Last_Mohican

From what i understand the BTm can pretty much retard the timing enough once under boost but before boost the timing needs to be retarded a little and the btm can not handle it. IN most cases it seems like the BTM works fine but then i hear people saying they are not that great. Best thing to do is chip your ecu so that it will retard timing but it is too hard to get my ECU chipped.

Dr.Boost

Yes, the btm will only retard the timing 4 degrees, but that is 4 degrees PER POUND OF BOOST. Meaning if you were running 10 psi, the btm will retard your timing 40 degrees at full boost Yes you can retard the timing at the distributer. That is what I am doing and I have no problems. Retarding the timing is a precaution in the prevention of the dreaded detonation. If you retard the timing and always run the max octane gas (91,92,93) you should be fine.
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Keehnel1414

How do you retard the timing with the distrubutor?

Tom-Guy

Your timing at idle is the same, but the stretching effect of the AFC hack places your peak ignition advance (which is in the middle of your maps in a NA car) right at transition into boost. Your problem is your ignition CURVE, so the linear retard of a BTM can't really compensate. If you want to run 8-10 psi, you can get your final timing where it should be, but you pass through a lower boost area with very high ignition advance.

Keehnel1414

Your timing at idle is the same, but the stretching effect of the AFC hack places your peak ignition advance (which is in the middle of your maps in a NA car) right at transition into boost. Your problem is your ignition CURVE, so the linear retard of a BTM can't really compensate. If you want to run 8-10 psi, you can get your final timing where it should be, but you pass through a lower boost area with very high ignition advance.

I don't understand any of this. Can you explain this in lammens terms? Thanks for the help

fork

Lamens terms:
When the distributor fires the spark plug in relation to the position of the piston is the timing. Advanced timing can usually give a couple of horsepower, but timing that is too advanced can cause detonation or pinging, which is bad. This is what all the people in this thread have been trying to avoid. Detonation is when the piston is still traveling up but the gas mixture ignites trying to forces the piston down which doesn't happen. It creates hot spots on the piston and can eventually blow chunks out of the pistons, litterally. To retard the timing you can loosen the three bolts that hold the distributor on and turn it back. Hope that clears it up for some people.

I know most of the people here know all this but it's for the inquisitive minds of the new people who were asking.

Keehnel1414

i understand all of that and know how that works but what is ignition curve and peak timing and all of that other stuff.