Crank Trigger Opinion?

[Guest |537|]

Hello Everyone,

How do you guys feel about a 4 tooth crank trigger running on the camshaft? I am hearing conflicting opinions about this setup, some say that 4 teeth is not sufficient while other are say i will be fine.

The people that are arguing that the 4 teeth setup is not good are saying that i will run into problems down the line and i could damage my motor. They say that the triggers are too spread apart and when the motor changes rpms the computer will not see the change until the next tooth and thereby this can lead to detonation

I have tried working through some of the math but it seems like there are too many variables to determine a definite answer.

Is this 4 tooth setup going to lead to engine damage?

PS- Thanks in Advance!

[rayhall]

If the engine is a four cylinder, then four teeth on the camshaft will be okay. At low engine rpm you will get a little ignition timing movement. This will not damage the engine.

There are many engines with distributors using just one tooth per cylinder and these are reliable and have no issues.

Using more teeth will help, but how much will be debatable on a camshaft based trigger, as there will be movement in the cam drive that could undo some of the gains with the extra teeth.

24 teeth on the crank is the best option if you want rock solid timing at all rpm. More teeth will not gain anything.

[Guest |537|]

Ray,

Thanks for quick response. yes the engine is a 4 cylinder.

if I had known about the 24 on the crank I woud have done it that way. I should have asked first.

I guess the good news is that I can work with the 4 trigger.

would there be any advantage advancing the 4 tooth trigger wheel before cyc 1 tdc? thereby having the trigger occure before actual cyc1 tdc. I could use the tigger offset to conpensate. Or just leave it as rising edge of the trigger on cyc 1 tdc?

thank you.

[rayhall]

would there be any advantage advancing the 4 tooth trigger wheel before cyc 1 tdc? thereby having the trigger occure before actual cyc1 tdc. I could use the tigger offset to conpensate. Or just leave it as rising edge of the trigger on cyc 1 tdc?

The best position for a tooth is before the ignition is fired, so around 50 deg BTDC.

Ray.

[Guest |537|]

Got it, i will advance the trigger wheel.

Should the Trigger Mode be set to Multi-Tooth or 1 tooth per TDC?

[rayhall]

Select multi tooth. To use 1 tooth per TDC the teeth need to be at TDC and you will have to move the trigger wheel to set the timing as there is no offset.

Ray.

[Guest |537|]

Ray,

Thanks for the help. Seems to be working good.

I am thinking of adding a knock sensor to the v-44 but it doesn't support a knock sensor does it? I am thinking of using it for tuning/detecting knock. The V-44 does not have the capabilities of decrease timing from an input of a knock sensor, correct?

So, could i install a knock sensor just for tuning and detecting knock at the dyno? Maybe have a output LED when knock is happening? What do you suggest?

[rayhall]

The V44 has knock control. It requires an external knock amplifier. These are available from Ramon.

This knock amplifier has a output for headphones, so you can listen for knock while tuning.

Ray.

[Guest |229|]

Hi.

Were do i find this Ramon?

Is he a user, a company? any link? Were to buy..

Thanks

[Guest |537|]

At low engine rpm you will get a little ignition timing movement. This will not damage the engine.

Ray,

This is exactly what i am experiencing now. At about 1500rpms if i set the reference timing to 20deg and look at the crank with a timing light set to 20deg the timing will jump ever few seconds then go back to 20deg. If rise the engine to about 2500rpms this goes away and the timing stays at 20deg. I am not doubting you but i am curious to why this is? I thought that if the engine is off time it would get worse at higher rpms. I also observed the live ignition status and it stand at 20deg so that would tell me that the reference lock is working. So where is the timing jump coming from? the triggers?

[rayhall]

An engine at low rpm does not turn at a constant rate. It slows down coming on the compression stroke and accelerates on the power stroke. The more cylinders you have and the heavier the flywheel the more this effect is reduced. Single cylinder engines with light flywheels are the worst.

If you only have one tooth per TDC on the crank trigger, then the timing will move due to this acceleration and deceleration. The reason for this is, the ECU predicts when the next tooth will occur based on the time between the last to teeth. I has to fire the ignition before it sees the actual position of the next tooth. Example:- you have 32 deg BTDC in the ignition table. If the engine speed has changed, then the ignition will be in the wrong place.

The more teeth you have the less the error (time difference) can be between teeth.

Ray.