What temp should the exhaust ports indicate?
03-24-2009, 01:29 PM
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What temp should the exhaust ports indicate?
For a good running stock engine, what's a good temp the exhaust manifolds should be at idle? Ages ago, I bought a temp gun (the laser thermometer) to try and tell which ports on my 2nd gen were not firing, and wanted to put it to good use again. I would imagine you can tell a good bit about each cylinder by the temp of the exhaust, eh?
03-24-2009, 01:41 PM
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Re: What temp should the exhaust ports indicate?
Some info I found while googling for this info, figured someone would enjoy it
Another good read
Exhaust Gas Temperature Sensors (EGT) Sensors for Tuning Internal Combustion Engines Installation information: Exhaust Gas Temperature (EGT) Probe placement in the exhaust path requires special attention. If it is closer than 1½ inches to the cylinder head, probe life will be limited, too far away the probe will be less responsive. Should there be doubt concerning in which exhaust tube or specific placement of the probe, you should check with the engine manufacturer or your engine builder.
There are two basic ways EGT probes are installed in multiple cylinder engines either for monitoring a bank cylinders or each individual cylinder.
Monitoring a bank of cylinders give you information on the over all exhaust gas temperature generated by the cylinder bank. For example when installed in a "V8" cylinder engine two EGT probes can be used by placing them in the exhaust header collector just past the point where tubes from one side become common. The probes are connected to high temperature thermocouple wire and a connector and then to a dual channel meter for monitoring. The consideration to this installation is the distance from the combustion chamber, making the EGT reading lower and giving an average of the four cylinders in each bank. This keeps the ability to gather the necessary temperature information simple.
If you require more exact temperature readings you may consider installation of probes near combustion chambers. This maybe be requirement in situations where you have the ability to tune fuel supply or air for each cylinder. This is more complicated and requires proper installation and placement of the probes. The constancy in probe distance from combustion chamber is very important in order to get reliable readings.
EGT systems are not complex or expensive to install. An advantage of the EGT monitoring verses monitoring the cylinder head temperature is the close to immediate response to change in temperature verses the fuel to air ratio. The peak or point of maximum temperature is the basic reference for performance management. If you have experimented with the exhaust gas temperature sensors at the engine builder’s dyno or engine manufacturers recommended maximum horsepower, you have observed during the tuning process results in the peaking of the exhaust gas temperature via the gradual leaning of fuel and air ratio adjustments.
The peak temperature in each cylinder will vary with different power settings, changes in altitude, and ambient temperature. So tuning for specific atmospheric conditions can be critical on race day. Typically a hand held digital readout like the dual channel or single channel meters The Sensor Connection offers will have the ability to read individual cylinder exhausts or cylinder banks. Multiple channel data acquisition systems will gather and display data from all exhaust port temperature readings simultaneously. The requirements for precision of the data collection of your application will determine the type of data collection system you will need.
Tuning the fuel to air ratio for peak efficiency with an EGT Probe
Tips:Tuning for Power When tuning for power typically it is in the range of plus 100 degree F on the rich side of peak temperature. It is generally not considered a practical economic fuel / air ratio for cruising purposes Tip: Tuning for Economy
Advantages and benefits of an exhaust gas temperature (EGT) sensor / probes Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings meaning less pitting for fuel (increased range) as well as less likelihood of spark plug fouling.
There are two basic ways EGT probes are installed in multiple cylinder engines either for monitoring a bank cylinders or each individual cylinder.
Monitoring a bank of cylinders give you information on the over all exhaust gas temperature generated by the cylinder bank. For example when installed in a "V8" cylinder engine two EGT probes can be used by placing them in the exhaust header collector just past the point where tubes from one side become common. The probes are connected to high temperature thermocouple wire and a connector and then to a dual channel meter for monitoring. The consideration to this installation is the distance from the combustion chamber, making the EGT reading lower and giving an average of the four cylinders in each bank. This keeps the ability to gather the necessary temperature information simple.
If you require more exact temperature readings you may consider installation of probes near combustion chambers. This maybe be requirement in situations where you have the ability to tune fuel supply or air for each cylinder. This is more complicated and requires proper installation and placement of the probes. The constancy in probe distance from combustion chamber is very important in order to get reliable readings.
