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Analyzing crank position sensor and cam position sensor capture on a B6304T

Meatball

Meatball

Well-known member
Joined
Jul 30, 2004
Location
Living in my 245
Guys, can someone here comment on my capture?

I have included a screenshot and have several questions regarding what I have found.

The crank signal is variable reluctance obviously. I see 60-2.

The intake cam signal is a hall effect and seems to trigger twice each 720*. Would either of the pulses indicate the duration of the valve lift? If so, that would be the first window and not the second window on the waveform, correct?

This is a monolithic engine and therefore, I am not sure how I can easily find the first TDC angle. I am hoping that it can be done analytically with the capture.

Also, I have wired this to an EcuMasters EMU Pro 8.

Thanks for your time in advance,

GregVolvo_B6304_CamCrankSync.02.jpg
 
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I’m pretty sure this car has cariable cam timing. So the two pulses might be the full retard and the full advance window of the cam? Or something along those lines.
 
You might have the ability to set your cam trigger to “leading edge” or something similar to that.

Might get you started until you figure out the cam timing stuff.
 
HiSPL said:
You might have the ability to set your cam trigger to “leading edge” or something similar to that.

Might get you started until you figure out the cam timing stuff.
Click to expand...
Wait, sorry. Leading edge gets you full advance. “Trailing edge” gets you full retard.

Not sure what the second blip is for.
 
HiSPL said:
I’m pretty sure this car has cariable cam timing. So the two pulses might be the full retard and the full advance window of the cam? Or something along those lines.
Click to expand...

Well, you are not wrong. There is VVT on the engine but that solenoid is not connected.

I took this a waveform off of the N/A engine while it sat on the ground. I have a battery, the oscilloscope and a 12V to 5V trimming circuit on the camshaft sensor power side.
 
Is it this engine: https://en.wikipedia.org/wiki/Volvo_SI6_engine
If so, wikipedia says that the turbo version has both intake and exhaust VVT, so I'd expect 2 cam sensors.

I haven't worked with aftermarket ECUs and VVT, but I think the usual setup is a non-symmetric tooth pattern on the cam(s) that shifts left/right in time as the VVT shifts. Usually, the ECU needs special programming for each VVT crank/cam/cam setup. I'd contact EcuMasters and see if they support your engine.

If you have a picture of the engine at TDC with the missing tooth 60-2 section shown, you might be able to get close to the tooth #1 angle on the crank, and then use a timing light to fine tune it.
 
This is definitely a rising edge trigger for the red waveform. I did a little more homework after I made this post.

A rising edge trigger can be seen when the waveform is increasing in voltage before the next event occurs
 
bobxyz said:
Is it this engine: https://en.wikipedia.org/wiki/Volvo_SI6_engine
If so, wikipedia says that the turbo version has both intake and exhaust VVT, so I'd expect 2 cam sensors.

I haven't worked with aftermarket ECUs and VVT, but I think the usual setup is a non-symmetric tooth pattern on the cam(s) that shifts left/right in time as the VVT shifts. Usually, the ECU needs special programming for each VVT crank/cam/cam setup. I'd contact EcuMasters and see if they support your engine.

If you have a picture of the engine at TDC with the missing tooth 60-2 section shown, you might be able to get close to the tooth #1 angle on the crank, and then use a timing light to fine tune it.
Click to expand...

Again. I have the oscilloscope hooked up on the old engine.

I'm decoding the triggers and the sensors (already have tables for CLT, LSU4.9 and OEM O2) I also have the "signal specifications" from VIDA. However, the pattern for the cam sensor output is not discussed.

This is what it says:

"U= pulsed signal, Umax. > 4.5 V, Umin. < 1 V"

This cam trigger wheel is not like the other engines (2.4, 2.5, 2.9). I know because those waveforms are in a library on a site that I subscribe to.
 
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bobxyz said:
If you have a picture of the engine at TDC with the missing tooth 60-2 section shown, you might be able to get close to the tooth #1 angle on the crank, and then use a timing light to fine tune it.
Click to expand...

Also, the engine is "monolithic". I.E. NO harmonic balancer. I think you are going to have a time putting a timing light on this engine.
 
OK, please confirm that it's the newer SI6 turbo engine with both intake and exhaust VVT, or are you adding a turbo to a NA engine with a single cam sensor?

Are you trying to run VVT or do you plan on disabling the VVT and just run fixed cams?

Without being able to use a timing light, I don't know how you'll accurately dial in the crank tooth #1 angle. Maybe measure it mechanically with the crank wheel exposed? Normally for a missing tooth VR signal, you want to use the falling edge of the 1st tooth after the missing tooth section for alignment.
 
