Technical > Wiring & Sensors

Air and Coolant temp sensor scaling

<< < (2/5) > >>

Sprocket:
Ok so i uploaded the 2063_256 sensor factor tables and everything read right at room temp, I had the CLT MAT, EGT1 and my calibrated digi thermometer read 22 :D

Upon imersing in a cup of boiling water and allowing the temps to settle out, the coolant temp sensor reads out low by 5 degrees at 75c. It would apear that my sensor is FUBAR'd. I have ordered some new ones, and shall repete this test.

Looks like im finally getting to the bottom of this ;D

Sprocket:
Problems problems :-\

I have new sensors, and they read pretty much the same as the ones i had. I have spent hours with boiling water watching the temperatures, i uploaded new sensor scales to read correct at above 60c, that caused the lower temps to slowly read out, eventualy by 5 degrees, I uploaded sensor scales to read correct at 40 and the sensors read out at both high and low temp, I uploaded scales to read correct at 20 and the high temps read out by 5c.

I think i need some new hex files specific to these sensors, Easytherm? whats required. I found this on the Wiki, so there is some truth in this. http://www.vems.hu/wiki/index.php?page=MembersPage%2FRichardBarrington%2FRangeRoverClassic%2FConfig

I think this is screwing up the speed density algorythms, may be why when the engine gets warmer it starts to run rough and the EGC starts to run away??

rob@vems.co.uk:
You can make and patch using EasyTherm, dnb has done a load of work on this subject, you can see his write-up here:
http://www.vems.hu/wiki/index.php?page=MembersPage%2FDavidBlades%2FSenTest
"I recorded the temperature reported by the ECU for a selection of known resistances with the original GM curves compiled into the firmware. This let me know what A to D bin each resistance fitted in, so I could then build correction tables using an excel workbook for my sensors and compiled these into the firmware."

So it might be worth giving him a nudge for the spreadsheets.

Rob

dnb:
EasyTherm can be made to produce good curves.  It can also produce some extremely silly ones...  The Steinhart-Hart algorithm it uses is not ideal for thermisters that are used over a wide operating range.

The trouble is that you can't tell the difference a good and bad curve by simply looking...

Coolant temperature isn't all that critical.  I'd be happy with 5 degrees error when cold and say 2 or 3 when hot.  Intake would be better if it were 2 to 3 degrees all the time, but a constant(ish) offset from reality won't hurt - you'll more than compensate for this in the VE table, lambda table & closed loop control.

What have you got the "fake airden low limit" parameter set to in the config?  This caused me no end of problems.

The spreadsheets Rob is refering to are indeed available, but I'd need to comment them so they make sense to someone seeing it "cold".  Not a problem, but it'll take me a couple of days to do. 

Sprocket:
Interesting,

still dont get the easyterm bit, lol.

The only factual information i can get hold of on the coolant sensor is that its a Lucas jobbie and 2000 ohm at 25c and 182 ohm at 100c, so if you transpose those points onto the 2252_256 curve it shows that it reads high at 25 and low at 100c, the curve is not as steep.

what i was getting at when commenting on the speed density algorythms, is, when the engine idles, the temperature rises, as does the under bonet temperature. As this happens, you can watch the ECG start to correct and the engine does start to run a little rough. I dont think just letting EGC sort everything out is the right way to go about it :-\  You can tune the VE table for normal running temp and warm up enrichments for cold running but if the engine temp rises the algorythm kicks out the wrong response and then EGC corrects its mistake, how will this affect acceleration enrichments where EGC is not switched on?

One thing that is odd, is that since fitting VEMS, the engine temp at idle seems to rise quite quickly and the electric fan kicks in, this is a thermostatic switch, not the fan control on Vems. when driving the coolant temp reads 78c yet there is an 88c stat fitted. Temp gauge is now controled via a standard temp sender where before it was controlled by the ECU, nothing tallies up hence why i am talking here.

Everything will be back on the car and new, including the thermostat, gauge temp sender was replaced about 8 weeks ago, as that deffo was reading out, the gauge never read above 1/4, lol.

I cant easily fit any other sensors as the holes are all the wrong sizes and there just isnt enough space to fit them anywhere else, and im not taking the head off just to drill a hole for a sensor ;D ;)

I'll have a look at this easythrm thing again tonight, other than that i'll have to use the 2252_256 hex files for now as i have been doing since the begining, even though its not right, i just dont have faith in it :-[

Just want to get to the bottom of it as its a bit daunting not knowing the true engine temperature.

Navigation

[0] Message Index

[#] Next page

[*] Previous page