fast XFI cam sync BTDC re-visited

[norbs]

Running into some confusion on things on cam sync BTDC. It is my opinion that the logged number is based on the time after the crank signal takes place and its reference to the cam precedes cylinder. I am going to experiment changing the cam sync precedes number to see if this effects my cam sync readings. This is the situation

I have installed the cam sync signal physically to sync at approx 80 BTDC based on the balance marks and measurements. XFI is showing cam sync to be 25 BTDC. This is impossible as it is not installed at that position. However, I am going to change the precedes number to #1 instead of #6 and report the new cam sync numbers.

 

[norbs]

I guess that theory is wrong, cam sync number stayed the same, regardless of cam precedes number, changed it to #1 made no difference on how the car runs either. Lets think of this logically, the xfi can only know the cam sync based on the time between it seeing the pulse before the crank signal. It then converts this time frame into a BTDC number.

 

[HighPSI]

Changing the cam sync preceds number will affect your individual cylinder corrections not your cam sync (BTDC) number. The cylinders are all EQUALLY 120* apart. When I first came out with my CNP set up, I found the cam sync value changed when swapping to the ignition even though the sensors were never moved just the ignition strategy changed. I notified FAST about this, but it doesn't seem to be a priority since it really doesn't matter. Rather than get wrapped up in the little things that don't matter, I moved on.

 

[norbs]

I understand, but based on my readings do I need to move my cam sync position in the distributor? 25 is OK? I know for a fact that I have installed it at 80 BTDC approx a few degrees.

 

[kidglok]

Try checking Buick dis since your using a stock type crank sensor?

 

[HighPSI]

Why do you have to move your cam sync? As long as it's at least 10 degrees away from your crank signal you are good to go. Once you get your other, more serious problems sorted out, put a timing light on it and pull timing out of #1 and verify it retards that cyllinder. If it does, you are all set. If it doesn't, adjust the cam sync precedes value

 

[HighPSI]

Try checking Buick dis since your using a stock type crank sensor?

The type of sensor you are using does NOT dictate what ignition strategy you are using. The location of the signal is what dictates it. If you are using the stock sensor in the stock location, then choose Buick DIS. If you have reclocked the sensor to 50* BTDC then choose IPU ignition strategy.

 

[norbs]

Try checking Buick dis since your using a stock type crank sensor?

I have put a msd crank inductive sensor on the car and it is set at 60 btdc, it will not hold any steady timing using the factory crank sensor, for some reason.

 

[norbs]

Why do you have to move your cam sync? As long as it's at least 10 degrees away from your crank signal you are good to go.

Its at least 20 degrees away...I really dont want to move it but that displayed value of 25 seems not right.