Egt

[20gst]

Ok just hooked up my new EGT. I got it in #1 runner, and started the car up and it went to about 600 real quick from a cold start. I held the rpms to about 3500-4000 for a few and it went to around 1100. I let off the gas and it went down to around 900 slowly.
I took it out for one pass down the block up to 3rd gear at full th. and I hit around 1400.
I never used this before and want to tune a little with it if it will help me. I got a 20g, 625cc injectors 255 warlboro. Im just wondering if this is to hot....

 

[RipperXX]

from what i understand unless your geting around 1500 your fine.. (dont take my unsure post as a fact)

 

[Kevin Jewer]

I have learned by experience that tuning by EGT is completely useless. But if you must, the rule of thumb is ~1600 F or 900C. But like I have posted a thousand times in the past, EGT only tells you your ignition timing, which can more accurately be read from a datalogger. And I have had no knock at 950+ C and have knocked like hell at 850C. Depends on fuel settings, mod list, etc. Plus thermocouples usually fail on the low side, which is obviously bad. Just my expereinces.

 

[20gst]

Thanks for the info.

 

[samuraitekno]

what are you talking about.. egt tells you the temp of your exhaust gasses. a very very important tuning tool. run too hot and say goodbye to your engine.

 

[Kevin Jewer]

I will repeat what I said in my last post again. EGT tells you your ignition timing. If it gets too hot you are knocking. Knock is what kills parts, not high temperatures. Also, an overly rich mixture will leave fuel burning in the manifold which will register a high EGT temp, but your engine is perfectly safe. I cant count how many times I have seen poeple keep dumping in more and more fuel and EGT doesnt come down. Again, its not a very useful tuning tool. Unles you know the implications of tuning by it, and how everything is related. I alsways hear about how parts melt when EGT gets too high, etc. Well, combustion temps are more than twice as hot as your EGT temps, so there goes that theory The temp fo the gasses has nothing to do with tuning in our case, but what it says about timing does. Just be sure you know how to accurately translate a EGT value into a timing value.

The bottom line is I have tuned with everything from AF ratio and EGT gauge, to pocketlogger (2g), and DSMlink. So I can see what the readings from the EGT guage and AF guage really mean. And the answer is nothing. I could go on for pages with data and numbers, but no one bother to listen Anyone can do a search and find this in dozens of threads. If you want to tune with those things, by all means, dont let me discourage you. That is not my intent. Just be very aware of the lack of, and indirectness of, the information you are using to tune. You can get pretty close, but you have to know what you are doing, and be careful.

So before you reply rudely with "what are you talking about," make sure you know what you are talking about. Just here to help. My initial intent was not to say that EGT isnt a good way to tune (though I do believe it is not a good way), but to illustrate that actuall numbers tossed around on the internet are meaningless, refering to the original posters question. You need to know what those numbers represent on your setup, at that particular time for EGT temps to be useful. And for that you need to know your timing and/or knock from a datalogger. With a datalogger however, you dont have much use for a EGT guage, especially on a 1g where you can read knock. The money spent on a EGT guage can easily be put toward a datalogger.

Hope the helps clarify my point a bit.

 

[samuraitekno]

yeah but an egt gauge measures exhaust gas temp. ... otherwise it would be called a knock gauge. . so before you say someone is being rude maybe you should examine your sentence and try not to over think something.. sometimes things are what they say they are. if it was a gauge that measured your ignition timing i really doubt you would stick it in your exhaust stream.

 

[Kevin Jewer]

I Cant believe what I'm reading... Obviously it measures temperature. But the single largest factor that determines what that temp is (in our case) is ignition timing. Which is largely determined by knock. So Like I said, an EGT guage is really telling you about knock and timing, not your mixture, as poeple mistakenly believe because all the internet forum racers tell them so. Anyone that has made the effort to verify with other instruments what the EGT readings really mean will agree with me on this. Thank you, please drive through.

 

[TRBOTSI]

It's no wonder the import scene is in its' current state..Lots of smart people out there, so there is...

