[darkpuppet]

funny_canuck,Apr 1 2004, 10:49 PM Wrote:What type of signal is being sent from the MAF to the PCM?

If it's digital then the reason for max 5V should be obvious, considering the PCM likely uses something like TTL logic. YES, with TTL inputs higher then 5V will work but they will not do anything more. TTL devices have a tolerance and differnet voltage ranges reperesent the inputs.

I've never metered the outputs form the MAF but if they are digital then increasing voltage beyond 5 V will be useless. Varying the frequency/ pulse width would be a differnet issue.

Increasing the voltage could also have the reverse effect when you look at what is happening at the receive end of the PCM. If the input voltage is higher then designed for the electronic components in the PCM could heat up. HEat in electronics = bad performance, more power loss and ineffciencies.

Just my $0.02 on a few other things to consider.

If someone is serious about doing this sort of modification they should be looking at more then whether or not something physically burns out o doesn't turn on at a higher voltage.

the 5V cutoff is a limitation of the PCM, and the digital/analog converter that feeds it.

The PCM tables only hold values up to about 4.76V (apparently), with 30 spots in the table, and the last spot being 15V, which is considered an infinite value (15V is definitely higher than the system voltage while the car is running).

that, and the digital/analog converter will only allow up to 5V before it clips the signal from the sounds of things, so there's another limitation.

The MAF itself is capable of 12V max.. it's an analog cicuit, that appears to incorporate a thermoresistor, wheatstone bridge, etc to make it run (all analog).

What this means is that it is theoretically possible to make a divider circuit to basically 'calibrate' te stock MAF so that anything over 5V is translated below 5V, and then you can get your custom tuned solution to plot the extra airflow in the MAF translation tables.

The trick is to create a MAF translator to cut the voltage, and to translate that 6th degree polynomial function of the MAF sensor to the increased airflows so you can enter the proper information into the MAF translation tables.

In short, the MAF probably won't burn out at higher airflows, it's just a matter to get the signal below 5V so your custom tune can pull values out of the translation tables.

or something like that :P