DIY Thermostat Temp Mod & Coolant Fan Temp Mod
05-15-2003, 06:37 PM
#1
DIY Thermostat Temp Mod & Coolant Fan Temp Mod
I have been able to reduce my thermostat opening temp and cooling fan start temp by 10 deg F. Not sure if anyone is interested but if so let me know and I will post a how to for each.
After playing with my OBDII reader for a few weeks I have observed the start and stop temps of the fan (204 start-195 stop). This is not anything to lose sleep over (its normal) but I wanted to try and reduce the temp somewhat for racing because I believe lower et's can be achieved by reduced temps. We are not trying to reduce by great gobs here just a minimal amount (ie 10 deg F) to start and see how it goes.
These mods are completely separate of each other and require a totally different fix but I believe that you must have both to achieve the overall reduction in temp.
Pretty easy to do, just took me a while to figure it out and get the correct size of resistor and pill to get it to do exactly what I wanted. Plus watching my thermostat open and close with a thermometer in my open kettle through numerous cycles.
It would be quite easy to reduce more but I don't want to outsmart the computer and more is not always better. As of yet I still have not proven that 10 deg is better so the jury is still out. However I still feel much better with my engine running between 185-195 rather than 195-205.
If you are watching your dash gauge you can't even see this increment, actually through observation I have noticed it does not change from about 140 to 205 deg F so it is absolutely useless for anything but extreme moves.
Regardless if anyone is interested I will try and do a how to and post some pics of how to do this on a 4th Gen. I am sure it can be adapted to the other gens with the FSM.
Cheers
Jim
After playing with my OBDII reader for a few weeks I have observed the start and stop temps of the fan (204 start-195 stop). This is not anything to lose sleep over (its normal) but I wanted to try and reduce the temp somewhat for racing because I believe lower et's can be achieved by reduced temps. We are not trying to reduce by great gobs here just a minimal amount (ie 10 deg F) to start and see how it goes.
These mods are completely separate of each other and require a totally different fix but I believe that you must have both to achieve the overall reduction in temp.
Pretty easy to do, just took me a while to figure it out and get the correct size of resistor and pill to get it to do exactly what I wanted. Plus watching my thermostat open and close with a thermometer in my open kettle through numerous cycles.
It would be quite easy to reduce more but I don't want to outsmart the computer and more is not always better. As of yet I still have not proven that 10 deg is better so the jury is still out. However I still feel much better with my engine running between 185-195 rather than 195-205.
If you are watching your dash gauge you can't even see this increment, actually through observation I have noticed it does not change from about 140 to 205 deg F so it is absolutely useless for anything but extreme moves.
Regardless if anyone is interested I will try and do a how to and post some pics of how to do this on a 4th Gen. I am sure it can be adapted to the other gens with the FSM.
Cheers
Jim
05-15-2003, 06:48 PM
#3
Very interested! BTW: Did you ever hook up the WOT switch for the drop resistor? I had mine working but I disconnected the switch because I got tired of getting a CEL each time I floored it. =P I've been flooring it more and more with the VI. =P
ZuM
ZuM
05-15-2003, 06:54 PM
#4
Originally posted by ZuMBLe
Very interested! BTW: Did you ever hook up the WOT switch for the drop resistor? I had mine working but I disconnected the switch because I got tired of getting a CEL each time I floored it. =P I've been flooring it more and more with the VI. =P
ZuM
Very interested! BTW: Did you ever hook up the WOT switch for the drop resistor? I had mine working but I disconnected the switch because I got tired of getting a CEL each time I floored it. =P I've been flooring it more and more with the VI. =P
ZuM
Thanks for the idea.
Jim
05-15-2003, 08:44 PM
#6
Just wait till I figure out how to hook up a switch to the CEL. 
Anyways, more info on the thermo.
Anyways, more info on the thermo.
Originally posted by Jime
Hey Zum it works great. I got a relay for less than 5 bucks and mounted in on one of the drop resistor bolts. Tried it out today a couple of times and its fine.
Thanks for the idea.
