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Old 10th June 2006, 21:51   #1
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Default Temperature Gauge links to Fuel Efficieny

Well I wanted to share this with you guys.

Two days back i had been to "a" mech for a routine check of my dash meter llight check which was not working.
When he saw my dash he asked me how long i had been driving? i mentioned approx 2 hrs. he then said theres some problem with ur temp gauge then as its not even reached half its marking. As my car does not show any degrees it has a certain point marked a bit "bold" which is the actual operating temperature. So i asked him to check it.
He found the Heat Radiator was not working and so got it flushed and got it working sending hot air when selected on the inside AC controls i.e hot cold. Temperature not showed any major change.
He then inspected the thermostat which is located after the large hose on top from radiator to engine. on engine is located the thermostat.
The thermostat was not opening full as inspected and he showed me that in a separate method. the thermostat replaced.
Now the car temp needle moved to close to half after a short drive of 30 minutes.
Now the result of this change.
Earlier I used to do 480 to 500 kms with 70 ltrs gas from Abu Dhabi to Dubai driving at average speed of 120kmph.
After change of thermostat the car has started to return 720 to 740kms for every 70ltrs filled.
Now this is a whopping 3+kms per litre.
I checked with the mech as to how this significant change and he mentioned that the car was not reaching operating temperature and so was not fully utilising the heat energy for motion.
I mentioned to him i ve been driving this car for 4 yrs and always saw the needle low down, the car starts with one twitch of the key, no problems of any kind and he said all thats fine but if i were to race the car for long period of time at higher speeds then the friction to other parts would be more and the wear would be more.

Whatever this guys theory but the result has been significant.
just some info to share with you guys.
btw the thermostat costs just approx 430Rs.
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Old 10th June 2006, 22:28   #2
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How can a sensor affect efficiency, except that if it shows overheating the it will shut of the AC.
Yes if your cooling system is not working properly, this will effect efficieny. But not the sensor.
The increase was due to flushing of the cooling system which led to better efficieny. Even if the sensor stops working the car will still run, you wont see on the engine how hot is your meter.
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Old 10th June 2006, 22:42   #3
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Quote:
Quote:
Originally Posted by 2fast4u
I checked with the mech as to how this significant change and he mentioned that the car was not reaching operating temperature and so was not fully utilising the heat energy for motion.
I mentioned to him i ve been driving this car for 4 yrs and always saw the needle low down, the car starts with one twitch of the key, no problems of any kind and he said all thats fine but if i were to race the car for long period of time at higher speeds then the friction to other parts would be more and the wear would be more.
Find it hard to believe but it could be possible. I think it needs to be explained in more detail as to the real function of this Thermostat. BTW, which car are we talking about.

So long....
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Old 11th June 2006, 00:05   #4
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Quote:
Originally Posted by varunroy
Find it hard to believe but it could be possible. I think it needs to be explained in more detail as to the real function of this Thermostat. BTW, which car are we talking about.

So long....
A thermostat is a switch which sees the engine cooling mechanism. A struck thermostat would mean that the coolant wouldnt circulate properly. So I guess I was wrong. I confused the thermostat with the sensor. They are two different components. So yes if the thermostat is stuck, coolant wouldn't circulate properly. resulting in overheating engine and therefore low mileage
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Old 11th June 2006, 00:43   #5
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Quote:
Originally Posted by tsk1979
A thermostat is a switch which sees the engine cooling mechanism. A struck thermostat would mean that the coolant wouldnt circulate properly. So I guess I was wrong. I confused the thermostat with the sensor. They are two different components. So yes if the thermostat is stuck, coolant wouldn't circulate properly. resulting in overheating engine and therefore low mileage
I never found the engine hot anytime as i drive 2 to 2 hrs at a stretch thats 130 to 140 kms and never did i notice it or maybe i was lucky in some way to have no damage done as the climate here is hot. The sensor u r talking about is what they call "sending unit" is that right??

varunroy@ nissan altima 1992
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Old 12th June 2006, 15:38   #6
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Quote:
Originally Posted by tsk1979
A thermostat is a switch which sees the engine cooling mechanism. A struck thermostat would mean that the coolant wouldnt circulate properly.
Good that someone brought up this question.
I think the thermostat in question controls the radiator fan. The coolant is always circulated as long as the engine is running, bu the radiator fan switches on when the coolent temp reaches a level that activates the thermostat.

This is very easy to test, once you reach the so called operating temp, you can hear the radiator fan kicking in. So if you are driving in sweltering heat, your fan would be working most of the time. If the heat is more than it can handle, the needle will move up to red.
Diesel wehicles like jeeps have a system where the radiator fan is working all the time

The thermostat is adjustable (I believe). I wanted to experiment with the setting to see what is the max efficiency operating temp.

Most mechanics put it exactly at the 1/2 of the gauge. I wonder whether they have any idea about it?
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Old 12th June 2006, 20:58   #7
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Quote:
Quote:
Originally Posted by tsk1979
A thermostat is a switch which sees the engine cooling mechanism. A struck thermostat would mean that the coolant wouldnt circulate properly. So I guess I was wrong. I confused the thermostat with the sensor. They are two different components. So yes if the thermostat is stuck, coolant wouldn't circulate properly. resulting in overheating engine and therefore low mileage
A thermostat is a device that reads the temperature of the coolant that circulates the entire engine. Most thermostats have a sensor on one end of it which is always in contact with the coolant. Modern Thermostats are a tiny compact thing unlike the ones in Premeir Padminis & Ambys that had a long copper strand with a probe attached on one end. The Thermostat does not circulate the water in the engine and this job is done by the Water pump which is doing its job right from the time the engine fires to life. Some vehicles have a fan fitted directly on the water pump which is driven by a V-belt directly connected to the crankshaft and operates all the time thereby cooling the water without bothering whether the water in the Engine is hot or cold adding additional stain on the Engine. The job of the Thermo here is just to read the Temp of the Engine and reflect it onto the meter on the Dash.

