Exhaust Gas Temperature Ranges
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Joined: Dec 2000
Posts: 147
From: Carlsbad, CA USA
Exhaust Gas Temperature Ranges
I'm planning to do some road racing and am therefore adding an EGT gauge to help keep track of how my motor is doing. What are the normal ranges I'm looking to keep?
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Exhaust Gas Temperature Ranges
Originally Posted by Blown 96 WS-6
I'm planning to do some road racing and am therefore adding an EGT gauge to help keep track of how my motor is doing. What are the normal ranges I'm looking to keep?
No higher than 1300* for any length of time.
Registered User
Joined: Dec 1998
Posts: 2,161
From: Haslett, Michigan
Re: Exhaust Gas Temperature Ranges
Originally Posted by 1racerdude
No higher than 1300* for any length of time.
EGT is a function of not only mixture but ignition timing. It is also a function of where in the exhaust stream you put the probe. If you put it close to the header tube wall the temperature will be colder than if you pop the tip into the true center of the exhaust stream. Exhaust velocity will also affect the temperature so if you put the probe into a slow velocity portion of the stream like just behind the inside radius of a sharp bend, the temperature may appear lower.
When I instrumented up ALL EIGHT cylinders and logged simulataneous temperatures this fall, a wide-open throttle blast took the temperatures to within ninety degrees of one another, from 1250 to 1340 degrees. Idle temperatures were hard-pressed to stay above 800 degrees. Regular cruise temperatures were somewhere inbetween and cylinder to cylinder temperature deviation varied much more at part throttle than at WOT .
Turbo, supercharged, and nitrous engines may very well see transient spikes of 1700 degrees with no apparent damage.
The convention is this: It is mostly irrelevant as to what the temperature is at the port; It's the air/fuel ratio, ignition timing, knock sensor that tell what is good or bad for the engine. EGT will generally assist you in determining if a cylinder is running lean or rich RELATIVE to another cylinder, but only after you have established the AFR with wide-band O2 logging.
Hope this helps,
--Dan Burk
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Exhaust Gas Temperature Ranges
Originally Posted by ws6transam
Not necessarily true.
EGT is a function of not only mixture but ignition timing. It is also a function of where in the exhaust stream you put the probe. If you put it close to the header tube wall the temperature will be colder than if you pop the tip into the true center of the exhaust stream. Exhaust velocity will also affect the temperature so if you put the probe into a slow velocity portion of the stream like just behind the inside radius of a sharp bend, the temperature may appear lower.
When I instrumented up ALL EIGHT cylinders and logged simulataneous temperatures this fall, a wide-open throttle blast took the temperatures to within ninety degrees of one another, from 1250 to 1340 degrees. Idle temperatures were hard-pressed to stay above 800 degrees. Regular cruise temperatures were somewhere inbetween and cylinder to cylinder temperature deviation varied much more at part throttle than at WOT .
Turbo, supercharged, and nitrous engines may very well see transient spikes of 1700 degrees with no apparent damage.
The convention is this: It is mostly irrelevant as to what the temperature is at the port; It's the air/fuel ratio, ignition timing, knock sensor that tell what is good or bad for the engine. EGT will generally assist you in determining if a cylinder is running lean or rich RELATIVE to another cylinder, but only after you have established the AFR with wide-band O2 logging.
Hope this helps,
--Dan Burk
EGT is a function of not only mixture but ignition timing. It is also a function of where in the exhaust stream you put the probe. If you put it close to the header tube wall the temperature will be colder than if you pop the tip into the true center of the exhaust stream. Exhaust velocity will also affect the temperature so if you put the probe into a slow velocity portion of the stream like just behind the inside radius of a sharp bend, the temperature may appear lower.
When I instrumented up ALL EIGHT cylinders and logged simulataneous temperatures this fall, a wide-open throttle blast took the temperatures to within ninety degrees of one another, from 1250 to 1340 degrees. Idle temperatures were hard-pressed to stay above 800 degrees. Regular cruise temperatures were somewhere inbetween and cylinder to cylinder temperature deviation varied much more at part throttle than at WOT .
Turbo, supercharged, and nitrous engines may very well see transient spikes of 1700 degrees with no apparent damage.
The convention is this: It is mostly irrelevant as to what the temperature is at the port; It's the air/fuel ratio, ignition timing, knock sensor that tell what is good or bad for the engine. EGT will generally assist you in determining if a cylinder is running lean or rich RELATIVE to another cylinder, but only after you have established the AFR with wide-band O2 logging.
Hope this helps,
--Dan Burk
Spike it to 1700* for 30 seconds, a few times like he would road racing and see what happens.
Something gonna start melting ie. pistons.
Egt depends on a lot of thing and isn't good to tune with unless ya got the numbers from an engine dyno as a baseline.
1300* is safe and 1500* is MAX for very short periods.
Ya can take it to 15-1700 if ya want but bring your checkbook unless your pistons are made of chromemoly.
Your probe's should be 3-4 inches from the header flange as per instructions on the one's I use.
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Re: Exhaust Gas Temperature Ranges
EGT's can range anywhere from maybe 900-1500 deg F. Impossible to say what your ideal temp will be.
A/F ratio, ignition timing and compression ratio play a big part in what "ideal" will be for any given combination. Move the compression up a point on a rebuild and your EGT's will drop. So what is "right"?
