What sig con is used for. (For Reference)

19th February 2003, 12:15

The standard map sensor is designed to give voltages between 1v and 4.5v for a range of 1 BAR (atmospheric Pressure) Anything above atmospheric is classed as boost. Going on this, if you apply boost to a standard MAP sensor, it is going to be stuck reading 5v. The ECU, having all sorts of self diagnostic code written into it will register this as an error and in the case of the old ECUs, will register a fault. In the case of the new 3 plug ones, it will Put the car into 'limp home mode' IE: Running on 3 cylds and probably destroying the cat, engine mounts or exhaust system if it happens regularly.

To get round this problem, GMC have introduced the Sig-con. This alows you to use a MAP sensor with a range of 2/3bar to feed a fueling device, and also amplify and clamp the signal at 4.5v to feed your ECU, as

The signal from a 2 bar sensor would be half the voltage, per MAP of the 1 bar sensor.

Also. At anything less than full throtle, the Lambda system would see any extra fuel in the exhaust and will Stop the standard injectors from fueling as much, to compensate.

The Sigcon gets around this problem by sending a full TPS voltage input to the ECU upon Boost. ECU sees this and dis-arms lambda fuelling, allowing you to add as much extra fuel as you want!.

To All contemplating Running without one

DONT DO IT. It's Not worth the headache!!</font></font>

Hope this answers your Sigcon queries

19th February 2003, 18:27

so basically you are saying that when the standard sensor see's boost ie over 4.5 volts the ecu says what the feck and puts a fault code and it stops the lamda working correctly ?

so if the standard sensor works between 1v & 4.5v's

how does the 2bar 1 work,does it start at ov then as soon as it reads boost it goes to 5v's is that correct ?

as i was thinking of wiring them both in and using a tenstiomiter in the signal wire from the 2bar wire so that i can set it to the correct voltage so it doesnt make the ecu log a fault then have a volt switch in the standard map wire worked of the 2bar wire so when the car hits boost it opens the switch cutting the standard volt and uses the pre set volt on he 2bar wire so that the ecu only see's the correct voltage when on boost,

i just dont want to pay all that money for a sigcon if i dont have to it will cost me pennys to try this and if it doesnt work then i will have to buy a sigcon but if it does i am laughing

thanks

19th February 2003, 23:08

Hi Mate.

No the 2 bar will rise progressively. 1-2.5v atmosphere, 2.5-5v pressure (Half the voltage of the 1 bar sensor per pound of vaccum/preassure) That's why if you use this input for your ECU, you need the sigcon to amplify the 2bar sensor to give the same reading at the same vaccum as the standard. The standard ECU doesnt know what boost is, so the sig-con 'Clamps' The voltage at 4.5v (Or what ever pressure your old sensor read at vaccum) You can find your vaccum voltage by connecting up a digital multimeter to ur std map sensor and turning the ignition on but with engine not running.

If your ECU defaults to Limp home mode, you will have to pay Citroen £40 a go for a fault decode and reset. May as well pay £250 for the sigcon and enjoy a better conversion.

19th February 2003, 23:11

Also, You need sig-con to disable Lambda fuelling at boost, or you will not be able to add extra fuel. You could disconnect the lambda sensors, but the ECU will bring on the fault light, your economy will go up the wall and the car will not pass an emmisions test.

20th February 2003, 04:42

so the ecu see's a 4.5v signal from the sigcon all the time no matter what the car does?

to switch off the lamda when on boost you need to send a full throttle signal to the ecu ?

sorry for all the questions

20th February 2003, 06:06

Hi m8, I like Questions, and I have another stonking great big reply.

The ECU Still sees a voltage between 0 and 4.5v dependant on vaccum pressure.

(All voltages are theoretical)

E.G: manifold Pressure= -2lbs, Voltage into fuel/comp&sigcon from 2 bar sensor=1.8v, voltage out of sigcon to ECU=3.6v, same as reading would have been with Std map sensor at this pressure.

Pressure= -1lbs, voltage into fuel/comp&sigcon=2.1v, Voltage out of sigcon=4.2v, same as reading would have been with Std map sensor at this pressure.