 

[laser92awd]

I think somebody somebody totally missed the point (gesture with hand zipping over head while making "woosh" sound).

But you know, you DID say "EGT tells you your ignition timing" and you aren't going to fool us because we KNOW it stands for "Exhaust Gas Temperature", not "EGnition Timing"

Jonathan

 

[Kevin Jewer]

It does tell you ingnition timing. If EGT is high, timing is low (or misture is rich), if EGT is low, timing is high. Whats the problem here? I know I have to break things down to the most basic level for 90% of people to understand it, but I thought I could get away with that one Now I know better.

I just figured out the whole problem. No one cares what EGT tells you. Wether its timing, af ratio, or just the temp of the exhaust. People actually believe that over 900 means add fuel, and under 900 means take away fuel. Regardless of what those numbers actually mean and how they relate to tuning. Now I understand.... Pardon my intrusion

 

[Defiant]

o mi gawwwd..... he can't figure out a sigfile, but he's explaining how timing is set by the knock sensor.....

Pardon, I have to go wax the cat.

 

[Kevin Jewer]

Originally posted by Defiant
o mi gawwwd..... he can't figure out a sigfile

And you can't spell....

Read this:


Signature Rules
No mod lists, 1/4 mile times, car info, homepage link, etc - that stuff goes in your profile.
No vendor logos, links, URLs, addresses or phone numbers. Shop name is okay.
No half-naked models - no models period.
DSM related photos only, preferably your own car - no larger than 300x300 pixels.
A profile photo can be uploaded here.
Any text should be DSM or car related.
Animated files are not allowed and will be removed.

Your signature should only be used for a 300 pixel or smaller photo of your car and your name. That's all. Signatures may be modified or removed by moderators if they're found to be inappropriate.

Originally posted by Defiant
but he's explaining how timing is set by the knock sensor.....

Pardon, I have to go wax the cat.

Now, are you trying to tell me timing is NOT affected by knock? happened to this forum...

 

[Kevin Jewer]

I'm going to go a little more in depth, since some people are still having a hard time grasping this concept, despite the fact that it has been discussed to death on various forums for at least the last 3 years that I can recall.

People think that high EGTs equal high combustion temps, which would indicate a lean mixture. So when they see high temps, the typically add fuel. And when it is low they lean out. This method of tuning is flawed for various reasons, and I will touch on all of them.

Myth number one: The internal engine parts will melt at over 900 degrees C or 1650 F. Here is some big news. Combustion temps are over 2000 degrees and can reach 3 to 4 thousand. So why dont the parts melt? Just a few quick reasons. One is heat sink capacity. Two is heat transfer from the piston to the cylinder wall through the rings. Three is heat transfer to the oil that is splashed up or squirted on the piston and other parts. Four is heat transfer into the cooling system through the head or block. In fact, so much heat is taken out through these methods that by the time the combustion gasses get to the manifold and EGT probe, temp is down to 900 c or 1650 f ;o) Some heat is also lost in the conversion of heat energy to mechanical energy in the form of gas expansion. So that myth goes down the terlet.

Myth number two. If EGT is high the mixture is too lean. Well what happens when the mixture is (way) too rich? It is still burning as the exhaust valve opens. Fire in the manifold WILL heat up the probe. Not rocket science. I have seen a dozen people add fuel and add fuel and EGT temps dont go down. Lean out to where they are supposed to be though and its all normal again. I know it goes against the "Internet Laws of EGT Guages," but its the truth. Also, what happens when the mixture is WAY too lean? Temps go down. Why? Less fuel to support combustion. It is entirely possible to be so lean that combustion temps drop so low that there isnt enough heat energy to increase pressure enough to cause knock. I have seen this happen on my car after a baro wire mod gone wrong.

Myth number three. If EGT is too low, the mixture is too rich. Not necessarily, though this is way more possible than vice versa. It depends entirely on the setup. The more knock prone you are the more fuel you need. That slight difference in EGT temp will show itself if and only if you are getting maximum timing advance for your setup.

