Adding coolant temp gauge?

[Darwood]

you are now wanting to calcualte what a 110 R1 will do with a 100 ohm diode replacemnt resistor? the R1 110 center point is well documented and should nto change, R1 110 and 100 replacemnt shoul just move the whole scale down proportionally from where you are now.

I wasn't thinking well yesterday. I ment to say the diode replacement. Thanks for the catch.

I am not familair with Martinez, CA, is it a very hot climate? are you sure you are happy with a 215-218 operating temp?

Martinez has been quite cool lately (and rainy!), it's the hills that have been getting my temperatures up. Idling my truck is usually around 195. On a long slight incline at 70-80mph the temperature likes to go to 208.

After looking at what E9999 and CDan have said in the past, 215-218 seems to be normal operating temperature spikes in high load conditions. If I stopped my motor every time I got to these temperatures I wouldn't get very far. Yes they are high and are cause for concern, but Toyota didn't seem to think they were that bad since the stock gauge doesn't even move when these temperatures are reached. Had I not done the gauge mod I would have never seen my gauge move at all during my towing trip and would have been happy as a clam.

My cooling system does need some attention but I know of some other guys who's stock gauges regularly move which means they are well in the 220+ range for normal operating temperatures. Once again I think this is cause for concern but it's won't ruin your day.

what does it do on more level ground agian? so far mine has not gone that high but all I have seen are upper 80's and lower 90's with the mod,

On level ground I get about 190-205 depending on speed. At 45-55 it runs at about 190.

Right now I'm thinking a redline of 230 or so might be nice. It's a little more conservative than Toyota, and it would retain the poop your pants moment that should be reserved when the gauge is in the red. When the gauge is near the red I want it to represent a temperature that will get the adrenaline flowing, yet won't require me to pull over immediately.

 

[semlin]

so raven, did you by any chance take photos of the 93 gauge?

with the 93 test gauge in my truck I am running a temp similar to these two. taking into account parralax it is probably closer to the lower one which i think you said is 198 on the 97 gauge. whatever it is it is noticably higher than the neutral line on my old gauge because the truck will initially warm up to a line that is already higher than my old centre line and then move up again to this one after about 10 minutes.

the other interesting thing is that the gauge is much slower to respond from cold. my heater now blows hot well before the gauge crosses the bottom line. with the old gauge it would not do so until it was most of the way to the centre line.

truck just had a flush, new oem t-stat all new hoses and a new fan clutch because of the h/g job. I am wondering whether I need to add a new rad to my list to try to address this running temp.

 

[Rookie2]

the other interesting thing is that the gauge is much slower to respond from cold. my heater now blows hot well before the gauge crosses the bottom line. with the old gauge it would not do so until it was most of the way to the centre line.

That's correct. The temperature at which the modified gauge begins to move is higher than what it was for the unmodified gauge , so it doesn't start moving until later than before. If you're taking out the dead spot and redefining the range, you've got to give up that range somewhere else (unless you want to drop a couple of bills on a Geddy). I can't remember what the starting temp changed to, but Raven has listed it here somewhere.


Rookie2

 

[Darwood]

semlin, if I recall correctly your guage is showing 205 ish and 200 ish from top to bottom from those pics. It is a little warm but not too bad in my opinion. You don't happen to have an OBDII scanner that you can attach to confirm the ECU temperatures do you?

What you are seeing is why I've been trying out different resistor values. For me that is too close to red for a relatively low temperature.

 

[RavenTai]

Semlin the upper one is about 200, the lower about 194, warm but not hot,

I have a full series of pics of the 93 guage both before and after mod, about 427MB I would be glad to send them to you just need to figure out what kind of client you want to use to make the transfer, you do have broadband correct?

Like R2 said the cold line has changed, on the 93 stock the cold line was about 130, after mod it is about 155

 

[RavenTai]

BTW I am afraid I can no longer work on this mod until I am relocated and have a garrage up and runing again, I do not know how long this will take but it could be a year. (hopefully less)

anybody want to cary the torch for now?