EGT systems are not complex or expensive to install. An advantage of the EGT monitoring verses monitoring the cylinder head temperature is the close to immediate response to change in temperature verses the fuel to air ratio. The peak or point of maximum temperature is the basic reference for performance management. If you have experimented with the exhaust gas temperature sensors at the engine builder’s dyno or engine manufacturers recommended maximum horsepower, you have observed during the tuning process results in the peaking of the exhaust gas temperature via the gradual leaning of fuel and air ratio adjustments.
The peak temperature in each cylinder will vary with different power settings, changes in altitude, and ambient temperature. So tuning for specific atmospheric conditions can be critical on race day. Typically a hand held digital readout like the dual channel or single channel meters The Sensor Connection offers will have the ability to read individual cylinder exhausts or cylinder banks. Multiple channel data acquisition systems will gather and display data from all exhaust port temperature readings simultaneously. The requirements for precision of the data collection of your application will determine the type of data collection system you will need.
Tuning the fuel to air ratio for peak efficiency with an EGT Probe
From the peak EGT, either increasing or decreasing the fuel to air ratio causes a decrease in EGT. Richer than peak EGT cooling occurs because there is excess fuel, and leaner than peak, cooling occurs because there is excess air. So you must have a basic idea of where you are starting from regarding base cylinder exhaust gas temperatures and rich or lean condition of the fuel delivery system.
Peaking exhaust gas temperature (EGT) with a carbureted engine is frequently a vague point because of less efficient atomization compared to electronic fuel injection to the individual cylinders. As a result, carbureted engines tend to operate smoother at +25 degree +50 degree F on the rich side of peak exhaust gas temperature (EGT).
Fuel injected engines typically provide a more precise peak exhaust gas temperature, therefore the EGT system is likewise a more precise method of performance tuning with fuel injection.
A simple definition of peak EGT is the chemically correct mixture of fuel and air, which gives 100% utilization of all the fuel and all the air.
Benefits of EGT sensors for engine tuning:
Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings meaning less pitting for fuel (increased range) as well as less likelihood of spark plug fouling.
Temperature variations will occur between in between individual cylinders when using a probe for every cylinder. Typical variations of about 100 degree F between each individual cylinder can be observed with fuel injection systems, and about 200 degree F with conventional carburetion. Carburetion variation is greater because the atomization of the fuel is not as effective when compared with fuel injectors. In colder air temperatures, the mixture atomization is poorer for both fuel injected and carbureted engines. However, with the carburetor, the fuel/air ration and atomization is less effective resulting in larger temperature variations when comparing individual cylinders.
Fuel injected engines typically provide a more precise peak exhaust gas temperature, therefore the EGT system is likewise a more precise method of performance tuning with fuel injection.
A simple definition of peak EGT is the chemically correct mixture of fuel and air, which gives 100% utilization of all the fuel and all the air.
Benefits of EGT sensors for engine tuning:
Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings meaning less pitting for fuel (increased range) as well as less likelihood of spark plug fouling.
Temperature variations will occur between in between individual cylinders when using a probe for every cylinder. Typical variations of about 100 degree F between each individual cylinder can be observed with fuel injection systems, and about 200 degree F with conventional carburetion. Carburetion variation is greater because the atomization of the fuel is not as effective when compared with fuel injectors. In colder air temperatures, the mixture atomization is poorer for both fuel injected and carbureted engines. However, with the carburetor, the fuel/air ration and atomization is less effective resulting in larger temperature variations when comparing individual cylinders.
Tips:Tuning for Power When tuning for power typically it is in the range of plus 100 degree F on the rich side of peak temperature. It is generally not considered a practical economic fuel / air ratio for cruising purposes Tip: Tuning for Economy
If you want to tune for economy, care must be taken not to create an excessive lean condition can cause detonation and/or pre-ignition resulting in possible engine failure. Damage is caused by maximum leaning in higher engine rpms.
Advantages and benefits of an exhaust gas temperature (EGT) sensor / probes Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings meaning less pitting for fuel (increased range) as well as less likelihood of spark plug fouling.
- Aids in making proper adjustment to the fuel / air mixture ratio
- Increased precision in fuel and performance management.
