vems trigger problems on aan

[diesel des]

Paul, it seems that it is to do with filtering. On the wiki page the guys are saying that the cam sensor output is normally high and drops low during its window. This seems the opposite to what we have found. But they say it needs inverted to go high and maybe enable the waiting for the crank pin. But why are our outputs already high during the window. There is nothing weird or inverted in the scope is there. Maybe I need to remove the inverter in the vems.

[diesel des]

Ok just checked, my cam signal is inverted compared to everyone else's! Wtf . What pins or wire colours were you on Paul on the cam sensor. Think I need to retest tomorrow night.

[a4kquattro]

If vems is plug and play then why is hall cam signal inverted ?

"inverted" might be a bad term for it, but its what the vems guys call it.

VEMS has two trigger inputs, so the function of the hall inverter is to tie a transistor to the hall sensor that basically prevents the reference pin from sending a signal to the secondary input channel unless the hall sensor is in-window. This is critical on the 7a flywheel due to the large extrusions on the flywheel that show up as triggers without the hall transistor in place.

[diesel des]

I'm thinking if I put my scope ground on the 5 v sensor supply by mistake with dc coupling input the signal would look inverted. Must test this tommorow.

[newsh]

"inverted" might be a bad term for it, but its what the vems guys call it.

VEMS has two trigger inputs, so the function of the hall inverter is to tie a transistor to the hall sensor that basically prevents the reference pin from sending a signal to the secondary input channel unless the hall sensor is in-window. This is critical on the 7a flywheel due to the large extrusions on the flywheel that show up as triggers without the hall transistor in place.

This absolutely makes loads of sense, I would say that "gated" would be a better term than inverted though.

[S2central.net]

CAM sensor signal is at pin 2 - should be 5V except during the window when it is low (0V).

If the VEMS gurus cannot filter out your rogue pulses I will have a look into for a small cheap box that eliminates... There is plenty of help I can call on from some fantastic analog electronics engineers if I get stuck.

Something like this might be a good starting point. All you need is an opamp and couple resistors/pots which can be used as the gate control for the G4 signal - preventing these low amplitude pulses from getting into the VEMS unit.

http://en.wikipedia.org/wiki/Thresho...ith_hysteresis

[a4kquattro]

CAM sensor signal is at pin 2 - should be 5V except during the window when it is low (0V).

If the VEMS gurus cannot filter out your rogue pulses I will have a look into for a small cheap box that eliminates... There is plenty of help I can call on from some fantastic analog electronics engineers if I get stuck.

Something like this might be a good starting point. All you need is an opamp and couple resistors/pots which can be used as the gate control for the G4 signal - preventing these low amplitude pulses from getting into the VEMS unit.

http://en.wikipedia.org/wiki/Thresho...ith_hysteresis

as I mentioned to Des before, he must get the details of the filtering resistors used in his ECU on the primary and secondary trigger inputs. whoever he ordered the ECU from should have spec'd this at the time of the order.

[diesel des]

Thanks guys, I'm going to try more testing with the scope tonight to confirm the pulses. And also try 58 teeth timing. Basically at the moment the car shows some small amount of triggering error on vems when cold. Then when warm vems shows no triggering faults on the screen but I get ping coming almost randomly when I shouldn't. I Think due to false triggering.
Eg afr at 0.82 at 3k rpm boost 1 bar and timing 9 deg advance. That shouldnt ping should it. Cheers des

[a4kquattro]

Thanks guys, I'm going to try more testing with the scope tonight to confirm the pulses. And also try 58 teeth timing. Basically at the moment the car shows some small amount of triggering error on vems when cold. Then when warm vems shows no triggering faults on the screen but I get ping coming almost randomly when I shouldn't. I Think due to false triggering.
Eg afr at 0.82 at 3k rpm boost 1 bar and timing 9 deg advance. That shouldnt ping should it. Cheers des

there is a difference between trigger error and trigger OFFSET. ping can be caused by a trigger offset if the timing should make sense for the given boost. if vemstune/megatune is reporting trigger ERROR, thats a different problem.

[diesel des]

Yea there are some trigger faults shown in vems when cold. Then vems thinks its ok when warm with no indicated trigger errors shown.. more testing required I thinks

[diesel des]

Quick update. Burnt half tank of petrol tonight testing. From cold car starts well but has the odd trigger error. Vems flashes trigger fault light and rev counter pulses and engine misses. Happens most between 1.5 k and 2k rpm. But went warmed up no trigger faults.

Adjusted the tdc teeth to 58 and no more ping with a similar timing curve to motronic. I'm 99% happy now. Just need to scope the trigger faults when engine is cold.

Why faulty when cold?
Thanks des

[Jamo]

Good! don't know why it was 53!

Try setting your cold ignition cold adjust and retard clamp to -5 instead of 0 under ignition settings.

Only try it with idle wouldn't go for a drive, I played with this setting but put it back to 0 as I didn't need it in the end.

Marc probably best to advise from here

[diesel des]

I logged motronic advance curve to see what the timing numbers were, then loaded them into vems. Now with the way I have the inlet temp retard map setup my actual advance numbers are about 4 deg more retarded than with motronic. I'm at about 15 deg advance at 6 to 7k rpm 1.5 bar. Anyone like to post up there table of advance please. Would give me some confidence. At least retarded is safe for quick blasts. Wont be doing any track days till its sorted. How do you listen for ping. Det cans? Where did you get or make these. Cheers

[Bram]

I logged motronic advance curve to see what the timing numbers were, then loaded them into vems. Now with the way I have the inlet temp retard map setup my actual advance numbers are about 4 deg more retarded than with motronic. I'm at about 15 deg advance at 6 to 7k rpm 1.5 bar. Anyone like to post up there table of advance please. Would give me some confidence. At least retarded is safe for quick blasts. Wont be doing any track days till its sorted. How do you listen for ping. Det cans? Where did you get or make these. Cheers

You can only be confident if you listen for knock dude.

Other people's spark/VE tables can not be trusted, since every engine setup behaves differently.
E.g. I have 20-21 degrees of advance in my setup at those ranges and boost profiles, however run a different turbo, exhaust, cam timing, cyl. head flow, probably different fuel, etc, etc..

Please use a knock detection solution like the cheap headphones Terrybullwon and myself are using, or an electronic solution as Marc Swanson is selling. This is the only way to be on the safe side when mapping your own car.

[diesel des]

Any pictures of your headphone setup. Where did you get it. Yea I fully understand each person spark table is different, but it would be interesting to see spark advance at part load sites compared to full load.

Did about 60 miles tonight of normal driving with wife in car etc. I still get some rare trigger errors always between 2k and 2.2k rpm. When it happens the car lurches badly and the exhaust actually bangs the underside of the car. Sounds bad. it can happen even on the overrun.

I must get the scope out this weekend. Driving it is just too much fun. Lol cheers des.