For those that might want to know why those of us use EGT gages and Scoff at A/F gages.......


http://www.sdsefi.com/techegt.htm




Rocks

 

I am seeing about 1450 at WOT at the top of 3rd gear.

My readings might be slightly higher than yours due to the EGT probe being nearer the cylinder head.

I get about 800 degrees at idle as another reference point.

It is interesting to compare how mounitng points may affect temp readings.

here is some info on the different probes from autometer. The higher level ones are supposed to react more quickly to temp changes and be more accurate.

http://hp.autometer.com/products/acc...cessories.html

I think the one included with the gauges is the 5249 street series probe kit.

 

Your readings are the same I had before my built short block and Kenne Bell.

I did the block and Kenne Bell about a month ago. Granted, we are still working on the tune, but the EGT pegs at 1200 now and runs as low as 800. I really am thinking it should be higher, but like I said....it is a work in progress. I can tell you that right now, I am not making the power I feel I should for my Mods. At 16 lbs of boost....my best 1/4 time is a 11.84 with this configuration. I got an 11.81 on my stock motor and heaton with 16lbs of boost.

I feel that the exaust gas temp is telling us that we are possibly not getting a complete combustion.....we will see though.


Rocks


Oh...thanks for the link...I'll check it out.

 

I would investigate spark blowout and coil pack issues. Your diagnosis of incomplete burn seems correct to me.

 

Those where my first two moves. I put in new coil packs and have been dropping the gap down. I am at .030 with my IT22's right now. I am about to try a different brand of plugs with a larger flame front.


I picked a bad time to be jerking around with my truck though. I am running in the FFW series, trying to hit them all....so time for tuning and major changes is limited. Right now I am most concerned with being consistent.....

Thanks for the help.......


Rocks

 

Good read, but I don't see anything in there that would make me scoff at wideband A/F gauges.

The only negative thing I read was that the sensor would fail quicker if used with race gas and the EGT sensor would not. I have no experience with EGT gauges, and just very little with the wideband i just got, but like that article stated it would be nice to have both.

 

Maybe choosing the words.."scoff at", was not exactly accurate.

Rocks

 

Would a EGT gauge be able to detect bad gas. For example if the gas didnt have enough Octane would the EGT start to rise and thus warn you that something was wrong. I dont think that a wideband can tell the difference between octane it just knows how much fuel is there.

With a Wideband I can plainly see at what RPM I need more fuel, how would an EGT gauge help you in this situation? Is it sensative enough to give you quick changes as the RPM rises?

I might add a EGT to my list of gauges.

Thanks
Mike

 

Mike.....I will take a shot at answering your question. If your octane level is too low for the timing you are running...your exhaust gas temps will start to rise. Heat is what causes detonation. For instance, knowing that you are running 1450 degrees if your engine is performing properely, you would see the exhaust temps start to hit 1500 degrees or higher and know that you need to get the heck out of the throttle.

The inverse is if you are seeing 1200 degrees you know, like I do that you very well may not be getting complete combustion and are not making the power you could be.

The readings are instant since your seeing the temps coming right out of your exhaust.

The point is...heat causes detonation. Lean A/F causes heat.

I may have just over simplified it...but that will get ya started. Check out the link above. I will look for some others I have and post them in a bit.


Rocks

 

Sorry it is taking a few minutes...I am on a different laptop than my usual one. I am having to look at it and then come back on this one.


This is in reference to 4 cycle motors, but the princables are similar. http://www.foxvalleykart.com/egt.html

 

I am a big fan of EGT. Plainly put, heat hurts parts. Keep the heat under control, while creeping up on it (temps) slowly, all the while your MPH/ET picking up, you are going about it the right way, and you will not hurt any parts. I tuned my 9.11/154 MPH Mustang strictly on EGT, never going on a dyno. EGT can not tell you much regarding how much timing to run. However, I've never detonated an engine that I was running EGT gauge on (too expensive of an engine). That's generally an octane vs best-power setting. In my opinion, you could use EGT at the track, tuning your fuel mixture for MPH/ET and never visit a dyno. I've already done it that way. And since O2 sensors give innaccurate readings when they get lead on them, I'd rather stay with EGT anyway. They don't give erroneous readings; they simply quit all together when the probe goes bad.

 

Well mistergadget,

You caused me to get off my lazy **** and go look. My probe is actually about an inch further down than yours, right at the first bend......... #5 cylinder of coarse.


Rocks

 

I used to have regular conversations with an automotive engineer who designed and sold aftermarket turbo kits, with about 25 - 30 years of experience. He gave many examples of how using only an EGT could be VERY misleading. His recommendation was first to have an a/f ratio. After that, an EGT could be helpful.

Sorry to say, I fully believe the wideband A/F guage is quite a bit more important than an EGT.

 

More good info, thanks guys. Have to get around to installing my gauge before the new reflashed computer comes in.

 

I think a wideband a/f monitor is a great tool. Wouldn't replace that with an EGT. However an EGT is a 100% better alternative than using a stupid A/F gauge like the autometer ones that are just light shows.

The EGT is a great alternative because it allows you to monitor the most critical part of your motor at much less cost than a wideband. I think the best setup for most people is to have an EGT in the truck and use a wideband on the dyno. KEep track of where your EGT usually is on a safe tune, if you see it getting hotter or colder than usual that is indicative of a problem. I use the EGT in conjuction with a fuel pressure gauge (that would tell me instantaneouly if something happened like the hi-lo pump relay failing, with low fuel pressure and an EGT spike at the same time)

REmember EGT can also change with weather, like anything else by itself it's not the greatest tool to use, but in conjunction with others it helps to give a much better complete picture when using this gauge.

The only thing i would replace my EGT with would be a wideband commander, but I'm holding out for those to come in the lunar series.