Temp sensor pull-up resistor

Ecu Hardware Modifications
Post Reply
BennVenn
Posts: 475
Joined: Fri Mar 04, 2016 10:35 am
cars: R33 GTST, '60 Vw Bug, Express (4G63T), GW X200
Location: Windellama, NSW
Contact:

Temp sensor pull-up resistor

Post by BennVenn »

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
User avatar
vlad01
Posts: 7780
Joined: Mon Oct 08, 2012 6:41 pm
cars: VP I S
VP I executive
VP II executive
VP II executive #2
VR II executive
Location: Kyneton, Vic

Re: Temp sensor pull-up resistor

Post by vlad01 »

150c is the max 12P will do.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
Charlescrown
Posts: 1831
Joined: Sat Aug 06, 2011 7:58 am
cars: V8 VR Commodore BT1
LB Lancer 2L turbo & Delco
Starion TBI with Delco
Mitsubishi Lancer EVO4 track car
NA MX5
3 vintage motor bikes
Location: Padstow NSW

Re: Temp sensor pull-up resistor

Post by Charlescrown »

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.
User avatar
vlad01
Posts: 7780
Joined: Mon Oct 08, 2012 6:41 pm
cars: VP I S
VP I executive
VP II executive
VP II executive #2
VR II executive
Location: Kyneton, Vic

Re: Temp sensor pull-up resistor

Post by vlad01 »

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.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
User avatar
VL400
Posts: 4991
Joined: Sun Mar 01, 2009 2:54 pm
cars: VL Calais and Toyota Landcruiser. Plus some toys :)
Location: Perth, WA
Contact:

Re: Temp sensor pull-up resistor

Post by VL400 »

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.
BennVenn
Posts: 475
Joined: Fri Mar 04, 2016 10:35 am
cars: R33 GTST, '60 Vw Bug, Express (4G63T), GW X200
Location: Windellama, NSW
Contact:

Re: Temp sensor pull-up resistor

Post by BennVenn »

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.
User avatar
antus
Site Admin
Posts: 8237
Joined: Sat Feb 28, 2009 8:34 pm
cars: TX Gemini 2L Twincam
TX Gemini SR20 18psi
Datsun 1200 Ute
Subaru Blitzen '06 EZ30 4th gen, 3.0R Spec B
Contact:

Re: Temp sensor pull-up resistor

Post by antus »

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.
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
Post Reply