BMW E30 M20 Firing or VR sensor problem

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xst
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BMW E30 M20 Firing or VR sensor problem

Post by xst »

Hi guys, I have serious problem with the firing or the VR sensor, I dont know excatly, which causes the following problem: only 3 cyl works(2-4-6), although there r sparks on each of them(for example compare the 2nd cyl with the 3rd cyl , the 3rd cyl has less spark, the coil, the spark plug and the cables r good) , I used wasted spark ignition as well, the problem is always same with standard BMW single coil. Here is my tooth log, which is quite interesting, as far as I know, the height of the tooth suppose to be the same, and where the 58th tooth comin' , the column is 3 times higher than the normal one. Any idea? Any help could be appreciated. PS.: Sorry if my post is in the false the topic...

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jharvey
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Re: BMW E30 M20 Firing or VR sensor problem

Post by jharvey »

It appears this is a MS project? I don't see how this is FreeEMS, so I'm confused why it would be in this part of the forum. I think this would be more appropriate under the users ride forum. I would need to know more about your VR input circuit before I can help. I believe you are being caught by the poor VR pickup circuit used in MS. Project pictures also help.
xst
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Re: BMW E30 M20 Firing or VR sensor problem

Post by xst »

Hi jharvey, thanks, here is my setup:

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I solder the ignition IGBT-s like in the manual:
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jharvey
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Re: BMW E30 M20 Firing or VR sensor problem

Post by jharvey »

I believe your top post indicates you are having trouble getting your RPM input signals correct at the MSII. Is that correct? I'm guessing your aware of the grounding issues with MS. You may want to search this forum for a post from DaveBMW. He did some extensive work to separate the grounds and lower the noise floor caused by the bad grounding techniques. I think you are using the stock VR input, but I'm not certain. Also seeing where the wires are routed and how the sensor is mounted is helpful.

On a good note, it would appear that MSEFI has removed my ban, so I can once again look at the mega manual. I just looked over the VR input, and I had forgotten how bad that was. The common mode rejection is really bad, as well it uses the gnd as one of the signal wires, so it's directly coupling the gnd currents with the signal. Also it's not very good with skipped tooth, you can tune it for the average tooth, but when a skipped tooth comes along, it has a bunch of warp-age issues. DFH is currently drawn with the LM1815 which helps resolve many of those issues by increasing the common mode rejection and having a faster response time, such that it minimizes skipped tooth warping. However, it's not as ideal as what is drawn in 5554, which uses the max9926 which has even higher common mode rejection, and eliminates the skipped tooth warping.

So I guess the question is, do you want to fix or mostly fix the RPM input signal via max9926 or LM1815, or are you looking to try to fix what you have? My gut feel is that you can get what you have working, but it's going to be a tough battle. An add-on board that helps clean up your input signal is likely the easier route.
xst
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Re: BMW E30 M20 Firing or VR sensor problem

Post by xst »

Thanks for the help, the problem was the voltage level of the injector, it was too low, now the car is working again 8-) ...
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