BS3...how important is the crank referancing??
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TECH Junkie
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From: East Brady, Pa
BS3...how important is the crank referancing?? How important is the crank referance part of the BS3 install. I have the heads off the car and have #1 at TDC. I don't understand what they want me to do after that. In the general BS3 manual it says LS1's should be at 350 and from what I've searched on here most are very close to that. I also see that you can set it in 1/4 degrees so that kinda worried me. Can I just put in 350 or should I try what they say and get it exact?
starting at 350 will let you start and run the car.
But all of your timing numbers will be based off this as being accurate relative to real TDC cylinder 1. Get it started, set the fixed timing test and hit it with a timing light to dial it in after it's together.
Accuracy of the crank sensor signal all depends on if the guy installing the crank target wheel was hung over or not
But all of your timing numbers will be based off this as being accurate relative to real TDC cylinder 1. Get it started, set the fixed timing test and hit it with a timing light to dial it in after it's together.
Accuracy of the crank sensor signal all depends on if the guy installing the crank target wheel was hung over or not
Its something you have to do, my last engine was 348.5, this one 348.25, I have seen one that was 365 and one that was 345. Thats a heck of a spread and like Harlan said all the timing is referenced off that number. Make sure to find and mark TDC accurately and have a solid pointer, if you dont you may as well just guess 
Speed Inc did mine, mine was on the higher side. If you just used say 350 but really need to be at 360, your timing values would be skewed, and someone could potentially burn up a their engine as a result.
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From: Norn Iron
Are the timing discrepancies down to the BS3, or the trigger wheel itself ??
Surely if there are such variations when fitting a BS3, and testing......then base timing with stock ecu's could be all over the place too ??
Surely if there are such variations when fitting a BS3, and testing......then base timing with stock ecu's could be all over the place too ??
Yes the stock ECUs can be off, mine was a few degrees off when I checked it with an indexed damper and a light. But I think the stock ECU uses a more complex way of coming up with the timing than the BS3.
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From: Norn Iron
Complex or not, if the relevent tooth or gap on the trigger wheel and No1 Piston at TDC are not in line with each other, unless the ecu is told the reference position, it can never be correct.
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Or maybe some people arent marking their balancers correctly for TDC or have funky timing lights when doing the BS3 thing. I have checked three stock ECU cars and they have all been fairly close, +/- 3 degrees or so, mine was 5 degrees off but was it me or the crank wheel? On the 346 my COP was 348.5 and the new engine with a stock crank (different crank) was 348.25, thats pretty darn close for two different cranks/blocks/sensors.
Its funny the Gen7 I used to use didnt have you check the timing, neither does the FAST I believe.
With the BS3 I really made sure TDC was marked perfect and I used two different lights. There is several teeth they use for spark reference and I think they also use the cam for reference as well. They also use the crank wheel for misfire detection so there is more going on there, of course if the whole wheel is off some it should be off but since I dont know the system they use to determine spark TDC all I can say is I dont know
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From: Norn Iron
Camshafts are usually only used to indicate when No1 is firing, for sequential fuel injection operation, and true coil on plug firing.
Its also common, that once the engine has started...and No1 TDC firing is referenced, it actually ignores the cam signal, until the engine is re-cranked.
it doesnt matter how fancy, or stupid the crank trigger pattern is. Unless there is a cam/phase reference, it can never know No1's actual firing position. With crank only, cyls 1+6 look the same.
I just just use a basic 36-1 crank trigger only on mine. So its group injection, and I fire the coils in pairs.
Its also common, that once the engine has started...and No1 TDC firing is referenced, it actually ignores the cam signal, until the engine is re-cranked.
it doesnt matter how fancy, or stupid the crank trigger pattern is. Unless there is a cam/phase reference, it can never know No1's actual firing position. With crank only, cyls 1+6 look the same.
I just just use a basic 36-1 crank trigger only on mine. So its group injection, and I fire the coils in pairs.
Camshafts are usually only used to indicate when No1 is firing, for sequential fuel injection operation, and true coil on plug firing.
Its also common, that once the engine has started...and No1 TDC firing is referenced, it actually ignores the cam signal, until the engine is re-cranked.
it doesnt matter how fancy, or stupid the crank trigger pattern is. Unless there is a cam/phase reference, it can never know No1's actual firing position. With crank only, cyls 1+6 look the same.
I just just use a basic 36-1 crank trigger only on mine. So its group injection, and I fire the coils in pairs.
Its also common, that once the engine has started...and No1 TDC firing is referenced, it actually ignores the cam signal, until the engine is re-cranked.
it doesnt matter how fancy, or stupid the crank trigger pattern is. Unless there is a cam/phase reference, it can never know No1's actual firing position. With crank only, cyls 1+6 look the same.
I just just use a basic 36-1 crank trigger only on mine. So its group injection, and I fire the coils in pairs.
Its not really 20 degrees off from crank to crank. The crank teeth are 15 degrees apart, but the timing event happens after number one or six go by on the cam. If your cam moves back 4 or 5 degrees, it could move your crank reference to the leading edge of the next tooth (15 degrees). Not sure if I explained that right, but you need to recheck if you change a cam. It will be right, or 15 degrees off.
Kurt
Kurt
Its not really 20 degrees off from crank to crank. The crank teeth are 15 degrees apart, but the timing event happens after number one or six go by on the cam. If your cam moves back 4 or 5 degrees, it could move your crank reference to the leading edge of the next tooth (15 degrees). Not sure if I explained that right, but you need to recheck if you change a cam. It will be right, or 15 degrees off.
Kurt
Kurt
So I assume the BS3 does things a little different than the stock ECM, since I would think 15 degrees would would really screw with the timing maps if you swapped in a cam (or timing chain on LS2) that was a little off.
Out of curiiousity since I never had one off, what indexes the stock wheel to the crank, can it only go on in one position?
Stock PCM decodes the tooth pattern on the wheel for position and only uses the cam pulse for bank identification. So it's a lot more forgiving on cam to crank variation, but it will still suffer from a poorly placed crank wheel.
BS3 also only uses the cam target for bank ID, but relies a little more on the relative position of the cam edge to the first tooth at TDC #1. And it doesn't care about the pattern of the teeth, just the initial edges.
