speed input & noise

[multiplex]

well after a few weeks of testing, i've resorted to posting my issue here 

i've been using the speed input since it was introduced with varying degrees of success. I'm using the ps/2 wiring from the vems store. it is getting its input signal from a dakota digital speedo converter. this takes my VR wheel sensor, calibrates it and outputs a pulse wave to work with my stock e30 speedo.

i've noticed the newer firmware does away with the min pulse setting - older firmware seemed to have less noise for me.

the noise only appears under boost. i did a number of things, which i thought could be contributing.

- disabled racelogic traction control
- turned off map based dwell (thought maybe it was overcharging)
- went from 208hz and 1 divider, to 52 and 4 divider

I'm inches away from doing a dedicated hall sensor on the driveshaft, however i noticed something else strange...

i graphed speed input #2.  this also shows the exact same noise!

i'm not sure where it could be coming from or what input #2 uses?

any ideas? at this point, i don't think the dedicated sensor will work

sorry for the large image

[multiplex]

ok when looking in vemstune, the 2nd input is flat - so that must be an error in MLV.

however noise still shows on input #1.

ideas 

[boostd audi]

what kind of wire do you have.. vr need good quality shielded wire that is also grounded

i had issues with a noisy coilback i had to upgrade to thicker wire with thicker shielding for vr sensor or it picked up noise

[z0tya]

I have tested a marelli crank vr sensor with vemsshop ps2-wheelspeed converter and ihave strange noise too, when engine running. On trigger log seems that wheelspeed get noise from spark. The cable are shielded and grounded.
Is possible to suppress noise with modifying the converter circuit in the dsub connector?

[mattias]

A harder filter on the signal could be useful :
http://www.vems.hu/wiki/index.php?page=MembersPage%2FMarcellGal%2FPowerAndTraction%2FSpeedoMeter

[multiplex]

funny, i actually saw that post last night and threw the capacitor in there. for me it didn't seem to do much.

good point about the coil pack. maybe i'll check over those.

i'm also going to forge ahead with my dedicated hall sensor and see what happens.

[multiplex]

little more info on what i've discovered.

with the dedicated hall sensor i went to, i was still getting noise. It was picking up noise from the chassis ground i was using. Luckily the hall sensor can run off 5v so i powered it by the PS/2 wiring - that removed the noise during running.

It still didn't completely solve my problem though.  I decided to abandon the webshop Ps/2 converter and opted for a direct resistor and protection diode (assuming thats how it is now done from the 'factory').  This is working reasonabily well, however i still get noise at high load / high RPM.

from looking at the firmware notes, they did make a change relating to speed input around 1.1.84 which removed some filtering.

to combat this, last night i added in a simple low pass RC filter set to 400hz.  I had calculated my highest input was 325hz.  It worked great, however the cutoff is a little too low, so tonight i'm going to change it to 1khz and see what happens.

what a mess 

[boostd audi]

anyluck?

[multiplex]

still have it. I did change my filter to 1000hz  (.68uF cap and 220R).  Speed input looks good, tested to about 100mph under no boost (slow accel). Then tested in 3rd gear, full throttle - speed jumps around although not as much.

i've submitted an official report to the 'vems sharing center' in hopes of some ideas.  not sure if its noise related or code related or what!  as i typed this out, maybe acceleration is a factor? too quick of a change not being picked up?

[MWfire]

still have it. I did change my filter to 1000hz  (.68uF cap and 220R).  Speed input looks good, tested to about 100mph under no boost (slow accel). Then tested in 3rd gear, full throttle - speed jumps around although not as much.

i've submitted an official report to the 'vems sharing center' in hopes of some ideas.  not sure if its noise related or code related or what!  as i typed this out, maybe acceleration is a factor? too quick of a change not being picked up?

if you have problem only when boost, then you have problems with enelctrical noise. Check spark plugs wires and spark plugs.