just dumping fuel like a firehose, they “pulse” and provide different volumes of fuel depending on your fuel map and where you are currently located in the load table. The way injectors work in detail could be a total writeup on its own, so I won’t go too deep into this.

But since they are pulsing, you are not automatically receiving fuel delivery like the carb was previously delivering, and thus, if not configured properly, you will exacerbate the charge-robbing issues.

How do you fix this?

In some of the legacy EFI kits on the market today, such as the one from Specialist Components, you will find some pretty creative wiring to “double-fire” the injectors, as well as some interesting mapping going on with injector angles. Setups like this did this because at the time, ECUs didn’t have a good solution built into them from the manufacturers.

In 2025, this issue is completely managable with the correct ECU configuration: injector firing method, injector angle setup, and correct injector sizing.

Correct Injector Sizing

This one is probably the most important. And that is the selection of the most suitable injectors for your setup. Many people think “bigger injectors = more better” which is not the case. You need to have the correct amount of flow for the engine size and power expectations. Larger injectors tend to have a harder time dealing with idle, while smaller injectors tend to max out at the top end. This is not an absolute rule, though, and in recent years, we have seen some pretty amazing advancements in the high-flow injector space. Below you will find a very high-level table of injectors for the Classic Mini.

• Siemens Deka 630cc - Good for standard A-series or A-Series with lower boost

  • https://geni.us/SiemensInjector

• Bosch 731cc - Best tested for High Boost/High Flow Engines

  • https://geni.us/BoschBoostInjector

After installing your injectors, it is also absolutely vital that you input your injector dead times. If you purchase them from the links above, Speeding Parts can provide you with this documentation. This tells your ECU have quickly the injectors can pulse and how long it takes to “recharge” between pulses.

Firing Pattern/Method

Most ECUs available these days offer a wide variety of injector firing options. With most Mini EFI setups, you are going to be targeting the same underlying behavior that the carb was producing. Each ECU company names this something slightly different, but for Haltech ECUs and Speeduino setups, you will be using batch firing.

Batch firing

As it works in the Haltech setups, it divides your injector outputs (2 outputs/injectors in our setups) into two groups, which are fired alternately.1

Pair this with an injector firing order of “every 180 degrees” to ensure one injector is firing every stroke. Operating your injectors in this method will ensure they are not maxing out their duty cycle and will set you up for configuration of your Injector Angle. Which I will get into next.

Some people may be tempted to use Multipoint firing; however, we have found that with our modern setups, this will quickly max out the duty cycle of your injectors, leading to underfueling or your injectors dropping out and not providing fuel at the correct time. This may, however, be a viable option for some really advanced and low-latency Injector Dynamics injectors; however, we have not yet tested this theory in our test bench.

Injector Firing Angle

Now we get to the last item in our configuration. Injector firing angle, which, put plainly, is how soon before TDC the injectors are triggering (based on the length of your intake and velocity of air). This is the “silver bullet” of information that many who have attempted injection setups in the past have overlooked or not been privy to.

The reason this is important is that it dictates and controls when the fuel begins its (extremely fast) journey into the engine from the injectors. Timing this firing of the fuel is vital to ensuring your fuel makes it to the correct cylinder and isn’t sent to the wrong cylinder in the shared port.

After extensive time on the dyno, Classic Mini DIY has established a preliminary set of firing angles for the Bad Wolf Turbo Build, which can be adopted in other builds as a great starting point.

Some things to note:

• Based on the use of the Bosch 731cc Injectors

• Based on a drive-by-wire setup, not cable-driven throttle bodies

• These are a baseline and may require tweaking for your setup

The link below is to our Google sheet where I will keep these values updated in the future. Additionally, if you would like to support the channel or have an EFI Mini project you are working on, consider purchasing the base map available in my store.

• Injector Firing Angles - https://docs.google.com/spreadsheets/d/1pS5iifM54nkaMmotSRnsUrgD_CEoOhWv2oUcj9mGvBk/edit?usp=sharing

• Base Map - https://store.classicminidiy.com/collections/efi-base-maps

Notable Mention

When considering your setup, it is worth mentioning that in addition to these advances in easy control in your ECU, advances in throttlebody design, such as drive by wire, have made EFI conversions even easier on older vehicles with unique fueling needs. These electronic throttles are considerably safer and more reliable when compared to the standard cable throttle. Allowing automatic fine-tooth control of idle with simple configuration in your ECU.

