Temperature guage Options

[Montreal914]

Hello everyone, after being on the 914 club for almost a year, I finally decided to join the 914 world. I don't know what the story is but there has to be something in common here, other than the main topic of course... (IMG:style_emoticons/default/idea.gif)

Now to the main subject. I was driving on the highway at about 70-75mph for about a half hour yesterday and this is what my temperature gauge was showing. The outside temperature was about 80-85 SoCal.
[img]
As a matter of fact, the guage takes the longest time to get up. So, I guess there is only two things that can be wrong, the guage or the sensor in the taco plate. Is there a simple way to verify them? Is there some measurement that I can do with a standard voltmeter?

Thank you

[VaccaRabite]

that is an oil temp gauge, not a head temp gauge. Therefore, it will take a longish time to get up, as you have to wait for 4 quarts of oil to warm up.

Oil temps and head temps can be (but are not always) unrelated.

Oil temps go up with engine revs. So, if you are doing a lot of driving in 5th at 70 you are only barely turning 3K rpm. This will keep your oil cool. Doing the same 1/2 hour run in 4th will raise your revs about 1000rpm and you will see your oil temps rise too.

As an example, before I put my secondary oil cooler in...
my way to work in the morning is 45 miles, mostly freeway, and almost all of it is downhill. The trip takes about 45 minutes, and at the end of it my oil temps may only barely be 190 degrees. The trip is in 5 gear, and even though the car is moving quick, the engine is spinning slow.

on my way home, the same 45 mile drive is still freeway, but almost all uphill. I have to keep the car in 4th to keep head temps down, and this revs the engine to about 4K+ for the entire drive home. Even with the oil cooler, my OTs are pushing near 220 - though my head temps are very happy around 365 - even after 30 minutes of constant climbing at 70+ mph.

I'd say you are probably fine.

Zach

[Montreal914]

that is an oil temp gauge, not a head temp gauge. Therefore, it will take a longish time to get up, as you have to wait for 4 quarts of oil to warm up.

Oil temps and head temps can be (but are not always) unrelated.

Oil temps go up with engine revs. So, if you are doing a lot of driving in 5th at 70 you are only barely turning 3K rpm. This will keep your oil cool. Doing the same 1/2 hour run in 4th will raise your revs about 1000rpm and you will see your oil temps rise too.

As an example, before I put my secondary oil cooler in...
my way to work in the morning is 45 miles, mostly freeway, and almost all of it is downhill. The trip takes about 45 minutes, and at the end of it my oil temps may only barely be 190 degrees. The trip is in 5 gear, and even though the car is moving quick, the engine is spinning slow.

on my way home, the same 45 mile drive is still freeway, but almost all uphill. I have to keep the car in 4th to keep head temps down, and this revs the engine to about 4K+ for the entire drive home. Even with the oil cooler, my OTs are pushing near 220 - though my head temps are very happy around 365 - even after 30 minutes of constant climbing at 70+ mph.

I'd say you are probably fine.

Zach

Thank you for this information, what kind of head temperature gauge do you have. 20 years ago, I had a vw beetle with a 1776cc dual dellortos and had installed the VDO one with the ring that goes under the spark plug. Do you feel this gauge is a must? Do 2.0 heads typically run hot?

[VaccaRabite]

I changed out all of the console gauges to 2 1/16" VDO gauges, instead of the larger stock types.

For my OT gauge, I bought a 2 1/16 inch VDO calibrated gauge AND sender. I like calibrated gauges, I don't like guessing.

For my head temps I did not buy VDO. The Dakota Digital head temp gauge with a spark plug type sender came very highly recommended from several different sources. It is the only gauge on my car that is not VDO and looks a little out of place, but it is also the easiest gauge to read in my car, and I know in a glance EXACTLY how hot my heads are, to the degree. I like it a LOT.

I have a VDO voltage gauge, but I do not trust it. Many many people have commented on how the wire path to the gauge is too attenuated to give an accurate view of your charging system. I only use it to be sure that the charging system is charging properly and that I am not one day making 18 volts out of the alternator and boiling my battery. Turning on the lights and the windshield wipers at the same time causes the gauge to read at 10 volts, which is silly.

I plan to add a wideband to my exhaust maybe over the winter and will need to run a wire for it, and find a place to put another gauge. Dunno where the gauge is going to go. maybe replace the clock?