Meatball said:
The crank signal is variable reluctance obviously. I see 60-2.

The intake cam signal is a hall effect and seems to trigger twice each 720*. Would either of the pulses indicate the duration of the valve lift? If so, that would be the first window and not the second window on the waveform, correct?
Click to expand...
 
From looking at the waveform it looks to me like the cam trigger wheel on your engine is one short tooth and one long tooth roughly 180° apart. You can look at the intake valves and pull the cam sensor so you can see the trigger wheel to figure out which cylinder is on its intake stroke with the long and short tooth. The missing tooth on the regular whiteblocks is 90° BTDC so that might also be the same on your engine

At least on the non SI6 VVT whiteblocks the cam trigger is nothing more than an oddly shaped trigger wheel with a hall effect sensor. The ECU looks at the time between a specific crank tooth and a cam tooth triggering to figure out how many degrees advanced the cam is and adjusts the VVT solenoid. You may have to take an engine apart to see the specific cam trigger pattern since Volvo might have changed it for the SI6 engine. This cam trigger wheel is from a ~2004 B6294T engine for example
Screenshot 2025-10-28 104620.png
 
"Would either of the pulses indicate the duration of the valve lift? If so, that would be the first window and not the second window on the waveform, correct?"
No, the pulses are just the rotational position of the camshaft and have nothing to do with lift or duration. The waveform will be identical for fat lobes, skinny lobes, or even wiped out lobes. As the VVT rotate the cam +/-, the cam waveform will shift early/late (or left/right) relative to the crank missing tooth position.

You could email your waveforms to EcuMasters, or post them if they have a support forum, and ask them if it they're supported. If so, ask what configuration you need to setup before running the wizard.
 
AnthonyHardy2 said:
From looking at the waveform it looks to me like the cam trigger wheel on your engine is one short tooth and one long tooth roughly 180° apart. You can look at the intake valves and pull the cam sensor so you can see the trigger wheel to figure out which cylinder is on its intake stroke with the long and short tooth. The missing tooth on the regular whiteblocks is 90° BTDC so that might also be the same on your engine

At least on the non SI6 VVT whiteblocks the cam trigger is nothing more than an oddly shaped trigger wheel with a hall effect sensor. The ECU looks at the time between a specific crank tooth and a cam tooth triggering to figure out how many degrees advanced the cam is and adjusts the VVT solenoid. You may have to take an engine apart to see the specific cam trigger pattern since Volvo might have changed it for the SI6 engine. This cam trigger wheel is from a ~2004 B6294T engine for example
View attachment 35349
Click to expand...

Yeah, I was just turning the crank by hand and watching the wheel as it turned. Not the easiest thing to do by the way.

I think that pulling the vacuum pump will help because I will have a better idea of where the cam is.

The vacuum pump is already leaking a ton of oil all over the place because the seal is bad on the old, core engine. (Actually, I swapped it from the turbo engine but anyway...). I guess I need to go buy some pigmat or set some carboard under this thing because the oil pump definitely works, lol.
 
bobxyz said:
"Would either of the pulses indicate the duration of the valve lift? If so, that would be the first window and not the second window on the waveform, correct?"
No, the pulses are just the rotational position of the camshaft and have nothing to do with lift or duration. The waveform will be identical for fat lobes, skinny lobes, or even wiped out lobes. As the VVT rotate the cam +/-, the cam waveform will shift early/late (or left/right) relative to the crank missing tooth position.
Click to expand...

I don't think that you understand what I am asking.

Does the "big gap" happen in relation to the 720* rotation when the lobes are in position to lift the valve.

The VVT aint doing shit right now because it isn't powered up. It gets a square wave signal from the ECM (again, not connected) that allows oil to return from the cam phasor. All of that is clearly laid out in VIDA. Since I am not modulating the VVT solenoid, ALL of the oil pressure is pushing the cam phasor. ALL of it. So, the cam timing is essentially static. If... BIG if, I was actually running the engine, I would have to a) power it all the way up b) modulate it c) "block it off" which would essentially be the same as a steady 5V power supply to it.

I am trying not to run the engine backwards or blow the intake off of the engine. Copy?
 
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In case you doubt that the oil pressure is essentially pushing the cam phasors to full tilt, I can assure you that they "rest" after spinning the engine on the starter. It took me a minute to realize where the solid "thunk" was coming from after letting off of the excitor wire. It was the cam phasors falling back into place when the oil pressure falls off shortly after the engine stops spinning.
 
According to VIDA, this particular engine does NOT have VVT for the exhaust.

That's in alignment with what I thought already but I brought proof.

Edit:// #31 is the phasor for the intake cam. The exhaust cam has only a sprocket. It is #32
b6304t.png
 
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