yegoshin Posted February 2, 2007 Share Posted February 2, 2007 That would allow the gauge to read correctly at normal operating temperature, but it would mess up the scale, rendering it useless. The gauge wouldn't read all the way cold when the engine was cold, or all the way hot when overheating. Yes I am aware of that, you have 2 options there. The red part of your statement is actually partly incorrect I belive. 1) design an actual circuit that will make those 2 graph lines match 2) Live with it and know that your guage will actually be MORE sencetive on the HOT side and LESS on the cold site. EDIT: I have now applied the resistance formula and it seems that the graphs will line up practically perfectly see below Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 2, 2007 Share Posted February 2, 2007 I have my haltech set to keep the temp between 185 and 205 on my EJ20G. Quote Link to comment Share on other sites More sharing options...
yegoshin Posted February 2, 2007 Share Posted February 2, 2007 Ok here we go: To make the EJ temp sensor work almost in the EA guage you need to do the following: hook up a 275 Ohm resistor with one lead going to Ground and the other lead going to the wire from the Temp sender to the guage. This will do the following to your Temp Scale: (you can view there "excell" file here http://dima.brandtshaft.com/Subaru/SubaruTemp.htm) A little EE here for those that are interested: R_total=1 / ( (1/R_temp_sender) + (1/R_extra_resistor)) so when we plug in the 2 EJ temp sender values and the value of the extra resistor we get the values that the gauge would be reading. Looking at the graph those values make a line that almost perfectly matches the EA temp sender line. I belive this will work but haven't tried it yet. If someone does try let me know. This is the way I am going to go with my swap as its much EASIER then tapping the engine or welding something into the rad/hose. Quote Link to comment Share on other sites More sharing options...
rguyver Posted February 2, 2007 Share Posted February 2, 2007 Do you recall what tap you used?>?? cant remember what tap but its a regular metric tap i had in my kit it took me all of 1/2 h to put in the sensor in the water crossover under the intake , it was also a good time to change the coolent o rings and intake gaskets they needed to be they were leaking . try the risistor if you think thats easer . Quote Link to comment Share on other sites More sharing options...
Phizinza Posted February 2, 2007 Share Posted February 2, 2007 I will give this a go in a couple of weeks when I get my EJ in.. Thanks for doing all the math Quote Link to comment Share on other sites More sharing options...
baccaruda Posted February 2, 2007 Share Posted February 2, 2007 Yegoshin, thanks for doing the work on that. So installing the resistor as you described will ground the hotwire to the gauge (to whatever degree allowed by the resistor) and sap off the appropriate amount of voltage to compensate? (the resistor is not installed inline in the hotwire, right?) Quote Link to comment Share on other sites More sharing options...
yegoshin Posted February 2, 2007 Share Posted February 2, 2007 Yegoshin, thanks for doing the work on that. So installing the resistor as you described will ground the hotwire to the gauge (to whatever degree allowed by the resistor) and sap off the appropriate amount of voltage to compensate? (the resistor is not installed inline in the hotwire, right?) this is what you want to do: Quote Link to comment Share on other sites More sharing options...
baccaruda Posted February 2, 2007 Share Posted February 2, 2007 Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 2, 2007 Share Posted February 2, 2007 radioshack has 250 ohm resistors... would that suffice? Quote Link to comment Share on other sites More sharing options...
yegoshin Posted February 2, 2007 Share Posted February 2, 2007 radioshack has 250 ohm resistors... would that suffice? they *should*, I doubt that the temp sensor is drawing much current but just double check if you can. Put an ammeter between the gage and the sensor to check the current. Multiply the current by current by the resistor value and you should get the Power that resistor needs to dessipate. That value should be stated on the RadioShack resistors. Quote Link to comment Share on other sites More sharing options...
baccaruda Posted February 3, 2007 Share Posted February 3, 2007 Call Radar Electric; they have a shop in Bothell... radioshack has 250 ohm resistors... would that suffice? Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 3, 2007 Share Posted February 3, 2007 Call Radar Electric; they have a shop in Bothell... Been there, done that, I feel retarded just walking in there... Radioshack is much more my speed Quote Link to comment Share on other sites More sharing options...
baccaruda Posted February 3, 2007 Share Posted February 3, 2007 ah cmon, i'm electrostupid too and I go to the Spo' branch once in a while. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 3, 2007 Share Posted February 3, 2007 radioshack has 250 ohm resistors... would that suffice? I assume you are going to try it....let me know what you come up with. I'm dragging my feet on the final touches of the write-up to get some concrete info about this.... Quote Link to comment Share on other sites More sharing options...
baccaruda Posted February 27, 2007 Share Posted February 27, 2007 so would this resistor be suitable? Obviously 270 is close enough to 275 where stock gauges are concerned.. I don't know about the "1/2w 5%" mumbojumbo though... Quote Link to comment Share on other sites More sharing options...
Phizinza Posted February 28, 2007 Share Posted February 28, 2007 I don't know about the "1/2w 5%" mumbojumbo though... the 5% means a 5 percent accuracy. So basiclly plus or minus 5% on the 270ohm. The 1/2W I would assume means the risistor is good for upto half a watt of power through it, but I've never seen a risistor marked with a wattage rating before :-\ I think I might try this. EA81 and EA82 guages read the same right? Like a EA82 bung would work with the EA81 guage? Quote Link to comment Share on other sites More sharing options...
Huck369 Posted March 2, 2007 Share Posted March 2, 2007 I had this same issue with the temp gauge on FrankenWedge (My EG33 powered XT6:grin: )... The EG33's temp sensor is "Tiny" so no way to plumb in a ER/EA series one in the same location. I was going to plumb the ER one into the heater hose line, but instead added a Potentiometer in line with the gauge wire, one leg to ground and one leg to the sender and one leg to the gauge, then used a laser termometer to check the temp of the motor against the one in my SVX and "Dialed" it in so the gauge read middle of the gauge when it is at operating temp. SO if it getts hot it shows up, it's a little in-accurate when it's warming up, but once it gets warmed up seems to work fairly well. Total cost....about $3.00 Hope this helps someone else... Huck Creator of "FrankenWedge" Quote Link to comment Share on other sites More sharing options...
Phizinza Posted March 3, 2007 Share Posted March 3, 2007 Huck, that is a great idea. Although there could be a problem if it is bumped. But if it's in a good place it should work great. Quote Link to comment Share on other sites More sharing options...
Huck369 Posted March 3, 2007 Share Posted March 3, 2007 Huck, that is a great idea. Although there could be a problem if it is bumped. But if it's in a good place it should work great. It's definitly not in a very good place, and is only held in place by the wires attaced to it, but it's been in for about 9 months now and is still working fine....(knocking on wood right now:rolleyes: ) Quote Link to comment Share on other sites More sharing options...
ShawnW Posted March 3, 2007 Share Posted March 3, 2007 I am using the ea81T one on mine and my coworker Adam and I put his in the water crossover pipe. What we did was use an EJ22 turbo crossover which has additional spots for sensors....One side has them angled up and has the sensors and the other side has the places where the NA sensors would be normally. Leave the sensors in the turbo side and tap out the ones on the NA side for your EA sensor to thread into. Use liquid teflon tape to seal any imperfections. Both of our gauges read perfectly. Of course any lack of coolant in EITHER setup is going to make the gauge worthless. Be sure to pressure test your cooling system before driving it far. The EJ engines overheat RAPIDLY when theres any sort of leak. Quote Link to comment Share on other sites More sharing options...
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