Zach

that is an oil temp gauge, not a head temp gauge. Therefore, it will take a longish time to get up, as you have to wait for 4 quarts of oil to warm up.

Oil temps and head temps can be (but are not always) unrelated.

Oil temps go up with engine revs. So, if you are doing a lot of driving in 5th at 70 you are only barely turning 3K rpm. This will keep your oil cool. Doing the same 1/2 hour run in 4th will raise your revs about 1000rpm and you will see your oil temps rise too.

As an example, before I put my secondary oil cooler in...
my way to work in the morning is 45 miles, mostly freeway, and almost all of it is downhill. The trip takes about 45 minutes, and at the end of it my oil temps may only barely be 190 degrees. The trip is in 5 gear, and even though the car is moving quick, the engine is spinning slow.

on my way home, the same 45 mile drive is still freeway, but almost all uphill. I have to keep the car in 4th to keep head temps down, and this revs the engine to about 4K+ for the entire drive home. Even with the oil cooler, my OTs are pushing near 220 - though my head temps are very happy around 365 - even after 30 minutes of constant climbing at 70+ mph.

I'd say you are probably fine.

Zach

Thank you for this information, what kind of head temperature gauge do you have. 20 years ago, I had a vw beetle with a 1776cc dual dellortos and had installed the VDO one with the ring that goes under the spark plug. Do you feel this gauge is a must? Do 2.0 heads typically run hot?

[realred914]

[quote name='Vacca Rabite' date='Aug 13 2010, 06:41 AM' post='1355865']
I changed out all of the console gauges to 2 1/16" VDO gauges, instead of the larger stock types.

For my OT gauge, I bought a 2 1/16 inch VDO calibrated gauge AND sender. I like calibrated gauges, I don't like guessing.

For my head temps I did not buy VDO. The Dakota Digital head temp gauge with a spark plug type sender came very highly recommended from several different sources. It is the only gauge on my car that is not VDO and looks a little out of place, but it is also the easiest gauge to read in my car, and I know in a glance EXACTLY how hot my heads are, to the degree. I like it a LOT.

I have a VDO voltage gauge, but I do not trust it. Many many people have commented on how the wire path to the gauge is too attenuated to give an accurate view of your charging system. I only use it to be sure that the charging system is charging properly and that I am not one day making 18 volts out of the alternator and boiling my battery. Turning on the lights and the windshield wipers at the same time causes the gauge to read at 10 volts, which is silly.

I plan to add a wideband to my exhaust maybe over the winter and will need to run a wire for it, and find a place to put another gauge. Dunno where the gauge is going to go. maybe replace the clock?

Zach



just wonder how you buy a calibrated gage and sendor???? how can you trust the calibration if it is not wired all togther and working in your car????

to assure you got calibration, the gage should be installed with sendor, then tested aginst a known good standard, then it can be calibrated with your own marks on the gage. if you change the wiring (with assosiacted resistances) such when installing, you cant be sure the calibration done outside of the car is still correct.

i suggest for best results to calibrate once installed. then you can be assured it is right.

[jeffdon]

[quote name='realred914' date='Aug 13 2010, 09:24 AM' post='1355930']
[quote name='Vacca Rabite' date='Aug 13 2010, 06:41 AM' post='1355865']
I changed out all of the console gauges to 2 1/16" VDO gauges, instead of the larger stock types.

For my OT gauge, I bought a 2 1/16 inch VDO calibrated gauge AND sender. I like calibrated gauges, I don't like guessing.

For my head temps I did not buy VDO. The Dakota Digital head temp gauge with a spark plug type sender came very highly recommended from several different sources. It is the only gauge on my car that is not VDO and looks a little out of place, but it is also the easiest gauge to read in my car, and I know in a glance EXACTLY how hot my heads are, to the degree. I like it a LOT.

I have a VDO voltage gauge, but I do not trust it. Many many people have commented on how the wire path to the gauge is too attenuated to give an accurate view of your charging system. I only use it to be sure that the charging system is charging properly and that I am not one day making 18 volts out of the alternator and boiling my battery. Turning on the lights and the windshield wipers at the same time causes the gauge to read at 10 volts, which is silly.