Shameless plug - Classic Mini DIY Drive By Wire Throttlebody

Summary

Hopefully, for those of you who have previously been concerned about fuel injection on these old Minis, after reading, you are feeling a bit more confident in these setups in 2025. With a little bit of configuration and using the right parts, you will be ripping down mountain roads in a super reliable fuel-injected mini in no time.

As always, feel free to ask any questions here, or message me at classicminidiy@gmail.com.

Enjoy those minis, and motor on!

The wild and wonderful world of fuel injected throttle bodies. Lets discuss a few different variants and why you may or may not what to pick one over another.

For the sake of this article we are making a few assumptions:

• You are using an A-Series Engine

• You are planning on sticking with a standard 5-port A-series head

• You have an HIF44 intake manifold

• You have not selected your ECU yet

Below are the two CMDIY throttle-bodies we produce and carry in house. You can see the primary differences between our two models. One with the built in Bosch motor for the throttle butterfly, while the other has your traditional throttle sweep and cable mount. Both run two injectors and roughly the same engine side flange. The only difference is the operation of the throttle butterfly.

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Deciding which option you want is more than just deciding which item to click buy on. The biggest deciding factor for your fueling choice is related to the ECU you plan to run, and what it can manage. However, the short answer is, if your ECU supports Drive by Wire (DBW), it is the clear and absolute best choice every time in my opinion. Although it appears more complex, drive by wire provides so much more reliability, control, and functionality over your traditional cable throttle setup. To help you decide whats right for you, lets break down the pros and cons.

Questions? Make sure to post a comment!

Leave a comment

Cable EFI Throttle body:

Pros:

• Works with just about any ECU on the market with largely no limitation in functionality.

• Slightly less expensive up front costs

• Less complex setup of wiring

• More of a “Bolt-on” option as you can just run your existing throttle cable to the throttle body.

• Comes with a variety of flanges (KN filter flange, tube flange, etc)

Cons:

• Much harder to get a reliable idle than Drive by Wire (DBW)

  • Note: You can add an Idle Air Control Valve if your ECU supports it however this is added complexity

• Cable is potentially a failure point

• Objectively less safe when compared to DBW 1

  • Chance of stuck pedal

  • No throttle sensor redundancy

  • No safety cut outs

  • No brake pedal or clutch safety checks

• Inability to implement custom throttle curves or have different driving modes

• Cannot implement features like cruise control or valet mode

• No ability to implement Launch Control

Drive by Wire Throttle body:

The throttle we use in our setups is a genuine Bosch motor attached to a 44mm throttle mouth. This is a serviceable and easily replaceable part used on many small bore OEM vehicles today. Namely most Fiat/Chrysler vehicles you drive past every day.

Pros:

• Safer Operation2

  • Throttle Sensor Redundancy

  • No chance for stuck pedal

  • Configurable Safety cut out (ECU Dependent)

  • Brake and Clutch pedal Safety check (ECU Dependent)

• Considerably more reliable with less points of mechanical failure

• Dramatically better idle and cold start behavior

• Ability to implement custom pedal curves

  • This allows custom configuration of how reactive you want your pedal

    

• Launch Control (ECU Dependent)

• Cruise Control (ECU Dependent)

Cons:

• Not all ECU’s support Drive by Wire

• Requires Drive by wire pedal or modified mini pedal

  • See Info below about DBW Pedal

• More complexity in wiring at initial setup

• Only available with hose attach flange

• More expensive due to ECU required to operate

Drive by wire pedal

One of the drawbacks of the drive by wire setups is the requirement for a pedal sensor. This means either retrofitting your existing pedal to work with a pedal sensor or purchasing a bolt in pedal and replacing your existing one. In my setup I am running the retrofitted option modeled after a setup by Steve Blakemore or @turbocoopersport on Instagram. Essentially a small rose joint connecting the DSN Retrosport pedal to the Honda pedal sensor pictured above.

