My piano shop is in the air park here in GAithesburg MD, and one day a helicopter mechanic came in asking for scrap ivory for a guitar he was making. I gave it to him for free, and we struck up a friendship. The next time he came back we got to talking engine tuning and he shared an idea with me which I will relate here. I don;t have it completely right yet, but I know where he works, and will go write it down and come back and share it. It goes like this:

When an airplane pilot flies, he watches an EGT gauge, and watches the temperature. There is a certain pattern of warm up that he watches for. He continues to lean the mixture until the temp reaches this certain pattern, and then he dials the mixture back up until the temperature goes down 50 degrees from this point. He is then set for maximim cruise economy. There is a certain degree of saftey built into this procedure to accomodate changes in mixture if he has to reduce altitude. I will talk about this when I go back.

So, you guessed it, I ordered an EGT gauge. I am thinking of installing it on cylinder number two since I can get to that on the Dutra Dual with out removing anything but the intercooler tube. Any knowledge or advice out there about how far from the valve to place it?

It seems that this would be such an easy thing to program into an ECU, you really wonder why the auto industry has not followed the airplane industry's lead here. Maybe it would not pass emissions if run too lean.

Sam

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Many racers use a EGT gauge as a tuning aid. I had one on my turbo slant, back in the early 80's. It was between the exhaust manifold and the turbo inlet. I used a aircraft type, as that was all that was readily available, at that time. Today there are many sources, and many types. It is even possible to install a thermocouple in each exhaust port, and "data log" all cyliners at the same time. This will help to determine, cyl to cyl fuel distribution.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Tuning large diesels involves monitoring EGTs and Maximum firing pressures. (We are talking 10"bore 10"stroke V16 3000 hp)

Run engine for 1/2 hour at maximum revs....check exhaust pyrometers for each cyl and record.

Check firing pressure on each cyl . ( around 800 psi at 24psi boost)

Adjust each injector individually to achieve the ideal firing pressure at the optimum pyrometer setting at max RPM. (it takes seconds to change the temp...pressure changes instantly)

Lower RPM to normal operating range. Recheck pyrometers to ensure even temps.

Ideally you need a pyrometer for each cyl.

We used to do 2 - 16cyl 3000hp prime movers in an hour.


You can buy infra red pyrometers that are hand held and can "probe"each exhaust branch.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

EGT sensors react to a couple things - they respond to both fuel mixture and ignition timing. They're often used on engine dynos for reading cylinder to cylinder mixture variations, with each bank having a wideband oxygen sensor to read the overall air/fuel mixture.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

EGT is not as good a tuning tool for a car as a wideband o2 sensor and I know you already own one of those. EGT responds more slowly than the wideband and are affected my more than just A/F ratio. Aircraft engines are operated mostly at 60% load and above. Auto engines usually operate under light load. Most gasoline engines are never operated lean of peak. Regular catalysts don't operate properly with excess o2 so emissions soar. Would you ever run your turbo engine with a lean mixture under boost? Pilots do it all the time. The problem of running lean under boost is maintaining a safe TIT (turbine inlet temperature), but an auto engine runs rich under boost because maximum power is desired and it's safer. A greater mass of a lean mixture maxes more power than a smaller mass of a rich mixture. This is a very complicated subject and I've only glossed over a couple of points.

So tell me again why you bought an EGT gauge and thermocouple?

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Joshua

I have been cruising and tuning leaner and leaner as I get more comfortable with the drivability of the car familiar with the affect leaning the mixture has on the way the car feels on the road. So far I have gotten the car to drive pretty nicely on the highway at 16-17:1 at highway speed. And the mileage has gone up as a result. So the question is, what is the upper limit of this? You certainly can go too lean here. I guess it would start lose power at some point, but that might be hard to tell by the seat of your pants. You can;t use the AF ratio, since I am already way leaner than stochiometric as it is. AF ratio can be known, and quanitfied, but it no longer a guide. So how far is too lean?

I have talked to car tuners who have used EGT to tune for cruise economy, but never asked how they did it. That did not seem relevant to me at the time, since I had no way to tune AF ratio easily anyway. The guy who sold me the ACcel system in the first place, said he uses EGT to tune.

