18 Tooth Trigger Wheel w/ 4 Cyl

[seeking.christ]

Hello all,
I'm setting up a 4 cyl running wasted spark and semi-sequential injection. I was given an 18 tooth trigger (1 missing tooth) wheel to use with my VR sensor, but when I finish the basic setup, Tuner Studio tells me that there is a conflict between the number of teeth and the number of cylinders. Even if I change it to a 2 cylinder with 18 teeth, it throws the error.

Is there any work-around for this issue?

Thanks!

[Matt Cramer]

Can you post a copy of your MSQ?

[seeking.christ]

Hope this helps. Thanks!

[Matt Cramer]

The current firmware can use an 18-1 crank wheel, but not an 18-1 cam wheel.

Why are you running 3.1.0 code?

[seeking.christ]

3.1.0 is just what I had on there. Can later firmware use an 18t cam wheel?

[seeking.christ]

Suppose I could grind off half of the teeth... Will it run a 9 tooth cam wheel?

EDIT: The literature says that you have to have an even number of teeth for an even number of cylinders...

[jsmcortina]

Suppose I could grind off half of the teeth... Will it run a 9 tooth cam wheel?

EDIT: The literature says that you have to have an even number of teeth for an even number of cylinders...

18teeth at cam speed = 9 teeth at crank speed which is not enough teeth.
12, 24, 36 etc. would be ok, but not 18.

3.1.0 firmware is somewhat old. As this is a fresh install I would strongly suggest that you start with the current firmware - currently 3.2.5

James

[racingmini_mtl]

You need an integer number of teeth between the ignition events. Since 18 can't be divided by 4 you can't use that (it would work on a crank wheel because there are only 2 ignition events per crank rotation).

Jean

[seeking.christ]

Thanks for your replies. I have gone ahead and updated firmware anyhow.

I understand the logic behind "integer number of teeth between ignition events", but the fact is that the computer uses prediction to determine when the next tooth will pass the sensor anyway... Our ignition events don't occur at the beginning or end of a tooth, they occur a certain number of degrees advanced of one face of a tooth. So what difference does it make if my ignition event happens directly in the middle of two teeth, since I already know that the computer is capable of handling math LIKE that?

I can buy a different wheel and make it work if I have to, it just seems like there might be a way to use the prediction already programmed into the firmware to handle teeth fractionally when necessary. But, I guess I understand if there's not much demand for that kind of thing... Do you have any thoughts?

Thanks

[racingmini_mtl]

It simplifies computations to do it like this in part because the timing is expressed as an angle with respect to TDC of each cylinder and not with respect to the position of the missing tooth.

Jean