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When does the intake manifold adjustor (DISA Valve) close?

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119K views 25 replies 10 participants last post by  AudriusTech  
C
#1 ·
Just noticed how dirty my intake manifold adjustor (DISA valve) en route to cleaning my idle control valve. I drive a 2000 528iT.

By this thread, http://www.bimmerfest.com/forums/showthread.php?t=260833, it seems that this flap is used to make the intake manifold longer or shorter.

Is the flap open or closed below 4000 rpm? I rarely drive above 4000, so I'm not too concerned if it's typically open. On the other hand, if it's trying to stay closed below 4000 rpm, I'm going to open it up again and clean it.
 
#7 ·
cambrian123456 said:
it seems that this flap is used to make the intake manifold longer or shorter
Click to expand...
This is the clearest explanation yet (if it's correct) of what the DISA valve purports to accomplish ...

Quote:
To be exact, the DISA valve does not change the length of the intake system on the six-cylinder engines from the M52TU onwards - its function is to be open at low speeds, so feeding all six intake pipes together.

At mid-range speeds it closes, seperating the front and rear groups of three cylinders from each other. At higher speeds it opens again, joining the cylinder groups together. It therefore acts like a massive balance pipe which can be closed when required.

The effect of this is to give more mid-range torque without interfering with bottpm and top-end torque.
*******> ********>
 
#9 ·
I just looked up DISA in the VERY best of E39 Links and have one question.
- DISA VALVE FLAP BREAKS: the DISA valve flap breaks, sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) or the disa valve o-ring fails (1) (2) & where to get just the DISA valve o-ring (1) & when the DISA valve flap closes (1) (2)

QUESTION: Is it a binary open/closed or variable opening/closing of the flap?
- Below about 4,000 RPM --> DISA flap is closed
- Above about 4,000 RPM --> DISA flap is open
- At what RPM does the DISA flap close again?
 
R
#14 · (Edited)
bluebee said:
I just looked up DISA
...stuff deleted ...

QUESTION: Is it a binary open/closed or variable opening/closing of the flap?
- Below about 4,000 RPM --> DISA flap is closed
- Above about 4,000 RPM --> DISA flap is open
- At what RPM does the DISA flap close again?
Click to expand...
Pages 42 -44 describe DISA operation
below ~ 4000 RPM closed
above ~ 4000 RPM open
rest position, i.e. when removed - flap open

Regards
RDL
 

Attachments

C
#11 ·
I'm considering video taping the device at the same time as my tach to figure this out, that is, figure out when it moves. There's a little rod that goes into the bulb on the end. Feels like there a spring or diaphram in the bulb that pushes back against the rod, keeping the flap in an open position. Although the rod is somewhat obscurred by the electrical connector, I should be able to mark it and catch it in action.
 
#12 ·
Just for the record, here's a thread where the DISA valve disintegration is a bad thing!

  • 2002 530i, known bad waterpump, possible overheating
  • The DISA valve variable intake vane broke off into the intake manifold and the plate shaft apparently sailed through cylinder #3 before disintegrating inside cylinder #3
    • Spark plug electrodes on cylinder #3 smashed into ceramic (ceramic intact) presumably by metal & plastic DISA parts flying about
    • Hundreds of little pits in the piston head presumably as hot parts embedded into the aluminum as they burnt to a crisp
    • Both exhaust valves bent presumably by the force of the sandwiched DISA parts between the piston & the valve head
    • One intake valve seat damaged by burning hot parts presumably getting sandwiched between the valve and the seat
  • Subsequently, the M54 appears to have been run on 5 cylinders (even with almost zero compression on cylinder #3 due to leaking on at least one intake and on both exhaust valves)
  • Subsequently, the leaking water pump appears to have been fixed
  • Subsequently, the spark plugs appear to have been removed and replaced (with the crushed-electrode plug moved to cylinder #6
Summary of potential DISA deletes?

