2007 2.5i DISA Valve Check

lucasxdiniz

lucasxdiniz

Active member
 Northamptonshire
Hi, everyone.

I've watched videos and read loads of forum posts on DISA valves, what to check, how to check, etc. So as a bit of preventive maintenance when servicing my car I took the DISA valve out of the intake manifold (I only have one as I have a 2.5i). I first left it connected and checked for play and there was none (yay!), then I tried moving that flap to see if it would get stuck, then I realised it wouldn't move. I then disconnected it from the wiring and had a better look and I realised that it is not similar to the ones I've seen -- this one doesn't seem to use vacuum, so must be electronic only. Could someone watch the video below and tell me if I have a faulty valve?

I'm keen to learn more about these engines and the car in general so feel free to give me any tips.

https://youtu.be/RBjW7FYbVGw
 
I decided to start the car with the DISA connected to see if it closed. It moved an insignificant amount. Is the motor buggered?

https://youtu.be/nFnR5OypzbE
 
You’ve probably worked out by now that your earlier research was probably on the M54 engine which has a different type of DISA to the N52. The latter do not tend to give many issues (they are driven electrically by a geared motor) but they should either be open or closed (not halfway between). If you read the N52 tech bible here... https://z4-forum.com/forum/viewtopic.php?f=2&t=113354

...it shows a diagram of how they are connected. What it doesn’t say is at what rpm they flip over but I have a feeling you weren’t revving the engine high enough for them to change state.
 
ph001 said:
You’ve probably worked out by now that your earlier research was probably on the M54 engine which has a different type of DISA to the N52. The latter do not tend to give many issues (they are driven electrically by a geared motor) but they should either be open or closed (not halfway between). If you read the N52 tech bible here... https://z4-forum.com/forum/viewtopic.php?f=2&t=113354

...it shows a diagram of how they are connected. What it doesn’t say is at what rpm they flip over but I have a feeling you weren’t revving the engine high enough for them to change state.
Click to expand...

I was looking at DISA valves without looking at N52 ones specifically as I had assumed they were the same between different engines. I've managed to find a few videos of it now, but I still want a confirmation that mine's definitely buggered before I spend money on another one. I'm concerned because of what I read on a E90 forum (https://www.e90post.com/forums/showthread.php?t=1491906). The DISA seems to be very similar, if not the same, and it seems they are meant to close when the engine starts and open again at some point around 3-4krpm.

I've logged some data (engine RPM, DISA Position %) after assembling everything back together, if you feel like having a look:
https://1drv.ms/x/s!AoAAw4ET48j5gtN-sFsPteAwr5-IHQ
 
Update for posterity:

A fully working DISA valve should definitely go from open to closed on start-up. So the videos above show a faulty DISA valve trying to close the flap. However, you shouldn't be able to move the flap with your hands, it is quite stiff. I checked this in two other Z4s now.
 
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