radiator hysterisis when restarting hot engine

[spatz]

After I had this problem with the dead battery yesterday I noticed one problem with my ECU and maybe there is a similar
thing with other ultima owner using other setups.
When the engine is hot the DATFAST ECU will turn the rads on immediately after I apply power to it. This is not a very good
behaviour as I now have to start the engine with the radiators on (sucking 30 amps or so).
I do not want to install a mechanical switch as this has the disadvantage in case you forget it to end up with an overheated
engine.
I wrote DTAFAST an email to see if they can add this in their firmware. If there would be enough demand
I could actually make a board with stronger relays (the factory supplied ones are too weak in my opinion) that can actually
connect and disconnect the heavy inductive load of the fans reliable and have a hysterisis of a 1 min or so after power has
been applied by the main ignition. this would give you enough time to start the engine before the fans are kicking in.
I am manufacturing electronics and we could probably add a few boards to our prototypes that we are ordering on a regular
basis. This could keep costs down.
I could design this board to either work on a negative or positive control signal, so it could also be used with the radiator switch
in non ECU setups. The radiator switch would become merely a control switch and not swichting the heave fan load any longer.


Hi guys,

I am running your ECU in an Ultima with a LS7. After having
some problems with my battery and starting the car with help of
another battery I noticed that the radiator switching could do with a little
hysteresis after applying power to the ECU. Currently when the engine is hot
and I apply power the ECU immediately is turning on the radiator circuit.
If the ECU would wait 30s or 1 min before turning on the Rads that would give
enough time to start the engine without the load fo the fans which is 30 amps
in case of my ultima setup.
Is there a setting in the current software for this or do you think you can add
this in a future firmware update ?
I could probably make a small board myself for this (we are an electronic manufacturer)
but if you add it to your firmware that would be a more elegant way to do it.

Edited by spatz on Thursday 19th August 10:10

[Steve_D]

As the supply for the fans is already routed through a relay(s) you could add an additional relay which does not allow the fan relay(s) to be switched during cranking. This extra relay can be supplied via the auxiliary position on the ignition switch which goes dead when the switch is in the start position.

Steve

[spatz]

did not know about this additional contact in the ignition switch, very good idea though.
I am having a seperate starter button, that might have additional contacts that are opening when pressing, could route the fan relay signal from the ECU through that.
for a mechanic you are a very good electrician ! very smart and simple solution.

Edited by spatz on Thursday 19th August 14:41

[spatz]

ok the new battery is installed and it seems that the first one was no good from start. The new one cranks the engine like hell even with the radiators on. That is making confidence ! So if you use the yellow top battery and it is ok, no real need to disable the radiators while cranking, enought beef in this battery.