Why are the stock value for B1978 different in E38 and E40

[wesam]

I noticed the values for the B1978 are different between E38 and E40 stock files while they have the same knock sensors
the value for all E38 ECMs are 120 Millivolts
while the values for E40 are 400 Millivolts
the description says that "Initial knock threshold voltage to define a real knock event"
so if we could guaranty that 400 is correct for E38 that mean we can advance the timming more

Any help will be appreciated

[wesam]

Any body have any idea ?

[joecar]

E40: runs an LS2 (which is physically quite similar to LS1/6)...

E38: runs an LS3 (which is physically different from LS1/6)...

[wesam]

joe
E38 also comes in LS2 for 2006-2007 C6

[Taz]

If you use a value of 400 mV for the knock threshold (B1978) with an E38 / E67 ECM and LS2/3 knock sensors, you will not have any knock protection whatsoever.

Recall basic electrical formula (Ohms Law, etc.) when considering this question. In this instance the simple V = I x R equation is helpful. The voltage of the closed system is a function of both amperage and resistance. Change the amperage, and you change the voltage. Change the resistance, and you change the voltage.

A number of years back I spent a lot of R&D on getting an LS1-B PCM to correctly operate LS2 style knock sensors. It became evident that the hardware inside an LS1-B, E40, and E38 was quite different - controller to controller.

My two cents is that the difference in B1978 values between the E40 and the E38 is a function of their own unique architecture.

[wesam]

Thanks Taz
So its not a sensor variation its a ECM variation
I found some tunes from Diablo and SCT puts the values for E38 210 mv
what do you think about this 75% difference than the stock value ?