Ferrari 308 with ITB's, Link Extreme G4X

[The TIG]

I'm converting to ITB's on a Ferrari 308 and using one Link Extreme G4X and planning to run sequential injection and ignition.  I've set up a few standalone ECU's on my own on other engines in the past.  What I would like to do is run the factory Ferrari crank angle sensor with it's 144 teeth with zero missing and then run my own camshaft trigger set up with one tooth for synching purposes.

My understanding is that the number of crank teeth should divide evenly into 360 degrees but I have seen that there is an F40 trigger set up in the Link software.  I know there are many similaries between these engines, however I have been unable to find the details and was hoping somehow I can make that setting work. 

In one crank rotation the OEM system uses the 144 teeth (non missing) on the crank with one crank angle sensor, and 2 teeth on the camshaft and two separate cam angle sensors.  There are 2 separate ignition control units, distributors and ignition coils.

I also read in another post on this forum that "You generally want your gap to be in an area of least crank acceleration.  For a 1, 2 or 4 cylinder, 90deg before or after TDC is a good position.  For most engines 5 cylinders and up the crank acceleration is smooth enough that position is less critical (ignoring odd-balls like flat plane V8's)."  So I was also wondering what other advice I should have being that the 308 engine does have a flat plane crank.

I appreciate any guidance any of you can provide for my set up.  Thank you in advance.

[Adamw]

The F40 has just 4 teeth on the crank and 2 on the cam.  

144 on the flywheel is not going to work with a cam sensor.  The problem is there is only 2.5deg of space between each crank tooth.  So if you center the cam tooth exactly half way between two crank teeth then it would only take 1.25deg of cam movement either way due to drive backlash (cam belt/chain/tension/keyways etc), then the cam tooth would would suddenly occur 1 crank tooth earlier or later than expected so this would cause a trigger error.  

Usually engines with a high tooth count flywheel trigger would have an extra sensor with a single "TDC peg" somewhere on the flywheel to sync - but they are typically not capable of direct spark or sequential.     

You are probably best to fit a missing tooth trigger wheel at the front.

[The TIG]

Where would be the best place to put the missing tooth on a high revving flat plane crank V8?  What would be the ideal tooth count 36-1, 36-2 or something else?

[Adamw]

The missing tooth location is now really not that critical on most engines.  On very high compression, low inertia engines with small batteries like for example superbike engines where the crankshaft speed is very unstable during cranking it could be more important.  G4X has an advanced missing tooth algorithm where it not only looks for the gap based on the teeth spacing before the gap it but it also does a further validation after the gap by comparing with the teeth spacing following the gap.  So it is pretty fool proof and I havent yet seen it mis-detect a gap during cranking (was common in older ECU's).

Ideal location missing tooth location for a 180deg crank with a 90deg V, I would go for about 45deg ATDC.  Then it is outside the normal range of ignition timing on any cylinder and should be away from any TDC compression "slowdown" that happens at cranking speeds. 

As for trigger wheel, 36-1 or 36-2 is usually my go-to.  I havent seen any noticeable increase in timing stability or precision (by eye) above that tooth count and to go higher tooth count the wheel tooth design and sensor selection becomes much more critical.  

[The TIG]

I machined my own 36-1 trigger wheel for the crank and used a MAP sensor on intake runner 1 instead of a cam angle sensor.  I roughed in a base tune and it fired right up and idled okay.  Since I've been working at getting the ITB's synced up and obviously plenty more time will be spent on the laptop.