Looking for expert on Merc PCM555 ECU
 

Does anyone do programing of Merc PCM555 ECUs?

Does the Merc PCM555 have as part of its knock / detonation protection program a "learning mode" algorithm. The Merc brochure on the PCM555 says that it backs off the timing and increases the fuel delivery to any cylinder where detonation / knock is detected by the knock sensor. Specifically the ECU monitours each cylinder individually and applys this fix as needed on a cylinder by cylinder basis.

Some have also mentioned in this ECU a "learning mode" that once a knock event has been detected and a response made (of backing off the spark advance and increasing the fuel flow) these new fuel and spark adjustments are retained for a period of time after which the ECU will gradually creep back to the stock fuel and spark settings. This I guess is then loosely described as a learning mode or that the ECU learns for a while what fuel and spark settings will not produce a knock event under current conditions.

I am interested in as much detail about how this ECU works in this regard.

Thanks!

Re: Looking for expert on Merc PCM555 ECU
 

Good luck,from what Ive seen no one has yet to reprogram one or can even tell you alot about it,Smitty

Re: Looking for expert on Merc PCM555 ECU
 

I'm pretty sure Whipple has exclusive rights to reprogram the pcm 555.

Re: Looking for expert on Merc PCM555 ECU
 

There are two knock sensors. My understanding is it can retard one group of 4 cylinders instead of all eight. I'm not aware that anyone can reprogram the 555. What does Raylar say?

Re: Looking for expert on Merc PCM555 ECU
 

I believe you are right. I think Dustin even posted one time recently that this is correct as well.

Re: Looking for expert on Merc PCM555 ECU
 

The Merc ECM is a PCM555 and Mercury owns the company Mototronics who developed the ECM and the proprietary program. The ecm is a unit that uses a speed density type calculation based on the volumetric efficiency of the motor at 200 rpm increments and adjusts fuel delivery and spark timing accordingly. The knock sensor system consists of two block mounted pizeo electronic sensors. When knock is detected the program uses a preset decay rate to decrease timing and add fuel to the offending side of the engine in as Tom replied a bank response only. There is no individual cylinder monitoring or changes and there is also no learned state or remembering of of conditions other than to record events in history. The ecm will record knock events and can reduce power levels and set a trouble code if the knock intensity or frequency gets increased to a preset programmed danger level. The system is very similar in operation to the MEFI 4 systems except Mercury's system has an enhanced guardian protection mode, where power levels and rpms are limited to various programmed levels when condtions arise such as low oil pressure, low water pressure, high coolant temperature, excessive knock, and failures of various sensors on the motor, which inturn initiates a warning buzzer.
To date, Dustin at Whipple is the only company that has an agreement to input changed data to Mercury via Motortronics who can inturn modify the original program and send Dustin at Whipple a new program to download into the ECM.

Hope this answers some questions

Ray @ Raylar

Re: Looking for expert on Merc PCM555 ECU
 

Raylar, What is/does your electronic box on your 600 actually do?

Re: Looking for expert on Merc PCM555 ECU
 

try arizona speed ( my spelling sucks today)

Re: Looking for expert on Merc PCM555 ECU
 

Ray,

This clarifies a lot. Thanks once again.

In your opinion does an unmodified PCM555 prevent any serious detonation damage from ever occuring to the engine as a result of bad fuel, incorrect fuel-timing, A/F ratio, etc. setup for an engine modification?

Re: Looking for expert on Merc PCM555 ECU
 

Ummmm, NO...... Mototron is a subsidiary of Motorola. Motorola made the MPC555 processor not to be confused with the PCM555 which uses the MPC555 microcontroller, hence, its name. I don't know all the specifics of the PCM555 that Mercury is using but I would bet it could do individual spark retard and additional retard fueling. The Mefi4 can use 2 knock sensors and do individual cylinder retard as well, if set up correctly. The "guardian" modes can be set up in the Mefi also and have been for a long time. More enhancement is available in the Mefi4's than in previous Mefi versions. As with anything, newer versions usually have more "power" or control.

Other than that, Raylar is spot on in saying that both the Mefi4 and the PCM555 have about the same "power" in controls. The knock parameters are completely programmable to set trouble codes as well as engine safety.

More details in next post ;)