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Electrical noise interrupting trigger during cranking.

EFI Wiring Fundamentals

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Hi all.

I'm very new to this forum so go easy on me ha.

I'm almost complete my turbocharged G13b suzuki sierra build but still having starting issues due to electrical noise coming from somewhere, that is disrupting the trigger pattern.

I'm sure a few of you are familiar with the engine ( Swift GTi) and know its a reluctor type trigger system, located in the dizzy. Also running an old WolfV4, which seems to do the job very nicely other than when cranking.

I have double/triple checked all my earthing and its all going to a single point on the block, so there shouldn't be any issues there. The only other thing I have heard of is starter motor's that are old ( its the original from 1997 ) can internally pole ( whatever that means ha) and create electrical interferencr whilst cranking.

Once running, it runs absolutely beautifully so I feel everything else is pretty much spot on.

Any ideas?

Appreciate any help.

You need to look at the signal with an oscilloscope to determine what the real issue is. Does it drop out, are the extra pulses? Is the wiring to the crank sensor shielded?

Is the real issue a voltage drop caused by starter draw? There are many possibilities, but using proper test equipment will help you determine the root cause.

What would you reccomend testing starter draw with? I am going to change the starter motor over just for the sake of ruling that internal poling issue out. Its not expensive and will knock that out of the equation.

I dont have an oscilloscope on hand, but if it means I have to buy one to work this out, then I will. Obviously that's a worst case scenario, but nlt even the Engine tuner could work it out. He put it down to " wiring problems", which I have double/triple checked.

Appreciate your help.

Only an issue under 1000rpm. When idle drops below, it stalls hence why the tuner set it to idle at 1100 ish. Its running the standard trigger wheel in the CAS that has been modified to run sequential injection, so its a 4 +1 tooth pattern.

Just can't figure out what would generate this noise under 1000rpm. Mind boggling.

OK, so not being able to run below 1000 RPM rules out the starter (since it's not active).

For a variable reluctance sensor, the amplitude of the signal changes with the speed, so normally you have a table with a trigger arm (called hysteresis in some ECUs) voltage for a given RPM. Perhaps your trigger arm/hysteresis voltage for below 1000 RPM is too high.

It has stepped voltage setting option, so maybe Ill lower the voltage right down below 1000rpm, then raise it back up over 1000rpm so there's no chance it'll pick anything up and misfire in the higher rev range. If that doesn't work, do you think it's worth swapping the reluctor out for a Hall sensor, as they work better at lower remit? Very, very muchly appreciative of your help mate, thank you.

You are on the right track. If you had an oscilloscope, you would see what the voltage need to be. For example, here are the values used by a Motec M84 on a Porsche 911 engine with 60-tooth trigger:

RPM Voltage

0 0.3v

500 1.0v

1000 2.0v

2000 3.4v

4000 5.3v

6000 7.5v

8000 8.0v

I like VR sensors better than Hall Effect they seem to be more noise tollerant (due to the high voltages at high RPM). But they do need the proper RPM voltage settings. This really sounds like your problem.

BTW -- have you tried contacting Wolf EMS for help? Seems like they are very willing to provide support: https://www.wolfems.com/support.html

Awesome. So do you reccomend purchasing an oscilloscope to set these, or could I just maybe lower the voltage below 1000rpm and leave as is above 1000. See what happens?

I have contacted Robbie at Wolf but he is a very busy man and I believe he's not really doing it anymore, so it has been hard to get an answer back.

Do you think the tooth pattern, only being 4+1 could be an issue? The tuner thought that is what might be the issue, but wasn't 100% sure.

Thanks again

Just lower the voltages below 1000 RPM.

There will only be three results of a change -- Better, Worse or the Same. You should be able to tell if it's Better or Worse :) You can always set it back. What are the current values?

I wouldn't buy an oscilloscope unless you are planning to do this work professionally. But you might want to check around and see if you can borrow one from somebody.

I'm not entirely where it's currently at. The ECU only gives you set voltage levels. VERY LOW, LOW, LOW MEDIUM, MEDIUM-HIGH then High. Lretty vague. But I do have an oscilloscope video the tuner tool whilst fault finding. Its really hard to see but it looks like 2.0V at cranking.

I'm trying to attach photos, but I'm not sure if its worked.

x Screenshot_20201222-055344_Drive.jpg

x Screenshot_20201222-055816_Gallery.jpg

Is it worth adjusting the air gap? Right now it's at factory spec which is .2mm

Correct me if I'm wrong but, the larger the gal, the higher the voltage output, or opposite?

Generally, the smaller the gap, higher the voltage. You should change the ECU to LOW or VERY LOW and try it.

