Today’s patient: N53 in its most powerful version (N53B30O0). The engine has lost “surge”/torque, especially in the range of high RPM. Accordingly – the task is to find the problem and solve it. 

Subjectively, the car accelerates languidly, and the torque loss can especially be felt at higher (above 3500 .. 4000 ) RPM. The “push” of large DISA cannot be felt at all. It feels like DISA is not working. 

A long time ago, I wrote an entry on making sure that the engine is providing full torque; if not – instructions on how to understand where the problem is. So this time, I followed my own list. 

Shortlist: there are no error messages in DME and DSC modules (at least the ones that can cause this problem). The throttle is opening completely. DISA live data indicate that both valves are managed. 

Yes, at first, the status of the “right side” DISA changes to 67%. Above 5000 RPM the reading of the large DISA also indicates that DME has requested its opening. 

Here we have to understand that DME sends the management command, and DISA only confirms the receipt of the electrical management signal and its electrical actuation. Does the valve really open? Is the sealing ring in good technical order – it can be evaluated only visually. But, in any case – DISA is connected; there are no error messages regarding them. Their statuses change. There is no doubt – the engine works according to the Power_Class 02H, which means, according to the version of 200kW. 

Let’s check the fuel mixture data in kickdown mode. Wait, what’s that?

The fuel mixture is too rich! Already by 3000 .. 3500 RPM, Lambda in both banks drops to 0.80 .. 0.85. When DME switches in Closed-loop mode (it happens 2 .. 3 seconds after opening the throttle), we see that such Lambda is reached by Integrator values -15 .. -20%. There is at least 15 .. 20% more fuel in cylinders than necessary; in addition, such a situation happens when DME has already reduced its amount by 15 .. 20%. So, the total “overuse” of the fuel is even 30 .. 35%!


a. either too much fuel gets in the cylinders;

b. the cylinders are experiencing a lack of air. 

Problems with the fuel amount are doubtful. The fuel pressure is measured and stabilized continuously. Indications of the Rail sensor are verified and adapted to different driving conditions; everything is fine with the fuel mixture (correct Multiplicative type LTFT; correct live data of the fuel mixture). Also, the injectors behave correctly in all other conditions.

An insufficient amount of air could be (if we dismiss already checked things – throttle, which position is controlled by two sensors, electrical part of the DISA valves): 

a. DISA valves – their mechanical part;

b. air filter. 

Let’s start with the simplest version – I took out the air filter element and repeated the test:

Well, completely different picture! As we see, Lamdba in both banks is 0.95, which corresponds to the correct (slightly rich) fuel mixture. Integrators are very close to 0 (around -2 .. -5%). Perfectly projected and maintained fuel mixture! 

At this moment, the performance of the large DISA could be felt very well.

When checking the filter element, I had to admit – visually, it was not in a terrible shape. As if a regular filter, it is possible that during winter, it “got” some water – it happens if you drive your car in wet weather (air humidity close to 100%), heavy rain or snow, and, of course, if you go thru some deeper puddle of water. 

I already predict the comments – “you had to start with it”. “What to measure – just take a test drive.”

Objection regarding the second part – “bottommeasurer” is a very unreliable measuring tool. And it won’t help if the problem is more complicated or if there are several problems. Only live data give an objective picture!

Objection regarding filter – I have witnessed the situation when the mechanic is visually inspecting the filter to evaluate its performance. In this situation, such a test would fail. The same filter would be put back with the note, “well, everything looks fine there”.

One more nuance has to be taken into account. For example, in the case of E60, the identical air filter is used for all 6-cylinder engines. Starting from deforced M54 (520i) to 200kW N53 (530i; N53). The difference in the power generated by these engines – is double! Accordingly, the engine’s difference or air “consumed” is double! Of course, the most powerful engine is much more demanding of the quality of the filter and its technical conditions. The cheapest filters, which will correctly work with M54, will not fit the most powerful version of N53! This has to be kept in mind by mechanics, who choose the budget versions and “analogs” in the spare part catalogs. 

For example, in this case, the filter code is 13717521033. When checking the available versions, we see:

a. BMW original filter costs EUR 28;

b. MANN filter costs EUR 22;

c. Bosch filter costs only EUR 11 (surprise because there are doubts that at least 2x times cheaper filter can be made of quality materials);

d. range of other “analogs” – Mahle, Valeo, Purflux, Meyle, Clean, Denckermann, Mapco, etc. – price category from EUR 6 to EUR 10. 

Of course, it would be pretty interesting to perform tests for these analogs on the airflow and the ability to filter microparticles, but I suppose there won’t be any miracles. Doubtfully the 5x cheaper filter will give excellent results.