- Gives you the ability to tune for fuel economy
- Decrease in fuel stops.
- Detects some types of engine troubles.
- Aids peak engine performance at cruising speeds.
- Help to prevent spark plug fouling.
- Fits any internal combustion engine.
How do I read an EGT (Exhaust Gas Temperature) gauge?
Among the gauges considered when going aftermarket forced induction on a car is the EGT gauge. Along with the A/F ratio gauge (which I will explain in another write up), you can get a very good idea of how well your engine is running, and if it's running safely. Although much more critical to very high boost/ race car applications, having an EGT gauge on a FI street car isn't a bad idea. There are different schools of thought on the subject, but since most of our customers aren't running carburated open wheel carts for endurance racing, this information is going to be biased towards turbocharged or supercharged four or six cylinder imports. Also keep in mind that this writeup is a generalization. If you're running mild boost on a safe, professional tune, there really isn't a need for an EGT gauge. Also, this writeup is applicable only to those using the EGT gauge to monitor the running condition of their engine. When using the EGT gauge for tuning, there are slightly different rules.
For the comfort of those reading this page, I'm going to try to explain the EGT in terms of it's use, and not the engineering behind the device (for that, you can email me). Although I'll try to be as simple as possible, It's likely this may get a little technical. Also keep in mind that although we strive to give the clearest, most accurate information we can, we can't be held responsible if you destroy your car by misinterpreting this information.
Some of the most common gauge-related questions I get here at JTune are about the EGT gauge. Usually, it's one of two questions:
Question one: "where do I install the probe?"
Question two: "what should the temperature be?"
Although the first question is a valid one, the second one can get people into trouble. I'll start with the basics. There are two kinds of probes available for EGT gauges. Assuming you purchased the gauge at JTune, it comes with a thermocouple probe. Although almost all EGT gauges come with a thermocouple probe, some of the very cheap gauges come with Resistive Temperature Detection (RTD) probes instead (read: eBay). If you are one of the unlucky few who decided to save some money and ended up with a RTD probe in your gauge kit, go ahead and throw it away. The RTD probes aren't capable of reaching the temperatures we require, and are much less accurate and responsive. Luckily, all of the decent gauges come with thermocouple type probes.
Probe location. This is a very critical (and somewhat debated) subject. The short answer is that you want the probe as close to the combustion chamber as possible (sort of). Generally, about 1 to 3 inches away from the head is considered correct. You also want to try to get it in an individual exhaust runner (before two or more cylinders combustion gasses meet), although this isn't absolutely critical. Personally, I try to put the probe about one inch from the header flange in the number three cylinder's runner. Why number three? For one, it's what I was taught to do, but I've seen some instructions call for cyl. one instead. Moreover, I tend to always place my probes in the same place because it makes it better for comparison purposes (more on that later). The reason to get the probe as close to the head as possible is simple; better response. The further you go from the head, the more ambient air is able to cool the exhaust. If the probe is installed too far away from the head, the gauge is unable to respond quickly enough to changes in temperature, making the gauge useless.
