A few questions regarding I/O and sensors

[macromraco]

Hi,

I'm just trying to learn more about the Syvecs Unit I have in my car (S6PnP in a MY99 STi). I started mapping all the sensors and ECU wiring to understand the I/O and sensors configuration, and some questions came up while doing that:

I have a fuel pressure sensor to wire to the ECU. It is a 5v 3-wire sensor and I was wondering if it could be wired to connectors C12 (TPS +5V), C24 (TPS GND) and then the signal wire to any spare input without interfering in the TPS operation. Also, if it can be wired this way, how many 3-wire 5v sensors can be wired to this TPS 5V source? I mean, is there a current draw limit, right?

Regarding the outputs, just double checking if I understood it right. For instance, in the S6PnP Pinout, the INJ7 is listed as A/C Clutch or Rad fan 2. In SCal, I can see the "Output: Air Con Control connected" to FUEL 07 - which I assume is INJ7. So this output could be any of the two above, but in my case it is used to control A/C, right?

Still about the outputs, there is another one FUEL 5 connected to Water Injection, and listed as INJ5 IC Auto Wash - A10 - in the pinout guide. In this case my car doesn't have the IC Spray, so I'm probably wasting the FUEL 5 output correct? In case I wanted to run IC Spray, I just have to wire the IC water pump straight to A10 wire and then configure it under "Output Functions" -> "Water Injection" to have it working? Or should I use a relay in the A10 wire / FUEL 5 output to control the water pump?

Thanks for the help and sorry for any silly questions.

[stevieturbo]

Hi,

I'm just trying to learn more about the Syvecs Unit I have in my car (S6PnP in a MY99 STi). I started mapping all the sensors and ECU wiring to understand the I/O and sensors configuration, and some questions came up while doing that:

I have a fuel pressure sensor to wire to the ECU. It is a 5v 3-wire sensor and I was wondering if it could be wired to connectors C12 (TPS +5V), C24 (TPS GND) and then the signal wire to any spare input without interfering in the TPS operation. Also, if it can be wired this way, how many 3-wire 5v sensors can be wired to this TPS 5V source? I mean, is there a current draw limit, right?

Sensors draw minimal current, so you can easily connect multiple to the 5v output. It isnt dedicated for TPS or any other sensor. Likewise what you see as TPS ground is a generic sensor ground to be used for 3 wire sensors.

Regarding the outputs, just double checking if I understood it right. For instance, in the S6PnP Pinout, the INJ7 is listed as A/C Clutch or Rad fan 2. In SCal, I can see the "Output: Air Con Control connected" to FUEL 07 - which I assume is INJ7. So this output could be any of the two above, but in my case it is used to control A/C, right?

Correct

Still about the outputs, there is another one FUEL 5 connected to Water Injection, and listed as INJ5 IC Auto Wash - A10 - in the pinout guide. In this case my car doesn't have the IC Spray, so I'm probably wasting the FUEL 5 output correct? In case I wanted to run IC Spray, I just have to wire the IC water pump straight to A10 wire and then configure it under "Output Functions" -> "Water Injection" to have it working? Or should I use a relay in the A10 wire / FUEL 5 output to control the water pump?

Thanks for the help and sorry for any silly questions.

All INJ outputs provide a ground trigger to relevant actuators/devices. So in theory if the current draw is below the abilities of the output then yes you could wire direct.
Motors can draw more current on startup than once actually running. So if it's just off/on you need, a relay is always a safe and sensible option.

[macromraco]

Thank you for confirming my understanding and the explanations.

I'll wire the fuel sensor and also tap into signal wires from other gauge sensors I have over the weekend and update here with the results.

Thanks again.

[stevieturbo]

Thank you for confirming my understanding and the explanations.

I'll wire the fuel sensor and also tap into signal wires from other gauge sensors I have over the weekend and update here with the results.

Thanks again.

If those gauges have 3 wire/5v sensors then yes you can tap into the signal and use it's output for both ecu and gauge.

If they are two wire resistive only, you cannot tap into them as it will skew readings. You would need to run a dedicated sensor to the ecu or gauge as necessary.

[macromraco]

If those gauges have 3 wire/5v sensors then yes you can tap into the signal and use it's output for both ecu and gauge.

If they are two wire resistive only, you cannot tap into them as it will skew readings. You would need to run a dedicated sensor to the ecu or gauge as necessary.

Hi Steve,

Thanks again. I took a look at the sensors and most of them are 3 wire/5v. There is only one that is a 2 wire sensor, it is the oil temperature one.

In the 2 wire sensor case, if I decided to remove the gauge and connect it straight to the ECU as you recommended (no tap into wires in this case) what should be the correct way to wire and configure it on Syvecs?

Also, I already have the linearisation file for the fuel pressure sensor, but no information about the gauges' sensors. Is there a default linearisation configuration for Defi-style sensors?

Regards,

[stevieturbo]

Connecting it to ecu only would be fine.

Pretty sure you can use any "unipolar" input or "resistive" input.

1 wire to sensor ground, the other to the relevant input.

Cant help on the sensor scaling though. There are various sensors in the database, no idea if yours would be one of them.

[macromraco]

Hi,

Thanks again for the help. A few updates about the progress (and also a few more questions):

The fuel pressure sensor is installed and seems to be working fine. I can see the pressure readings when I turn the ignition on but I haven't start it so far, just finishing wiring everything before giving it a decent test with the engine on.

For the oil pressure, I only tapped into the oil pressure sensor signal wire and kept the gauge. First time I turned the ignition on the gauge reading got skewed - reading 2bar of pressure with the engine turned off. Then I assigned it to the AN07/AU3 input the sensor voltage immediately dropped to -0.9v as well as the gauge reading. I read in the link below that some offset or noise is expected but that it will only affect the gauge:

http://www.syvecs.co.uk/forum/viewtopic.php?f=6&t=340

Now I'm not sure if I did something wrong or if I can go ahead and start the engine that the sensor is going to get back to its default 0-5v reading. Any ideas?

For the oil temperature sensor: it is a 2-wire sensor, wired the white wire to the signal input and the red wire to the ECU sensor ground, assigned it to the AN15/AR3 input and when I program the ECU the calibration doesn't pass the test and I get the message below:



According to the Pin Names and info topic, the AR3 should be ok for temp readings, shouldn't it?

Am I missing something in the oil temp and press sensor cases?

[macromraco]

Just a little update: got the oil temperature sensor "kind of" working now, at least the ECU is getting voltage readings from it and there are no more error messages after programming the calibration.

But the voltage reading difference between it wired to the ECU and it wired to the Gauge is about 1,7v. For instance: fluid at some 55ºC was read as 3,75v by the gauge while it was read as some 2v by the ECU. Should this difference be fixed by the adjusting the linearisation or is there any other configuration to adjust it?

Regards,

[stevieturbo]

You CANNOT wire 2 wire sensors to two different devices and expect them to work as normal.

Use 1 sensor per device or buy 3 wire powered sensors.

[macromraco]

You CANNOT wire 2 wire sensors to two different devices and expect them to work as normal.

Sorry,I believe I didn't explain it very well.

If the temperature sensor is wired ONLY to the gauge, hot fluid - 55ºC - is read as 3,75v (according to a working voltmeter hooked to the sensor wires).

If the sensor is removed from the gauge, then wired ONLY to the ECU, heat se same fluid to the same 55ºC as before and put the sensor in it, the reading changes to 2v (according to eot1V), even the temperature being the same as it was when tested with the gauge.

The 2 wire sensor was not wired to two or more devices at the same time (as you instructed before - to choose only one of them gauge OR ECU ), and I get the different readings above.

Thanks,