Car alarm and MS3 disable engine

[arran]

Hi,

Just an idea....I need to purchase a new car alarm and am wondering if I can use the "immobilise" function of the alarm to connect to a MS digital input (I have flex fuel IP available) and disable the engine from starting. It could be a more elegant solution to immobilising the car than chopping the stock wiring to insert a relay.

I have had a look around Tuner Studio and the Flex Fuel function seems a possibility. Would it remove all fuel if I specified the high/low frequency at 0Hz (so it is looking for DC) and the fuel add to 0%?

I also looked at the "Table Switching" menu, Table switch/dual fuel window. If I turn on "Fuel table switching" and select "PE2 Flex", hardware, I can select ve3, it becomes un-gray. I could set all values in the table to 0 which will stop the engine from starting.

Has anybody done this with a Megasquirt, any better ideas!!??

[Matt Cramer]

Here's another idea that would cause maximum annoyance: If not using launch control, set that as the launch input, with a 1000 RPM limiter and active above 2% TPS.

[nathaninwa]

I like Matt's annoyance feature, but another option is do enable alternate req fuel and set it to the lowest setting.

[arran]

Two splendid ideas!

Are there any concerns about needing to use "Signal Ground"? As the immobilisation signal from the alarm is an input, and assuming that the alarm will be grounding it's output pin to immobilise the car, does it need to be referenced to the ECU's signal ground?

[DaveEFI]

Two splendid ideas!

Are there any concerns about needing to use "Signal Ground"? As the immobilisation signal from the alarm is an input, and assuming that the alarm will be grounding it's output pin to immobilise the car, does it need to be referenced to the ECU's signal ground?

What I'd be concerned about is that unplugging the alarm would also remove the ground?

[arran]

Are there any special considerations for using the flex input to perform functions such as table switch or alt req fuel?

I have exposed the flex input wire and am grounding/not grounding the wire and am expecting to see that action switch tables. It does not seem to be doing that.

I have added a dash indicator to show VE1/2 or VE3/4 and it does not change when I ground the flex fuel input, nor does the car stop running (which is the desired outcome here)

Thanks in advance
Arran

[arran]

It is working!

The loom is back together, the alarm is connected to the MS3X flex fuel input (on PE2).

The scenario is this:
Car off, alarm armed, immobiliser active. I am sitting in the car. I turn on the ignition, the alarm activates.
I open TS and open "Basic settings", "realtime display" and then "All Output channels" I can see the value of PE2 (among the hundreds of other IO going on!) at 0, I disarm the alarm and PE2 changes the value from 0 to 1. All good so far.

In TS I have gone into "Table choices", "Table switch/dual fuel", "Fuel table switching" = on as shown:

https://www.dropbox.com/s/9qjqj4elgxi1w ... .09.04.png

I have zeroed out the VE3 table:
https://www.dropbox.com/s/uam74evqfddhq ... .10.14.png

If I start the car interestingly it will sort of just run if I pump the throttle, I have only just come in from the garage and the wife wants me to do some jobs around the house so I will have to investigate later, I would not think that the car would be drivable so I think it is job done!

I mentioned to the wife what it was I was doing (immobilising the car) and I guess not surprisingly she was disappointed. "You mean if someone breaks into your car to steel it, now they can't drive it away?"

Arran

[DaveEFI]

Although what you've done may well help security, I'd also have the immobiliser disable the starter and fuel pump.

[arran]

What about reversing the logic, zero out VE1 and run the main fuel map from VE3
I think I'd need to invert the immobiliser signal via a transistor in the proto area.

So what that would mean is that the alarm MUST be present for the car to go.

[DaveEFI]

Thing is an educated thief will know that many aftermarket alarms issue a simple on/off as an immobiliser signal, so what you actually do with that may not be very important. What can be worthwhile is making the alarm unit difficult to access. Ie, well hidden.

[jsmcortina]

Another useful trick, if you are concerned, is to park with the wheels turned to full lock. This can make it more difficult to prevent a tow-away theft.

I have photos of one such theft from a work car park. "The garage has collected your car." "What garage."

James

[arran]

Amusing James!

I've updated the ECU config though not yet had a chance to test....
Along with ve3 being all 0 I have made required fuel also = 0

[arran]

A quick update....after changing the "reg fuel" setting = 0 activate also by PE2 flex as shown below the car will absolutely not start:

https://www.dropbox.com/s/6sy0y3zpxe5s5 ... .42.18.png

I repeated the scenario tonight...sitting in the car I activated the alarm then tried to start the car. The alarm immediately activated when the ignition came on, the engine kicked for a sec until the fuel ran out and after that it just turned over with no hint of starting.

Arran

[DaveEFI]

So rather like just disabling the fuel pump?

[Hey_Allen]

With the added advantage that someone can't just jumper the fuel pump supply and bypass the fuel pump disable.

One of my concerns when I've seen various disable schemes is that so many of them are fairly obvious, and easy to bypass once spotted.
I'm thinking I may have to do this, or just a table switch disable on it. I like the idea!

[arran]

The reasons I like this method for disabling the engine are:
1) It is unusual, a theif will be highly unlikely to work it out in the couple of minutes available to steel the car and just like with other methods of disable the bypass would be to destroy the alarm
2) If for whatever reason the alarm misbehaves I can simply disable the table switch in software. Immobilisers do play up.
3) my ignition wiring is not chopped up unnecessarily, nor do I have to install a relay that I'd rather not have.
4) The wiring route connecting alarm to ecu is simple, if I was going to disable the coils or fuel pump on my car I would want to unwrap the neat wiring I have installed through the engine bay just for one wire, which is a massive pain.

[Matt Cramer]

One of my concerns when I've seen various disable schemes is that so many of them are fairly obvious, and easy to bypass once spotted.
I'm thinking I may have to do this, or just a table switch disable on it. I like the idea!

That was why I had suggested using the launch control to set an undrivable RPM. An even more fiendish option would be to AND the signal with the clutch switch in such a way that the rev limiter drops to 20 RPM when you release the clutch, making for an engine that will start but die as soon as you try to drive off. The idea is to make the engine behave in a way that's undrivable but doesn't even look like it's a theft deterent. Usually theft deterents either shut down the starter, or rig things so the engine will crank but not start. Get a more complicated drivability problem in there, and a thief is likely to think something is mechanically wrong instead.