Conclusions

So between those two lists, there are always trade offs between the two systems however I feel the Drive by Wire system if you can accept the up front slightly harder setup, will reward you many times over when running your Mini and driving it day to day. If you need any more detail about the ECU’s you should choose or what each one supports, I have put together a small list below.

Side Note: Some Info about ECU’s

With the large variety of ECUs on the market, *Which ECU should I get? is the question I get asked the most. The short answer to this question is, "The one that offers you all the features you need for your setup". However, this answer is obviously not very helpful. So below I have put together a table of ECUs and the features they offer compared to what you may need for your setup. All the ECUs below will run an A-Series engine with varying degrees of complexity.

Some ECU’s you could use:

• Haltech Elite 750

  • DBW - ❌

  • CMDIY Base Map - Purchase or Download

• Haltech Elite 1500

  • DBW - ✅

  • CMDIY Base Map - Purchase or Download

• Haltech Nexus R3

  • DBW - ✅

  • CMDIY Base Map - Purchase or Download

• Emerald K6

  • DBW - ✅

  • CMDIY Base Map - Purchase or Download

• Speeduino - DIY

  • DBW - ✅

  • CMDIY Base Map - Purchase or Download

• MegaSquirt - DIY

  • DBW - ✅

  • CMDIY Base Map - Purchase or Download

• Specialist Components (SCS) - Delta 4003

  • DBW - ❌

  • CMDIY Base Map - ❌

• Specialist Components (SCS) - Delta 7004

  • DBW - ✅

  • CMDIY Base Map - ❌

Now this is not a comprehensive list of every ECU on the market. But these are the common ECUs I see people using in their Minis these days. My top pick for the Classic Mini owner is by far the Haltech Elite 1500 with Wiring Harness. This will sort out almost every EFI conversion I come across and they offer unparalleled support for their hardware via phone/email/chat.

Next up in the fuel injection journey, the fuel system itself! The fuel system requirements for EFI are a little bit different than a carb with some key differences you need to consider.

• EFI requires a high-pressure fuel pump (40psi+)

• You must put in a return line for excess fuel

• You need fuel lines that can handle pressure

• EFI requires a fuel pressure regulator

None of these are especially difficult to accomplish but all must be considered when building out a conversion kit for your Classic Mini.

How is fueling different?

The key difference between fueling injectors versus a carb is pressure and flow rate. With fuel injectors, they are both firing fuel into the inlet manifold and handling the job of atomizing the fuel. In more modern engines these injectors live directly in the cylinders. In our mini's they will live in the intake manifold doing something called "port injection". Injectors are very sensitive to low pressure and require a constant stable flow and pressure to operate correctly. This is why your new pump and regulator are so important.

Routing the Fuel Lines

Routing fuel lines for EFI may seem like a complicated task but there are a couple of options for routing you can use when setting up your system. In both options, you will need to run a supply and return for your fuel lines to and from the tank.

Of these two options above the "Return System" is the most desirable. Putting your fuel rail (which lives in your engine bay) before the fuel pressure regulator will reduce the overall heat being added to your fuel by virtue of pressure. Allowing all the "warmer" excess to pass out into the return and never enter your injectors.

What you need

High-Pressure Fuel Pump

With EFI you must have a high pressure 40 psi+ for your fuel injectors. This is not like a carb with a low-pressure 3psi pump. I find the easiest way to do this is to install this in an MPI Classic Mini tank. These accept universal "in-tank" fuel pumps and arrives setup with a fuel return. All EFI fueling systems require a return line for excess pressure and fuel. You can of course drill your own return line in your own tank but the MPI tank is the cleanest setup.

Order yours here: MPI Fuel Pump

Order yours here: MPI Fuel Tank

Fuel Pressure Regulator

There are many fuel pressure regulators on the market. I've chosen the Aeromotive units as they are reliable and offer rising rate ports for boosted engines. These units will allow you to accurately stabilize and set a constant fuel pressure for NA applications, or a rising rate for boosted applications.

