DISA or not to DISA? that is the question. N52

[Naylz]

Ok fellow Zed people, I have a 2.5i 2008 Z4 N52 with approx 90000 miles on the clock. It is the one with a single DISA, black and green electric type. Can anyone tell me what typically happens when they start to fail, do they get slower in reacting or do they simply just stop working, do they throw codes up specifically for the DISA or will it cause some other code to trigger. Also what is the best replacement, seems they range from £45 to £270, obviously the latter being the BMW genuine part.......but who makes those and can you get them cheaper?

Thanks in advance

[lucasxdiniz]

They don't tend to be a problem, but they can fail. Have a read through this thread:

https://www.e90post.com/forums/showthread.php?t=1491906

[Naylz]

Thanks for the link, I have read that one before but they seem to be talking about the engines with two DiSA, small and large. Mine just has one large. Really want to know what happens in the early stages of failure, do you think if the motor is gunking up they would get slower in operation? I'm experiencing a slightly rough idle and lumpy lower rev acceleration which goes away above approx 3000rpm. I have already had new vanos solenoids, valvetronic motor, eccentric shaft sensor, plugs, filters. The only codes coming up at this point were knock sensor 1 and 2, so I recently renewed the knock sensors, reset the codes and cleared adaptions. All was well at first couple of drives, then I got knock sensor 1 again and a mixture code with orange engine light. These reset ok, however I tried driving with the code reader connected and whenever I accelerate hard, I get a kind of hesitation as it gets past the 2000-3000rpm zone and this is when the knock sensor faults 1 and 2 kick in. If I drive with a lighter right foot and gradually accelerate through and past 3000rpm the codes don't come in. My thinking is "DISA", if this were failing, i.e. Slow to operate then surely the air flow read by the MAF isn't flowing as expected into the engine so maybe that is causing "Knock", which my nice new knock sensors pick up. Because it is detecting Knock I believe I'm right in thinking the "adaptive" part of the engine brain alters the timing slightly?? Which will give me my rough idle and worse lumpy acceleration???. From the links it seems people have DISA valves only partially opening, I have had mine out and ran the engine, it does go from open to closed, I just can't gauge if it is doing it bang on the right rpm, or at the right speed??

[Capa]

Is a 2008 2.5i An N52 lump?

[ph001]

It is defo N52 but I have to admit I thought the intake was the same as the 3.0si with 2 DISA. That’s a pretty major difference if what the OP says is correct???

[Davz]

Yes it is an n52, it will be the lower power version at 177hp. The same engine is used in the 2006 on 2.5si, the difference is the intake, twin disa on the si which, with a different ECU software programme raises the power 218 I recall or thereabouts.
When on wot do you get a power surge when it comes on cam at 4500rpm or is it flat progressive power?

[Naylz]

It surges on acceleration which then clears above approx 3000rpm. Sorry for delay in responding been away climbing Ben Nevis

[Capa]

ph001. I was actually having a look at INPA a couple of days back and it does say that the small DISA isn't present on the 2.5, so the story check out.

Not sure what the problem is mind. Would have said that it could have been the small DISA given the range that it seems to happen at.

I think if I were you I'd test the DISA in the manner described in the above link. At least that rules it out and you can then move on to another area.

Think crankcase ventilation or valvetronic or camshaft position sensor.

[Markos_Z4]

clean your air mass meter with air intake cleaner ! i had the same problem
don't use brake cleaner