Tune for best performance and then record your EGT's. Use them as a tuning reference.
-Mindgame
A/F ratio, ignition timing and compression ratio play a big part in what "ideal" will be for any given combination. Move the compression up a point on a rebuild and your EGT's will drop. So what is "right"?
Tune for best performance and then record your EGT's. Use them as a tuning reference.
-Mindgame
Registered User
Joined: Mar 2005
Posts: 849
From: Shawnee Kansas
Re: Exhaust Gas Temperature Ranges
One thing to keep in mind is that the maximum egt will occur at stoich and fall off from either side of that. This is why wideband tuning is so valueable and a more benificial channel to monitor than say 1 or 2 channels of egt. The wideband can also show a misfiring cylinder. Also the more efficient combustion is the cooler the egt will be for a given afr.
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Exhaust Gas Temperature Ranges
Originally Posted by A/G
Not all WB controllers have this capability. It depends on the product. Only one that I am aware of is digital. Not saying there are not others. 
It has been (and STILL is) a misconception and accepted as fact, that the leaner the AFR, the hotter the exhaust. This is not true. Beyond (leaner) stoich (appr), the cooler not hotter, the exhaust temp becomes. It becomes cooler and cooler, til the flame eventually goes out. So much for the 'lean' misfire proponents.
It has been (and STILL is) a misconception and accepted as fact, that the leaner the AFR, the hotter the exhaust. This is not true. Beyond (leaner) stoich (appr), the cooler not hotter, the exhaust temp becomes. It becomes cooler and cooler, til the flame eventually goes out. So much for the 'lean' misfire proponents.
Correct.
Ya can tune it lean enough it looks rich,and rich enough it looks lean. Got to read the plugs to tell.
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Exhaust Gas Temperature Ranges
Originally Posted by A/G
Agree racer. As far as reading plugs is concerned, it is more than looking at the electrode. It is an art as much as a science. It also takes the right (read quality) equipment to read accurately. A downside, what you see is the result of the valiable input from the type of service and RPM the motor sees. It may have (or had) it's place but consider it 'old school'. An accurate measuring WB is a better alternative. However, a WB controller with just one (maybe two) sensor input would be no more representative a reading than reading plugs subjected to varied engine useage.
EDIT: One other point I'd like to add about EGT. It is probably more important as a 'safety' monitor than as a tuning aid. Safety as in a shutdown measure such as too high a water temp or too low an oil pressure.
EDIT: One other point I'd like to add about EGT. It is probably more important as a 'safety' monitor than as a tuning aid. Safety as in a shutdown measure such as too high a water temp or too low an oil pressure.
I don't consider plug reading "old school". NASCAR top brass still use it and I have been doing it for 40+ years and I notice a "few" NHRA guys doing it. A wide ban O2 is valuable also but is of it's most value to bring an engine "in" on the dyno and at the track.
I broke out in a time when there were no fancy instruments and plugs were the only means to try to put your finger on what was going on inside your engine. If ya learned to do it well ya had an edge on the competition.
Banned
Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Exhaust Gas Temperature Ranges
Originally Posted by A/G
Hey racer, we've gotten a bit off topic, haven't we?
I won't deny the value that plug reading has given. Also noted, your experience which originated at a time when there was no alternative, was (and is) invaluable in reading plugs.
By 'old school' I implied outdated. I did not suggest plug reading is no longer in use. You will find however, that more and more pro teams, regardless of racing assn., are subscribing to newer tech in the way of the WB. The true value is in on track tuning with the WB. The more progressive and insightful teams have been using the WB for a few years now as on track means of tuning. I gotta believe those teams would be the first to admit the superior value of WB tuning, maybe doing some plug reading as a backup notwithstanding. Being able to evaluate and react to cylinder to cylinder AFR variation, and as noted above, with latest digital tech, being able to identify an igniton miss a pro would swear did not exist, is as of now far superior. This is just the way I see it.
I won't deny the value that plug reading has given. Also noted, your experience which originated at a time when there was no alternative, was (and is) invaluable in reading plugs.
By 'old school' I implied outdated. I did not suggest plug reading is no longer in use. You will find however, that more and more pro teams, regardless of racing assn., are subscribing to newer tech in the way of the WB. The true value is in on track tuning with the WB. The more progressive and insightful teams have been using the WB for a few years now as on track means of tuning. I gotta believe those teams would be the first to admit the superior value of WB tuning, maybe doing some plug reading as a backup notwithstanding. Being able to evaluate and react to cylinder to cylinder AFR variation, and as noted above, with latest digital tech, being able to identify an igniton miss a pro would swear did not exist, is as of now far superior. This is just the way I see it.
Didn't say plug reading was the end all for tuning a car.
They gather sooo much info on every pass these days it's hard to digest. As I stated in a previous post the EGT by it self is not a good way to tune if ya haven't got a baseline from the dyno. Then,that info is only good for your set up and to do it right it should have a probe in all header tubes.
I will agree that A/F ratio is very important,but in the caliber of racing that most do it isn't easy to change your whole tune to match the weather.
The tune changes are for the few that have a Fast system or the likes and want the car to stay on the money all day long and have the money and knowledge to use that type of set up.
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