I plan to add a wideband to my exhaust maybe over the winter and will need to run a wire for it, and find a place to put another gauge. Dunno where the gauge is going to go. maybe replace the clock?

Zach



just wonder how you buy a calibrated gage and sendor???? how can you trust the calibration if it is not wired all togther and working in your car????

to assure you got calibration, the gage should be installed with sendor, then tested aginst a known good standard, then it can be calibrated with your own marks on the gage. if you change the wiring (with assosiacted resistances) such when installing, you cant be sure the calibration done outside of the car is still correct.

i suggest for best results to calibrate once installed. then you can be assured it is right.
[/quote]

Actually, I think what you want is temperature compesating gauges. Check this link out. These are meant for aircraft, so I would assume the calibration standards are rigid.

http://www.aircraftspruce.com/menus/in/cht..._micro1000.html

[realred914]

[quote name='jeffdon' date='Aug 13 2010, 09:44 AM' post='1355936']
[quote name='realred914' date='Aug 13 2010, 09:24 AM' post='1355930']
[quote name='Vacca Rabite' date='Aug 13 2010, 06:41 AM' post='1355865']
I changed out all of the console gauges to 2 1/16" VDO gauges, instead of the larger stock types.

For my OT gauge, I bought a 2 1/16 inch VDO calibrated gauge AND sender. I like calibrated gauges, I don't like guessing.

For my head temps I did not buy VDO. The Dakota Digital head temp gauge with a spark plug type sender came very highly recommended from several different sources. It is the only gauge on my car that is not VDO and looks a little out of place, but it is also the easiest gauge to read in my car, and I know in a glance EXACTLY how hot my heads are, to the degree. I like it a LOT.

I have a VDO voltage gauge, but I do not trust it. Many many people have commented on how the wire path to the gauge is too attenuated to give an accurate view of your charging system. I only use it to be sure that the charging system is charging properly and that I am not one day making 18 volts out of the alternator and boiling my battery. Turning on the lights and the windshield wipers at the same time causes the gauge to read at 10 volts, which is silly.

I plan to add a wideband to my exhaust maybe over the winter and will need to run a wire for it, and find a place to put another gauge. Dunno where the gauge is going to go. maybe replace the clock?

Zach



just wonder how you buy a calibrated gage and sendor???? how can you trust the calibration if it is not wired all togther and working in your car????

to assure you got calibration, the gage should be installed with sendor, then tested aginst a known good standard, then it can be calibrated with your own marks on the gage. if you change the wiring (with assosiacted resistances) such when installing, you cant be sure the calibration done outside of the car is still correct.

i suggest for best results to calibrate once installed. then you can be assured it is right.
[/quote]

Actually, I think what you want is temperature compesating gauges. Check this link out. These are meant for aircraft, so I would assume the calibration standards are rigid.

http://www.aircraftspruce.com/menus/in/cht..._micro1000.html
[/quote]


a compensting gage is usually done with thermocouple (TC) gages, as they read the difference in temps (millivolt signal) between the thermocouple junction and the gage itself. so on a hot day your gage may be at 90F and on a cold day the cockpit gage might be 40F tyhat would result in a 50F difference in the same junction temperature. hence the need for compensation for thermocouple based systems. (ie head temps and exhuast temps are often Thermocouple based.) my head temp gage reads cooler on a hot day than a cold day! all becuase of the differances in the cockpit (gage) ambient temp! I dont have this temp comnpensated.

the resistance type gage (used for oil temp) does not require temp compensation as the TC gage does. in this system you not measuring millivolt signals generated by the TC junction, instead your reading the resistance at the sendor this will not change much with amibeint temp chnages at teh gage, hence temp compensation is not generally needed for a resistance gage.

the compensating TC type of system uses a resistance type temp sensor inside the gage (in the cockpit) to get the cockpit temp, then uses that value to compensate the TC reading from the sendor.

remember a TC systemn actually generates a voltage (two disimular metal wires when tied togterh tat one end, will genertate a small voltage if there is a temperature differeance between teh junction end and the measurement end. that voltage is dependant on the temp differance from the junction end (sendor) and the meter (gage) hence compensation is needed for the most accurate readings with a thermocouple.

however final calibration should be done with the gage(s) installed, so that all voltage drops and wire resistance is taken into account and then the scale on the gage can be corrected as needed.