So what does the EGT tell you? I've said it a thousand times before, as have hundreds of other DSMers, but ponder this. You are knocking. For ANY reason, not just lean mixture. The knock sensor picks this up and reports to the ECU. Now this may be hard for some of you to believe apparently, but when the ECU senses knock, it pulls timing. The amount of timing it pulls will vary based on the "normal" knock sensor noise threshold, how strong the signal is, and how long it has been going on, among other factors. The ECU comes up with a kncok retard value, and that amount of timing is pulled back from where the full timing would be based on the timing map you are currently on. Here is what I mean by this. The timing map you are currently on is based on airflow mostly, but also coolant temp and intake temp and other factors. This map or table includes timing values for each rpm point. So lets say for where your car curently is, you are on a map that says at this rpm maximum advance would be 17 degrees. But knock retard is 3 degrees. What will your timing be? Get out the calculators. 14 degrees is what you will get.

Now what does retarded timing have to do with this... If the timing is retarded enough, as in LESS ADVANCE, the ignition event occurs LATER in the combustion cycle, in degrees of crank rotation. If the mixture is ignited late enough, it is still burning as the exhaust valve opens. Refer to "Myth number two." Fire in the hole will heat up the probe. THIS IS WHY high EGT temps mean that you are getting knock and reduced timing advance. Read it a few times. Let it soak in.

Furthermore, the amount of change in EGT temps per change in air fuel ratio is MINOR, while conversely, the change in exhaust gas temps is SUBSTANTIAL when the timing is retarded and there is fire on the probe. Why? The increased heat caused by a leaner mixture is mostly absorbed by the motor or converted to additional mechanical engery. The latter is the cause for the increase in power when you can lean out without knocking (<- key phrase, pay attention). By the time the combustion gasses get to the probe, the difference is now slight. In contrast, the difference in temps between normal exhaust gasses and fire is very significant and it show up easily on the guage. Now it is important to remember that the higher combustion temperatures caused by a lean mixture not only increase mechanical output, but increase a motor's (or cylinder's) tendency to knock. And again, this knock brings on timing retard, which brings on fire in the hole, which brings on a high EGT temp reported on the guage. THIS IS WHY poeple confuse high EGT temps caused by mixture with high EGT temps caused by knock. Because both usually happen at the same time when fuel tuning. You can also have one without the other, as is the case with mechanical knock or phantom knock.

So now that we got that straight...

Other reasons why EGT is not a good way to tune, without a logger. The ideal temperature will vary with EVERY car and EVERY setup and EVERY set of conditions. I do upwards of 300 drag passes a year and have clearly observed and datalogged this. With that established, the only way to find the ideal EGT temp for your setup/car/conditions/gear is to datalog to see what your timing is. At the point you develop knock you can get an idea of where you want EGT. The problem is, as I stated above, when you have full timing the difference in temperature effected by changes in air fuel ratio is very small. This is complicated even more by my next point:

EGT guages are not very accurate, nor are they precise. Yet another reason to need a datalogger to verify and validate what you are seeing on the EGT guage... The probes are slow to respond, and I will explain why. The rate at which an object changes temperature varies directly as the the difference between the temperature of the object and the temperature of its surroundings. In this case the object is the probe, and the surroundings are the exhaust gasses. What this tells us is that the greater the difference in the temp of the probe and the temp of the gasses the greater the RATE OF CHANGE of temperature. So as the temp of the probe rises (or falls) to match the temp of the exhaust gasses, the difference between the two temps is decreasing. This slows the rate of change. And the cycle continues... So as you can see this is not a linear function, its a curve. This is why poeple often say that the guage reacts slow, or to estimate how fast the needle is moving to estimate where it would really be if it was faster, etc. This is a fundamental problem for both accuracy (especially) and precision (not so much). Another problem is that in general they tend to fail on the low side, meaning they will read colder than what the case really is. So you'll lean out more and more. What happens then is you seem knock "easier" and the tuning window (based on EGT temps) becomes very small and touchy. I have been there, and done that. This is not the way I would choose to tune my car But if so many people insist this is the way to go, what can I say.

