MoTeC Global Forum

Hey guys,

BMW E46 M3 chassis, E92 M3 S65 engine, M150 ecu.

Quick question about the battery backup pin (D12 on the M150). We've got a bunch of relays that need to be switched on with the key. Normally, this is handled by the factory ECU. It receives a key on signal, and then clicks on all the relays (injectors, ignition coils, main system for things like throttles, ICV, ECU itself, etc).

Does the battery backup pin allow for this sort of operation? Does it keep the M150 in a 'low power' state that can still do things like switch on relays? Or is it just for storing volatile memory?

I'd really like to be able to use the M150 to trigger the relays, as this will be a street car, so kill switches are less than ideal.

Thanks!

Also interested...just hadn't got that far yet!.

The M1 currently has no software support for battery backed non volatile memory. If you connect the pin to an uninterrupted power supply it won't do any harm and has the advantage that you won't need to change your loom if MoTeC release software support for this.

You can simply power on the M1 with the key to achieve what you need. The GPR has an "ECU Power Relay" output which is intended to hold power to the ECU and sounds similar to one of the relays in the BMW.

If you intend to use the "ECU Power Relay" output to power things other than the ECU make sure you use at least the July 2015 version of GPR as versions before this did not activate the relay while the engine was cranking.

Are all of those BMW relays switched from one ECU pin?

The way the BMWs work is that the ECU has two separate power supplies, one switched, and one constant battery. The constant battery supply is for a low power "off" state when the key is off. This exists so that when the ECU receives a "key on" signal, it has a power supply to click the main system relay on, which supplies it with its switched power for actual engine operation.

I did a little more research and asked around about the Motec. The battery backup pin is currently unused, as you said.

The ECU.Power Relay works fine for turning the ECU off, but there is no 'low power' state available with the M150 as best I can tell, which means I won't be able to configure it like a factory car. Not a huge deal, I was just trying to avoid having to add an additional relay for the sole purpose of turning on the main system relay.

TylerC wrote:The way the BMWs work is that the ECU has two separate power supplies, one switched, and one constant battery. The constant battery supply is for a low power "off" state when the key is off. This exists so that when the ECU receives a "key on" signal, it has a power supply to click the main system relay on, which supplies it with its switched power for actual engine operation.

I did a little more research and asked around about the Motec. The battery backup pin is currently unused, as you said.

The ECU.Power Relay works fine for turning the ECU off, but there is no 'low power' state available with the M150 as best I can tell, which means I won't be able to configure it like a factory car. Not a huge deal, I was just trying to avoid having to add an additional relay for the sole purpose of turning on the main system relay.

Motec PDMs have this "stay alive" low voltage function. Owner of the car is clearly a baller (S65 in and E46 M3), so maybe he wants to spring for the PDM. Could add a keypad and all sorts of fun stuff!

--Peter

Herrubermensch wrote:Motec PDMs have this "stay alive" low voltage function. Owner of the car is clearly a baller (S65 in and E46 M3), so maybe he wants to spring for the PDM. Could add a keypad and all sorts of fun stuff!

--Peter

Ahh, good to know. PDM is likely out of the budget, but there's also no real need for it, or a keypad in this car.

It's a street car, and we've hacked all of the OE chassis CAN and integrated it into the M150. We'll have full instrument cluster control, full control over the S65 CAN throttle motors, etc. All the factory buttons will still work as normal, with some additional features added in as well.

TylerC wrote:

Herrubermensch wrote:Motec PDMs have this "stay alive" low voltage function. Owner of the car is clearly a baller (S65 in and E46 M3), so maybe he wants to spring for the PDM. Could add a keypad and all sorts of fun stuff!

--Peter

Ahh, good to know. PDM is likely out of the budget, but there's also no real need for it, or a keypad in this car.

It's a street car, and we've hacked all of the OE chassis CAN and integrated it into the M150. We'll have full instrument cluster control, full control over the S65 CAN throttle motors, etc. All the factory buttons will still work as normal, with some additional features added in as well.

Very cool! CAN integration is a PITA, especially with the DBW motors. I know many folks who gave up and just rewired the S65 DBW motors to run off the half bridges rather than CAN. Great work!

--Peter

Herrubermensch wrote:Very cool! CAN integration is a PITA, especially with the DBW motors. I know many folks who gave up and just rewired the S65 DBW motors to run off the half bridges rather than CAN. Great work!

--Peter

Thanks! That's exactly what we didn't want to do, hah. We didn't want to deal with having to modify new DBW motors every time one of them went bad (which happens often). As far as we know, we're the only people to have hacked the throttle CAN.

TylerC wrote:

Herrubermensch wrote:Very cool! CAN integration is a PITA, especially with the DBW motors. I know many folks who gave up and just rewired the S65 DBW motors to run off the half bridges rather than CAN. Great work!

--Peter

Thanks! That's exactly what we didn't want to do, hah. We didn't want to deal with having to modify new DBW motors every time one of them went bad (which happens often). As far as we know, we're the only people to have hacked the throttle CAN.

There is at least one other group that I happen to know of!

--Peter

Herrubermensch wrote:There is at least one other group that I happen to know of!

--Peter

I'm curious who that is, if you're willing to share.