Jim
Hey Zum it works great. I got a relay for less than 5 bucks and mounted in on one of the drop resistor bolts. Tried it out today a couple of times and its fine.
Thanks for the idea.
Jim
05-16-2003, 08:17 AM
#11
Senior Member
Join Date: Nov 2000
Posts: 387
Re: DIY Thermostat Temp Mod & Coolant Fan Temp Mod
I agree w/ your original post, lower isn't always better. Try to do some research and see if going any lower would inefficiant. Z's have a 160* thermostat and they actually sell a 145+/- thermostat but through research I have found that only track ****** need them. There's people w/ 400+ RWHP and still have a stock thermostat. I have a HOWE radiator which is 3" thick and that helps keep thinks cool as well. W/ 10* you're probably prolonging your engine life by a little. You may be able to go down to 180* and still be safe.
Good job on your find, play it safe and go down an extra 10*.
Good job on your find, play it safe and go down an extra 10*.
05-16-2003, 02:04 PM
#13
Thermostat Mod
Coolant Thermostat Mod
This is what the thermostat looks like removed. They are designed as a once piece unit which includes the outer casing which connects to the hose from the rad. To find it follow the rad hose. There are 3-10 mm head bolts connecting it to the engine block and it removes quite easily after draining the rad and removing the radiator hose. For an explanation of how they actually work read this. http://auto.howstuffworks.com/question248.htm
Two screws connect the actual thermostat to the housing. Try and keep the parts together so they don’t get mixed up. In the bottom of the housing you can see the thermostat shaft channel where the end of the shaft is inserted.
The theory behind the mod is that the wax which controls the opening and closing of the thermostat through it's expansion, shortens and lengthens the shaft inside this thermostat shaft channel. What we are going to do is make the shaft longer therefore opening the thermostat sooner. We accomplish this by inserting a small spacer in the bottom of this channel. The length of the spacer that I used was approximately 1/16” or .0625”. You just place the spacer in the channel and reinsert the shaft and screw the thermostat back together. My thermostat now opens 10 Deg F sooner.
After screwing it back together I then placed the whole assembly into my electric kettle with a thermometer and turned it on and watched to see what temp it opened and closed at. It moves a considerable amount so its very easy to monitor its progress. If yours doesn’t open and close at the temperature you want you simply remove the two screws and insert a longer or shorter spacer and repeat until you get the temperature opening you want. It may be best to try this before modification so you can log the opening and closing temps of the stock thermostat.
Note: Make sure when you assemble the thermostat that the jiggle valve is located in the top of the housing. You will understand what the jiggle valve is when you look at the thermostat seat. It just allows a trickle of fluid through at all times.
This is the size of spacer I used. It is a PC board standoff spacer that I cut off with a hacksaw. The other colored spacers I located later are pins from a door lock tumbler which I got from our local locksmith. This just gave me a bunch of different sizes to try which is easier than cutting your own.
Anyway that’s it, very simple just a small simple metal spacer in the bottom of this channel and the thermostat will open sooner, at what temp depends on how long the spacer is, adjust to your choice or just make one the same length as mine, make sure to test before reinstalling.
BTW Stock thermostat opening is 180 deg F so mine is now opening at 170 deg F.
Next installment is the Cooling Fan Temp Mod which I am working on.
This is what the thermostat looks like removed. They are designed as a once piece unit which includes the outer casing which connects to the hose from the rad. To find it follow the rad hose. There are 3-10 mm head bolts connecting it to the engine block and it removes quite easily after draining the rad and removing the radiator hose. For an explanation of how they actually work read this. http://auto.howstuffworks.com/question248.htm
Two screws connect the actual thermostat to the housing. Try and keep the parts together so they don’t get mixed up. In the bottom of the housing you can see the thermostat shaft channel where the end of the shaft is inserted.
