Why do we use A/F Ratio as opposed to Exhaust Gas Temp?
From what I have seen and heard A/F gauges are not exactly the most scientific and accurate systems in the world. It’s understandable. Its very hard to accurately measure A/F ratios with A/F ratio monitors supplied with dyno’s and those for the most part are stand alone “units” that are by no means compact and simple. When dyno testing the smallest of things can skew the A/F ratio results. It is of no surprise then that a simple A/F ratio gauge will have a hard time keeping up and being as accurate as lets say a tach.
I would like to run a small, preferably flat LCD type A/F monitor that I can hide in my dash somewhere opposed to a 2 3/8” gauge that I will have to mount out in the open. Anyone have something like this? Happy with it? What is it?
Now for the other part of the question. Why aren’t “we” (as in hot rodders) just using EGT gauges? From what I know, and that may not be everything you can tell if you’re a/F ratio is lean or rich simply by the exhaust gas temps. And EGT’s are very accurate and quick to react to changing conditions. All my “Pro” snowmobile buddies use EGT gauges on their sleds, 2 stroke or 4. They even talked me into running one but I have not ridden the sled since I put it on.
So who is running a “stealth” A/F ratio gauge? Does it seem accurate and fast to react to changes? Any other input?
And why aren’t we keeping an eye on our fueling with an EGT which I don’t think can be argued is a lot more accurate ad fast to react to changes. I think they are less money too.
So there ya go, a photo negative of an Oil, header, gearing, CAI, etc, etc, etc post. Something that can be researched, discussed and debated. And maybe someone is an expert on the subject.
Bottom line I would like to be able to keep track of my A/F ratio or EGT in a stealthy way and as accurately as possible. For those of you with gauges, etc school me.
Thanks!
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From what I have seen and heard A/F gauges are not exactly the most scientific and accurate systems in the world.
Not really true OEM's spend lots of money on AFR monitors its vital for emissions and performance reasons. I can guarantee they spend WAY more than $300 for AFR monitor, hence when you say they aren't the most scientific you mean the $300 units aren't the most scientific. The absolute best consumer unit is the NGK AFX. They have a LCD display but its fixed to the unit, I don't know if you could somehow take the display out and relocate or not.
Fueling by EGT alone is tough, as there are way more variables that affect EGT than affect AFR, clear down to the input temp of the incoming air. The one thing EGT is decent about telling is a lean cylinder if over all AFR is correct and you have one hot cylinder it is more than likely lean, and your other cylinders are slightly overly rich to make up for it.
There are some vehicles that run closed loop (meaning about 14.6 AFR) all the time and they still keep EGT's in check with other variables.
The reason snowmobilers use EGT's is because the same reason Mustang guys use AFR. This a keep up with Jones's / monkey see monkey do society and if one guy has it there must be some important advantage that its giving him so I want one. I would be interested to hear the snowmobilers answer to why he shoots for a certain EGT temperature.
To be honest you need both to do it half assed right, if that makes sense. EGT an AFR are actually two totally different things, your fueling can be spot on and you have high EGT's. Since high EGT's is usually what everyone worries about that monitors EGT's.
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93 Cobra Supercharged 342 Vortech T-trim...all sorts of stuff, by Thrill Ride Unlimited Mt. Vernon Oh.
To be honest you need both to do it half assed right, if that makes sense. EGT an AFR are actually two totally different things, your fueling can be spot on and you have high EGT's.
Right. I run dual widebands and dual EGT probes. Timing will also affect EGT. The sensors on the market now are actually very accurate when paired with a good controller. The bosch LSU4.2 sensor is the same one that VW and Cadillac use to run closed loop wot. No free air "calibration" bs with them. Here is some more info. EGT Explained http://www.tricktuners.com/TT%20Pict...Technology.pdf
It would be great to hear a tuners veiw on this subject.
You've heard from 2 already. Myself and jgorm.
Quote:
Originally Posted by Muckerpuck
The DSM guys add EGT's For tuning their stand alone fuel controllers.A land where W/B's are seldom used.
I wouldn't hang my hat on anything most of the DSM guys do, no doubt some of them know whats going on, but remember the monkey see monkey do thing....BIG TIME
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93 Cobra Supercharged 342 Vortech T-trim...all sorts of stuff, by Thrill Ride Unlimited Mt. Vernon Oh.
