MSefi.com read only forum (Jan.15,2018)

Hey guys,

Just want to gauge a feel for how some of you guys run the wires your VR sensor, whether they be distributor or crank trigger. I'm more curious about V configuration engines as at the moment I have run a V8 with the distributor still in it to throw the sparks around BUT my EFI loom runs under the intake manifold, right next to the distributor back through the firewall into the computer mounted inside the dash. The tach signal is single core shielded belden cable (a DIY Autotune harness) but I snipped it at the back of the engine when I originally set it up for the distributor, but soldered the rest back on when I setup the crank trigger & heat shrunk the join closed.

What I notice is that when I put a very high power coil on the MSD6AL like the HVC ones, I will get all sorts of noise coming in on the tach line and even occasionally get a "flutter" sent to the MSD - can tell as the tacho flutters in the car. But when running the little weak canister Blaster 2 coil, I rarely see any hiccups. The car runs fantastic with the Blaster 2 coil don't get me wrong but i've always refused to let this beat me... I must know why I can't use the BlasterSS or HVC coils and why it's doing this!

Before I start unravelling my loom looking at where I can possible run the VR wires through the engine so they're RIGHT away from any HT leads etc, it'd be good to get some feedback as I know tach signal is what plagues ALOT of people who run mag sensors (and it's not just us squirters, MoTeC, FAST, EMS... they all have issues with em!!!).

Cheers lads
Kris

Single-core shielded cable is not really shielded in this instance as the sheild can pick up EMI. You could consider using a twin core shielded cable with the shield grounded, and the 2 cores carry the VR signal. Otherwise route the cable around the other side of the engine or straight across to the chassis and back via the long way. Belden cable is really nice quality cable, good to hear DIY use it. My thoughts do not come from a "hands on V8 install" but from a different electrical background. Just my 2c.

Ian.

So perhaps I could have been headbutting my head against a brick wall all this time.... I might try knocking the pins out of the DB37 as they are crimped pins instead of solder cups and running the 2 VR wires to the ECU, then ground the shield at the sensor end perhaps?

The EB-EL Ford Falcon I got the sensor harness plug off, it only had a twisted pair of wires, no shield unless it used the engine as its ground plane because I had to pull off a few covers to get the little harness out without just cutting it....

krisr wrote:... I might try knocking the pins out of the DB37 as they are crimped pins instead of solder cups and running the 2 VR wires to the ECU, then ground the shield at the sensor end perhaps?

Sounds like a good plan to me...

Ian.

Well after 3 hours on Sunday, coupled with a bit of blood, sweat and swearing I managed to get the crank angle sensor wire changes to a belden twin core + shield jobby and so far I cannot find any hint of RFI on the input side of things now. I am going to put a pullup resistor on the output of the coil driver just incase my MSD6AL is playing up too and i'm a bit paranoid that because the signal floats/goes low it may be picking up some noise too as that wire isn't shielded, nor should it be really.... but the coil I want to run will definite put out some electrical music when I get a chance to put it on!