What should the temperature be? This is a common question I get from people who already have an EGT gauge installed in their car. Before I can answer this question, you first have to understand a little about what the gauge is actually reading. Some engines have aluminum blocks, some cars have iron. Some have open decks, some have closed decks. Some have incredibly efficient cooling systems, some don't. Some cars have long exhaust ports in the head, and others are short, while others have radical bends. All these things affect the temperature of the exhaust gas, often times enough to change the EGT reading at the probe by hundreds of degrees. So comparing the EGT reading of, lets say, a Nissan Skyline, and a Subaru Impreza, even if the probes on both cars are in the exact same place, can be wildly different. Okay, so we know that comparing the EGT of different cars is useless, but how do you know what the temperature really should be? I think it would be better if we changed the question to "what should I be looking for in the EGT gauge reading?". To really understand the EGT gauge, you have to understand that the temperature reading at any given time isn't really important. That is to say that there isn't a set rule to what the temperature is supposed to be. You can't say that "the idle EGT of a SR20DET is xxx degrees" any more than you can say "the entrance speed of this corner is 70 MPH". In either case, it all depends on the car and how it's set up. (There are some exceptions, like how I was saying before that I always place the EGT gauge in the same place on all the cars I work on, that way I have a general idea of what the temperature should be on two identical cars (say for instance, two stock SR20DETs). Also, some engines run hotter than others, but if you see temperatures above 1700 degrees, in most cases, something is seriously wrong)
It's all about air/fuel mixture. That's the secret to understanding the readings from the EGT gauge. It's not the temperature of the exhaust gas that you're looking for, it's the changes in temperature that are important. It's generally understood that richer (more fuel) mixtures cool the exhaust gas, while leaner (more air) mixtures cause it to become hotter. In most cases, this is true, so if you're hard on the gas (like during acceleration) you should see the EGT going up as well, and when you take your foot off the gas you should see the temperature fall (this is all relative, while an A/F ratio of 14.7:1 is good for idle, at full throttle you want to be much more rich to be safe. An A/F ratio of 12.8:1 at idle would usually be considered rich, but at full throttle on a turbocharged car, it can be dangerously lean. See the AFR write up for more information). This is where the EGT gauge becomes useful. Say for instance you are hard on the gas, watching the EGT climb. If at any time during acceleration the temperature abruptly drops, or for that matter, ceases to increase, it means that you're going to be detonating very, very soon (see the detonation write up for more info). In fact, the EGT gauge can pick up on this so fast that if you see it happening, you can immediately let off the gas and save yourself from an engine rebuild (I'd like to explain how this works, but like I said earlier, I'm trying to keep this as light as possible). That being said, if you also had an air/ fuel ratio gauge in the car, you might have seen that you were running lean up to that point. (keeping in mind that 'lean' is relative to the conditions at that time) Also, with a baseline understanding of what the usual EGT is of your car, you will be able to see a large variation of temperature from normal as a warning sign of something gone wrong that may not have been immediately apparent otherwise.
Generally, if you have a properly built street car with quality components that was tuned by a professional, the need for an EGT gauge is debatable. Remember, it only works if you're looking at it. Even the quality gauges with a peak temperature alarm won't alert you to a sudden drop of temperature. On the other hand, if you've spent the money on a proper build and want to take your car to the next level, investing in an EGT gauge wouldn't be a bad idea (especially now that you know how to read it).
Ryan Hickey
Ryan@jtuneperformance.com
Among the gauges considered when going aftermarket forced induction on a car is the EGT gauge. Along with the A/F ratio gauge (which I will explain in another write up), you can get a very good idea of how well your engine is running, and if it's running safely. Although much more critical to very high boost/ race car applications, having an EGT gauge on a FI street car isn't a bad idea. There are different schools of thought on the subject, but since most of our customers aren't running carburated open wheel carts for endurance racing, this information is going to be biased towards turbocharged or supercharged four or six cylinder imports. Also keep in mind that this writeup is a generalization. If you're running mild boost on a safe, professional tune, there really isn't a need for an EGT gauge. Also, this writeup is applicable only to those using the EGT gauge to monitor the running condition of their engine. When using the EGT gauge for tuning, there are slightly different rules.
For the comfort of those reading this page, I'm going to try to explain the EGT in terms of it's use, and not the engineering behind the device (for that, you can email me). Although I'll try to be as simple as possible, It's likely this may get a little technical. Also keep in mind that although we strive to give the clearest, most accurate information we can, we can't be held responsible if you destroy your car by misinterpreting this information.
Some of the most common gauge-related questions I get here at JTune are about the EGT gauge. Usually, it's one of two questions:
Question one: "where do I install the probe?"
Question two: "what should the temperature be?"
Although the first question is a valid one, the second one can get people into trouble. I'll start with the basics. There are two kinds of probes available for EGT gauges. Assuming you purchased the gauge at JTune, it comes with a thermocouple probe. Although almost all EGT gauges come with a thermocouple probe, some of the very cheap gauges come with Resistive Temperature Detection (RTD) probes instead (read: eBay). If you are one of the unlucky few who decided to save some money and ended up with a RTD probe in your gauge kit, go ahead and throw it away. The RTD probes aren't capable of reaching the temperatures we require, and are much less accurate and responsive. Luckily, all of the decent gauges come with thermocouple type probes.
