Trigger wheel setup

[Niponeoff]

The initial message was deleted from this topic on 27 February 2025 at 16:49

[Sardonicus]

All the info is out there https://www.youtube.com/watch?v=HW0ENqcxNSg bracket wise security is key i.e CPS not mounted onto a flimsy metal bracket for example with the air gap fluctuating due to vibration etc loss of sync will give you problems for sure

[Sardonicus]

Niponeoff said:

Sardonicus said:

All the info is out there https://www.youtube.com/watch?v=HW0ENqcxNSg bracket wise security is key i.e CPS not mounted onto a flimsy metal bracket for example with the air gap fluctuating due to vibration etc loss of sync will give you problems for sure

I was after advice on which tooth to remove on the trigger wheel, not the setup in the ECU. Thanks though, I watched the video, was good.

And yes, unlike the pic where he's used one bolt hole, I plan to use two for my bracket.

I think most state 90 degrees before TDC, so I think tooth 18 should be removed. No harm in checking with some PH beards though

Edited by Niponeoff on Wednesday 24th May 12:52

You mean tooth 9 surely?

[stevieturbo]

Niponeoff said:

I was after advice on which tooth to remove on the trigger wheel, not the setup in the ECU. Thanks though, I watched the video, was good.

And yes, unlike the pic where he's used one bolt hole, I plan to use two for my bracket.

I think most state 90 degrees before TDC, so I think tooth 18 should be removed. No harm in checking with some PH beards though

it's simple. Refer to your ecu instructions and what is is happy with. No point someone telling you what their ecu was happy with. It's your ecu, whatever it is.....so keep it happy. Not someone elses.

[stevieturbo]

Niponeoff said:

I'm going to use an ECU masters pro 8, wasn't much in the manual, just programming options which I believe is anything. Maybe I'll email them.

And are there any caveats in the software ? help file to guide ?

Some ecu's can be very picky, some really don't care where the missing tooth is, some reference off the first tooth after it, some the second.

They're just all different.

I'd say you'd struggle to be wrong at around 70, 80, 90 deg BTDC or thereabouts, but best to find out if your ecu has any oddities regarding it.
It's usually the lower end stuff is more fussy.

[fatjon]

A typical setup is that sensor sees first tooth after the missing tooth 90 degrees BTDC.

[stevieturbo]

fatjon said:

A typical setup is that sensor sees first tooth after the missing tooth 90 degrees BTDC.

there is no typical setup.

Some care, some are very particular, some really don't care. He needs to find out specifically what his ecu needs or wants. A glance at the instructions doesn't offer much info, maybe the software might. Or maybe it is another that really doesn't care where it is

But from a user diagnostic point of view, that is a fairly sensible position. But again, not all ecu's use the first tooth after the missing. Mine uses the second ( although I guess I could probably program it to use any number )

[Mikey G]

I fitted an aftermarket flywheel to my ST170 build and I dont think the triggering was exactly the same as an OEM flywheel.
To set it up properly I had to best guess the trigger offset using a timing light to get it to fire and run before setting the ECU to fixed 10 degree advance and gradually altering the trigger offset to get it correct.

The point is nothing is exact in such a setup and you will need to apply a correction somewhere anyway wether thats altering the trigger wheel position, sensor or an offset in the ECU.

[stevieturbo]

Mikey G said:

I fitted an aftermarket flywheel to my ST170 build and I dont think the triggering was exactly the same as an OEM flywheel.
To set it up properly I had to best guess the trigger offset using a timing light to get it to fire and run before setting the ECU to fixed 10 degree advance and gradually altering the trigger offset to get it correct.

The point is nothing is exact in such a setup and you will need to apply a correction somewhere anyway wether thats altering the trigger wheel position, sensor or an offset in the ECU.

The reason you tell the ecu where the missing tooth is relative to cyl1 TDC ( that's only half the picture really as it will also coincide with another TDC event during a full 720 cycle ), is so the ecu does know exactly where this is.

