cjernigan

iTrader: (13)

Morning fellas, Aloha.
I'm using 1544 for my clt bias with R7 removed.

How do you know, do you have a '94 ECU to test? Did you even test your own?

paul

iTrader: (21)

so what is the stock ECU's resistor bias? anyone? i measured my stock 94 ecu at the clt and ground pins and got ~675. this is with the ecu on my kitchen table.

as far as sharing the GM IAT with the stock ecu, the stock ecu doesn't control fueling or timing so does it matter what values it sees? it was the easiest way to wire it and still be able to swap back to the maf when i take the MS out and swap in my PNP which they recommend you wired the GM IAT through the stock wiring.

So with the MS wired in parallel to the stock ecu what bias resistance does it see since its wired directly to the wiring harness also. both IAT and CLT leads in the factory wiring harness split off after the parallel harness connector. both stock ecu(via stock type ecu connectors) and the ms(via db37) are fed the IAT and CLT wires. the MS is not getting fed from the stock ecu. so why is the stock ecu bias taken into consideration at all?


i just want to know how this works. i would like someone who wants to stand behind their explanation and their numbers to confirm those 2 by testing both the CLT and IAT sensors in a controlled temperature environment such as ice water and hot water that you can measure with a thermometer at the same time. is that too hard to ask? has anyone actually done this other than me in my apparently flawed methods?

Saml01

iTrader: (9)

yea, and arkmages test proved nothing or I just really suck at math.

I measured the resistance of the sensor at the harness just like he says, and uh, it fluctuates as the engine cools down. The voltage at the harness is a stable 12 volts. How is that supposed to tell me the bias resistance?

paul

iTrader: (21)

yeah, you gotta do that when the temps are stable, ie not after you just shut down the car.

cjernigan

iTrader: (13)

You're supposed to do that with the car cold so it doesn't fluctuate.
You could also just probe back through the harness the other way and measure the actual resistor.
I measured mine the way arkmage's writeup said to, and my clt readings are accurate from what i can tell. The fans come on right around 207-210 and the clt and IAT read within a few degrees of each, with me using 2490 as my bias value for the iat sensor.

Braineack

iTrader: (62)

my junk is spot on. i did the water trick with my CLT sensor and it matched what everyone is doing. however i have a 93 so im to no help to you if there is a difference.

paul

iTrader: (21)

another question for you all.

you are adding in the bias resistance of the stock ecu in your figures. from that i infer that the bias resistance of the stock ecu affects how the MS reads the temperature. so isn't it fair to say that since they are in parallel and the bias resistors in the stock ecu affect the MS the bias resistor at R4 in the MS must affect the stock ecu's reading of air temperature?

if so, then someone with a 99+ and a OBDII scanner should be able to read the air temp through the scanner and watch it change as the MS is unplugged. No?

and is that why r7 is pulled? so the stock ecu reading of CLT isn't fucked up by the ms?

Braineack

iTrader: (62)

who cares what the stock ecu does. unless it throw a CEL. im sure it screw up its readings the same way it would screw up the MS's.

basically the bias throw the curve off....like advancing your exhaust cam might move your powerband higher up.

paul

iTrader: (21)

well i would care if the ecu turns on the cooling fans. that seems kinda important to me but what do i know.

so the question is does the ECU control the cooling fans in a 94?

or any year, you think that aussie guy would want to know.... since he actually has the r7 installed

Saml01

iTrader: (9)

Probing backwards make sense. I dont see how arkmages formula is supposed to work though. The voltage at the harness is always 12 volts, and the resistance of the sensor fluctuates with temperature. The result of the equation will always be different based on the temp of the atmosphere.

ECU trips the fans.

Saml01

iTrader: (9)

I would think so. We also pull it to have a more accurate resistance curve that the ECU can use based on the resistor because then the resistor on the board and the sensor are the same.

Braineack

iTrader: (62)

doesn't the thermoswitch still trigger the 94-95 fans?

Saml01

iTrader: (9)

Easy way to find out, call Jerry and find out if they incorporate the FET for fan triggering in their PNP units. In my mind I think the ECU will do it because when the AC turns on, both fans turn on with it.

paul

iTrader: (21)

i don't think so. i know there is the clt sensor on the back of the head in the heater core outlet. that feeds the ecu. then there is the one on the back but on the driver side of the head that feeds the gauge i thought. so i think the ecu switches the fans on and off.

paul

iTrader: (21)

again this doesn't affect most of us because we don't have R7, but that aussie guy does, what year is his car? member list is disabled by admin

grippgoat

iTrader: (1)

I'm not sure this is useful info without seeing a circuit diagram, but when resistors are in parallel, the resistance across the pair is not the sum of the two resistors. I think the equation is 1/Rtotal = 1/R1 + 1/R2 + .... I'll let you guys do the algebra. In any case, the combined resistance is lower than either individual resistor. You only add resistance when the resistors are in series.

-Mike

paul

iTrader: (21)

yeah, here's a dandy calculator for resistors in parallel http://www.1728.com/resistrs.htm

that much i remember from my car stereo days

paul

iTrader: (21)

so gripgoat, is your MSI parallel or stand alone? if parallel what easytherm values are you running? do they seem accurate?

grippgoat

iTrader: (1)

Mine's standalone. :/

-Mike

paul

iTrader: (21)

mine will be once the standalone harness is done. then it'll go into my gutted car that has no AC. then all this discussion is pointless.