This is not rocket science. This is not new information. It has been documented, measured, qualified, quantified, and posted about for as long as I have been into DSMs. But not enough apparently. I am going to copy this into a file on my PC, so I can paste it into the next 500 posts I read about this. If I have to type all of this again I'm gonna snap...

 

[nine5raptor]

very informative, thanks for the time to put all of that down (you explained why I choose to never get an EGT, even though they are all the craze).

 

[snox135]

You are right egt gauges are not the best thing to tune by, kind of. With all the senors and other means of doing so on our cars there are better ways out there. But for motors you can't datalog you tune with your spark plugs and egt's. EGT's can be a usefull tool in the right hands and situation.

When your egt's get around 1600* the combustion temp. gets close to a range that will melt pistons. I have seen it done many times. Saying it won't is just completly wrong. For the situation where your egt's are high because you are running extremely rich. Well any person who can't firgure out that they are running that rich should not being "tuning" a motor.

 

[1gTURD]

95gsxracer... I second everything you have been trying to tell these people, but i must be honest, never once have i thought of an egt monitoring exhaust gas temp tells about ignition timing. Infact even tho i know ignition timing has alot to do with +/- af ratio, i never thought of using the egt to determine such things as knock (or even lack of showing knock)

bottom line is (now that i grasped this from your 1st post even) is that even if your "precious" egt reading is 900 or some other "ok to back fuel off reading" does NOT mean that you will not melt your pistons or snap ring lands, ect ect. even if the temp says "ok back fuel off.... its ok, your at 900 degrees" this does NOT mean that your ignition timing is so far advanced that ur getting knock...

Im sure i do not stand alone when i say THANK YOU for putting your 2 cents in here and even more so, the essay you wrote just to prove your knowledge to a few people who think whatever they read about egt's (amoung other things) on some forum must be true because of popular belief or "word on the street". im sure that u will save a few dsmer's engines just from posting in this thread, mine being one

thanks again, you are a TRUE dsmer, keep up the good work

 

[Kevin Jewer]

Originally posted by 1gTURD
95gsxracer... I second everything you have been trying to tell these people, but i must be honest, never once have i thought of an egt monitoring exhaust gas temp tells about ignition timing. Infact even tho i know ignition timing has alot to do with +/- af ratio, i never thought of using the egt to determine such things as knock (or even lack of showing knock)

I think you meant to say that EGT has a lot to do with AF ratio, but mistyped it. You arent alone on this. Many people do believe that EGT is only used to show AF ratio. On a NT car it is, but for turbo cars where timing is always changing based on knock, timing is the primary factor in EGT temps, unless there is no knock. Then it can be a decently reliable measure of af ratio.

Im sure i do not stand alone when i say THANK YOU for putting your 2 cents in here and even more so, the essay you wrote just to prove your knowledge to a few people who think whatever they read about egt's (amoung other things) on some forum must be true because of popular belief or "word on the street". im sure that u will save a few dsmer's engines just from posting in this thread, mine being one

thanks again, you are a TRUE dsmer, keep up the good work

Well, thank you for the kind words. Good to see that all the time I put into over a dozen different forums still helps people. After posting that i decided to put it on other forums too. It seems to be helping a lot of poeple, and its "sticky" on a few sites. I used to post here with an average of about 10 posts a day. But after a while I get tired of everyone arguing with me, and I would much rather work on the car with that time. I see a lot of other good posters gradually dissapear, I'm sure for the same reason. I think the issue is that too many people would rather argue on the internet instead of going out and actually testing these theories we argue about all day. That being said, this week I'll be installing HKS 272s, and logging the increase in airflow over the HKS 264s I ran for 3 months.

 

[Kevin Jewer]

Originally posted by snox135
When your egt's get around 1600* the combustion temp. gets close to a range that will melt pistons. I have seen it done many times. Saying it won't is just completly wrong.

