Zener diode method to cheat MAP sensor?

[HKS-GT2835R]

..anyone ever tried?

If you do a Google search for DIY FCD you'll see tons of schematics.
i found a simple diagram, quite clear, IMO.
3 Wires coming out of MAP

instead of using the HKS FCD, the zener diode 'bleed' the MAP signal to ground when it gets to a certain voltage so in short the ECU never 'sees' the voltage that will trigger boost cut. The diode is going to let the MAP sensor to send the ecu the actual signal until it reaches some level and then flat amount of voltage above that (the amount that ECU sees & triggers boost cut). I expect all map sensor to read on a 0-5V range, so boost cut happens when MAP generates signal equivalent to 5V? how does the FCD works anyway?

Having said that, using this type of circuit will take away a very important safeguard, which is the ECU's ability to close the throttle/reduce boost (boost cut) if you go overboard, but the zener mod is the same thing with installing a FCD what?

My question is, you're now 'fooling' MAP to let the engine to accept extra boost, but now *since the MAP is blinded* how do you add the appropriate amount of fuel to prevent detonation?

correct me.

 

[140dB]

yeah since ur ecu is 'blinded' at hi boost u can only tune for full throttle open loop using a piggy....remember hi boosting below WOT may cause the ecu to deliver less fuel than needed....so beware...

afaik, emanage, when using the 'boost cut' function is similar to this. but since the airflow map and extra injection maps can be referenced to an external map sensor (obviously 1 that can read more boost than the stock map) tuning is no problem at all

good luck

 

[Maxx]

the zener diode must have specified voltage "bleed" just below the boost cut level.
ie:if boostcut around 4.8v, around 4.7v diode must be used.
we need to know our map voltage boost cut 1st b4 installing the appropriate diode.