The theory behind the mod is that the wax which controls the opening and closing of the thermostat through it's expansion, shortens and lengthens the shaft inside this thermostat shaft channel. What we are going to do is make the shaft longer therefore opening the thermostat sooner. We accomplish this by inserting a small spacer in the bottom of this channel. The length of the spacer that I used was approximately 1/16” or .0625”. You just place the spacer in the channel and reinsert the shaft and screw the thermostat back together. My thermostat now opens 10 Deg F sooner.
After screwing it back together I then placed the whole assembly into my electric kettle with a thermometer and turned it on and watched to see what temp it opened and closed at. It moves a considerable amount so its very easy to monitor its progress. If yours doesn’t open and close at the temperature you want you simply remove the two screws and insert a longer or shorter spacer and repeat until you get the temperature opening you want. It may be best to try this before modification so you can log the opening and closing temps of the stock thermostat.
Note: Make sure when you assemble the thermostat that the jiggle valve is located in the top of the housing. You will understand what the jiggle valve is when you look at the thermostat seat. It just allows a trickle of fluid through at all times.
This is the size of spacer I used. It is a PC board standoff spacer that I cut off with a hacksaw. The other colored spacers I located later are pins from a door lock tumbler which I got from our local locksmith. This just gave me a bunch of different sizes to try which is easier than cutting your own.
Anyway that’s it, very simple just a small simple metal spacer in the bottom of this channel and the thermostat will open sooner, at what temp depends on how long the spacer is, adjust to your choice or just make one the same length as mine, make sure to test before reinstalling.
BTW Stock thermostat opening is 180 deg F so mine is now opening at 170 deg F.
Next installment is the Cooling Fan Temp Mod which I am working on.
05-16-2003, 02:25 PM
#14
Originally posted by oldmanmax
Jime
What kind of OBII scanner do you have?
Jime
What kind of OBII scanner do you have?
I have this one, with the Palm and Windows software and all interfaces so it will work on all OBDII vehicles.
05-16-2003, 05:14 PM
#16
Coolant Fan Temperature Mod
Coolant Fan Temperature Mod
This one is real simple, all that is required is to solder a resistor across the two wires going to the “Engine Coolant Temperature Sensor (ECTS)”.
These are pins 59 (Yellow) and 43 (Black) on the ECM or you can do it right at the sensor located on the cooling line coming from the radiator, very close to the battery. The wires are the same color there too.
The sensor is comprised of a thermistor which is sensitive to changes in temperature and its resistance decreases as temperature rises. It modifies a voltage signal from the ECM and returns as the engine coolant temperature input.
Initially I used a 10 turn 5k trimpot to find out the resistance required. I hooked it up across the sensor and kept adjusting until it reduced the indicated temperature by exactly 10 deg F. Then I measured the resistance and found it to be very close to 1k, so I then just replaced the trimpot with a 1k ½ watt resistor. I also put in a switch so I could turn it on or off.
Because it modifies the signal coming back to the ECM your coolant temperature will read 10 deg higher than it actually is so instead of your fan coming on at 203 deg it will now come on at 193 deg. You can adjust this resistor up or down to increase or decrease the output, but because I changed my thermostat by 10 deg I desired this to be the same.
I installed mine right at the ECM, by the passengers left foot and put the switch right on the little cover plate.
The picture is actually the install of my S-AFC II but because I don’t have the original pic without the mods I will just indicate where it is on there. Ignore the other arrows.
Don't cut any wires just bare the indicated wires and solder the resistor and switch across them and tape or cover the connections so they won't short out.
This one is real simple, all that is required is to solder a resistor across the two wires going to the “Engine Coolant Temperature Sensor (ECTS)”.
These are pins 59 (Yellow) and 43 (Black) on the ECM or you can do it right at the sensor located on the cooling line coming from the radiator, very close to the battery. The wires are the same color there too.
The sensor is comprised of a thermistor which is sensitive to changes in temperature and its resistance decreases as temperature rises. It modifies a voltage signal from the ECM and returns as the engine coolant temperature input.
Initially I used a 10 turn 5k trimpot to find out the resistance required. I hooked it up across the sensor and kept adjusting until it reduced the indicated temperature by exactly 10 deg F. Then I measured the resistance and found it to be very close to 1k, so I then just replaced the trimpot with a 1k ½ watt resistor. I also put in a switch so I could turn it on or off.