Order yours here: Fuel Pressure Regulator

Fuel Injectors

As the name states, these are used to inject fuel into the engine. These are replacing your SU old carburetor and are controlled from the ECU with a PW (pulse width). This allows for a precise amount of fuel to be injected as needed. Once this fuel is burned your wideband 02 sensor is used to sniff the burned fuel mixture. This allows a closed-loop control to take place (EGO correction) where the ECU can make small changes to the fueling and compensates for changing conditions.

Injector Notes

• Denso 280cc - Good for small bore engines

• Denso 320cc - Best tested for large bore NA Engines

• Denso 380cc - Untested at this time

• Bosch 440cc - Standard for other EFI kits on the market

• Siemens Deka 630cc - Good for high boost/high flow engines

• Bosch 630cc - Alternative to Siemens injectors

Conclusion

The fuel system, while having a fair bit of special requirements is not overly complex when you get down to installing it. These are the core items required to get this set up but purchasing rubber or PTFE fuel lines as well as fixings will be required as well.

Below you will find a (relatively) comprehensive list of the parts and things you may need to accomplish this on your own car. If you are keen to do this to your car, start here as we go through the various aspects of a conversion like this. Strap in and get ready. It's time to learn about EFI and the Classic Mini.

Why would I want to fuel-inject my old Mini?

This is a question I receive a lot concerning this type of project.

- What's wrong with the carb?

- What's the point?

- Why would you want to put all those wires in there?

- And on, and on...

The truth is a carburetor is the simplest way to run your car. That said it is far from the most reliable, most efficient, and highest-performing way to run your car. A whole technical article could be written purely on why EFI is objectively better than a carburetor in almost every way but we won't get too far into that in this article.

Fuel injection will solve a few primary things

• Optimize fueling so you are always burning as efficiently as possible

• Control your timing to pull out all the horsepower in your engine

• Increase reliability as it scales with weather conditions

• Decrease failure points (yes I know this is counter-intuitive)

What parts will I need?

With that background out of the way, let's get into the meat and potatoes. What exactly will you need to fuel inject your mini, and where can you get it? Some items below are offered directly in my store, while others are items you must source yourself. I will do my best to make this as easy as possible. But should you have any questions feel free to comment below!

Leave a comment

EFI Carburettor Replacement - EFI Throttle Body

The first thing you will need is a way to deliver fuel and manage your throttle opening. This is the most mechanically complicated portion of the conversion process and will directly replace your carburetor. For this, there are two primary options that will directly bolt on.

Note: I will not be covering cross-flow cylinder heads or their fuel injection throttle bodies in this article.

Edit 2026 - We no longer recommend the Cable throttle bodies for conversions. Offering now the drive-by-wire options exclusively, as they are considerably more reliable and safe, as well as being easier to tune.

Option 1 - Cable Driven Throttle Body

The simplest solution is to install a cable-driven throttle body. This will provide you the ability to easily connect your existing throttle cable. This simplifies the swap but doesn't yield all the advanced features that option 2 provides such as idle control, cruise control, and more. Classic Mini DIY offers the most affordable CNC unit on the market. It comes with a built-in Throttle Position Sensor and the wiring pigtail to connect it to your ECU.

Order yours here: CMDIY Cable Throttlebody

"Drive by Wire" Throttle Body

The more advanced but significantly more feature-rich solution is a Drive by Wire setup. This would require an electronic pedal and an ECU that supports this setup. However, the benefits of this setup include things like full automatic idle control, launch control, cruise control, custom throttle curves and more.

Order yours here: CMDIY Drive by Wire Throttlebody

Crank Position Sensor

After the throttle bodies, the next important piece of hardware will be your Crankshaft Position Sensor. This small sensor and bracket system will tell your ECU where your engine is in its rotation. This is absolutely essential for your ECU to properly understand when to fire the spark plugs.

Order yours here: MED Crank Pulley + Trigger Wheel

Coilpack Ignition Coil

In a distributor system, your distributor combined with an ignition coil handles the job of firing your spark plugs. With a fuel injection system, you need something a bit more sophisticated to get the job done. That is where the Coilpack comes in. This gets connected to your ECU and allows uniform and reliable firing of your spark plugs using its built-in ignitor.

