Author Topic: Survey - Does anyone actually use the Secondary Trigger?  (Read 11909 times)

Offline lugnuts

  • Full Member
  • ***
  • Posts: 249
  • BHP: 2
Survey - Does anyone actually use the Secondary Trigger?
« on: December 10, 2009, 03:04:21 am »
Does anyone use the secondary trigger?

With other systems, I connect both triggers, and the engine runs perfect.

With VEMS, I try to use secondary trigger / true sequential fueling for hours at a time, and the engine never sounds as good as it does without the cam sensor.

With the upcoming injector trim options, I'd like to figure this out. An ounce of documentation would help a lot.

Just wondering.

Offline GintsK

  • Hero Member
  • *****
  • Posts: 1257
  • BHP: 50
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #1 on: December 10, 2009, 03:24:18 am »
I use it always if possible.

Offline lugnuts

  • Full Member
  • ***
  • Posts: 249
  • BHP: 2
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #2 on: March 05, 2010, 10:10:32 pm »
That's it? One user on the entire forum?  Not too promising.

Gints, what settings do you use for secondary(list engine set-up also please)?

Does the engine die when you unplug the cam sensor?

Offline GintsK

  • Hero Member
  • *****
  • Posts: 1257
  • BHP: 50
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #3 on: March 05, 2010, 10:20:15 pm »
Yes die.

Usually I try to make cam signal right before missing.
We have lack of clear documentation. May be any other position works too  ;D

Settings is 24 or 25 raw depending Hall or VR...

Offline Sprocket

  • Hero Member
  • *****
  • Posts: 867
  • BHP: 29
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #4 on: March 06, 2010, 12:13:02 am »
I intend to use it, I have everything ready to go, just have to replace the burnt piston and swap out the jackshaft for the one with the sync tooth on it :D

Offline lugnuts

  • Full Member
  • ***
  • Posts: 249
  • BHP: 2
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #5 on: March 06, 2010, 01:32:26 am »
Yes die.

Usually I try to make cam signal right before missing.
We have lack of clear documentation. May be any other position works too  ;D

Settings is 24 or 25 raw depending Hall or VR...

- From memory, I had to put strange settings for sequential to work on my own car (Distributor VW VR6) - such as "alien advance" instead of "cam sync" (1.0.78fw)
- I won't know for sure if my set-up works 100%, until I use it on a coilpack engine (no dist.). I'm running 1.1.67fw now so I can re-do the tests soon.

Offline lugnuts

  • Full Member
  • ***
  • Posts: 249
  • BHP: 2
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #6 on: March 06, 2010, 01:42:43 am »
Also, other ecu makes preferred cam sync position is as far away from crank tooth as possible.

60-2 wheel, ecu dumbs down the trigger to 2 teeth 180 degrees apart (4 cylinder)
- if first tooth is 84 degrees BTDC ,
- then next tooth is 96 degrees ATDC. (84 BTDC + 180 degrees rotation)

The ideal cam sync location would be 6 degrees ATDC (84 BTDC + 90 degrees rotation)

Because the ecu does not like when the crank tooth and the cam tooth trigger at the same time.

The engines I work with, typically have the cam sync at #1 TDC, so it usually works with most ecu's.

It would be nice to be able to use current VEMS wiring and not have to offset injector events, etc.

Offline dnb

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 837
  • BHP: 19
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #7 on: March 06, 2010, 02:07:48 am »
I have used the cam trigger on some cars.  It's not currently in use on my test car due to clumsiness and a broken sensor...

Offline hilly

  • Jr. Member
  • **
  • Posts: 53
  • BHP: 6
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #8 on: March 06, 2010, 04:56:15 am »
I always use the cam sync on all the Audi V8 installs I modify looms for.
I have never tried disconnecting it while running, but the engine certainly will not start without the cam sensor fitted.

Once you get your head around how the cam sync works and the sightly odd firing order it requires (certainly on the Audi V8 anyway) then it is easy to understand, have a look at http://195.159.109.134/vemsuk/forum/index.php/topic,214.0.html as the cam sync was covered.

Hilly

Offline mattias

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1075
  • BHP: 41
    • Sävar Turbo Site
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #9 on: March 06, 2010, 05:06:23 am »
With the latest firmware 1.1.x the position of the camsync has natural limitatios for N+1 triggers because you have to time it exactly before or after events so that there is no way to confuse them. This is easy with simple trigger on the crank, like 2 teeth for a 4 cyl as you just place the cam tooth in between the primary trigger events.
For Porsche/Audi with their 135+1 you really need the masking signal from the crank home tooth to get the timing right, people seem to erroneously assume that this works with other systems without the home signal to mask the cam signal, they have apparently not strobed the timing at all loads and rpms - there is a big risk that you get a 360/135 = 3 degree error in the Audi case when it skips a tooth.

With N-x (60-2, 36-1, etc) you must make sure it does not race with the trigger teeth of choice (your trigger tooth ref table). Someone mentioned it earlier, the cam pulse is usually at TDC for cyl #1 on many engines and means it is normally just a matter of setting it up and go.

