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Old 02-24-2006, 07:34 PM   #1
drkg
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Member#: 108441
Join Date: Feb 2006
Location: Twin Lakes WI
Vehicle:
'02 WRX

Default Gages: EGT or AFR

Which is a more important engine monitor/tuning tool
Part of this spring's round of mods is going to be putting in some gages to help me watch what my engine is doing. I can't decide which will be more useful in monitoring my fuel ration: an acutal AF gage or Exhaust Gas Temp. My Buschur Racing TBE icludes a high flow cat(emmissions testing), and I'm using a factory O2 sensor.
Also, since its the first set of aftermarket gages I'm installing in my WRX and I'd like any others I may add later to match what I'm going to install now- this would be the perfect time to take reccommendations as to which brand to use. I'm leaning toward Stewart Warner.
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Old 02-24-2006, 07:38 PM   #2
-Kevlar-
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Chapter/Region: South East
Location: SC
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an A/F ratio gauge is, for lack of a better term, a light show. its fairly accurate, but i wouldnt trust money on it. for more accurate readings, monitoring, tuning, get a egt gauge. (and a wide band O2)
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Old 02-24-2006, 09:19 PM   #3
drkg
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Thanks. That's kind of what I was figuring, but I don't like to buy anything without getting at least some recommendations.
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Old 02-24-2006, 09:54 PM   #4
powerlabs
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Location: New Jersey
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I have both.
Air fuel ratio is indeed useless, unless you get a wideband one. I own a PLX Devices M300 and I will never attempt to modify another car without of of those; it is just so incredibly useful! It will tell you almost everything you need to know, instantly, and with extreme accuracy.
I also have a Greddy Digital EGT gauge. The probe is mounted right at the meeting point of cylinders 1 and 3, some 2 inches from the head.
It reads its highest at high speed cruise; 90MPH in 5th will show 810C when the AFRs are close to 14:1. If I nail the throttle boost builds, the AFR will *instantly* drop, but the EGT takes a while to get moving. Similarly, if I floor the car from a low speed the AFR will respond in a microsecond, but it may take 5 seconds untill the EGT probe has warmed up to the real temperature of the gases going around it. It just takes time to heat things up; there is no way around it.
As such I will say that, for experience, an EGT probe is nearly useless. If your tune is bad enough that it will cause unsafe EGTs, your engine will pop before you ever get to see them. AFR is a much faster way of knowing what is up inside your engine.


Gauge pillar: Boost and EGT (top and bottom)
Center Pod: Apexi S-AFC-2 (Knock, air/fuel ratio control, engine RPM, %airflow into engine, battery voltage)
Ashtray (under stereo): Wideband Air/Fuel Ratio.
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Old 02-24-2006, 10:23 PM   #5
cdvma
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2009 BMW X5

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Quote:
Originally Posted by powerlabs
As such I will say that, for experience, an EGT probe is nearly useless. If your tune is bad enough that it will cause unsafe EGTs, your engine will pop before you ever get to see them.
I disagree. If you get a probe that isn't slow like molassas in January you will see EGTs in very close to real time. I've had great AFRs and a non-agressive timing curve (street tuned) but watched my AFRs skyrocket quickly. A little more timing I was all set. I wouldn't have known this without my EGT gauge and would probably be posting "crap, lost a ringland" by now if I haven't had it. IMHO if you are tuning you need a wideband and EGT to do the job properly.
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Old 02-25-2006, 10:04 PM   #6
jigga
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2002 Impreza WRX
WRBlue Perl

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Quote:
Originally Posted by powerlabs
I have both.
Air fuel ratio is indeed useless, unless you get a wideband one. I own a PLX Devices M300 and I will never attempt to modify another car without of of those; it is just so incredibly useful! It will tell you almost everything you need to know, instantly, and with extreme accuracy.
I also have a Greddy Digital EGT gauge. The probe is mounted right at the meeting point of cylinders 1 and 3, some 2 inches from the head.
It reads its highest at high speed cruise; 90MPH in 5th will show 810C when the AFRs are close to 14:1. If I nail the throttle boost builds, the AFR will *instantly* drop, but the EGT takes a while to get moving. Similarly, if I floor the car from a low speed the AFR will respond in a microsecond, but it may take 5 seconds untill the EGT probe has warmed up to the real temperature of the gases going around it. It just takes time to heat things up; there is no way around it.
As such I will say that, for experience, an EGT probe is nearly useless. If your tune is bad enough that it will cause unsafe EGTs, your engine will pop before you ever get to see them. AFR is a much faster way of knowing what is up inside your engine.


Gauge pillar: Boost and EGT (top and bottom)
Center Pod: Apexi S-AFC-2 (Knock, air/fuel ratio control, engine RPM, %airflow into engine, battery voltage)
Ashtray (under stereo): Wideband Air/Fuel Ratio.
Thats funny..... it looks like on your speedo, after the 80mph mark, the next indicated speed is 400mph.....
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Old 02-25-2006, 10:57 PM   #7
the_colombian
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Chapter/Region: SCIC
Location: San Diego
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2003 2.5L bugeye now
with 6 spd 20g!

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^ haha, your right,looks like 400.
I agree with powerlabs, if you have the money, get a wideband.
zietronix offers an awesome setup with little cluter, it includes AFR, boost, egt and lambda in a small, yet readable screen. I love mine. for all it does, its very cheap.

Last edited by the_colombian; 02-25-2006 at 11:05 PM.
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Old 02-25-2006, 10:59 PM   #8
hondaeater69
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if you're going to tune your own car, you need a WB. If you just want to monitor things, get an EGT.
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