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Old 08-07-2009, 08:28 AM
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Detuning a blower motor for the street refers to underdriving the blower ( ususally) to keep the max boost created under power to a reasonable modrate level. (5-7psi typical) also the spark timing is retarded a bit from the max power point by 4 to 8deg. This is all an effort to eliminate the risk of engine detonation at WOT while running on pump gas.

High octane gas (110-114) will allow more blower boost (1-1 pully ratio or overdriven pulley ratio) and more spark timing.

Running the blower pulleys "underdriven" does reduce low rpm boost responce and power below 3000.
The spark timing curve is very critial. A street blower set up wants a lot of inital timing (especially with a big cam and low mechanical compression ratio) but modest total timing under boost.
Increasing the inital timing will make the low end much more responsive.
How much depends on the cam duration. around 24 to 30 deg is good.
But you only want around 28-32deg total timing under boost on pump gas.
So, to increase the low rpm responce try locking out the mechanical spark advance and setting the now frozen timing at 28-30deg BTDC.
If this motor has a fairly big cam in it (as indicated by the poor low end responce, the increased timing at idle will make it idle much cleaner and improve the low rpm response.
Do not run excessive spark timing under boost while using pump gas.
Do not guess at the spark timing.
Get a advance type timing light and learn how to use it.
I recomend the type with the advance dial as opposed to the electronic digitial type (tend to be innacurate and unreliable).
see what the timing is now. Idle timing and max mechanical advance timing.
Does this car have a boost retard box installed? How much boost retard?
Leave the blower pulleys alone for now.
Does this car have a high stall torque converter or a "stock" torque converter?
What is the rear tire diameter?

Last edited by F-BIRD'88; 08-07-2009 at 08:38 AM.
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