Because it modifies the signal coming back to the ECM your coolant temperature will read 10 deg higher than it actually is so instead of your fan coming on at 203 deg it will now come on at 193 deg. You can adjust this resistor up or down to increase or decrease the output, but because I changed my thermostat by 10 deg I desired this to be the same.
I installed mine right at the ECM, by the passengers left foot and put the switch right on the little cover plate.
The picture is actually the install of my S-AFC II but because I don’t have the original pic without the mods I will just indicate where it is on there. Ignore the other arrows.
Don't cut any wires just bare the indicated wires and solder the resistor and switch across them and tape or cover the connections so they won't short out.
05-17-2003, 02:10 PM
#19
Originally posted by NightRider
There's only one problem with this. Lower temperature in coolant means your heater will not be as hot in the winter. This may be useful for me anyway as my heater is extra hot anyway.
There's only one problem with this. Lower temperature in coolant means your heater will not be as hot in the winter. This may be useful for me anyway as my heater is extra hot anyway.
I do keep an old thermostat as a spare and I change my coolant from 50-50 toyota red/distilled water in the winter to water wetter/10% toyota red and the rest distilled water in the summer, so its easy to change thermostats as long as the rad is drained.
05-17-2003, 03:55 PM
#20
Supporting Maxima.org Member
Join Date: Feb 2002
Location: Gainesville, FL
Posts: 562
so can u see the difference on your temp guage with these mods? i have a lower temp thermo in my VE (they make 2 for us) and i swear the needle sits just a tad below the middle...very cule stuff...innovators 
05-17-2003, 05:10 PM
#21
Originally posted by Maximajism94se
so can u see the difference on your temp guage with these mods? i have a lower temp thermo in my VE (they make 2 for us) and i swear the needle sits just a tad below the middle...very cule stuff...innovators
so can u see the difference on your temp guage with these mods? i have a lower temp thermo in my VE (they make 2 for us) and i swear the needle sits just a tad below the middle...very cule stuff...innovators
The stock gauges are made for dummies, not anyone who is interested in knowing what the exact temp really is.
05-18-2003, 10:53 AM
#23
Guest
Posts: n/a
Anyone considering doing these mods, please read the article below"
http://ca.autos.yahoo.com/maintain/coolant_answer8.html
Jime and you others here, I know you guys know the risks/impact of these mods so this article is not intended for you.
FWIW, cylinder wear is actually *worse* on a cooler running motor. Most engines like to run at the higher 195 deg temp. In my opinion, only modified cars that are prone to detonation (and I mean real detonation, not the normal occasional clacking we all get from time to time) could see some benefit from running a low temp thermostat and fan switch.
http://ca.autos.yahoo.com/maintain/coolant_answer8.html
Jime and you others here, I know you guys know the risks/impact of these mods so this article is not intended for you.
FWIW, cylinder wear is actually *worse* on a cooler running motor. Most engines like to run at the higher 195 deg temp. In my opinion, only modified cars that are prone to detonation (and I mean real detonation, not the normal occasional clacking we all get from time to time) could see some benefit from running a low temp thermostat and fan switch.
05-18-2003, 11:29 AM
#24
Keep in mind his original post
Originally posted by JimeThis is not anything to lose sleep over (its normal) but I wanted to try and reduce the temp somewhat for racing because I believe lower et's can be achieved by reduced temps. We are not trying to reduce by great gobs here just a minimal amount (ie 10 deg F) to start and see how it goes.
It would be quite easy to reduce more but I don't want to outsmart the computer and more is not always better
It would be quite easy to reduce more but I don't want to outsmart the computer and more is not always better
05-30-2003, 05:46 AM
#27
Originally posted by mingo
=D great job jime.. this info is real real real useful.
=D great job jime.. this info is real real real useful.
However I have found an easier way to do a manual fan switch that I did a bit of a write up on some time ago and is posted on the FAQ's.
