How MS Reads Temperature (Roger Enns)

[Bernard Fife]

Hi,

The link below is to another forum (EasyTherm) where Roger has posted some excellent information that people might want to read on how MegaSquirt converts the temperature sensor resistance into something meaningful.

You can find it here:

http://www.msefi.com/viewtopic.php?t=4734

Lance (with thanks to Roger!)

[Reynolds]

I just made some tests with a Wells SU303 coolant/air temp sensor and thought I would post them here for others to use. Might make this list into a seperate sticky.

SU303 Test Values -

76F = 10.41Kohm (76F according to HVAC)
32F = 32.5Kohm (boiler pot with ice and water)
212F = .697Kohm (boiler with boiling water )

Resistance values were observed once they became steady.

[vx131r]

He noted a very good point which so many people (including tradesman, ie people that should know better) seem to miss, Test the sensor Voltage not the Resistance.
Yes a resistance test will tell you if you have an open circuit, but the m.squirt and any other engine ECU looks at Voltage. Resistance, or varying the Resistance is just what the sensor does to alter the Volatge.
5v ref input to sensor, varied through ground.
For the Home EFI builder should be easier to understand than ohms, and k.ohms.
With a good multimeter and a temperature probe, you can make you own table of (V) versus temp (C), (sorry (F) in your part of the world)

[vx131r]

Just scanned this out of one of my Bosch tech Books. Doesnt really say much, and the quality is crap, will have to work a better solution for uploading docs, but may help some

I'm an EFI Specialist and agent for Bosch in NZ...oh and also a keen M.squirter . Let me know if anyone needs any other info on Bosch product. Sorry I cant supply any, but am happy to help with tech info.

[efahl]

Just scanned this out of one of my Bosch tech Books.

Do you have any tables of resistance versus temperature, as Reynolds has posted above. That would be very useful.

Eric

[vx131r]

Sorry thought I attached this, cant have worked properly. Is very hard to read no doubt. will table up some values when I get a chance.

[ami8break]

Hello Eric,
most reliable BOSCH temperature datas I've ever found in www:
http://www.bosch-motorsport.de/en/senso ... sor17.shtm
http://www.bosch-motorsport.de/de/senso ... TC_M12.pdf

»Horst

[UJM]

Hi,

The link below is to another forum (EasyTherm) where Roger has posted some excellent information that people might want to read on how MegaSquirt converts the temperature sensor resistance into something meaningful.

You can find it here:

http://www.msefi.com/viewtopic.php?t=4734

Lance (with thanks to Roger!)

Clicked the link and got this:
The requested topic does not exist.

I see it is from 2005, so the link should be updated or removed.

[24c]

Hello Eric,most reliable BOSCH temperature datas I've ever found in www:

It was 2005 when this was posted, and I use the Bosch Motorsport website quite a bit, so I thought it might be useful to others if I updated & corrected the link (English version).
http://www.bosch-motorsport.de/content/ ... l/2895.htm

This site is a goldmine of information, and when cross referenced with Google & eBay can lead to some good parts for EFI projects.

PS UJM The MicroSquirt website has moved around a bit over the years, so you'd expect to see broken links, especially if you resurrect a 2005 thread.

[UJM]

No resurrection intended, it appears to be a "sticky" or some sort, and I had a CLT sensor problem (reading sub zero in 70 degree (F) weather). This thread (and a few other older ones) was near the top of the forum when I viewed it, which leads me to believe it was "stuck" or "pinned" there on purpose (I moderate an automotive forum and we do so for topics of recurring relevance). I've solved my CLT issue by using v. 3.77 instead of 3.83. Thanks for the updated link.