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Aftermarket 4G63 Trigger Setup

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Hey guys,

 

Just trying to fine tune my trigger setup on a 4G63T engine, late model evo 5 setup. I've purchased an aftermarket Kiggly crank trigger wheel, 12 tooth that runs off a standard mitsi hall sensor. Really nice piece of kit.

 

kiggly_crank_sensor3.thumb.png.d8638868a

 

My questions are directed at the cam sensor side of things. I have read that a crank sensor with a missing tooth arragement can be better, as the cam sensor tooth location is less important, but I don't really want to be hacking off a tooth from the new crank wheel.

 

The standard mitsi Cam sensor is also a hall sensor, and the pickup has one large, and one small vane on it, as so:

 

OEM_Cam_sensor_pickup.thumb.png.e437353d

 

I will obviously be removing one of these vanes all together, but my question is which one and how much?

 

Is there an ideal crank location for the cam pickup to be in? i.e 60 crank degrees either side of TDC. And tooth size on the modified vane can only be as small as the Hall sensor magnet? Or is tooth size irrelevant as it is only worried about leading edge? Obviously I dont have 360 degrees of choice to modifying this particular cam pickup, but I would like to put some thought into it. I.e I can flip the whole pickup 180deg if that allowed me to place a vane in a more desirable postion etc etc 

 

Cheers

Ian

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Hi Ian,

Crank wheel will be good as is - no need to remove any teeth.

For the cam target you will need to remove one of the teeth, Its a bit hard to guess which one is the best one to keep though without doing a trigger scope.  The position of the cam tooth (in terms of engine position) is not important, however we do ideally want to choose an edge that is roughly centered between two teeth edges on the crank.

I suggest fit the crank wheel first, but leave the two teeth on the cam initially.  Then crank the engine and do a trigger scope.  Post the scope image here and from that we will then be able to advise which is the best tooth to remove and which edges to select in the trigger settings.

WZHQXx8.png

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Hi Simon

The oem Evo crank trigger wheel has only two high and lows. Generally is there any benefit if the crank wheel is changed to a one with higher tooth count? For example 36-2 

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Hi Simon

The oem Evo crank trigger wheel has only two high and lows. Generally is there any benefit if the crank wheel is changed to a one with higher tooth count? For example 36-2 

At steady state RPM there is not a lot of noticeable difference between a high or low tooth count.  However there is a big difference when the crankshaft is accelerating or decelerating at high rates.  A low tooth count wheel doesnt update engine position as often so the ignition advance calculation will lag behind the change in engine speed.  That results in significantly more ignition advance being applied during acceleration.  Many years ago when I first started playing with EFI most ECU's could only decode "1 edge per TDC", back then it was not uncommon to see 10-20deg of timing drift with a quick throttle blip.  Starting was often an issue also as the crank acceleration at low RPM caused lots of timing scatter.

On low tooth count wheels like the OEM evo one we look at both the rising and falling edge to improve the situation a little (so 4 updates per rev) but still it is not ideal for a high performance engine.

Nowadays 36-2 is my favorite but really anything more than about 24 teeth you cant physically see much drift.  The higher tooth counts like 60-2 etc when used by an OEM I suspect are probably there more for strategies such as misfire detection etc rather than solely improving transient ignition.

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Okay, interessting. Means I'going to convert in feature high hp builts to another crank pulley. 

 I'm building a 700hp Subaru ej257 atmo. What i remeber the ej257 has no crank trigger and the keft sensor measure crank and cam position. Can you elaborate the how good the this  trigger is, please.

On the last  2jz i made there was a big timing drift with a quick throttlr blipped. Supra has about a 12tooth wheel. Wondering how it could be that bad. Is there i a common problem on the 2jz?

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 I'm building a 700hp Subaru ej257 atmo. What i remeber the ej257 has no crank trigger and the keft sensor measure crank and cam position. Can you elaborate the how good the this  trigger is, please.

Im fairly sure that engine should have the common Subaru 36-2-2-2 pattern on the crank.  It is a good trigger system.

 

On the last  2jz i made there was a big timing drift with a quick throttlr blipped. Supra has about a 12tooth wheel. Wondering how it could be that bad. Is there i a common problem on the 2jz?

The stock 2JZ trigger is usually pretty good.  If the polarity on the sensor is reversed you will see some drift with RPM so maybe the sensor was connected backwards?  It is hard to tell from a trigger scope on these engines as the waveform is almost symmetrical. 

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Can anyone help? I have a trigger system, do magnetic reluctors need a point or can they be flat faced

With VR type sensors it is important to have the tip of the wheel tooth about the same width as the "pole piece" in the sensor.  The pole is the metal core inside the sensor that the coil is wound around.  On some sensors the pole is exposed so that you can physically see it, on others it is hidden inside under the plastic cover.  On sensors that have a hidden pole you can get an approximate idea of the size by dragging a paperclip over the end of the sensor - the pole is magnetic so you can feel where it is.

I will attach some pictures that arent mine but will explain better than words:

D7IlzUq.png

6pHRnLj.png

 

Correct tooth width:

LN6MnG1.png

 

Tooth width too wide:

VzJSLAG.png

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Right, managed to do a simple power up and take a trigger scope under cranking conditions.

 

With the Hall effect sensor, does the voltage rise or fall when the metal tooth is passed over it?

 

Here is the scope image of the twin tooth cam pickup

 

DSORDA_Trig_scope_twin_tooth_wheel.thumb

 

I also had another pickup with the larger of the teeth already removed, so tried that and took another scope:

 

DSORDA_Trig_scope_single_tooth_wheel.thu

 

I took some closer resolution images of the rising/falling edges if there are any worth looking into.

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Your cam trigger in the second triggerscope will be good.  Notice the falling edge on trigger 2 is reasonably well centered between two falling edges on trig 1.   So set both trig 1 & 2 to falling edge and you will be golden. 

 

hMsJoCB.png

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Awesome, thanks Adam. So the voltage decreases when the tooth runs past the sensor? Just trying to get my head around the scope images for future reference thats all, as the 1st scope (with twin tooth, twin gap) shows up the way I was expecting.. but the second scope (with the single tooth pickup) I was expecting to see a hump rather than the dip shown, when the tooth ran past the sensor. It apears to me its the other way around, and infact the humps I am seeing in the first scope is in fact the large/small gaps between the teeth?

 

Here is a better resolution image of the falling edge anyway.

 

Zoom_Falling_edge.thumb.jpg.396840e96b67

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Awesome, thanks Adam. So the voltage decreases when the tooth runs past the sensor? Just trying to get my head around the scope images for future reference thats all, as the 1st scope (with twin tooth, twin gap) shows up the way I was expecting.. but the second scope (with the single tooth pickup) I was expecting to see a hump rather than the dip shown, when the tooth ran past the sensor. It apears to me its the other way around, and infact the humps I am seeing in the first scope is in fact the large/small gaps between the teeth?

Hall and optical sensors can work either way around.  Most commonly, the sensor pulls to ground when a tooth is in front of it, but there are exceptions like you are seeing here.  From memory the Evo cam sensor goes high when a tooth passes.  

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