Ok, I'll try that and see what happens. Once again, I sincerely appreciate your help David.

Fist of all I have done loads of these engines on standalone in the past never come across this problem so is the WolfV4 fit for this job? Maybe look for something better!

What about sensor polarity? Assuming you use the original distributor set-up? Please post an oscilloscope picture so I can have a look. Chance is if your sensor is connected wrong the ECU is having a hard time detecting the missing tooth @ low RPM as well. Falling/rising edge detection and so on.

Ive got a good friend who has run wolf V4 on both his Swifts ( same engine ) and has had absolutely no dramas at all with the V4. yes it might be outdated, but its got all of the functions for a good, reliable tune. Only thing is, he isn't running sequential, so it only has the 4 teeth on the trigger wheel. He has no issues starting, but the fuelling isn't as good as theres no reference to cylinder number 1.

As mentioned above, I dont own an Oscilloscope, but I can get the polarity for you.


From experience a low tooth count on a reluctor ring with a VR sensor isn't the best at low speed due to low voltages, high speed it should be fine but as mentioned previously an oscilloscope would highlight this straight away; it will also give you an indication on which edge to trigger and this will have a big effect on starting. look at options for an aftermarket trigger wheel and sensor that you could retro fit. Noise generally only becomes an issue at higher speeds but is easily solved by screening to a proper drain.

Using a timing light and ignition timing lock on in the ECU (if you have this option) while the engine is running can be an indication that sensor wires are swapped with ignition timing not consistent al do if only one teeth per 180 crank is used??? Not ideal.

Sequential or non sequential dos not make a HP difference on these engines. It’s how you build these engines that dos the trick of great performance.

Not trying to make maximum hp. We opted for sequential as its obviously the more efficient option. As mentioned at the start of the thread, It has no issues creating a trigger signal over 1000rpm runs very well and makes really good power on a really modest tune. The engine is built to the same specs as my good friends swift gti, that is churning out 197 RWKW, and has done so for the past 4 years with no issues at all.

I can assure you that the trigger wiring is sound and in the right orientation as per the ECU manufacturers reccomendation. Polarity is set to Falling edge.

If I can work out how to attach photos, it'll probably make everything easier.

Appreciate your help

Attached Files

Get your self an oscilloscope please and post That’s picture!

I have a picture of the oscilliscope that was taken when we tuned the car. Ive attached it to the thread but obviously didn't work. Are there any photos on the thread that you can click on?

Ive attached at the bottom of this reply.

Thanks mate

Attached Files

Great that looks good.

Some simple things you can still do.

Chance out the ECU to eliminate the possibility that the ECU is the problem.

Chance the distributor. In the picture of you last post two of the 4 teeth give a lower voltage reading so if 2 teeth stay just under the trigger voltage of the ECU??? shaft bent of air gap to sensor not the same?

Get a voltage reading. Take a good voltmeter and put in on AC and crank the engine and record the voltage.

Now some of the basics with a reluctor sensor that gives AC voltage. AC dos not give a peak to peak voltage like DC but a average reading for the peak to peak you need to ad Ö2 and that is 1.41 x AC voltage. Example if you read 1V AC x 1.41 = 1.41V DC.

This 1.41V DC is not how the ECU reads this as it reads from the zero line and the 1.41V is peak to peak so max positive to max negative voltage or + and - voltage.

The zero line is in the middle so we have to divide the DC voltage in 2 so the ECU reads 0,7V.

Now look into the ECU documentation what the minimum voltage should be what the ECU can read on the timing input. Same goes speed and ABS sensor as well.

Chance is it called minimum trigger voltage and the ECU records a signal as is goes over this min voltage level. If it stay under this voltage the ECU dos not record any signal.

Will test it after Christmas. Thanks for your help

Hope all have had a good Christmas. Finally got back into the shed. Attached is a video of the voltage reading direct from the VR.

I have searched high and low for the minimum voltage that the ECU will.read, but havent found anything. Tried reaching out to Wolf EMS (well before Christmas) and haven't heard anything still.

I know a friend of mine's one runs the same setup, but doesn't run the 5th tooth on the trigger wheel, so its just a batch fire setup. He has no isses, but obviously his fuelling isn't quite as good as there's no reference to where the engine is in its cycle.

I dont know what's happened since I last tested it but now it wont start at all . The noise counter on the ecu hand controller just keeps going up. I got it to idle a couple of times, then as soon as the noise counter read noise , it would stall immediately. Thinking I should just honestly bin the lot and start fresh with a Haltech Elite 550? Simple, but way enough power for this simple little setup.

Attached Files

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