  • Disconnect the DISA harness connector
  • Remove the DISA & close the hole with metal plate
  • Cut off the flapping part of the DISA so that it never closes
And, more to the topic at hand, here's yet another description of DISA operation (from the standpoint of what would happen if you deleted it) from that thread:

Just deleting it isn't exactly ideal since the entire manifold will be being used, whereas if it's in place, it will select the longer runners to give more low end torque then open up the shorter runners for higher RPM. Either way the power curve shouldn't decrease on the peak by much (if at all), the curve would just climb slower in the lower engine speeds.
Click to expand...
Image
 
#16 ·
For the record, this DISA-rebuild video shows clearly the item that most commonly fails is the all-important yellow plastic "eccentric" (for lack of a better name) that operates the DISA flap.

This yellow plastic has a non-circular shape (i.e., a flat edge) whose edges wear, causing the eccentric to no longer operate the mating flap because of a 'bad fit'.

The 'suggestion' in this video is to glue the yellow plastic eccentric to the black plastic DISA flap.
- hmm disa issue...

http://www.youtube.com/watch?v=CbHI477X8Ms&feature=related

(Note: While this will certainly work in the short term, there is some disagreement whether it's worth the risk of "saving" an old DISA simply due to the risk of something being aspired into the intake manifold due to the sheer age of the DISA plastic at this point of resurrection).
 
#17 ·
So that this excellent information from RDL and others is more easily available for the future, I just added this link to the bestlinks references as follows:

- DISA VALVE FLAP BREAKS: the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) or the disa valve o-ring fails (1) (2) & where to get just the DISA valve o-ring (1) & how the DISA valve operates (1) (2) (3) & an example of how this can ruin your engine (1) & how to test DISA operation (1) or rebuild your DISA valve for free (1)
 
#18 · (Edited)
For the record, a user recently had cause to remove the flap in the DISA valve and is testing how the engine runs sans an operative DISA:
- Bingo!! I may have solved the misfire and lean codes P0171, P0174, P0300

Image


See also:
- Why check the DISA at 85K miles to 90K miles or whenever the airbox is removed (1) (2) & how to repair a rattling DISA unit (1) (2) (3) & why the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) & how the disa valve o-ring fails (1) (2) & how it can cause all sorts of cold-engine rough idle problems (1) (2) & where to get just the DISA valve o-ring (1) & how the DISA valve operates (0) (1) (2) (3) (4) & an example of how a broken DISA valve can ruin your engine (1) & how to test DISA operation (1) (2) (3) (4).
 
#19 · (Edited)
For the record, yesterday I tested the DISA, and while some of the results were puzzling, I was able to ascertain there was alternator voltage (13.8 volts DC) at the harness connector at idle.
- Strange results from a simple test of the M54 DISA valve today

Image


When I disconnected the harness connector and manually energized the DISA with 12 volts DC from my battery charger, the flap moved from the open position (horizontal) to the closed position (vertical).

Image


Reading this document again (see pages 42 to 44):
- m54x5[1].pdf

We can take note of the following:
- Magnetic switch
- Vacuum accumulator

Here is a picture of the one-way valve of the vacuum accumulator:
Image


And, here is the description of operation, from the PDF above (with my additions in red):

The resonance system provides increased engine torque at low RPM, as well as additional power at high RPM. Both of these features are obtained by using a resonance flap (in the intake manifold) controlled by the ECM.

During the low to mid range rpm, the resonance flap is closed (i.e., the flap is actuated by alternator voltage such that it is held vertically against spring tension). This produces a long/single intake tube for velocity, which increases engine torque.

During mid range to high rpm, (the control voltage is reduced to zero which causes the flap to return to the horizontal rest position due to spring tension) the resonance flap is open. This allows the intake air to pull through both resonance tubes, providing the air volume necessary for additional power at the upper RPM range.

When the flap is closed , this creates another "dynamic" effect. For example, as the intake air is flowing into cylinder #1, the intake valves will close. This creates a "roadblock" for the in rushing air. The air flow will stop and expand back (resonance wave back pulse) with the in rushing air to cylinder #5. The resonance "wave", along with the intake velocity, enhances cylinder filling.

The ECM controls a (magnetic) solenoid valve for resonance flap activation. At speeds below 3750 RPM, the solenoid valve is energized (with alternator voltage at the harness connector) and vacuum supplied from an accumulator closes the resonance flap (where the vacuum accumulator is apparently a one-way flap valve with a 1/16" entrance hole in the side of the DISA) . This channels the intake air through one resonance tube, but increases the intake velocity.