I've set up cam sync on maybe 10 engines so far, the majority using 1.0.x firmware, there were no tricks with the settings really. I haven't really considered that there is any limp-home mode for it, I would like to see it as an option in case the sensor is not reliable and you're a long way from home.

If you think the engine runs better without the cam sync you're just fooling yourself. It's a gamble which injection sequence will be used on each startup. At least with cam sync it will always run as bad all the time, as it will use the same injection sequence every time. I've played with this plenty of times and on engines with hot cams where it should matter the most I can hardly discern a difference when rotating the injector group table, however slight - you see the problem is that with all VEMS firmwares so far you will never inject fuel at the "right time". You can always rotate the table but the injection events are started every "trigger tooth" (afaik) which is rarely at the correct time if you look at the cam/intake events.

 Do not mistake "injector trim" for phasing, trim is for compensating injection pulsewidth for varying VE between cylinders (strange intake runners) and in rare cases non-flow matched injectors, while phase compensates for injection timing and naturally needs cam sync while trim doesn't.
I'd say "trim" is really hard to get right, while it's nice to apply overall individual injector scaling for WOT and high duty cycle use, in a world of perfectionism the injector characteristics and errors are  non-linear which requires the input of injector flow curves for each injector.

Phasing has been written by Andrey, no idea on how much testing there has been but apparently not enough to be publically available, apparently  it was using just one fixed angle (enough really for a good idle).  I will push for getting it done sooner rather than later. A 4x4 table with TPSxRPM would suit most peoples desires?
« Last Edit: March 06, 2010, 05:09:26 am by mattias »

Offline dnb

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 837
  • BHP: 19
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #10 on: March 06, 2010, 05:50:20 am »
If you think the engine runs better without the cam sync you're just fooling yourself. It's a gamble which injection sequence will be used on each startup. At least with cam sync it will always run as bad all the time, as it will use the same injection sequence every time. I've played with this plenty of times and on engines with hot cams where it should matter the most I can hardly discern a difference when rotating the injector group table, however slight - you see the problem is that with all VEMS firmwares so far you will never inject fuel at the "right time". You can always rotate the table but the injection events are started every "trigger tooth" (afaik) which is rarely at the correct time if you look at the cam/intake events.

Phasing has been written by Andrey, no idea on how much testing there has been but apparently not enough to be publically available, apparently  it was using just one fixed angle (enough really for a good idle).  I will push for getting it done sooner rather than later. A 4x4 table with TPSxRPM would suit most peoples desires?

Lots of good stuff here.  A couple of my observations that back up a lot of what you say:
I can usually tell which "phase" the TVR syncs up to when it is started without a camsync input by the way the car drives - one way works well, the other feels "different".  (I have things set up so that the fuel is always injected at closed valves and this minimises the difference in feel between the 2 "modes")  It matters most in my case at low RPM.

There is a way to move the injection pulse around without rotating the injector groups.  It's not nice and has only the resolution of the toothwidth, but it is there - look at changing the TDC before trigger parameter and what you consider your trigger tooth to be.  In my case, I can move the injector point around in 10 crank-degree steps.

A 4x4 table would be sufficient for me.  It would also give me some much needed encouragement to fix my broken cam sensor!  I have always been willing to experiment with new stuff on this car, so I'm ready as soon as the code is.

Offline GintsK

  • Hero Member
  • *****
  • Posts: 1257
  • BHP: 50
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #11 on: March 06, 2010, 02:26:28 pm »
Quote
With N-x (60-2, 36-1, etc) you must make sure it does not race with the trigger teeth of choice (your trigger tooth ref table). Someone mentioned it earlier, the cam pulse is usually at TDC for cyl #1 on many engines and means it is normally just a matter of setting it up and go.
But racing with missing teeth is not problem?

Example: Audi with 60-2. 0-24-48-72-96. It will work ok when cam pulse stands between 96...0.
But how to deal when cam pulse is between 0...24?

Offline mattias

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1075
  • BHP: 41
    • Sävar Turbo Site
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #12 on: March 06, 2010, 03:46:48 pm »
GintsK: You never race with missing teeth since those give the ECU perfect sync, it doesn't need the cam sync to tell it the order of the primary teeth as they pass the trigger - the only thing that's important with "N-x" is that they don't race with the trigger teeth so that the ignition order is always correct, which boils down to the problem with "N+1" triggers.

dnb: Yes, it's actually possible to phase the injectors somewhat by playing around with different trigger teeth offsets but it's a lot of work to find out what works. I think we have the same ideas! ;)

Offline rob@vems.co.uk

  • Hero Member
  • *****
  • Posts: 3115
  • BHP: 49
    • VEMS Forum
Re: Survey - Does anyone actually use the Secondary Trigger?
« Reply #13 on: March 08, 2010, 12:34:55 am »
Every single Nissan and all the I5 engines use it.