Hi all,
Ive tried to calibrate the Inlet air sensor, and have confirmed the readings that i have taken with someone elses. They are all very similar,
however;
When i connect the sensor to the ECU, it reads 10 degrees C, and when breathed on, falls to below 0.
Anyone experienced this before? Ive reversed polarity on the off chance, and still no change as expected.
Temp sensors are just resistors, so nothing too clever there.
Have you got the resistance versus temperature datapoints?
I know that the Megasquirt default sensors are negative temperature coefficient.
"
MegaSquirt uses coolant and air temperature sensors to determine the warm-up characteristics of the engine and the density of the intake air. They are
essential to proper functioning of a MegaSquirt® controller. Both sensors are Negative Temperature Coefficient (NTC) thermistors. This means that they
are resistors whose resistance decreases as their temperature goes up."
If your sensor is PTC then that would cause the effect that you see. I don't know whether megasquirt can handle PTC sensors.
According to this site, EasyTherm isn't good with PTC sensors.
http://www.vems.hu/wiki/index.php?page=EasyTherm
Matt
quote:
Originally posted by matt_gsxr
Temp sensors are just resistors, so nothing too clever there.
Have you got the resistance versus temperature datapoints?
I know that the Megasquirt default sensors are negative temperature coefficient.
"
MegaSquirt uses coolant and air temperature sensors to determine the warm-up characteristics of the engine and the density of the intake air. They are essential to proper functioning of a MegaSquirt® controller. Both sensors are Negative Temperature Coefficient (NTC) thermistors. This means that they are resistors whose resistance decreases as their temperature goes up."
If your sensor is PTC then that would cause the effect that you see. I don't know whether megasquirt can handle PTC sensors.
According to this site, EasyTherm isn't good with PTC sensors.
http://www.vems.hu/wiki/index.php?page=EasyTherm
Matt
I thought I had nailed that one, but not this time!
So, I don't know.
The default resistor is 2490 Ohm. I don't know whether going as low as 110 Ohm will have some nasty effect.
As you can tell I am guessing.
Matt
quote:
Originally posted by matt_gsxr
I thought I had nailed that one, but not this time!
So, I don't know.
The default resistor is 2490 Ohm. I don't know whether going as low as 110 Ohm will have some nasty effect.
What does the bias resistor do amd what does this figure mean? Do i need to fit a resistor in line or does it act as an offset?
quote:
Originally posted by MakeEverything
What does the bias resistor do amd what does this figure mean? Do i need to fit a resistor in line or does it act as an offset?
Thanks, so i need to install a resistor physically then? I didnt see anything mentioned about this on Megamanual or Extra EFI??
Look at step 54 on this page
link to build manual
This is how it works.
The bias resistor is in the Megasquirt box, and is in series with the temperature sensor. The megasquirt applies voltage at the end of the bias
resistor and earths the return from the sensor. It detects the voltage across the bias resistor.
So you have:
5v
bias resistor
voltage sensing
temperature dependent resistor (sensor)
0v
As the resistance of the temperature sensor varies, the voltage detected by the MS ECU varies.
(the 0v and 5v may be swapped, I haven't looked at the actual circuit, as it is just a voltage divider, and in this context it doesn't
matter)
The default resistor is 2490 Ohm, and although my sensors are not well matched to the 2490 Ohm it still does a good job (absolute temperature
precision isn't even that critical).
Matt
[Edited on 26/9/10 by matt_gsxr]
Aaah i see. Thanks Matt. Still not sure how to overcome my problem, other than to try and enter the highest temperature first in the calibration table. If not, it looks like ill need another OEM sensor for my fault finding.
just go to the scrappie and get a few gm (e.g vauxhall saab) temp sensors and run the ms recommended setup. much easier than mucking about replacing the resistors.
quote:
Originally posted by ashg
just go to the scrappie and get a few gm (e.g vauxhall saab) temp sensors and run the ms recommended setup. much easier than mucking about replacing the resistors.
I don't really understand what you 110 Ohm bias resistor is doing? Do you have the stock 2490 Ohm one in the ECU? If not go back to the
original.
If using MS1 then use Easytherm to do the calibration.
If MS2 then do it using the sensor calibration options in TunerStudio.
If this doesn't help, the perhaps hit the MS forums, as someone will have seen your problem before.
Matt
quote:
Originally posted by matt_gsxr
I don't really understand what you 110 Ohm bias resistor is doing? Do you have the stock 2490 Ohm one in the ECU? If not go back to the original.
If using MS1 then use Easytherm to do the calibration.
If MS2 then do it using the sensor calibration options in TunerStudio.
If this doesn't help, the perhaps hit the MS forums, as someone will have seen your problem before.
Matt
So I am getting there now. You are running MS2. Excellent good choice.
You have the standard 2490 Ohm bias resistor.
You have a sensor that should work fine.
Where does the 110 Ohm value come from? Unless you have changed from the original bias resistor (which you haven't) then you should be typing
2490 in the bias resistor. Fiddling with this value isn't a good idea.
It might be worth checking the sensor wiring (especially the earth).
Matt
The 110 ohms is the bias that gets my sender on the gauge and able to see any changes. Anything else takes the sender reading off the scale.
I think it may be this that has just made my ECU smoke a bit!
Hi,
are you sharing the sensor with a gauge? The coolant sensor (like the air sensor) must only have a ground wire and the ECU connection, it cant be
shared with a gauge Im afraid. You must add another sensor for the gauge, if not you will damage your ECU,
Phil
[Edited on 8/10/10 by daxtojeiro]
quote:
Originally posted by daxtojeiro
Hi,
are you sharing the sensor with a gauge? The coolant sensor (like the air sensor) must only have a ground wire and the ECU connection, it cant be shared with a gauge Im afraid. You must add another sensor for the gauge, if not you will damage your ECU,
Phil
[Edited on 8/10/10 by daxtojeiro]