There are 2 ground wires from the fans that run to the ECU, one is for low speed and one is for hi speed, although both have to be grounded for high speed. All that is required is a switch to ground these wires so no requirement to run any wires out of the cockpit at all. I will post a diagram and pinout for the 4th Gen later.
I turn the hi speed fan switch on at the end of the 1/4 and immediately the temp starts to come down and by the time I get my tmeslip it is cooled off. You can actually see the temp numbers drop quite rapidly on my OBDII gizmo. Because it is ground from the relay activation the wires can be fairly small gauge and ditto for the switch.
The engine does not have to be running for it to work but the ignition has to be on. Also I am monitoring underhood temps and running this fan does increase underhood temp because of the hot air being drawn through the rad and into the engine bay but the increase is only temporary until it cools down a bit.
05-30-2003, 08:16 PM
#28
Originally posted by Jime
Just a quick follow up. I used this setup at the track last sunday and worked ok.
However I have found an easier way to do a manual fan switch that I did a bit of a write up on some time ago and is posted on the FAQ's.
There are 2 ground wires from the fans that run to the ECU, one is for low speed and one is for hi speed, although both have to be grounded for high speed. All that is required is a switch to ground these wires so no requirement to run any wires out of the cockpit at all. I will post a diagram and pinout for the 4th Gen later.
I turn the hi speed fan switch on at the end of the 1/4 and immediately the temp starts to come down and by the time I get my tmeslip it is cooled off. You can actually see the temp numbers drop quite rapidly on my OBDII gizmo. Because it is ground from the relay activation the wires can be fairly small gauge and ditto for the switch.
The engine does not have to be running for it to work but the ignition has to be on. Also I am monitoring underhood temps and running this fan does increase underhood temp because of the hot air being drawn through the rad and into the engine bay but the increase is only temporary until it cools down a bit.
Just a quick follow up. I used this setup at the track last sunday and worked ok.
However I have found an easier way to do a manual fan switch that I did a bit of a write up on some time ago and is posted on the FAQ's.
There are 2 ground wires from the fans that run to the ECU, one is for low speed and one is for hi speed, although both have to be grounded for high speed. All that is required is a switch to ground these wires so no requirement to run any wires out of the cockpit at all. I will post a diagram and pinout for the 4th Gen later.
I turn the hi speed fan switch on at the end of the 1/4 and immediately the temp starts to come down and by the time I get my tmeslip it is cooled off. You can actually see the temp numbers drop quite rapidly on my OBDII gizmo. Because it is ground from the relay activation the wires can be fairly small gauge and ditto for the switch.
The engine does not have to be running for it to work but the ignition has to be on. Also I am monitoring underhood temps and running this fan does increase underhood temp because of the hot air being drawn through the rad and into the engine bay but the increase is only temporary until it cools down a bit.
05-30-2003, 09:51 PM
#29
Guest
Posts: n/a
Re: Re: DIY Thermostat Temp Mod &amp; Coolant Fan Temp Mod
Originally posted by PiotrC70
I agree w/ your original post, lower isn't always better. Try to do some research and see if going any lower would inefficiant. Z's have a 160* thermostat and they actually sell a 145+/- thermostat but through research I have found that only track ****** need them. There's people w/ 400+ RWHP and still have a stock thermostat. I have a HOWE radiator which is 3" thick and that helps keep thinks cool as well. W/ 10* you're probably prolonging your engine life by a little. You may be able to go down to 180* and still be safe.
Good job on your find, play it safe and go down an extra 10*.
I agree w/ your original post, lower isn't always better. Try to do some research and see if going any lower would inefficiant. Z's have a 160* thermostat and they actually sell a 145+/- thermostat but through research I have found that only track ****** need them. There's people w/ 400+ RWHP and still have a stock thermostat. I have a HOWE radiator which is 3" thick and that helps keep thinks cool as well. W/ 10* you're probably prolonging your engine life by a little. You may be able to go down to 180* and still be safe.
Good job on your find, play it safe and go down an extra 10*.
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