 

[semlin]

well i took it on the longest sustained hill climb i could tonight -- up from sea level to 3000 feet in a sustained steep run plus some highway hill climbing and it went up to the top photo. if that is only 200 maybe I am ok but i agree with darwood that it is disturbing!

pm sent on the photos. As for the torch. I think you have pretty much carried it all the way into the staidum and lit it already

 

[semlin]

Ok, some quick operating temp data points after a 2500 mile road trip from vancouver to moab and back with raven's factory temp gauge mod installed in my 93. crossed over 5 mountain passes both ways with the highest elevation at 7500 feet and some plenty steep extended grades so I think I have the truck’s highway cooling propensities somewhat sussed out. these observations could be specific to my 93 truck but they may be useful to others, especially for those with numb factory gauges as far as what seems to work in reducing running temperature. I got it to run steadily cooler going home than outbound even though I was traveling faster and in slightly hotter weather.

Engine operating temps ranged from the top of the needle touching the red on a long hill climb in Oregon (213ish on mine) down to a couple of needle widths below centre downhill at night or maybe 186. On average on the flats it ran steadily in the daytime about 200 eastbound in low 60s temps and 194 westbound in high 60’s temps. Both ways I was running 70-80 mph and consistently faster homeward bound, but using some avoidance techniques noted below. At no time was I actually worried about the temps it was running (none would move a factory gauge) but I was interested in learning how to control temp to address future runs in hotter weather.

Anyway, my #1 conclusion is for a 93-94 is to either gun it or baby it on steep extended hill climbs. 2200 rpm or less or 3000 or more. In between causes the temp to steadily rise and I assume that the engine is lugging. This is likely a quirk of the A442f, but I found that when I got into a long steep hill starting in the high 2500+ rpm range (75-80 mph) it is best to lose speed down to under 2200 rpm then matt it to get the kickdown and you will bounce to 3000-3200 rpm (if you kick it down at higher rpm you will go to over 4000 rpm). A couple of times I actually got the temp to drop while climbing by going from 2800 to 3200 rpm this way and I was able to do long climbs this way with much lower temp spikes.

#2 conclusion, even in 60-70 degree weather the truck will not cool itself fully at 70mph plus on a flat after a long hill climb. It will partially cool down but the “steady state” flat temp will rise a step of 2 or 3 degrees per hill and over several hills these rises are cumulative. That is how I got it up all the way to 213 in Oregon after a series of passes. Short downhills temporarily cool it but it either won’t fall all the way or bounces back up on the flats. Cooling is also less and noticeable slower if you have the a/c on. If you let temp go up on big hills as I did on the way out then only a long sustained downhill or dropping down to 60 mph ish with no a/c will cool the motor down to its normal steady”flat” state and even then it seems to have a “memory” of the higher temp for a while.

#3 – outside temp makes less difference than I thought. It ran slightly cooler at night but I actually ran it cooler on the way home when it was hotter.

#4 - a/c makes a small difference on flat highway driving but on long hill runs it will cause a steady rise that is delayed until you are well into the climb. Once it hits all of a sudden your temp is way up. I stopped using it on hills altogether because I did not like the “memory” problem once I got back on the flats. That was overkill for sure since I was not near the a/c shut off but I just did not like the memory issue. The moral for me is that in summer I will not use a/c on any hills if I have a bunch to cover.

#5 -- on the trails at moab it would run or idle all day long in the low 190s unless I put the a/c on in which case it would creep up to above 200. jury is still out on how big an issue that is in hot summer.