Pressure=0lbs, voltage into fuel/comp&sigcon=2.5v voltage out of sigcon=clamped to 4.5v, zero Vaccum reading of std sensor.

Pressure=+2lbs Voltage into fuel/comp&sigcon=3v, Voltage out of sigcon= still Clamped to4.5v, zero Vaccum reading of std sensor.

End result, ECU and still gets an accurate vaccum reading, but upon entering boost, it just thinks you have a full throttle condition(Zero vaccum or 0bar).

This goes hand in hand with the TPS reading fully open and you control the manifold pressure (and as a result, engine speed) manually by opening/closing the throttle to shut out/let in the boost.

This works fine as the engine will be supplying the correct amount of fuel for atmospheric pressures, and you callibrate the MF2's starting map threshold at 0bar so it can start supplying enough fuel for positive pressure at whatever rate it is supplied per RPM.

(You callibrate this in the MF2 based on RPM Site of the engine, E.G 4000RPM=0.5bar boost= injector duty of 55%open,

5000RPM=0.7bar boost=injector duty of 80%open).

All you need to remember is that the perfect styochromatic rate of air and fuel is 14:1. A visual aid to achieving this (Or close to this) throught the rev/boost range is an Air to fuel ratio meter, or if mapped on a rolling road, a gas/Co analyser.

Rolling road is best, as you can identify leaks, keep a lookout for Pinking, engine temps, exhaust temps, power and a whole lot of extras on some RRs.

I have a headache now, but I believe Axsaxoman (John from GMC) or SIMO best help you with any more questions, as I have not mapped my car yet, due to A small problem with my TPS voltage being corrupted slightly at vaccum and the car not running properly.

21st February 2003, 02:09

hi ,

can you tell me the exact price for the sigcon 2 as i may justt buy it

thanks

21st February 2003, 02:45

hehe. I got mine from GMC @ £250+VAT

PS Sorry about all the loooong replies.

21st February 2003, 06:14

Tricky...

Good thread mate.. i'm sure this will be useful for quite a few peeps..

Simo'

21st February 2003, 06:36

I gave it my ALL!<img src= "smileys/smoker.gif">

21st February 2003, 06:53

Good effort.. <img src= "smileys/smoker.gif">

24th February 2003, 16:55

got a question for what is the most voltage that the ecu is ment to see before it starts f**king up the ecu

thanks

24th February 2003, 18:42

Ello M8.

Anywhere between 4.5 and 5v is the danger zone <img src= "smileys/happy.gif">

26th February 2003, 21:45

Great threat. I could ruin it with some TCAD shite, but because it's such a good threat I won't. Ain't I sweet? <img src= "smileys/laugh.gif">

27th February 2003, 04:29

Frevo, You nutter<img src= "smileys/grin.gif">

23rd March 2003, 01:16

right i bit the bullet and got the sigcon its all wired in and the car will idle but having a problem when the car hits about 3k or try to give it full throttle it just dies!!!

can some one please tell me what to do to fix this

thanks

23rd March 2003, 01:22

Have you adjusted the resistors on the circuit board... as the sigcon is not shipped out pre-setup?

It sounds like your full throttle signal is not being sent to the ecu..?

Do you have an air/fuel ratio meter?? Does it go very lean as it dies??

Simo'

23rd March 2003, 03:15

hi simo,

dont no if it goes lean as havent fitted the gauge yet, its just i set pot2 and pot4 and took the car for a drive it drove ok but the revs stayed upon lift off just for a second and when going up the revs i felt like one hesitation, so i turned pot three just a little and it all went to feck now the car just dies.

i set the pots again but it still does it

please help

thanks

23rd March 2003, 04:26

You really need to set the pots accurately with a digital voltmeter... also using a pressure gauge.

I'm not at home right now, and cant remember which pot does what off the top of my head...

I'll have a look later on and see what i rememebr..

Simo'

23rd March 2003, 16:21

cheers i will keep[ checking for your reply as i really want this thing set up

thanks