Temp sensor pull-up resistor

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Temp sensor pull-up resistor

Postby BennVenn » Mon Apr 04, 2016 3:40 pm

I read somewhere the 808 switches 2 different pull up resistors to gain accuracy in both lower and higher temp regions.

Can I swap out one of these and remap the table to suit an aircooled motor? It would be nice to have CHT's on my bug even if it's only up to 255deg

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Re: Temp sensor pull-up resistor

Postby vlad01 » Mon Apr 04, 2016 9:23 pm

150c is the max 12P will do.
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Re: Temp sensor pull-up resistor

Postby Charlescrown » Tue Apr 05, 2016 5:09 pm

There are 2 tables at the bottom of 12P but it says cannot be altered with TP so I guess VL400 doesn't want people to change those settings.
I hope to hell the 255 is degrees F not C. Boy if it's C at that temp it's meltdown. I know air temp engines run hotter but by that much I don't think so.

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Re: Temp sensor pull-up resistor

Postby vlad01 » Tue Apr 05, 2016 7:30 pm

Charlescrown wrote:There are 2 tables at the bottom of 12P but it says cannot be altered with TP so I guess VL400 doesn't want people to change those settings.
I hope to hell the 255 is degrees F not C. Boy if it's C at that temp it's meltdown. I know air temp engines run hotter but by that much I don't think so.


Not something you'd ever want to see, but 300-400F is normal for vw type 1 engines.
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Re: Temp sensor pull-up resistor

Postby VL400 » Tue Apr 05, 2016 11:08 pm

The temp sensor lookup tables are in the bin area, I ran out of room in the 12P cal so they had to live elsewhere. They can be edited in TunerPro and then burn the bin with a program, or write via flashtool as 'bin write'. You will need to update the checksum of the bin though.

But as for extending them beyond 150 degrees using a different sensor and pullup, you would need to modify many table headings along with the coolant temp calc for all items using '(X * 0.75) - 40' as this only allows for a range -40degC to 151.25degC. Its not impossible but not trivial either.

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Re: Temp sensor pull-up resistor

Postby BennVenn » Wed Apr 06, 2016 8:29 am

Ahhhh -40, I was wondering why it topped out at 150. I was hoping for a low/high mode lookup table where I could swap out the High resistor to flatten out the non-linear region up top then fix up the values, even if it meant having to double the indicated temp reading. 110 indicated = 220deg etc...

Might fall into the too hard basket but this is something that would be handy on aircooled engines, both bikes and bugs.

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Re: Temp sensor pull-up resistor

Postby antus » Wed Apr 06, 2016 9:33 am

If you just want the temp in the data stream you could fit an additional sender with the range you need on one a spare analog input. I think theres 2, and one is used for wideband. The other I think is a different voltage range so used with a 0-5v sensor you'll get reduced resolution, or there may be some home hardware hack to adjust its range.
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