 

[cpg]

I had the same experience with a 96

 

[RavenTai]

Semlin or anyone else, the pictures and other data are up on an FTP server, anyone who wants them is welcoem to them, abotu 1.3GB total

FTP server IP address
**************

username
***************

Password
************

let me know if it does or does not work

I'll try leave it up for a few days

 

[Cube Dweller]

Another data point on operating temps- assuming my ISSPRO gauge is accurate, temps on my '97 were around 185-188 in Sacramento. About 90-95 today. This was varied driving, some at 65 on flat highway, idling at stoplights, driving around town, A/C on.

Truck has 82K miles, coolant is 50-50 green, new oem fan clutch, new oem tstat, no noticible sediment in radiator or cooling system.

 

[Darwood]

I'm going to post one of the equations I've been using since Rich requested it in another thread. I'd like to post all of what I have but I have 20 pages of calulations and I'm just to lazy to post it all at this time.

Pretty much everything is based of thevenin equivalents for a wheatstone bridge.

To figure out R2 with the following given:

voltage across L1 = VL1
a resistor value for D1 = RD1
a resistor value for R1 = RR1
thevenin equivalent for L2 and L3 = L2||L3 = RL2L3
input voltage = VI
thevenin equivalent voltage for L2 and L3 = input voltage * L3/L2+L3 = VL2L3
current = VL1/L1 = I
voltage across RL2L3 = RL2L3 * I = VRL2L3
voltage across RD1 = RD1 * I = VRD1
a resistor value for R1 = R1

I use:

R2=-R1*(VRL2L3 + VRD1 + VL1 - VL2L3)/(R1*I+VRL2L3 + VRD1 + VL1 - VL2L3 + VI)

And now some interesting values for R2 I calculated based off of Raven's pictures of tempurature and voltage across L1.

161 degrees R2 = 110.092 ohms
200 degrees R2 = 50.6317 ohms
208 degrees R2 = 44.0578 ohms
218 degrees R2 = 36.8199 ohms
224 degrees R2 = 33.0365 ohms
236 degrees R2 = 29.2056 ohms

I'll post the results I calculated playing with R1 = 150 and 180 with RD1 = 100 later

 

[semlin]

darwood what exactly does that all mean?

 

[Darwood]

darwood what exactly does that all mean?

Good question. Say I want to know what R2's value is for a given voltage across L1. I would use that equation. The reason I would do this is the voltage across L1 directly correlates to the position of the needle on the gauge. If I know where I want the needle to be (i.e. I know what I want the voltage across L1 to be), I can calculate what temperature the sender is sensing at that needle height given a certain resistor value for the diode replacement and R1 (the centering resistor).

I would use this equation to test out different resistor values for the diode replacement.

For reference as to what L1 and R1 mean here is Raven's diagram for reference.

 

[semlin]

um cool. so... how about just a resister to position for dummies chart?

 

[Darwood]

um cool. so... how about just a resister to position for dummies chart?

that's something I need to work on.

 

[MoGas]

Has anyone checked to see if the temperature is the same where the factory sender is versus where CDan and others have put the aftermarket sensor/sender?

 

[RavenTai]

someone, maybe Lxtreme? has both an aux gauge and the mod, IIRC he stated they follow each other.

makes sense that they would they read water temperature a few inches apart, the stock gauge reads right before the water leaves the head, AM gauge right after it leaves the head.

I could see there being a slight variation during warm up as the water outlet (where an AM gauge picks up at) does not have much flow until the thermostat opens, but as far as I know no one has reported such.

 

[cpg]

someone, maybe Lxtreme? has both an aux gauge and the mod, IIRC he stated they follow each other.

makes sense that they would they read water temperature a few inches apart, the stock gauge reads right before the water leaves the head, AM gauge right after it leaves the head.

I could see there being a slight variation during warm up as the water outlet (where an AM gauge picks up at) does not have much flow until the thermostat opens, but as far as I know no one has reported such.

I have a scan gauge and ravens mod on the stock gauge. They follow each other very well. The modded stock gauge works great.

 

[MoGas]

I have a scan gauge and ravens mod on the stock gauge. They follow each other very well. The modded stock gauge works great.

But they both read from the same point right?