Discussion in 'Gen II Prius Technical Discussion' started by bnaccs, Dec 10, 2007.
Does the Prius have a temperature gauge? If not how do you know the coolant temp?
Not OEM, but aftermarket equipment is available.
Why is it that you need to know the coolant temp?
Many use a ScanGauge for engine temp and other operating parameters.
I can answer this for the poster.
A temperature gauge lets a driver know when the engine may overheat and allows one to shut down preventing damage. Warning or "idiot lights", do not give you enough warning nor do they let you know the engine has been running hotter than normal, to prevent damage.
I use my ScanGauge 2 to monitor the coolant temp.
I'm not yet convinced that this is true, but to each his own. You can purchase CanView or ScanGauge if you don't trust the warning lights to trigger in time.
For the 2001-03, North American, Prius, 70C is a boundary between warm-up with the engine always on and 'hybrid' mode when the ICE can be off. There are some other warm-up steps such as ICE shutdown at a stop or exceeding 35 mph. However, these steps require passing through 70C and staying above 60C thereafter.
In my case, mileage until 70C is typically 30-35 MPG. After reaching 70C, it jumps to 65+ depending upon weather and driving conditions. The trick is to minimize fuel burn until it reaches 70C.
I'm not sure what you mean. I used to race cars years ago and a temp gauge was very important. It even saved me one engine on my street driven vehicle, as I was able to shut down before the engine overheated and caused major damage. Granted you would have to know what the normal engine temp is for the vehicle.
Warning lights or "idiot lights", never provided enough of a safety margin, at least they never used to. Maybe things have changed with modern vehicles. Either way, I would much rather see the actual water temp myself. Just like I prefer to see the rpms of an engine. I am a numbers person and like to get as much info about my engine as possible.
bnaccs gave no indication that he is planning to race his Prius, thus my question as to why he wanted to know the coolant temp. If he indicated that he wanted to know which stage of operation his Prius was in so he could optimize his mileage, or if he indicated that he was planning to take his Prius to the track, then he could have followed up on the suggestions of myself and others of aftermarket devices.
I understand what bwilson4web uses a temp gauge for, and I understand what someone racing a Prius might use a temp gauge for. What I was asking is why bnaccs needed to know the coolant temp.
As to what I mean. I'm not convinced that in a modern vehicle, the warning light doesn't come on in time to shut the vehicle off before damage occurs. Perhaps you are right, and by the time the warning light comes on, it's too late and your engine is trashed, but I highly doubt it. In the one street driven vehicle that the temp gauge "saved [you] one engine", I'm not convinced that a warning light couldn't have done the same. Did that car have a warning light?
The problem with idiot lights is that they are either on or off. They don't get brighter as temperature rises.
You don't know if the "Overtemp" is a rapid increase in temperature due to major problem (example: Loss of coolant due to broken hose) or is it just a little above the limit (example: In an Interstate parking lot during "rush hour" and not enough air flowing through radiator to cool down coolant.)
In the first case: Stop car as soon as possible and investigate. Second case: As I was taught in Driver's Ed TOO MANY years ago: Turn on heater and set interior fan on HIGH. (Hey, it works.)
Without a gauge, you aren't sure of what the temp truly is and how much weight to place on the LED.
But, as you imply, or I infer from you: To each his/her own.
BTW, my Camry Hybrid has Temp gauge, and I have SGII. Once the SG-X codes are updated to show Inverter, MG temps, etc, I'll upgrade to that. I personally prefer gauges than idiot lights.
Well I do know that a low oil idiot light did not save my engine in another vehicle I had years ago. I did not have enough time to shut off the engine before damage was already done. Since water temp idiot lights work the same way, I am totally convinced a gauge is far better.
I don't plan on racing a Prius, but it scares me not to have a temp gauge. I like to monitor the engine temp, especially when in traffic in the summer. I suppose the Prius just has a light Just wondering.
It is amazing that the Prius doesn't have a water temp gauge, considering these have been the norm in most vehicles for decades.
But I'm sure if my wife was driving a car with a gauge, that unless the gauge said stop when it reaches this I think she would not take much notice. But if a big light came on then I am sure she would take notice.
Just my opinion.
Quite often with a total loss of coolant the gauge and light give no warning as there is no coolant in contact with the bulb on the sensor unit.
A gauge is handy if the radiator is marginal, it allows the driver to throttle back to reduce a rising temperature when climbing a hill which may allow you to keep moving rather than stop.
What could be better than to see the actual temperature? My Scanguage is always set for engine coolant temp, RPM, and battery voltage. I wish I could get oil temp out of it.
I mainly like to monitor the temperature in the morning when I first start out. One of the main reasons I bought the scanguage was to monitor the temp and RPM of the engine. Everything else is just icing on the cake.
The scanguage is a great little device. easy to install and cheap to boot.
P.S. Do I "need" to monitor the temp? Probably not but I choose to do so.
So would she also need a light to tell her when she reaches the speed limit? You could easily teach her how to read a temp gauge. All of them are designed to show a driver when the engine is over heating and usually have red areas to let you know it is to hot. Some also use a light in combination to get the drivers attention.
Since the Prius engine senses the information a gauge could display, it just makes no sense why Toyota only used idiot lights.
Can't make everyone happy, if you want a gauge, buy one. What about the guy that wants an oil pressure gauge. And the guy that wants an inverter temp gauge. Then there's the guy that wants the HV battery temp gauge. Don't forget about the tach. Of course you must throw in a tire pressure gauge, and a gauge indicating the strength of the SKS signal. A gauge that indicates the strenght of the FM radio signal might be nice too. What I really want is a gauge indicating how much electrical power is being generated by or sent to each of the electric motors.
No, with that many gauges, there would just be too much to keep track of to watch the road. I'll keep my car in good repair, so I don't need to track all that, and stick with the 3 gauges I've got. If anything is outside of operating parameters, I'll stop the car when the indicator light comes on, and get it fixed.
Again.....water temp gauges have been standard in many cars for decades. It is not like it is a special gauge or anything. Vehicles usually have a speedometer, water temp and fuel gauge. In the past many have had an amp or volt meter and tach. Tachs have made a come back in the last 20 years. But a water temp gauge has been pretty much standard like a speedometer and fuel gauge. And why do you suppose that is? Because it is an important gauge that anyone can read.
With a water temp gauge you can help a tech trouble shoot an overheating issue. For instance, even without numbers on the gauge, you can inform the tech that your engine has been close to being in the red for the last few days. You can't do that with an idiot light.
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