Duke

I will probably need to switch to a HALL setup instead of VR sensors to solve my interference problems.
Who's running a HALL setup? I have a few trigger ideas, but always open for other ideas as well

Chris White

I use Hall effects for cam sensors on the full sequential but not for crank triggers, mag works fine for those. Check you wire routing - keep it away from the alternator!

Raceboy

Are you using 951 stock trigger arrangement or 968 (60-2) or something else? Most Hall sensors are not capable of reading 60-2 wheel. I suggest you use known working trigger wheel + sensor combo. Like Ford Scorpio Cosworth (BOB engine) VR sensor with small diameter 60-2 wheels as those can read them easily. Many just read but induce much noise.
Is the cable for VR sensor correct impedance? Is it properly shielded?

I've used Hall sensor and simple trigger (1 event per cylinder) on many cars but the best approach is to use 60-2 wheel + VR sensor. Hall sensor for cam sync.

theedge

I am. Hall can be very tricky for 60-2 depending on the size of the wheel. 36-1 is easy with hall. 60-2 I think can be done depending on the sensor itself and the wheel. Dont even try using a hall on the stock starter ring

Duke

Hehe, no I wasn't going to try that

Something happend during an engine swap some time ago and I haven't been able to narrow the interference down.
My EMS can handle stock triggering, and those signals had some nasty interference. Switching to 60-2 trigger at the front reduced the interference a lot but over 6000 rpm I still have issues.

I've tried different EMS-systems, built a totally new engine harness, replaced sensors, new battery cables (Iceshark/Robby), etc. even ran the car without the alt. belt but the damn interference is still there.
Next will be the battery. Seems like a long shot but it should be possible to cause interference if the battery is bad and cannot totally absorb the spikes from the alternator.

I actually have a 36-2 machined alt. pulley. Will try that and see if it get's better. Theoretically it could get better due to fewer teeth readings.
If not, I'm thinking of a new trigger wheel more suited for a hall sensor.

theedge

Which EMS? I assume youre using the OEM VR sensors? Are the wires shielded the entire length and grounded at the EMS end only?

evil 944t

Duke,

You have got to have some strange wiring/mechanical issues. I use the stock VR sensors and have no problems up to 7200 rpms. I even hooked a scope up and watched the signal, They work good. Email me if you need suggestions.

ehall

I AM a Hall sensor!

Bri Bro

The biggest noise generator in a car comes from the spark of the ignition system.

theedge

Thats what she said!!

Duke, are you running resistor plugs? BPR7ES are resistor plugs if youre running those.

Duke

Haha!

I've soon gone through just about everything that's why I'm starting to look at other solutions (HALL-sensors) instead of keep looking for the source of the interference.

EMS is Link G3Plus. I had the same problems with my previous EMS (Tatech).
* I then made new shielded cables to the VR sensors.
* Replaced VR sensors
* Switched to Link G3Plus (this also meant a new ignitor etc in a completely different location)
* Made a completely new harness for the Link (with new power and ground locations compared to the Tatech)
* The harness is based on an unterminated loom from Link so the trigger cables are grounded correctly (also checked)
* Switched to ford VR sensor with 60-2 wheel at the front. 50% of the problems disapeared.
* Tested to run without alternator
* Tested another set of plug wires
* Tested another set of plugs (all of them resistor type)
* Tested another coil pack
* Replaced battery and neg cables. Lot's of supplementary ground cables. Voltage drop is OK with engine running.

So not many things left to check..


The good thing about the Link is that it's very configurable regarding filters and voltage tresholds for the VR sensors. What's odd is that I have to lower the filter levels and lower the voltage treshold at higher rpms in order not to get trigger errors counting up. As it is now it doesn't result in trigger errors, just like a soft rpm limiter. If I raise the filter levels and such to more correct levels I get trigger errors and some weird rpm numbers in the log.

What's very strange is that the dwell time is totally inconsistent from around 2000 rpm and up.
Every now and then I get down to 0.5 ms etc. I will post a log file...
What I want to know, that Link hasn't been able to tell me, is how the dwell is logged. If I knew that, perhaps I could backtrace it...

Duke

Another thing... When I scoped the stock VR sensors I got a pretty big voltage spike on the signal cable when I turned on the ignition. That spike disapeared when I switched to 60-2 at the front.
Since the problems were at worst with the stock VR-sensor and locations I suspected the starter for a long time. Replacing battery cables didn't solve it. But I'm still thinking about possible problems from that area. Perhaps the starter leaks power through the grounding?

Chris White

I do have a solution for you....
Keep a VR sensor and change out the rest of the system!
Sorry, couldn't resist a liitle pitch here.....

I wonder if it would work better with deeper teeth in the trigger wheel- it might give you a little crisper signal

evil 944t

Duke,

Are you having a problem under boost or free rev?

Regarding the LinkG3+, the Link works fine. There are a bunch of 944t's running with stock VR sensors. My car uses stock vr sensors and I redline at 7200rpm. Duke shoot me a email, I have a few things to ask that will probably answer your dwell question/problem.

The fact that you have the same problem with multiple ems's, triggers,parts, etc, means you have a problem somewhere other than the ems itself.

Duke

Yep completely agree.
Problems both during boost and free rev.

Chris, shameless pitch
I'm hoping the 36-2 wheel might work better due to fewer expected counts. Otherwise I think a deeper teeth trigger wheel like a 24 teeth or similar with a hall sensor is the way to go. But I'm just so tired of always making every project into something custom.