Using a timing light/locking timing and making adjustments is to ensure the position you tell the ecu is exact. This is a critical setting, it needs to be correct. ( that said, it can happily run wrong, all tuning numbers can end up wrong....it doesn't mean the engine still wont run and could not be tuned. But it would be extremely stupid and bad practise to run with it wrong, with wrong numbers elsewhere to try and make it "right" )

Much the same way as on this trace with crank, cam and cyl1 compression, you can determine all positions.

Cam position here 59deg ATDC, and 2nd missing tooth after the 36-1 gap on crank is 313deg ATDC ( relative to the cyl1 TDC, not cyl 4 as would also see a TDC event during the 720 shown )

Some ecu's want BTDC, some will use ATDC....again, no typical, each ecu may want different things, or view things in slightly different ways.
This ecu couldn't care less where you have these events. Just tell them where they are.




A visual like this, can often make it much easier for people and it does make initial setup easier too

Edited by stevieturbo on Friday 26th May 14:21

[GreenV8S]

Niponeoff said:

So which tooth then?

The one which is aligned with the pickup when the crank is at the position where you want the missing tooth to occur.

[GreenV8S]

Niponeoff said:

I knew it. You don't know either then.

You have to decide what crank position you want the missing tooth to occur at. This isn't a matter of somebody else knowing the answer and telling you. You have to decide what position you want it at based on the ECU type and how you're going to configure it.

Working out what numbered tooth that corresponds to in your picture is trivial once you have made that decision.

[stevieturbo]

Niponeoff said:

I knew it. You don't know either then.

Stop acting like an idiot. If you are incapable of understanding this very basic stuff, take the thing to someone who can

[Mikey G]

Niponeoff said:

I knew it. You don't know either then.

You come on here asking for advice and everyone has had a little input telling you it may be ECU specific but not an exact science and as you also stated in your first post :-

Niponeoff said:

Anyone got an idea of which tooth I remove? I don't suppose it matters too much, as I can set it up in the ECU, but I'm sure there is a preference or window where it's best/recommended?

Check the bold, you havent even told us which ECU you are using.

stevieturbo said:

Stop acting like an idiot. If you are incapable of understanding this very basic stuff, take the thing to someone who can

Best advice so far.

[stevieturbo]

Niponeoff said:

I've already asked the question academically, not practically. I found the previous response to be purposefully avoiding the question with a snarky tone, so it got a jovial response - I don't know why you've got on your high horse?

I'm asking because hypothetically I'm not sure, and no one is willing to say which tooth to confirm my thoughts. Forget the ECU and engine type in this instance, I already made that clear further down from initial post.

A) Which tooth for 90 degrees BTDC at the current sensor position?

B) Which tooth is the one after as discussed by someone else.

CW engine rotation as you look at the picture.

I've asked for confirmation is A = 18 and B = 17. At least I'll now I'm working it out correctly for this hypothetical scenario and will help a great deal. Not what ECU etc. It doesn't mean that is the one will remove and it doesn't mean that's what my ECU requires, it is just a question requiring confirmation.


You could help further by saying what others you may have encountered and which tooth that would represent on the diagram, so at least i can see visually what your words are describing. This is the problem I have had with other information on the internet. it isn't specific to an example.

I trust that is clear.

I don't have a problem with another snarky reply, you'll just get something back, but kindly take it in the spirit with which it is intended and refrain from calling me names.

Thanks.

A. Refer to your ecu instructions
B. Refer to your ecu instructions

Simplez.

The info you appear to be seeking is a variable, and has been stated more than multiple times by multiple users....will depend.

It will depend on what your ecu wants, sensor type, whether rising or falling edge signal, and which specific tooth it is looking for.

So, refer to A and B above. And has already been said multiple times, in most cases these days with anything decent, the ecu doesn't give a F*** where the reference tooth/gap falls.


Here is an old Motec webinar on the topic for their ecu.

It will be different than your ecu, but there will be similarities. YOU NEED TO DO WHAT YOUR SPECIFIC ECU WANTS.

https://www.youtube.com/watch?v=mv0-9_JS8oA

Edited by stevieturbo on Saturday 27th May 11:26

[Mikey G]

I have just gone through the specific instructions on my ECU (Motorsport Electronics) on setup of an aftermarket trigger wheel and there is not one single mention of which tooth or where to setup the gap in relation to TDC. It only mentions once the wheel and sensor is in place how to set the trigger offset to get cylinder 1 to fire at 10 degrees fixed advance.

