Way to simplify the DISA Valve??

[x3me__]

Hi everyone!

Its been a while I don't come here but recently I discovered that my DISA Valve membrane was bad (a literal 2cm cut in it) and I can only find the exact membrane selling in Russia, and it can take up to APRIL to get here in Portugal, the one I am talking about is this one.
https://www.ebay.com/itm/182430442539

I read a lot about the DISA valve in the m42 engines and all the membrane does (and DISA in general) is close the valve after 4000RPM, right?

So supposedly the membrane and the hole DISA thing can be replaced by a little servo motor (basically a thing that does the movement the membrane does) that opens and closes the valve after reading the engine current RPM no?

I already have a side ECU I made reading the engine RPM and other stuff, I can simply attach a servo motor where the membrane is and make it change the valve position inside the intake after 4000RPM right?

I'm getting a little repetitive but I really don't understand why BMW didnt do this instead of relying on rubber.
Maybe I'm missing something but I wanted your opinion on this.

I attached a DISA diagram, the membrane is in the corner of point 7, that little straight bar goes back and forward based on the vacuum inside the intake, when the membrane is broken it is always in the same position as there is no vacuum created. That's the thing I'm saying that can be replaced with a servo motor to open and close the valve inside the intake.

Thanks in advice to all of you

[bmwman91]

It does seem like a bit of an overcomplicated system, with the vacuum tank, vacuum control valve and then the vacuum-controlled DISA actuator. Presumably they determined that it would be more reliable than direct actuation with a long-throw solenoid. Leave it to the Germans...

There's likely a bit more to it than just switching at 4000RPM. You need to have some hysteresis, like maybe it opens at 4000RPM but only closes at 4000RPM if the engine revvs past 4500RPM, otherwise it closes at 3500RPM. Something like that, so that it is not constantly opening/closing if you happen to be driving with the RPM right above/below 4000RPM.

Anyway, maybe contact the company selling them through their website? The eBay item shows that this is the website for the company. Maybe they could get it to you faster if you asked them. eBay says that I could have the part by Jan-Feb here in the US, so I am guessing that eBay is just not very good at estimating delivery times.
https://vanos-bmw.com/?s=BMW+M42&post_type=product

[x3me__]

Hi! 
First of all, thanks for your reply

I have been reading more info about it and I got a more detailed version of when it opens and closes, and it is at 4800RPM, and yeah I have read about it being like so so it doesn't open and closes multiple times in a short time, even tho that is a nice reason they made it like that it is still possible to code with that in mind, like "when we send the signal to open or close, set a 5sec timer, only after that timer the valve can open or close again"

About contacting them to see if it's possible to have it delivered fast, I have already contacted them, and the only way is to pay 30$ for the shipping (noope!)

I'm still thinking about it but I think I will order a servo motor (like 2$ max) and code one and see where it takes me.

I'm still open to any reply!

[bmwman91]

Take it from me...trying to engineer a better solution will end up costing you a lot more than $40 in the end, and will likely not work as well as the original system. I have learned this the hard way multiple times in the last 20 years of working on these cars. You might as well buy 5 of them and pay extra for the shipping, and then see if you can sell the other 4 domestically for like $20 each to recover costs. While there are exceptions, the old saying "you get what you pay for" is true more often than not.

If you do decide to try to make your own servo solution, a simple timer is probably not going to be all that good. Certainly 5 seconds is a very long time. If you make a system that reads RPM in the first place, then it should not be too hard to have it add RPM-based hysteresis too.

[x3me__]

You are probably right, I was saying 5secs just for the example, a hysteresis would be much better.
I will see what I'll do, and post news here if I remember.
Thanks for the suggestions and opinions

[bmwman91]

Sounds good. If you do end up trying to make your own system, please post details. It is always interesting to see how people solve things!

To get an RPM signal, the easiest place to tap into one is likely at the diagnostic connector (wiring diagrams show pin 1 of the "data link connector" having the tach signal from the ECU). It produces one 12V pulse every time an ignition coil fires, so 2 pulses per revolution.

