More accurate??? EGT or Narrow A/F
11-26-2003, 05:38 PM
#1
Drive-by provocation guy
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More accurate??? EGT or Narrow A/F
Which is more accurate, an EGT guage or narrow band (standard) air fuel guage?? In terms of accurate air fuel readings??
Yes, I know a dyno or wideband is the most acurate.
Yes, I know a dyno or wideband is the most acurate.
11-26-2003, 07:09 PM
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Thats what I thought. And at this price :
MICROFLIGHT EGT
Includes probe
2-1/4", 600-1700°F
P/N EG004 $64.000
Hard to go wrong.
MICROFLIGHT EGT
Includes probe
2-1/4", 600-1700°F
P/N EG004 $64.000
Hard to go wrong.
11-26-2003, 09:18 PM
#6
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If its a choiced between an air fuel ratio gauge (regular narrow band) or an EGT, I'd go with the a/f ratio gauge.
EGT alone can be dangerous as temps will be the highest at stoich, then go down on either side from there (leaner or richer). If you don't know which side you're on, you could keep leaning the engine out thinking that because the EGT's are going down, you're going the proper direction with the a/f mix, when in fact, you should be going the other way..... a very easy mistake to make for sure.
TonyG
EGT alone can be dangerous as temps will be the highest at stoich, then go down on either side from there (leaner or richer). If you don't know which side you're on, you could keep leaning the engine out thinking that because the EGT's are going down, you're going the proper direction with the a/f mix, when in fact, you should be going the other way..... a very easy mistake to make for sure.
TonyG
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11-28-2003, 12:24 AM
#10
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toddk911
They just do... (at least on a 4 cycle gasoline engine).
There are many articles written at length about this subject. Just search google.
TonyG
They just do... (at least on a 4 cycle gasoline engine).
There are many articles written at length about this subject. Just search google.
TonyG
11-28-2003, 09:42 AM
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Oh, Tony, how much of a temp change do you notice when a/f changes??
i.e. 10, degrees 20 degrees, 50 degress??
Assuming this was not used for tuning but just a saftey deveice, how much of a degree change would there have to be for you to know something is wrong??
i.e. 10, degrees 20 degrees, 50 degress??
Assuming this was not used for tuning but just a saftey deveice, how much of a degree change would there have to be for you to know something is wrong??
11-28-2003, 08:54 PM
#13
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toddk911
The gauge I have (the Autometer) is a analog gauge with a range of 0F - 1600F.. all in a 270degree needle sweep. Thus the resulution is not really fine enough to tell a 10F change. You can see a 25F - 50F change, but the problem is that at least on the street or track, you can't really sit there and stare at the guage if you know what I mean.
>>>how much of a degree change would there have to be for you to know something is wrong??<<<
Over 1550F. If it goes past that by much, there's a problem. 1600F is too hot for sure. I try to keep it at 1450F to 1500F.. maybe 1525F... but that's it.
TonyG
The gauge I have (the Autometer) is a analog gauge with a range of 0F - 1600F.. all in a 270degree needle sweep. Thus the resulution is not really fine enough to tell a 10F change. You can see a 25F - 50F change, but the problem is that at least on the street or track, you can't really sit there and stare at the guage if you know what I mean.
>>>how much of a degree change would there have to be for you to know something is wrong??<<<
Over 1550F. If it goes past that by much, there's a problem. 1600F is too hot for sure. I try to keep it at 1450F to 1500F.. maybe 1525F... but that's it.
TonyG
11-29-2003, 01:48 AM
#14
If you want to do some research into EGT vs. A/F, just look into Aircraft instrumentation. Most gas engines in aircraft have the ability to adjust A/F ratios on the fly. This is required to get the best performance i.e. HP for take off and then get the most MPG for range. Most Aircraft engines monitor both head temperatures and EGT.
The Max EGT temp occurs at close to Lamda=1. If you go leaner, the EGT drops as you start into detonation. Why, because detonation causes heat to be transferred into the head and pistons, lowering the EGT and slowly destroying the engine. EGT also drops off when Lamda< 1. This results in a richer A/F ratio, but this is where the max HP is obtained. So, EGT by itself can't determine the best setup for the A/F ratio vs HP.
My thoughts. Use a WB monitor to determine the EGT for the desired A/F ratio, then rely on the EGT. The EGT is bulletproof, the WB is fragile.
The Max EGT temp occurs at close to Lamda=1. If you go leaner, the EGT drops as you start into detonation. Why, because detonation causes heat to be transferred into the head and pistons, lowering the EGT and slowly destroying the engine. EGT also drops off when Lamda< 1. This results in a richer A/F ratio, but this is where the max HP is obtained. So, EGT by itself can't determine the best setup for the A/F ratio vs HP.
My thoughts. Use a WB monitor to determine the EGT for the desired A/F ratio, then rely on the EGT. The EGT is bulletproof, the WB is fragile.
Last edited by Bri Bro; 11-29-2003 at 02:19 AM.
11-29-2003, 03:05 PM
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I understand the whole theory about dropping temps on the EGT gauge, but are you guys really saying that a "Narrow Band A/F Gauge" is better than an EGT? I seriously have to disagree here. I've seen three different narrow bands installed on three different cars and all were pretty much useless outside of idle.