Crank trigger for ATI rattler? for the injection illiterate

[fe66comet]

OK I have a ATI rattler 7" damper with a BB Chevy pulley pattern. I had the spacer machined 7/16 to return the pulley to the stock position. Now I need a crank trigger to run a FAST XFI box. How do I accomplish this as there is no kit for anything like that, or do I have to engineer one myself? ....Thanks guys Jon

[jayb]

I was able to adapt an MSD crank trigger for a 429-460 Ford to work with my ATI  damper.  If I recall correctly I had to egg-shape the bolt holes, and I made a sleeve on my lathe to keep the center hole of the crank trigger wheel concentric with the center nub on the harmonic balancer, but it was no big deal and any decent shop ought to be able to do that for you.  I mounted the trigger wheel between the harmonic balancer and pulley spacer.  I used the two bottom bolt holes for the timing cover on the left side to mount a bracket that the sensor assembly bolts onto.  It is a bunch of screwing around to make it work, but you can do it...

[fe66comet]

I was thinking of using this fast kit, what do you think?  http://www.fuelairspark.com/fas/efi-components/crank-triggers/big-block-chevy?mode=grid It would save machining the wheel I guess being the same pattern. So the wheel would go behind the damper? I hope I left room for that...
.Jon

[jayb]

I'm sure that one could be made to work too; it looks a lot like the MSD kit I used.

[fe66comet]

It is 1/8 thick so it saves a little space and has the correct bolt pattern was my thinking. So it will eliminate the one major step of adapting the wheel. The rest I think I can make brackets from steel to adapt. Next would be is how accurate does the sensor have to be placed? I am assuming that the sender is set to TDC so it would take place of the pointer.....Jon

[jayb]

Its actually not set to TDC, you want the sensor set about 60-70 degrees before top dead center.  The EFI system has to fire the spark, and so when your timing is advanced by, say, 40 degrees, the EFI system needs to fire it there.  So, it needs to have the crank sensor set up well before the point of maximum advance.  I think FAST recommends 60-70 degrees in most cases. 

So, for the sake of an example, let's say that you have the crank sensor at 70 degrees BTDC, and your idle timing is 16 degrees BTDC.  When the EFI box sees the pulse from the crank sensor, it will wait 54 more degrees and then fire the #1 plug, so that it fires at 16 degrees BTDC.

Also, after you have the engine up and running, you can adjust the crank trigger point in the software (at least on the FAST XFI box you can).  So, let's say that you have the crank sensor positioned at what you think is 70 degrees.  You put that 70 degrees into the software, then fire the engine, and after it warms up and is idling the timing map says your timing is 16 degrees BTDC.  But when you put the timing light on the engine, it says 20 degrees BTDC.  What that means is that your crank sensor is not actually at 70 degrees, it is at 74 degrees.  So, the EFI box is reading the crank sensor, and after it sees the pulse it waits 54 degrees and then fires number one.  Since the crank sensor is actually at 74 degrees, 54 degrees later is 20 degrees BTDC, so that is what your timing light is reading.

To correct this you would add four degrees to the crank sensor position in the software.  So, change the crank trigger point in the software from 70 degrees to 74 degrees.  Since the timing map in the EFI software wants to fire the #1 plug at 16 degrees BTDC, it will now wait 58 degrees after the crank trigger pulse to fire #1, not 54 degrees.  So, after making the software change you can put the timing light on the engine and you will see 16 degrees with the timing light.  Now, you have the EFI box synced up with what the engine is actually doing, and all your timing measurements shown in the EFI software will be correct.

[fe66comet]

I was thinking in terms of a stock ECM being not programmable. I see the trigger mount has slots for adjustment also, that should get me close I guess. Another concern I have is how will my MSD 6AL digital box and MSD billet mechanical advance distributor fit in the system? Do I need to disable the mechanical advance? Also the system advertises individual cylinder tuning,  is this accomplished with coil on plug ignition and how does it discriminate one cylinder from another? .....Jon

[jayb]

The MSD box and the distributor will work fine, but you will have to lock out the mechanical advance in the distributor so that the EFI box has control.  Alternatively, you can use the mechanical advance in the distributor, but just not put any change in timing into the spark map in the software.

To get individual cylinder tuning you need a cam sensor.  If the EFI box is going to be controlling your timing by referencing off the crank trigger, then you don't need the pickup in the MSD distributor.  Take the reluctor wheel in the distributor and saw off 7 of the 8 teeth.  The one remaining tooth will be your cam sensor.  You have to drop in the distributor so that the the tooth passes by the pickup between the firing points of #8 and #1, so that when the distributor sends a signal that the tooth just went by, the EFI box knows that the next cylinder to fire is #1.  Then you can do individual cylinder tuning and full sequential fuel injection, because you have the crank trigger and the cam trigger.

[fe66comet]

Wow this is kinda complicated to get right, that was what I an trying to accomplish though is a cam shaft angle and crank sensor like an LS. A lot to set up though and even more to screw up. I would guess these modifications are outlined in the instructions I hope. Yes for once I am going to read the directions first LOL. Thanks for the heads up Jay I am going to save the thread for further reference and more carb geek transformation lessons....Jon

[turbohunter]

Man I am loving this thread.
I am trying to soak in everything you guys are talking about.
I'm defiantly (I hate spell check)going to try this setup in the future just to learn.

[fe66comet]

Worked on the distributor last night all went well except I chipped the drive gear. Eighty bucks later the conversion is done. First the shaft had to be removed to rotate the plate, this locks out the advance.



Then I ground off all but one tab on the pickup rotor.



I completed assembling the distributor and test fitted......Jon

[jayb]

Looks good - Jay

[fe66comet]

Thanks Jay, wish I had not busted the gear but it happens ya know. I should have warmed it up a little but I never had one stick to the shaft like that. OH well I need to order some VHT three step engine paint from Summit anyhow so I can get the gear, crank trigger and water pump then. I need to get some undrilled adapters from you also......Jon