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Injector Flow

  • What size injectors do I need?

Types of Body

Types of Connections

Injector styles.jpg

Types of Outlets

One thing to consider when purchasing injectors is the spray pattern. This difference is most noticeable when comparing older <1990 injectors to newer >1990 injectors. The older injectors have a single exposed pintle (Fig. 1), whereas more modern injectors tend to have an internal pintle with a patterned nozzle (Fig. 2) that helps better disperse fuel into the intake air.

Fig. 1 — an exposed pintle.
Fig. 2 — a quad-hole nozzle.

It’s evident just from the physical difference that the spray pattern will differ. In the below image (Fig. 3) you can see a comparison of both of these two patterns.

Quad hole nozzle injector (left) vs. single hole nozzle injector (right). Notice the more dispersed pattern of the quad hole unit.

The patterned nozzle will provide better overall fuel efficiency which can lead to improved fuel economy and power output while also minimizing knock potential. Upgrading injectors to a patterned nozzle is a worthwhile upgrade for any vehicle equipped with an exposed pintle design.

BMW Injectors

So what do you need to use for your BMW? This depends on your year and engine. For pre-2014 vehicles it's most likely going to be a "long" body injector with EV1/Jetronic connection. There are some exceptions, such as the M44B19 which uses an unusual injector and requires an adapter for common injectors to be used. With direct injection and diesel engines, injectors vary drastically depending on engine.

M20 vs M50 injectors

A common upgrade that people make to their M20 is to use M50 injectors. It's often stated that these injectors flow more, and while that is true, it's a minimal difference of about 6.5%. What this means is that you can usually use M50 injectors with a tune meant for stock M20 injectors.

Please keep in mind that 86+ M20 models use a 3.0 bar fuel pressure regulator (M20B27 ETA and early M20B20 models use a 2.5 bar regulator), whereas M50 models use a 3.5 bar regulator. So while M50 injectors will flow around 190 cc/min @ 3.5 bar, they will flow only about 165 cc/min @ 3.0 bar. Compared to the 155 cc/min of the M20 injectors, this is not much of an upgrade in terms of flow rate. However, the M50 injectors do utilize a patterned nozzle instead of an exposed single pintle. This provides a much improved spray pattern and fuel dispersion into airflow and can provide slightly better combustion. Therefore it is a worthwhile upgrade for stock or near-stock M20 engines, but is not suitable for vehicles making above about 160 WHp without increasing the fuel line pressure.

A comparison of the flow rates between M20 injectors (0280150715) and M50 injectors (0280150415) can be seen below:

Caption text
Test 0280150415 0280150715
Static 3.0 bar 165 cc/min 155 cc/min
Static 3.5 bar 180 cc/min 192 cc/min
8000 RPM 3 MS 3.0 bar 65.5 cc/min 70 cc/min
8000 RPM 3 MS 3.5 bar 72 cc/min 76.5 cc/min
M20 vs M50 injectors