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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,223
Quote:
Originally Posted by mark houghton View Post
Jim, as you know I'm stuck at 8 degrees max static advance because I've reached the stops in distributor adjustment room. Since I have the IC currently off, I may just pull the dizzy and grind out the adjustment slot to get an additional few degrees.
Your 12 degrees advance is a good target, and 5psi as a threshold is probably where I'll end up as well (currenly mine is set at 2 psi).

Something to think about: With 5 psi as the threshold and 2 degrees retard for each 1 psi beyond the threshold, the MSD 8762 will deliver it's maxium 15 degrees of retard at a little over .8 bar of boost...ending up with 3 degrees more retard than stock settings (your initial 12 degrees of static advance, minus the 15 degrees of MSD retard). Probably not even a noticeable performance impact on full boost - and maybe some added assurance against detonation.

For those of us that have applied this technology (and happily, I would add) I think we can all agree that most if not all of the extra advance should be shaved off by the time the engine reaches peak torque.
Hi Mark, I have the line on the retard knob inside the car straight up which is halfway between 1 and 2 degrees retard per pound of boost starting at 5psi. The slope knob is a potentiometer with 3 soft notches as you turn it and seems to be linear and not just 1, 2, or 3 degrees retard.

As I start to turn the slope knob counterclockwise towards 1 degree retard per psi of boost while under full boost acceleration I start to hear trace ping which is just occasional random tink like crackleing noises from the cylinder heads up around 5000 - 6000rpms. If I turn it more towards 1 the detonation will increase so the one time I tried that I quickly turned it back to 1.5
Next summer when it's 95 degrees out I may have to turn it more towards 2. We'll see when the heat comes back in a few months.

I know the instructions and MSD tech support which is likely just some kid reading the PDF instructions off a monitor says the 8762 BTM will retard 15 degrees total but I don't think it does if you set the threshold to 5psi and the slope to 1 psi retard per psi because if it did you wouldn't get any detonation according to what you're saying and if you turn the slope knob to less than 1.5 degrees retard per psi you definately hear detonation start. If you have a loud muffler you won't hear it and you have to have the windows up and sunroof closed to hear it, you have to know what it sounds like. I've tuned alot of cars, especially BMW's by ear over the years so I do know what it sounds like.
When I turn the slope knob clockwise beyond 1.5 towards 2 or 3 degrees retard per psi starting at the 5psi threshold... I can feel the motor loose power while accelerating at full boost.
Old 02-09-2010, 10:11 AM
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