Probe location. This is a very critical (and somewhat debated) subject. The short answer is that you want the probe as close to the combustion chamber as possible (sort of). Generally, about 1 to 3 inches away from the head is considered correct. You also want to try to get it in an individual exhaust runner (before two or more cylinders combustion gasses meet), although this isn't absolutely critical. Personally, I try to put the probe about one inch from the header flange in the number three cylinder's runner. Why number three? For one, it's what I was taught to do, but I've seen some instructions call for cyl. one instead. Moreover, I tend to always place my probes in the same place because it makes it better for comparison purposes (more on that later). The reason to get the probe as close to the head as possible is simple; better response. The further you go from the head, the more ambient air is able to cool the exhaust. If the probe is installed too far away from the head, the gauge is unable to respond quickly enough to changes in temperature, making the gauge useless.
What should the temperature be? This is a common question I get from people who already have an EGT gauge installed in their car. Before I can answer this question, you first have to understand a little about what the gauge is actually reading. Some engines have aluminum blocks, some cars have iron. Some have open decks, some have closed decks. Some have incredibly efficient cooling systems, some don't. Some cars have long exhaust ports in the head, and others are short, while others have radical bends. All these things affect the temperature of the exhaust gas, often times enough to change the EGT reading at the probe by hundreds of degrees. So comparing the EGT reading of, lets say, a Nissan Skyline, and a Subaru Impreza, even if the probes on both cars are in the exact same place, can be wildly different. Okay, so we know that comparing the EGT of different cars is useless, but how do you know what the temperature really should be? I think it would be better if we changed the question to "what should I be looking for in the EGT gauge reading?". To really understand the EGT gauge, you have to understand that the temperature reading at any given time isn't really important. That is to say that there isn't a set rule to what the temperature is supposed to be. You can't say that "the idle EGT of a SR20DET is xxx degrees" any more than you can say "the entrance speed of this corner is 70 MPH". In either case, it all depends on the car and how it's set up. (There are some exceptions, like how I was saying before that I always place the EGT gauge in the same place on all the cars I work on, that way I have a general idea of what the temperature should be on two identical cars (say for instance, two stock SR20DETs). Also, some engines run hotter than others, but if you see temperatures above 1700 degrees, in most cases, something is seriously wrong)
It's all about air/fuel mixture. That's the secret to understanding the readings from the EGT gauge. It's not the temperature of the exhaust gas that you're looking for, it's the changes in temperature that are important. It's generally understood that richer (more fuel) mixtures cool the exhaust gas, while leaner (more air) mixtures cause it to become hotter. In most cases, this is true, so if you're hard on the gas (like during acceleration) you should see the EGT going up as well, and when you take your foot off the gas you should see the temperature fall (this is all relative, while an A/F ratio of 14.7:1 is good for idle, at full throttle you want to be much more rich to be safe. An A/F ratio of 12.8:1 at idle would usually be considered rich, but at full throttle on a turbocharged car, it can be dangerously lean. See the AFR write up for more information). This is where the EGT gauge becomes useful. Say for instance you are hard on the gas, watching the EGT climb. If at any time during acceleration the temperature abruptly drops, or for that matter, ceases to increase, it means that you're going to be detonating very, very soon (see the detonation write up for more info). In fact, the EGT gauge can pick up on this so fast that if you see it happening, you can immediately let off the gas and save yourself from an engine rebuild (I'd like to explain how this works, but like I said earlier, I'm trying to keep this as light as possible). That being said, if you also had an air/ fuel ratio gauge in the car, you might have seen that you were running lean up to that point. (keeping in mind that 'lean' is relative to the conditions at that time) Also, with a baseline understanding of what the usual EGT is of your car, you will be able to see a large variation of temperature from normal as a warning sign of something gone wrong that may not have been immediately apparent otherwise.
Generally, if you have a properly built street car with quality components that was tuned by a professional, the need for an EGT gauge is debatable. Remember, it only works if you're looking at it. Even the quality gauges with a peak temperature alarm won't alert you to a sudden drop of temperature. On the other hand, if you've spent the money on a proper build and want to take your car to the next level, investing in an EGT gauge wouldn't be a bad idea (especially now that you know how to read it).
Ryan Hickey
Ryan@jtuneperformance.com
Last edited by _87GTA_; 03-24-2009 at 01:45 PM.
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