I suggest you call ECUMASTER as you cant rely on (or wont listen to) a bunch of strangers on the internet.

[Skyedriver]

Mikey G said:

you cant rely on (or wont listen to) a bunch of strangers on the internet.

^^this^^

Using my mathematical, logical brain I'd say 17 is 10 degrees BTDC if the trigger is at 9 but as Stevie will confirm, I'm not the brightest with modern stuff. Happy to play with carbs and dizzys though.

Go to the manufacturer and ask.

[stevieturbo]

Mikey G said:

(or wont listen to) .

Seems more apt when he won't listen to someone who has done it a few hundred times.

It is so bizarre when people come online, get told the information they need, but just blatantly refuse to listen or accept it.

It's like flat earthers and many other such groups.

[stevieturbo]

Niponeoff said:

If my ECU says remove the tooth at 90 degrees BTDC, how will your answer help? Or maybe you can help and say - "in your example that would be tooth 18" feel free to answer my question.

Cheers anyway.

Which tooth ? Which side of edge of the tooth does it use ? Can it use any tooth, either edge ?

As already said, there are VARIABLES.

And as also said, most decent ecu's don't give a F*** which or where.

In short. It really will not matter a damn whether it's tooth 18, 19, 5, 30....the list goes on.


These threads are just unbelievable.

[stevieturbo]

Skyedriver said:

^^this^^

Using my mathematical, logical brain I'd say 17 is 10 degrees BTDC if the trigger is at 9 but as Stevie will confirm, I'm not the brightest with modern stuff. Happy to play with carbs and dizzys though.

Go to the manufacturer and ask.

Sort of....because once again, it depends. In terms of the trigger, it's not so much the gap, but which tooth after the gap the ecu uses to confirm it has seen the gap and uses that for position.

As stated before multiple times, that might be one, two, whatever amount of teeth after the gap. As I showed with absolute clarity on the scope trace the positions for a basic 36-1 setup where the ecu used the falling edge of the 2nd tooth after the gap

So if you removed tooth 17, the sync value you seeks is likely to be less than 90deg IF it uses the first tooth, IF it uses the falling edge, because those are then actually happening at tooth 16-15 so more likely deg

But again, almost certainly a moot point, because the ecu is unlikely to give one damn as long as it is told exactly where this trigger edge is, in relation to the relevant TDC.
Whether this is done via a scope, timing light, magic.....entirely up to the user. But it must be done.

And of course this also assumes the ecu wants it BTDC, as some use ATDC, which flips things about a bit.

[Skyedriver]

stevieturbo said:

Skyedriver said:

^^this^^

Using my mathematical, logical brain I'd say 17 is 10 degrees BTDC if the trigger is at 9 but as Stevie will confirm, I'm not the brightest with modern stuff. Happy to play with carbs and dizzys though.

Go to the manufacturer and ask.

Sort of....because once again, it depends. In terms of the trigger, it's not so much the gap, but which tooth after the gap the ecu uses to confirm it has seen the gap and uses that for position.

As stated before multiple times, that might be one, two, whatever amount of teeth after the gap. As I showed with absolute clarity on the scope trace the positions for a basic 36-1 setup where the ecu used the falling edge of the 2nd tooth after the gap

So if you removed tooth 17, the sync value you seeks is likely to be less than 90deg IF it uses the first tooth, IF it uses the falling edge, because those are then actually happening at tooth 16-15 so more likely deg

But again, almost certainly a moot point, because the ecu is unlikely to give one damn as long as it is told exactly where this trigger edge is, in relation to the relevant TDC.
Whether this is done via a scope, timing light, magic.....entirely up to the user. But it must be done.

And of course this also assumes the ecu wants it BTDC, as some use ATDC, which flips things about a bit.

My heads in a spin, Dizzys are so much easier. Mind you I struggle with Magnetos too.