Modern cars have a system where the fan kicks in only when the temperature has risen beyond the stipulated limit and this is activated by the thermostat. Here the fan is powered by the battery and even if the Engine is not running the fan could come on anytime without warning, provided that the ignition is switched ON. Since there is no load on the engine the FE is better .

As regard to the heat, 2fast4u would not have felt it because of the efficient and superior insulation used to keep the engine heat and sound out.

So long....
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Old 12th June 2006, 22:09   #8
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Dear all,
I have noticed something very stange with my zen, With the ac on 100% i get an average of only 10, but without the ac i get 13.5 in bombay traffic, this drop with the ac is most recent as eariler with 50% ac i used to get 12.5, could this have to do with the thermostat??
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Old 13th June 2006, 09:01   #9
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Quote:
Quote:
Originally Posted by Kaizer Sozay
Dear all,
I have noticed something very stange with my zen, With the ac on 100% i get an average of only 10, but without the ac i get 13.5 in bombay traffic, this drop with the ac is most recent as eariler with 50% ac i used to get 12.5, could this have to do with the thermostat??
The Thermostat of the AC and the one that shows the Engine temperature on the Dash are totally non related.

I think your situation is quite normal because with 100% AC in the city the Compressor would hardly be switching off and this put additional load on the Engine, hence less mileage. With 50% AC the compressor would switch on and off at regular intervals and that explains 12.5 Kmpl. Anyway check out the Airfilter .

So long....
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Old 14th June 2006, 23:38   #10
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Quote:
Originally Posted by Kaizer Sozay
Dear all,
I have noticed something very stange with my zen, With the ac on 100% i get an average of only 10, but without the ac i get 13.5 in bombay traffic, this drop with the ac is most recent as eariler with 50% ac i used to get 12.5, could this have to do with the thermostat??
If you are comparing results you got this week vs results you got in Jan it could just be that the AC is working harder (as ambient is now about 10-15 deg higher than in Jan).

some cars i have seen today have 2 fans. one that is always on and the other that is triggered by the thermostat; and in some rare cases the second fan will turn off only when the thermostat tells it no matter if the car is being used or not.
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Old 15th June 2006, 22:13   #11
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Quote:
Quote:
Originally Posted by navin
If you are comparing results you got this week vs results you got in Jan it could just be that the AC is working harder (as ambient is now about 10-15 deg higher than in Jan).
Moreover with 400+ cars been added each day, traffic condition are becoming a nightmare and thats not a good thing for FE.

So long....
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Old 21st June 2006, 15:23   #12
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Guys,

There is some confusion as to what the thermostat is.
Sure it can mean a lot of things, but in this particular case >
Quote:
Originally Posted by 2fast4u
He then inspected the thermostat which is located after the large hose on top from radiator to engine. on engine is located the thermostat.
The thermostat is nothing more than a piece of metal(s) that opens up when it is heated to a certain temperature (somewhere between 75*c- 95*c).

It is basically the temperature controlled gate between the coolant passages in the engine block and the radiator.

When it is cold, the thermostat is closed, and no coolant circulates through the radiator, until the coolant in the engine heats up to a level where the thermostat opens, and then the coolant circulates through the radiator.

Heres what a thermostat looks like >
It can be found in the thermostat housing where the top hose of the radiator reaches the engine block.


A simple way to test whether your thermostat works is to suspend* it in some water and heat it on a stove. Keep a thermometer suspended in the water to see at what temperature the thermostat opens.
Defective thermostats will either be open / closed all the time, or will open at a wrong temperature.

* i say suspend because the hotter bottom of the pot should not come into contact with the thermostat or thermometer.

cya
R

Last edited by Rehaan : 21st June 2006 at 15:36.
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Old 21st June 2006, 15:39   #13
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Quote:
Originally Posted by Rehaan
Guys,

There is some confusion as to what the thermostat is.
Sure it can mean a lot of things, but in this particular case >


The thermostat is nothing more than a piece of metal(s) that opens up when it is heated to a certain temperature (somewhere between 75*c- 95*c).

It is basically the temperature controlled gate between the coolant passages in the engine block and the radiator.

When it is cold, the thermostat is closed, and no coolant circulates through the radiator, until the coolant in the engine heats up to a level where the thermostat opens, and then the coolant circulates through the radiator.

Heres what a thermostat looks like >
It can be found in the thermostat housing where the top hose of the radiator reaches the engine block.


A simple way to test whether your thermostat works is to suspend* it in some water and heat it on a stove. Keep a thermometer suspended in the water to see at what temperature the thermostat opens.
Defective thermostats will either be open / closed all the time, or will open at a wrong temperature.

* i say suspend because the hotter bottom of the pot should not come into contact with the thermostat or thermometer.

cya
R
exactly it was closed the wax or something like that was not doing its job as per mech. i had to buy his words as it has done wonders to my FE. i am getting approx 200kms extra on every 75ltrs. not an issue in this part of world where fuel is cheaper than water.
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