When the engine speed is greater than 4100 RPM (which varies slightly - temperature influenced), the solenoid is de-energized (i.e., the harness control signal goes from 13.8 volts DC to zero volts DC) The resonance flap is sprung open (by spring tension), allowing flow through both resonance tubes, increasing volume.
Click to expand...
My main question:
Q: Since the magnetic solonoid can easily move the flap valve from the at-rest horizontal (open) position to the vertical closed position, why do we need the (additional) vacuum accumulator to 'close the resonance flap'?

Image
 

Attachments

#20 ·
For the record, apparently none of us actually knew HOW the DISA actually shut the valve.

See details here:
- Strange results from a simple test of the M54 DISA valve today

seemyad said:
You hit the nail on the head Blubee.

The diaphragm (when vacuum is applied) and the spring are two opposing forces on the flap. The spring is why the flap is open when you hold the DISA in your hand.

From the videos I linked in a previous post (above) I can see the spring tension on the flap when the guy is forcing the flap closed. He then closes the flap by hand and puts his finger over a small hole where the diaphragm is located. The vacuum seal he creates with his finger forces the flap to remain closed against the tension of the spring.

The electrical portion merely creates/completes the path for the vacuum giving the diaphragm enough "suction" to force the flap close (opposing the spring tension). When you exceed X RPM the 12 VDC is removed thereby opening an "escape root" for the vacuum (basically allowing air into the diaphragm). The tension from the spring then forces the flap open.

When the RPM drops back below the threshold, the 12 VDC is reapplied to the solenoid which then closes the path to allow a vacuum to form again which forces the diaphragm to close the flap.

"As soon as the solenoid valve switches (on dropping below the switching speed) the vacuum reservoir and vacuum unit..." (I believe the vacuum unit to be where the spring and diaphragm are located) "...are reconnected and the connecting flap closed." NOTE: As I have not held a DISA in my hand yet I am unsure as to the location of the "vacuum reservoir".

There is much more to the DISA than meets the eye. Although the parts that comprise the DISA are not expensive individually, I can better appreciate the cost. The reality is it is amazing that so many plastic moving parts and the rubber diaphragm hold up as long as they do under such extreme pressure, vibration, and temperature variations (below freezing to above boiling point of H2O).

I no longer view the DISA as an overpriced cheap piece of plastic. It's moving parts appear to last over ten years and over 100,000 miles under extreme; pressure, vibrations, and temperature variation. The DISA alone is engineered better than most American cars (sad fact).

Also, normal rubber would dry up and crack within a year under these conditions yet the diaphragm retains its properties for a decade or more (hot or cold).

Blubee, there IS value in your desire to understand how stuff works. Thank you for always going that extra mile.

You gave me the missing clue when you mentioned the "magnetic switch". I have an extensive electronics background (which paid for my BMW) so that is all I needed to put the rest of the puzzle together. That's what I call "team work".

.
Click to expand...
 
#23 ·
If you need them, here are the best of the links:

- Where to get a proper DISA valve repair kit (1) & how some jury-rig 'repair' a rattling DISA unit (1) (2) (3) & how the DISA valve operates (0) (1) (2) (3) (4) & how to test DISA operation (0) (1) (2) (3) (4) & a simple DIY to install an M54 DISA (1) & a nice DISA autopsy (1) (2) & a great DISA group buy (1) & how the disa valve o-ring fails (1) (2) & how it can reputedly cause all sorts of cold-engine rough idle problems (1) (2) & where to get just the DISA valve o-ring (1) & why you want to check the DISA at 100K miles or whenever the airbox is removed (1) (2) & why the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) & a well documented example of how a broken DISA flap can ruin your engine (1) & yet another seemingly complex set of misfire codes reputedly traced to a broken DISA valve (1)
 
#25 ·
I googled to find out what happens, in an emergency, if you remove the flap or if you bolt a plate over where the DISA is supposed to go.

I didn't find the answer, but I did find this simple video on how the DISA works:
 
A
#26 ·
I know the post might be dead, but just in case :) Rebuilded my disa, worked like a charm, but suddently start rattling something inside..(quiter then when flap is loose). Removed disa, all looks fine - clean, vacuum holds, flap is not loose. Any ideas? Once I disconnect disa, sound dissapears.

Sent from my SM-N930F using Tapatalk
 
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