If you are looking for stealth you can't beat the dm-200 obdii gauge in my mirror (avatar). It can display up to 4 parameters including AFR and EGT if you have the right modules. DM-200 pictures
I had a zeitronix for a while, but i didn't like the display. The datalogging is cool, and recording the max boost and egt was cool too. pic of zeitronix under my radio
If you are looking for stealth you can't beat the dm-200 obdii gauge in my mirror (avatar). It can display up to 4 parameters including AFR and EGT if you have the right modules. DM-200 pictures
I had a zeitronix for a while, but i didn't like the display. The datalogging is cool, and recording the max boost and egt was cool too. pic of zeitronix under my radio
I always like the plx units also. But that is a trick way to mount the display. Nice.
Can the plx display knock? I know the from the pontiac side of things they couldnt read knock yet.
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"I've got Cars, Guitars, And Guns. If your lucky, you'll only see the business end of Cars and Guitars". ZZ Top.
Squidd, you really need to find something to do with your time besides sit around and think of this stuff LOL.
I have had EGTs on everything tweaked up that I owned up to my 06 Stang. On my sleds, all it did was tick me off. Especially on my 205hp Thundercat. Was always in the carbs.
I had a very successful and well known sled racer tell me it was a waste of time and money to have EGTs on my sled. He told me the piston will melt under WOT before you can react to the Digitron reading. I also ran Top Fuel type exposed tip T/Cs on my stuff for the fastest response time.
Also had an EGT on my diesel Super Duty because I was always messing with it.
Now, to answer your main question...why don't more use it? Because most don't know what they should be looking for as far as temp goes.
Here you open a can of worms. Once again, you know what I have done for a living in the past. I have run V8 F/I engines with as many as 16 egt thermocouples. Port, collector, pre-cat, post cat, cat brick 1" from face and front and back, etc. etc.
With AFR it is easier to install, more common for DAQ, and the safe "zone" is more widely known. Start installing EGTS and you are going to have to know what your safe temp is for your config. Long tubes, cats, no cats. If you have a turbo...then pre and post turbine. And where in the pipe to located it for the temp you are after. I say 4" pre cat and limit to 850ºC.
Also as was said, inlet temps. If you really want to use your time and have gauges, start trying to get a better CAC. Monitor temp in & out on a charge cooler and try to get a greater delta.
While your at it, find a spot for an Exhaust Back Pressure reading, that REALLY changes exhaust temps LOL
By the way...will you please quit making me think!
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2006 Legend Lime GT: Samco, Metco, LPW, Brembo 6 pot brakes with floating rotors, Magnacharger with 8-Rib, LubeLocker, Royal Purple, FR500S front end, APR Performance Carbon Fiber Rear Wing, Roll bar, 10 qt upgraded oil system...Thank you Capaldi Racing for all your help! 2007 Mustang GT/CS : Wife's Car, Magnacharged too. 1966 Mustang GT-K Code Coupe: Restored
I have run V8 F/I engines with as many as 16 egt thermocouples. Port, collector, pre-cat, post cat, cat brick 1" from face and front and back, etc. etc.
DAMN! and i thought i was a data junkie! Nice job!
DAMN! and i thought i was a data junkie! Nice job!
That was a previous life (career), when the Detroit Auto Biz was doing good. Not much use for dyno techs on the outside anymore, all the car companies brought the stuff back in house. Been all downhill for people in my line of work since about 2007. Hence self employment. And to go to one of the former Big 3 as a contract worker won't pay the bills. About $14.00 an hour less than direct hire.
My record I think was the 2010 Duramax development I was running in 2006.
Dyno computer with 2 screens / Adapt CAS Combustion Analysis w/all 8 cylinders tapped for pressure / (2) Horiba Mexa 7100 DEGR Emissions Benches / AVL 415 Smoke Meter / ETAS INCA (Bosch) PC for ECU Control / 2nd INCA for diesel aftertreatment, 2 stage turbo and EGR control. Pretty much $1.5 Million in test equipment and test cell.
I think it was about 128 channels of data, (7) computer screens and (6) computers. And all the junk had to communicate with one another so when a data point was logged it was all there. What a freakin' nightmare.
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2006 Legend Lime GT: Samco, Metco, LPW, Brembo 6 pot brakes with floating rotors, Magnacharger with 8-Rib, LubeLocker, Royal Purple, FR500S front end, APR Performance Carbon Fiber Rear Wing, Roll bar, 10 qt upgraded oil system...Thank you Capaldi Racing for all your help! 2007 Mustang GT/CS : Wife's Car, Magnacharged too. 1966 Mustang GT-K Code Coupe: Restored
Why do we use A/F Ratio as opposed to Exhaust Gas Temp? 
