For anything you'd like to see added to Speeduino
By noisymime
#1164
Yeah, will always be 4 channel wasted with Speeduino anyway as there are only 4 ign outputs, but the addition of the cam signal makes decoding the crank signal a LOT easier.

With the cam pulse, you know easily where the start of the revolution occurs and can therefore just count out the 24 teeth on the crank wheel.

Without the cam pulse, you have to go through the process of tracking the long and short teeth to determine where you are.

It's no big deal, just thought I'd check as to how people tend to run them.
User avatar
By PSIG
#1169
Understood. Curious, though - how do you maintain accurate ignition timing without accurate tooth-to-tooth spacing information? I guess a different way to ask the question is - how you can accurately determine crank angle if you do not plot the long and short teeth anyway?
Image
David
By noisymime
#1171
If you look at the pattern for the 24X wheel:
24x.png
24x.png (105.43 KiB) Viewed 8645 times
If you know when the revolution starts, all you need to do is count the teeth and then look their angle up against a list of their degrees. Have an array with 24 entries in it, then just lookup each tooth.

Eg
Code: Select all
toothAngles[1] = 12
toothAngles[2] = 18
toothAngles[3] = 33
...
toothAngles[24] = 357
Once you've got the tooth angle, you then just add degrees to it based on how long ago that tooth was seen and the current RPM. Very, VERY simple and almost no processing required at all.

Without the cam pulse though, you don't have an obvious way of knowing which tooth is #1. You have to monitor the long and short pulses in order to figure out where you are in the revolution.
User avatar
By PSIG
#1172
Got it. I was hoping the gap detection of the missing-tooth wheels could perhaps be used to find #1 after the 5 wide gaps before it, or 5 wide teeth after it, or something similar. In the meantime, simple gets it for me, and the cam signal is assumed necessary at this point.
Image
David
By noisymime
#1174
I've written this decoder now and just testing. It does rely on the cam signal being present.

(No I haven't forgotten about 4G63 BTW, this just turned out to be fairly simple).
By noisymime
#1175
PSIG wrote:Got it. I was hoping the gap detection of the missing-tooth wheels could perhaps be used to find #1 after the 5 wide gaps before it, or 5 wide teeth after it, or something similar.
Yep, that is definitely possible, just takes more time and testing etc. Can look towards doing exactly that in the future if its needed.
By raven007
#1264
This would be helpful for me:

I have one that could be put on a test stand and two of these running around. Jeep 4.0 HO (non renix).


"Camshaft Position Sensor
The camshaft position sensor is located in distributor. This
Hall Effect type sensor works in conjunction with engine speed signal
of crankshaft position sensor providing PCM with inputs necessary to
establish and maintain proper fuel injector firing order.
When leading edge of pulse ring enters the sync signal
generator on the camshaft position sensor, the resulting change in the
magnetic field causes a 5-volt reference signal to be induced. On 4-
cylinder engines, this indicates to the PCM that piston No. 4 will be
the next piston at Top Dead Center (TDC). On 6-cylinder engine, it
indicates that piston No. 3 will be at TDC.
When trailing edge of pulse ring leaves the sync signal
generator on the camshaft position sensor, the resulting collapse of
the magnetic field causes reference signal to drop to zero volts. On
4-cylinder engines, this indicates that piston No. 1 will be the next
piston at TDC. On 6-cylinder engine, it indicates that piston No. 4
will be at TDC"
syncsignal.jpg
syncsignal.jpg (27.67 KiB) Viewed 8603 times
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