It is very unlikely on a DSM that we will get temps hot enough to melt parts, without getting a ton of knock first. Nw, if you are not monitoring knock, it is entirely possible that you oculd keep on going and melt parts. But aside from this case (anyone tuning a DSM should be watching knock very closely), we are much more likely to damage pistons, rings, ring lands, and valves, from knock, than high temps. Now I have niether broken internals nor melted them, fyi. This is one case where I would rather learn from others than try it myself

For the situation where your egt's are high because you are running extremely rich. Well any person who can't firgure out that they are running that rich should not being "tuning" a motor.

I completely agree. But for someone tuning with just an EGT gauge they may have a hard time knowing they are rich. Even by watching O2 voltage it can be quite hard to know what you mixture is. I have seen many very intelligent poeple fall into the too rich/high egt trap.. I did too many moons ago, but realized what was happening and straightened it out.

 

[laser92awd]

I would say most people (including myself) do not want to hurt their engines, so they taking the mistaken tuning approach of "add fuel" rather than "lean it out" because that's what logic seems to tell you to do. I can say I was one who saw my EGT's come down noticeably after I started leaning it out. The key for me was to get my intake temperatures down since I'm running a sidemount i/c. That let me reduce / eliminate the knock so that I could stop dumping so much fuel into it. Now I get no knock, more timing, less fuel, and lower EGT's.

Before I was still in the "safe" zone, but was basically using fuel to try to combat the real problem of high intake temps. The more fuel I dumped in trying to reduce knock, the higher my EGT's went. It's MUCH easier to tune a car when you aren't getting any knock, IMO.

Jonathan

 

[jdk906s]

In light of everyone's issues around the EGT gauge, why the heck don't I see more people making Knock LEDs? Their cheap and easy. Even if my pocketlogger tells me knock count the knock LED is a lot more noticable.

EGT is important to, you just have to understand it, just like O2 readings.

 

[laser92awd]

For an alert / warning, a Knock LED may be a good idea, except I know it will activate at times other than actual WOT knock which may be distracting. For tuning I think the actual knock count is more important.

Actually, I wish I could have a system that tied all my warnings into one loud programmable alert. EGT too high, A/F too low, Boost too high, Knock too high. For that matter might as well throw in low oil pressure and high coolant temperature. That is too much information to try to watch during a run when you want to focus on driving and shifting.

The pocketlogger is getting there, but I can't hear it's alert under WOT on my Palm 100 and it only allows for one alarm trigger.

Jonathan

 

[Kevin Jewer]

Thats one good thing about DSMlink, it turns on the CEL when timing gets pulled 5 degrees or more due to knock. Good stuff. And its only activated by knock retard, unlike a knock led. The reason you dont hear more about thos is that over time people realized how useless they were...

 

[wira4]

Originally posted by 95GSXracer
Now what does retarded timing have to do with this... If the timing is retarded enough, as in LESS ADVANCE, the ignition event occurs LATER in the combustion cycle, in degrees of crank rotation. If the mixture is ignited late enough, it is still burning as the exhaust valve opens. Refer to "Myth number two." Fire in the hole will heat up the probe. THIS IS WHY high EGT temps mean that you are getting knock and reduced timing advance. Read it a few times. Let it soak in.

I am using a programmble ecu which does not do knock detection nor timing retard when knock occurs. I have no way of knowing there was any knock but I could see a high EGT of 1700F at WOT and noticed AFR of 12.3 :1 on the wide band. I was running 98octane fuel and timing was 17* advance. What causes the high EGT at such fair AFR on my 2G DSM? Boost was 28psi with the Green and intercooling is via an Evo 3 FMIC.

 

[chaye]

i just had to post on this one even though i have no clue on what your talking bout..but im learning
95GSXracer you are a god my friend i admire your knowlege and your writing style..damn..you a english teacher?
honestly dude your amazing..
so the bottom line would be that a datalogger tops all the other tuning devices mentioned here ..correct?

this post is like the discovery channel....freaking amazing :laugh: