Removing the catalyst on the <em>Nissan Almera N16</em>: is it worth the trouble?

Owners Nissan Almera N16 With high mileage, they often encounter the problem of a clogged catalyst - the part begins to “choke” the engine, fuel consumption increases, and acceleration dynamics leave much to be desired. Many people consider removing the catalyst as a budget solution, but before you pick up an angle grinder or go to a service center, you should weigh everything pros and cons this procedure. In some cases, deletion is truly justified, in others it can lead to new problems.

In this article we will look at technical, legal and economic aspects removing the catalyst Almera N16 (including versions with engines QG15DE And QG18DE). You will learn how to check that the catalyst is clogged, what alternative solutions exist besides complete removal, and how to avoid mistakes when flashing the ECU. And also - real reviews from owners and data on changes in fuel consumption after modification.

Why does the catalyst fail? Nissan Almera N16?

Catalytic converter on Almera N16 designed for 150–200 thousand kilometers, but in practice problems begin after 100 thousand km. Main reasons:

• 🔥 Low fuel quality: Russian gasoline often contains sulfur and additives that “poison” the catalyst cells, clogging them with soot.
• 🛢️ Oil zhor: if the engine QG18DE the oil begins to eat up (a common problem after 150 thousand km), its remains burn in the catalyst, forming a dense soot.
• 💥 Mechanical damage: Impacts to the bottom (for example, on a bad road) can destroy the ceramic honeycombs, which will lead to their clogging with fragments.
• ⚡ Ignition system malfunctions: Misfire causes unburned fuel to enter the catalyst, where it burns out, overheating and destroying it.

The first symptoms of a clogged catalyst Almera N16:

• 🚗 Loss of power (the car “does not pull” at speeds above 3000).
• 💨 Increased fuel consumption by 1–2 liters per 100 km.
• 🔊 Characteristic “gurgling” or rattling noise under the bottom during acceleration.
• ⚠️ Lights up Check Engine with errors P0420 or P0430 (low catalyst efficiency).

⚠️ Attention: If the dashboard lights up Check Engine with an error P0420, this does not always mean that the catalyst is clogged. Sometimes the problem lies in lambda probes (oxygen sensors). Before removing the catalyst be sure to check them with a multimeter or for diagnostics.

Pros and cons of removing the catalyst: an honest analysis

Removing the catalyst is not a panacea, but a compromise. Let's figure it out real consequences this modification for Nissan Almera N16.

Pros	Cons
✅ Improved acceleration dynamics (especially at the “top”).	❌ Increased exhaust toxicity (you won’t pass eco-standards Euro 5).
✅ Reduced fuel consumption by 0.5–1.5 l/100 km (with correct ECU settings).	❌ Problems with passing technical inspection (if the decoy is not installed or the ECU is not reflashed).
✅ Reducing the load on the engine (no resistance to exhaust gases).	❌ Risk of overheating of the exhaust manifold (if a flame arrester is not installed).
✅ Cheaper than replacing with a new catalyst (price of the original - from 30,000 ₽).	❌ Possible problems with the operation of lambda probes (signal adjustment required).
✅ Easier to repair the exhaust system (no fragile ceramic block).	❌ The exhaust is noisier (if a high-quality flame arrester is not installed).

One of the main myths is that after removing the catalyst Almera N16 will become "volatile". In practice, the power increase is 5–10 hp, which is noticeable only when overtaking. Main effect - improved gas pedal responsiveness and lack of "thoughtfulness" during acceleration.

But what will definitely change is: exhaust sound. Without a catalyst, it will become rougher, especially at high speeds. If this bothers you, you will have to install a flame arrester (for example, from Bosal or Walker), which partially compensates for the lack of a catalyst.

Legal nuances: what does the law say?

From the point of view of Russian legislation, removing a catalyst is change in vehicle design, which requires approval from the traffic police. However, in practice:

• 📜 Technical regulations of the Customs Union prohibits the operation of a car with a removed catalyst if this leads to exceeding emission standards.
• 🚔 Punishment: when checking at a traffic police post or during a technical inspection, a fine may be issued 500 ₽ (Article 12.5 of the Administrative Code) or prohibit operation until the malfunction is eliminated.
• 🔧 Workaround: many services install universal catalysts (for example, from Magnetti Marelli) or lambda probe decoys, which formally preserve the “legality” of the modification.

The most reliable way to avoid problems is install a flame arrester with a built-in catalytic layer (For example, Eberspächer or HJS). Such devices are more expensive (from 15,000 ₽), but they undergo technical inspection and do not raise questions from inspectors.

⚠️ Attention: If you removed the catalyst and did not make changes to the title, when selling the car, the new owner can challenge the deal in court. In practice, there have been cases when a car was returned to the previous owner due to design inconsistencies.

Step-by-step instructions: how to remove a catalytic converter Almera N16

If you decide to delete, here step-by-step plan taking into account the specifics Nissan Almera N16.

1. Preparation of tools and materials

Angle grinder (grinder) with cutting wheel for metal | Set of sockets and ratchet wrench (for removing protection and fastenings) | Sealant for the exhaust system (for example, DoneDeal or Permatex>)|New gaskets for flanges (original - 14044-4M000)|Flame arrestor or insert instead of a catalyst (optional)|Lambda probe decoy or ECU firmware-->

2. Dismantling the catalyst

On Almera N16 The catalyst is located immediately behind the exhaust manifold (“spider”). Procedure:

1. Remove the engine protection (4 x 10mm bolts).
2. Disconnect the oxygen sensors (lambda probes) - first the lower one (after the catalyst), then the upper one (in front of it). Be careful: the sensors are fragile, do not pull the wires!
3. Unscrew the flange connection between the spider and the catalyst (2 14 mm bolts). If the bolts are stuck, use WD-40 or heat them with a gas torch.
4. Cut the catalyst using a grinder along the weld seam (carefully so as not to damage the rest of the exhaust system).

3. Installation of flame arrester or insert

If you decide to install a flame arrester (recommended for QG18DE), select a model with perforated pipe and stainless steel filler. Example of suitable options:

• 🔥 Bosal 255-141 - budget option (about 3,000 ₽).
• 🔥 Walker 20630 - more durable (about 5,000 ₽).
• 🔥 Homemade insert from a stainless pipe with holes (only if you have welding experience!).

After installing the flame arrester:

1. Secure it to its original location using clamps or weld it.
2. Install new gaskets on the flanges.
3. Connect the lambda probes (if you are not using decoys).

4. ECU adjustment or installation of blende

Without this step the dashboard will light up Check Engine. Solutions:

• 🔧 Mechanical snag (insert into the gap in the lambda probe wire) - cheap (500–1,000 rubles), but it may not work the first time.
• 🔧 Electronic snag (signal emulator) - more reliable, but more expensive (2,000–4,000 rubles).
• 🔧 Flashing the ECU (disabling the second lambda probe) is the best option, but requires turning to chip tuners (price from 3,000 ₽).

⚠️ Attention: On Almera N16 with engine QG18DE after removing the catalyst an error may appear P0134 (no signal from the sensor). In this case, mechanical trickery will not help - you need an emulator or firmware.

💡

If, after removing the catalyst, the car begins to become “stupid” at low speeds, the problem is most likely due to incorrect settings of the ECU fuel map. Contact a specialist to adjust the firmware.

Alternative solutions: what to do instead of deleting?

Removing the catalyst is not the only way to restore Almera N16 to life. Let's consider less radical options:

• 🔄 Washing the catalyst: special liquids (for example, Liqui Moly Pro-Line Katalysator-Reiniger) can clear soot from honeycombs. Efficiency - 30–50%, works only in the early stages of blockage.
• 🔧 Replacement with a universal catalyst: cheaper than the original (from 8,000 ₽), but will last 50–80 thousand km. Popular brands: Magnetti Marelli, NGK, Denso.
• 💡 Installation of a sports "spider" 4-2-1: improves cylinder purging and reduces the load on the catalyst. Suitable for tuned versions.
• 🛠️ Exhaust system repair: if the problem is a burnt corrugation or gaskets, replacing them will cost 2–3 times less than removing the catalyst.

If you still want to remove the catalyst, but are afraid of legal problems, consider installation of a catalyst with an increased resource. For example, models from HJS or Eberspächer serve up to 200 thousand km and pass eco-standards Euro 5.

What happens if you drive with a clogged catalyst?

Driving for a long time with a clogged catalyst leads to:

- Increased pressure in the exhaust tract, which creates additional load on the piston group.

- Risk of melting of the catalyst honeycombs and getting their fragments into the cylinders (a major engine overhaul may be required).

- Increased oil consumption due to increased back pressure.

- Loss of power up to 20–30% (especially noticeable on the engine QG15DE).

Owner reviews: real experience

To understand whether the game is worth the candle, we collected reviews from the owners Nissan Almera N16 after removing the catalyst:

Engine model	Mileage, thousand km	Effect after removal	Problems
QG15DE	140	Consumption dropped from 9.5 to 8.2 l/100 km, the car became “more lively”.	I had to install a lambda emulator (the trick didn’t work).
QG18DE	180	The dynamics improved, but a metallic ringing sound appeared in the exhaust.	After 10 thousand km the corrugation burned out and had to be replaced.
QG15DE	110	Removal + ECU firmware. Consumption has decreased by 1.3 liters, there are no errors.	The inspection passed only after installing a flame arrester with a catalytic coating.
QG18DE	200	The car stopped being dull, but the exhaust became louder.	I had to pay extra for soundproofing the bottom.

General conclusion: removal of the catalyst is justified, if:

• 🚗 The mileage is more than 150 thousand km, and the catalyst has already crumbled.
• 💰 There is no money for an original replacement (30,000+ ₽).
• 🔧 Are you ready to spend money on a flame arrester and ECU firmware.

If the car is under warranty or you are planning to sell, it is better to consider alternatives - flushing or a universal catalyst.

FAQ: Frequently asked questions about catalytic converter removal Almera N16

🔧 Is it possible to remove the catalyst yourself, without welding?

Yes, but this is a temporary solution. You can knock out the ceramic honeycomb through the hole for the lambda probe (after removing the sensor), but:

• Fragments may remain in the housing and enter the cylinders.
• Without welding or clamps, the catalytic converter housing will rattle.
• The dynamic effect will be minimal (it’s still better to cut with a grinder).

For complete removal you will need welding or at least high-quality clamps for the screed.

⚡ Will there be problems with the engine after removal?

When the flame arrester is installed correctly and the ECU is configured there won't be any problems. However:

• On the engine QG18DE Oil consumption may increase (due to changes in back pressure).
• If you do not install a flame arrester, the corrugations or flanges will burn out over time.
• On some cars, vibration appears at idle (solved by balancing the crankshaft).

💰 How much does it cost to remove a catalyst in the service?

Prices depend on the region and scope of work:

• Removing + inserting flame arrester: 5 000–10 000 ₽.
• Removal + ECU firmware: 8 000–15 000 ₽.
• Removal + installation of blende + welding: 6 000–12 000 ₽.

Self-removal will cost 2 000–4 000 ₽ (flame arrestor + materials).

📄 Is it possible to undergo technical inspection after removing the catalyst?

Formally, no, but there are workarounds:

• Install flame arrester with catalytic coating (passes test for CO/CH).
• Use lambda probe emulator (not all maintenance points check the exhaust with a gas analyzer).
• Contact a “loyal” service center (in some regions they only check lighting equipment and brakes).

Since 2026, the rules have become stricter - now the presence of a catalyst can be checked visually during a technical inspection.

🔊 Will the car become louder after removal?

Yes, but the degree of noise increase depends on:

• Type of flame arrester (perforated models are quieter than direct flow).
• The presence of a resonator in the exhaust system (on Almera N16 it is located closer to the muffler).
• Welding quality (bad welds can create whistling noise).

On average the sound becomes 10–15 dB louder (comparable to sports exhaust). If this is critical, install an additional resonator.