Aftermarket hardware

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This page lists the various aftermarket hardware.

Aftermarket ECU's intented for gasoline engines

In direct injection engines (1), open-source and closed-source (commercial) aftermarket ECU's allow setting the amount of air and fuel injected to the cylinders (liquids or gases) as well as alter the timing of the injection and activation of the spark plug. This is very important, as different fuels have different air/fuel ratio's and the timing too may be different.

It thus allows for ethanol, biogas, and even water, HHO or hydrogen injection to the engine. All of these allow to eliminate emissions (except for water and HHO/hydrogen -the first one just reduces knocking, and allows more fuel to be injected, and the second one tends to be injected to allow running on a leaner air/fuel mix). Speed/power may be increased as well (depending on what fuel is used and how the injection is done).

This hence allows people to make their car with conventional gasoline engine (with direct injection) both faster and more ecologic (if only the biofuel is injected, and no fossil fuels -so no dual injection-)

Open-source ECU's (intented for gasoline engines) include:

Ethanol kits

Many ethanol kits can be found/bought online, but most just alter the (stoichiometric) air/fuel mixture with standard ECU's. So you don't need that if you're using an open-source (aftermarket) ECU (and have set the air/fuel mixture to 9:1 -when using pure ethanol; aka E100-). What you do need to change though is any natural rubber and plastic parts (seals, hoses) that the ethanol comes in contact with. This, as the ethanol will eat through these materials over time. So, make sure you replace them with metal replacement parts.

Biogas kits

For converting your vehicle to biogas (or methane), CNG conversion kits can be used. Basically, you can just use an open-source ECU (for changing the air-fuel ratio to 17.2:1) -or alter the carburator if you have an indirect-injection gasoline engine-. You also have to add a strong tank to store the biogas in -most often, steel cylinders are used- (as the CNG/biogas tank must allow for pressures upto 3600 psi) and add a pressure reducer (which reduces pressure between the tank and the fuel injector). Your existing gasoline tank can be kept, or swapped for a smaller one (as you'll only need a small quantity of it anyway, just for starting/heating the engine). Also needed is a system to switch between the fuel in your first fuel tank (holding biobutanol or ethanol) and your second one (holding biogas). Keep in mind that since the biogas is stored at such high pressure, this can be dangerous, and your vehicle would only be road-legal if you let a certified CNG installer install it. Note that, although LPG conversion kits have similar parts you can't use an LPG conversion kit for using biogas, as the pressure that tank needs to be able to withstand is only 100-200 psi (so those tanks are generally too weak).

Some kits are:

Formic acid kits

As described at the Vehicle conversion FAQ, we do not promote on-board fuel systems in vehicles which use large compressed hydrogen tanks. This is due to the limited range (if using CNG parts) and safety issues. Using formic acid however (which is converted to hydrogen and then injected to an internal combustion engine) remains a possibility. The air-fuel ratio will need to be set to 34,3:1 (same as for hydrogen, because it is hydrogen which is injected to the engine). Safety is ensured due to the fact that formic acid will not explode or burn (so most of the energy you carry can never ignite or explode, only a very small portion of hydrogen, created temporarily, poses a slight risk). Another benefit of this system is that (besides being near carbon-neutral like the other fuels), it is also pollution-free. Existing CNG-parts (preferably made from aluminium) can theoretically be used to inject the hydrogen into the engine. A plastic tank needs to be used to hold the formic acid.

Aftermarket ECU's intented for Diesel engines

Today, ECU's are also used with direct-injection Diesel engines (in the past, a simple governor was used and the whole required no electric components at all (2)). Although using the direct injection method adds complexity, it does allows for less fuel consumption and so, it's now found on all contemporary Diesel vehicles.

It thus comes to no surprise that open-source ECU's have also come into existence. These aftermarket ECU's intented for Diesel engines can also allow for extra comfort when using pure plant oil. This, because the the fuel tank or fuel line requires heating. There are both electric heaters and water-based heat exchangers (running from the water coolant tank) for this. The electric heaters work immediately, the water-based heat exchangers don't work from the start (so require either an additional electric heater or a 2-tank system so they can be started on conventional diesel). It would be useful to integrate the ability to connect/disconnect electric heaters and/or open/close valves (the latter for if a 2-tank system is used). So far, most ECU's do not allow this, but it could be integrated in later versions allowing easier use with the heating system provided by PPO kits (see further down below).

Open-source ECU's (intented for Diesel engines) include:

Pure plant oil kits

Pure plant oil kits allow for running your Diesel engine on pure plant oil (PPO). They basically contain the heaters (or just heating pipes) along with filters and sometimes an extra fuel pump. They come in 2 forms: single and double tank kits. Single tank kits start directly from PPO, whereas 2-tank kits start from a lighter fuel (like petrodiesel or biodiesel), and then switch to PPO from the other tank, once the engine is hot. Some kits are:

HHO boosters

Our main open-source HHO generator plans are the plans from HydrogenFirstAid. You can download them here

HHO (or oxyhydrogen) generators produce oxyhydrogen, and mix it in with either biobutanol or ethanol (gasoline engines) or biodiesel/pure plant oil (diesel engines). By producing and injecting oxyhydrogen (by means of a chemical reaction created using power from your car battery), it allows running on a leaner air-fuel mixture and still allow for a good combustion (that is, if you use an EFIE). The air-fuel ratio can be as lean as 20:1 (normal with gasoline is 14.7:1). They hereby allow for 20%-40% more miles to the gallon. The correct amount of HHO to use is about 0,125 liter per minute per liter of engine size. Introduction to the engine can be done using indirect injection or direct injection (ie by using an open-source ECU like the speeduino, and attaching the HHO generator to the fuel lines running to the fuel injectors).

Some HHO boosters are:

Most of these HHO boosters can also be used to produce hydrogen instead. Distilled water can be used mixed with either baking soda, sodium or potassium hydroxide, and the generated oxygen and hydrogen can then be kept separate. When using it simply to mix it in with another fuel, a significant downside however would be that the efficiency of hydrogen electrolysis is lower.

Forced induction devices

Forced induction devices include things like turbochargers, superchargers and even fans, ... They are used to increase the amount of air introduced to the engine's ignition chambers. The increase in power that can be expected differs depending on the device used. With turbochargers, an increase of 35-60% can be expected since waste heat is used as the power source. Superchargers and fans increase power outputs significantly less, but are generally cheaper to acquire. The devices can be used mainly on indirect-injection engines, since the air inflow is not electronically controlled with these. Engines that do have electronic ignition systems would require changes in the system to allow using them.

Forced induction devices include:

Display systems

These include the:


For 2-stroke engine conversions, see the FAQ

Air/fuel ratio when using methane (i.e. generated via the Sabatier process) is 17.19 : 1
Air/fuel ratio when using pure hydrogen is 34.3 : 1
See wikipedia on stoichiometry


  • 1: Indirect injection engines allow changing to other fuels too, by altering the carburetor; see here and here
  • 2: In the past, gasoline engines too didn't require many electric components; rather the whole was accomplished using a carburetor and a ignition magneto (so didn't even require a battery)