[x3me__]

Didn't know it was possible through pin1, I already have that made, as I said I already have an ECU I made that controls the original ECU, doing things like launch control, the nice thing of having it controlled by another ECU is that I can change the launch control rpm in real-time or set a more delayed cut or something, here is a little video of it https://streamable.com/or3et4

I pushed a wire from the Cluster itself, and in order to read it I didn't to the normal "see pulses in a second, x 60 / 2" to get the current RPM, to have a faster read I have this algorithm

-12v Pulse comes into the ECU
-ECU starts a microsecond timer (timeLapsed)
-12v Pulse comes into the ECU
-ECU stops timer (timeLapsed)
RPM =   20000000(for 6cyl) / timeLapsed(microseconds)
RPM =   20080000(for 4cyl) / timeLapsed(microseconds) - I don't have the exact number here but its an 8 in the middle

This way we have the "current RPM" value each pulse.

There is a way of reading it by counting pulses but it's slower (isn't it?)

Tomorrow I will see what ill do about the DISA Valve

[bmwman91]

Yeah, using an input capture timer to calculate RPM from each pulse is the fastest way to do it, and you could always add a little averaging if needed. The "really fast" way is to use the crank position signal (either with an external signal conditioner, or by pulling the 5V signal from S600 in the ECU).

How did you integrate that secondary ECU? Is it intercepting the fuel & ignition signals and then changing timing / duration?

[x3me__]

Heyy!, since i already have this thread i didnt want to do a new one, I am making progress on the "conversion" but it took so long to get the thing I needed from ebay
I am now working on it and will keep this thread updated, but I have run into a super mysterious problem that I need to fix.
For some reason, only taking the intake manifold out, (and unplugging the 2 temperature wires and the oil one) and putting it back together made my temp gauge not work anymore.
Here are all the thing I have tested

For context (and after some research) "gauge temp sensor" is the one more in the middle, that only has 1 pin/wire.
 
-There is a 12v signal on the tip of the connector for the gauge temp sensor
-I assume the ECU temp sensor works fine since the car starts cold without an issue
-Gauge temp sensor is fine (tested it)
-Gauge itself is fine (mounted in another car and worked well)
-If I unplug the battery, wait a few minutes and put it back, the gauge reads full MAX, and keeps there, but if I start the car, after about 30 seconds it starts falling to COLD and after about 5 second its on full COLD and from there, it will never move again, even if I turn of the car and wait a day, the next day it will be on full COLD and doesn't move, only if I unplug the battery, wait a few minutes and put it back again, then it reads full MAX again.

This is driving me crazy
 

[bmwman91]

I assume that your oil pressure light is working and does not remain lit up when you start the car? It sounds a bit like the plugs got swapped.

[x3me__]

I think not, ill check that tomorrow its late here now,
But I don't think I have them swaped, there are 3, one only has 1 wire, that is for the temp gauge and connects to the first sensor, the one more in the middle, about the other 2 one of them as a blue rubber inside, that's supposed to be the ECU and connects to the other one, and the last one connects to the oil thing.
Right?
Btw forgot to mention, even tho it has 12v in the connector , having it plugged or unplugged makes no difference on what shows on the gauge, Im starting to think that it is something betwin that 12v and the gauge  but I don't know what goes in the middle, because the wire doesn't go directly to the cluster right?

[x3me__]

i cant belive it, i went to the garage and swaped the bottom one from the oil and the middle one for the gauge to make sure it wasn't bad connections as you sayd, and guess what you where right, I cant belive why I haven't tried this sooner and that means that this diagram is wrong? or is my m42 a special delivery hahaha
btw, here is an update to the thingy I'm trying to do with the DISA valve, testing some alignment for the servo motor
https://streamable.com/9rs2tu

[bmwman91]

I did the same thing myself once, and your symptoms sounded familiar. It's often the simple things.

Keep up the good work on the DISA hack.