We'll keep this post short as there isn't much to go into. The N20 and N26 are basically the same exact engine. Feel free to leave it at that and stop reading. None of the differences between the N20 and N26 are too important. Both make the same power and torque. Additionally, the N20 and N26 share over 95% of their part numbers. For those who want to learn about the minor differences, read on.
ULEV (N20) and SULEV (N26)
This relates to emissions regulations. ULEV stands for "Ultra-Low Emission Vehicles". Add the word Super and you've got SULEV. BMW's N20 engine qualifies as ULEV, while the N26 is SULEV. To accomplish this, the BMW N26 receives a few emissions related changes, including:
- Electric waste-gate actuator
- Catalytic converter
- Additional HC filter in air box
- Re-designed HPFP
- "Sorted" fuel injectors
- Stainless steel fuel lines
There are a few minor changes in addition to what is listed above. Most are rather boring and have zero impact on anything so we decided to leave them out.
N26 Electric Waste-Gate Actuator
To note, N20's produced after 07/2012 also received this update. Another note, the N20 and N26 turbochargers are exactly the same (apart from waste-gates on early model N20's). The electric waste-gate actuator is intended to assist in the rapid heating of the catalytic converter. Most emissions occur prior to the cat warming up. As such, this is an important piece of meeting SULEV regulations.
N26 Catalytic Converter
The N26 receives a more restrictive catalytic converter in the downpipe. Also, the N26 gets a second cat in the mid-pipe, which the N20 does not have. Again, this is intended to meet SULEV regulations. However, the restrictive N26 exhaust is slightly worse for performance. Regardless, the N20 and N26 make the same peak power and torque. The major difference is on the top-end where the N26 falls off a tiny bit compared to the N20.
N26 HC Filters
Nothing too interesting here. An additional HC fleece filter assists in preventing hydrocarbons from escaping. Hardly worth mentioning other than you may notice a slight difference in the appearance of the air box internals.
N26 HPFP Re-design
The N26 HPFP itself remains the same as the N20. However, the N26 pump is modified with a groove in the outlet valve. This allows the fuel to be cut in a shorter period when the engine is shut off. In essence, it reduces the risk of fuel leaking.
N26 "Sorted" Fuel Injectors
This is actually an interesting one in terms of N20 vs N26 reliability. Oddly, the N26 receives "sorted" injectors. They are exactly the same as the N20 and N55 engines. However, the N26 injectors are hand selected from a batch after testing for leakage. The injectors with the least leakage are applied to N26 engines. We're not sure if this is true, but we imagine that means they're less likely to be defective.
N26 Stainless Steel Fuel Lines
Finally, the N26 fuel lines are are modified to ensure no leakage occurs. The low pressure line from the tank to the engine compartment is plastic. The fuel line from the compartment to the HPFP is stainless steel. BMW implemented the partial stainless steel fuel line to prevent fuel leaks. This may help the N26 hold up in the longer run with E85 use. However, fuel lines on other BMW's haven't really had many issues. As such, this is probably rather meaningless apart from SULEV regulations.
N20 vs N26 Performance
We touched on this briefly throughout. However, expect minimal performance differences between the N20 and N26. The more restrictive cat in the downpipe and second cat limit N26 top-end performance ever so slightly. Most will likely not even feel the difference. Nonetheless, for the performance nuts, we recommend a catless downpipe anyways. Aside from the catalytic converter difference, these engines perform nearly identical.
Do I Have the N20 or N26?
This question comes up often: does my BMW have the N20 or N26 engine? Pop the hood and look on the underside of the hood. Right near the center you should see an emissions sticker. If the sticker shows ULEV then you have an N20. On the contrary, SULEV would indicate your BMW is an N26. You can also find various VIN searches to check.
*The below image indicates an ULEV N20 engine
N20 vs N26 Summary
There you have it. That's really all there is to N20 and N26 differences. Again, there are some other minor differences that we did not touch on. However, the purpose of the N26 was simply to meet stricter emission regulations. Updates to the exhaust system restrict performance slightly, but nothing too notable. The N26 injectors are "sorted" and may show to be more reliable than N20 or N55 injectors in the long run.
Otherwise, the N20 and N26 produce the same peak power and torque from the factory. They share over 95% of the same parts. Both the N20 and N26 are excellent, sporty, and efficient BMW engines.