rpm and thermo fan problem

[pane]

G'day

I built my ms11 way back in 2005.; It has been a great computer and love it. I have just fitted it to another car.

It is a v3 with 2.8xx something code. I have it running as ignition only in this application as the car is on straight lpg. I'm using the ford tfi dizzy in an aussie 4.1 crossflow in a falcon. Now it has been its whole life on a falcon and this type of engine and has never shown a problem untill now.

The first problem is the rpm. On the laptop from idle through the rev range it is showing about 150rpm behind what the car says and what a multimeter say. Both the multimeter and car give the same reading so i'm thinking that it is ms, but what can cause this??? I had a good look over all the settings and they are showing the right things according to the manual, so i'm a bit lost. What else should i be checking???

The next thing is the thermo fans and the aircon. When ever i turn the aircon on the thermos wont come on again causing the car to overheat.
Now i have this wired up this way. I have the output from ms switching 2 relays which then turn 2 fans on. I have them both running at the same time and speed and have a set temp that they come on at. Now where i think the problem is, i think its getting a back feed. The reason for this:
When i fitted the thermos and had the aircon hooked up again (ground up rebuild) the aircon bloke said i needed to have at least one fan running when the aircon was on. This is to stop the pressure building up to much in the system, it needs airflow through the condensor to stop it.
So to do this i put a wire from the low pressure switch in the system to the same wire that comes from ms to turn the thermos on.

So my question on this one, is there a way i can hook up the wire from the low pressure switch to ms so that when it see's 12volts the thermos are turned on regardless of engine temp???

Cheers

[trakkies]

Don't have a wiring diagram for your car, so this is just a general answer.

Does the low pressure switch give the same polarity output as the MS? IE, does it switch +12v or ground? If different from the MS fit a relay to the low pressure switch and use that to convert the output to the same as MS. The output from that relay (if needed) should then be connected to the MS feed to the fan relay via series diodes in both these feeds to prevent any 'back feed'. 1N4001 diodes will be fine and cost pennies. The black band on the diode points to ground, so if the MS grounds the fan relay, the black band should point to that.

[grippo]

As far as the rpm reading behind, I would trust a computer over an analog circuit to determine rpm. The timing in microsquirt can be read accurately to less than a microsecond, analog circuits in tachs have all kinds of phase delays and are just not accurate. I have a very "good" ($$$) Autometer tach and it is off by about the same.

It is possible to have a configuration problem that would make the rpm be really off, but this doesn't seem to be the case here.

[pane]

G'day

Thanks for the reply's

Sorted out the rpm readings. Turned out to be the % delay in megatune. It was set to %50, so i dropped it to zero and now reads the same as the tacho, mulitmeter and strobe light. So happy days.

Both the ms and pressure switch supply 12volt to the fan relays to switch them on. So i should be able to put a diode in the wire from the ms to stop the back feed???

Cheers