Order yours here: Bosch VW Coilpack

The ECU (Engine Control Unit)

With the large variety of ECUs on the market, *Which ECU should I get? is the question I get asked the most. The short answer to this question is, "The one that offers you all the features you need for your setup". However, this answer is obviously not very helpful. So below I have put together a table of ECUs and the features they offer compared to what you may need for your setup. All the ECUs below will run an A-Series engine with varying degrees of complexity.

Some ECU’s you could use:

• Haltech Elite 750 |

  • DBW - ❌

  • Support - 👍

  • CMDIY Base Map - Purchase or Download

• Haltech Elite 1500

  • DBW - ✅

  • Support - 👍

  • CMDIY Base Map - Purchase or Download

• Haltech Nexus R3

  • DBW - ✅

  • Support - 👍

  • CMDIY Base Map - Purchase or Download

• Emerald K6

  • DBW - ✅

  • Support - 👍

  • CMDIY Base Map - Purchase or Download

• Speeduino - DIY

  • DBW - ✅

  • Support - DIY

  • CMDIY Base Map - Purchase or Download

• MegaSquirt - DIY

  • DBW - ✅

  • Support - DIY

  • CMDIY Base Map - Purchase or Download

• Specialist Components (SCS) - Delta 400

  • DBW - ❌

  • Support - Contact SCS Direct not Specialist Components

  • CMDIY Base Map - ❌

• Specialist Components (SCS) - Delta 700

  • DBW - ✅

  • Support - Contact SCS Direct not Specialist Components

  • CMDIY Base Map - ❌

Now this is not a comprehensive list of every ECU on the market. But these are the common ECUs I see people using in their Minis these days. My top pick for the Classic Mini owner is by far the **Haltech Elite 1500 with Wiring Harness**. This will sort out almost every EFI conversion I come across and they offer unparalleled support for their hardware via phone/email/chat.

Order yours here: Halech Elite 1500

Intake Air Temp Sensor

This reads the temperature of the air coming into the engine so that the amount of fuel can be adjusted accordingly. In NA installs, this can go before the throttle body or in the air filter housing. In turbo applications, make sure this is mounted after the turbo and anything that will modify temperature (Intercooler, Water/Meth injection). This should also be after the throttle body in single-throttle body applications.

Order yours here: Air Temp Sensor

Coolant Temp Sensor

This sensor reads the temperature of the engine. In a Classic Mini, the best placement for this is directly in the thermostat housing. S-CAN (formerly DSN Retrosport) sells an excellent thermostat housing that supports the attachment of an M10 x 1 coolant temp sensor. This can be run in addition to your original factory item that is mounted directly to the cylinder head.

Order yours here: Coolant Temp Sensor

MAP(Manifold Absolute Pressure) Sensor

MAP is used to provide engine load information in the form of a vacuum signal to the ECU. It requires a vacuum reference from a port **_after_** the throttle plates. This fuel control method is known as SD or Speed Density and also uses intake temperature to calculate the fuel needed. This is my favorite way to map a car. In the Mini, I attach this to the intake manifold via a T-Pipe off the brake booster circuit.

Order yours here: 3 Bar Map Sensor

Wideband O2 Sensor (Air Fuel Ratio)

The final component to complete all of the sensors your ECU will need to understand the state of the cars is a Wideband O2 Sensor. These are also called Air Fuel Ratio gauges, or AFR sensors. This sensor is sniffing the exhaust as it exits the car and measures the amount of fuel present in that air. This creates a lambda value or a ratio percentage your ECU will use to adjust the amount of fuel it should be firing into the intake.

This sensor will require you to weld in a bung on your exhaust, which will allow you to screw in this new sensor. Depending on your setup it will need to be welded in at a specific location.

- NA Engines - Weld in after all 3 output branches from the engine

- Turbo engines - Weld in approx 5-6 inches after the hot side of the turbo on the downpipe.

Order yours here: AFR Sensor with Output to ECU

Conclusion

This is a high level of the core hardware you need to get started on your EFI journey. In the next article, we will be covering fuel systems and the parts/supplies you need to build out that portion of your build.