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Trigger systems

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Quick question here guys,

If you're running sequential injection on an engine, does it matter what type of sensor is used on the crankshaft Vs the type used on the camshaft? What I'm getting at is, could one be an optical/hall and the other magnetic or vice-versa or even perhaps both the same? Or is it most common to use a certain type at each location?

Secondly how do you go about making a decision on trigger wheel pattern configuration based on the engine you're tuning, supposing the engine never had these systems employed from the OE? Example how do I choose a 12-1 Vs a 36-1 or any other configuration for that matter?


I don't have a survey of various manufacturers' choices, but my first thought based on experience is that on more recent engines cam sensors are usually hall sensors, and crank sensors are split between Hall sensors and variable reluctors. For trigger patterns, the newer you go, the more resolution they are going to have as a general rule. Some of that is for variable valve timing, some of it is for emissions/OBD (misfire OBD monitor).

For trigger patterns, more teeth/resolution is better--on paper. In the day to day use however, reliability and availability tend to win out. If there's an off-the-shelf solution for your application that's a 36-1, I would take that over doing some kind of trying to rig up a custom 60-2 or one of the many weird patterns out there. You can't go wrong with something that was a high volume part on a GM or Ford for example. Ford 36-1 is popular. DIYautotune sells a bunch.

So my basic rules:

1. Don't reinvent the wheel (pun intended) unless you are specifically interested in making a project out of trigger systems. If there's a proven kit, buy it.

2. If there isn't a kit, don't do some oddball thing. Keep it simple and use widely available designs.

3. Reliability before precision. Sometimes an older, lower resolution factory system is more robust to electrical noise than swapping some in some unproven thing.

Thanks a lot for the insight Raymond. In your experience can you list some of the more popular patterns out there ?

My friend is currently setting up an aem EMS4 on a 1992 Suzuki Swift GTi, G13b engine. The engine is EFI but was running batch injection. He's converting it to sequential to use with the EMS4. The stock sensor inside of the distributor is a variable reluctor though and well they installed a 36-1 hall sensor on the crank. Looking back at all the info I have from HPA I've always seen the examples Andre referenced using a optical/hall sensor as the sync input hence my initial post/question.

I assume you kept the dizzy for cam timing?

VR sensors are often used for crankshafts due to them being generally more stout and failing less than digital. Both are equally accurate when compared against VR's operating range. If out of its operating range, ie cranking possibly, VR does not sync properly.

Hall supplies its own voltage, therefor engine speed doesn't affect it output.

G'day Chris.

Unfortunately I'm not completely familiar with the AEM EMS4, but I have seen many setups where a 36-1 trigger disc has been fitted to the crank for the main engine speed signal, and the original distributor modified to provide a sync signal for engine phase. The distributor most likely has a VR sensor in it, with a symmetrical trigger wheel that has evenly spaced teeth. Its common to modify the trigger wheel inside the distributor, removing all but one of the teeth, which gives you a sync input, as the distributor will be rotating the same speed as the cam. I'm making an assumption that the AEM EMS4 ecu can be configured to use a 36-1 wheel for engine speed input, and a single sync event to figure out the phase. I think every ecu I have dealt with has been able to.

This also assumes the original distributor has no mechanical or vacuum advance systems? Pretty sure that'd be the case though, but you never know!

To answer your original question however, it's very common to have a mix of VR and digital (hall) sensors on the engine. Personally? I like VR sensors, they just seem to be more robust, as they have no circuitry inside them, they're just a coil of wire around a magnet, nothing to really go wrong!

Zac thank you very much for your response, I really appreciate it. Understood on all that you said, no the distributor has no vacuum advance system. We ended up using two VR sensors, one on crank and one on the distributor.