I went back to the chopper mechanic, Wayne today, and had a long discussion with both the him, and the pilot. Here is how it works. You slowly lean out the mixture and watch the EGT go up. At some point, it will max out, and actually go down slightly. At that point, you enrich the mixture and watch as the temp goes back up to it's previous peak, and continue to enrich the mixture further until the temp drops again to 50-75 degrees below it's peak. That is the leanest safe mixure. At that point, I could look at my AF ratio meter and see what mixture actually was the most economical.

The pilot races go carts, and they use a similar system to tune their carts, but they use it in power applications.

The temp they end up with is usually around 1400* or there abouts, but it varies depending on fuel, barameter, and temperature. The temp would vary for a car, but the barameter would vary only a small amount compared to an aircraft. The fuel would vary as well, depending on the time of year, grade of gas, and age as well. So I am going to give this a try. I will report back what I find out. I don;t intend this to be a part of tuning for boost.

Sam

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Of course you can use A/F ratio when tuning for best economy. That's the beauty of the wideband. You can lean it out until it misfires. More modern engines can often tolerate 20:1 A/F.
Well, EGT has more variables than A/F ratio from an o2 sensor. Outside temp affects the EGT reading directly, but the resulting change in air density also changes the A/F ratio. An o2 sensor reads A/F ratio directly and eliminates one variable. A lower compression engine will have higher EGT than a similar engine with a higher CR or more correctly, a higher expansion ratio. It's a bit easier to come up with a target A/F ratio than a target EGT unless the combination is well known and extensively tested with EGT.

If all your injectors flow the same then the fuel part of the A/F is equal for each for each cylinder, but differing air mass upsets the ratio from cylinder to cylinder. Unless you have EGT or an o2 sensor for each cylinder you can't correct for individual sensors becuase you just don't have the data.
You sure about that? 75 degrees rich of peak is usually close to lean best torque which is the minimum fuel required for best torque, not best economy. Read this: http://www.gami.com/future.html
Sounds like you got the EGT tuning story for power not economy.
Care to know what a Mazda rotary runs for EGT? They have such a poor expansion ratio thermocouples don't last very long. Pumping all this energy out the exhaust is also why they get bad mileage and are really loud.

Don't try to run under high load conditions close to stoichiometric. Not being lean enough can cause problems very similar to not being rich enough. I would say lean it out only with 6.5" manifold vacuum maybe more.

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Joshua

Sam, here is a artical you should read. In this artical they explane how they run there engine to lean side of this peak. I understand that your guy is saying to run it to the rich side of the peak, and that is probably safer, and is normal practice with most pilots. But this whole artical
( three pages if you look close) explains the whole process,reasons, and problems that can be incountered.


It is called the WAD procedure. I recamend you read the artical a few times as it can be a little hard to follow. Also when they start talking about fuel mixture they are refering to Gallons per hour, and not A/F ratio. Although it was/is how they determan mixer and relates to A/F even though that it is not what they are measuring. So dont misstake there 12:1 fuel mix as 12 to 1 A/F, it is not.


http://www.gami.com/future.html



Oh yea, be very careful because EGT gauges can react a little slow some times.


Jess

Jess that was absolutely cool, and another example of why this slant forum is so awesome. That was a huge help. The good news is that it shows that the EGT curves are very close to the dyno curves on their graphs. That has got to be worth alot. I also understand that how you use the throttle in an aircraft is very, very different from in a car. The aircraft is kind of like having a super high stall torque converter.

I understand now, that these pilots are indeed tuning their engines for max HP at 65% power. I also understand that IF the cylindars are absolutely balanced, (which is not likely to happen with a batch fire MPI), the engine will run rough on the lean side of peak EGT, but not run rough on the Rich side of peak EGT. The rich mixture masks uneveness in firing in a way that lean does not. Beyond a certain point as you lean it out, the temp begins to drop bck down, which would be great if it continued to run smoothly. This explains why there is greater potential with sequential tuning than batch fire, if you tune it correctly. So there you are. I will still put the EGT gauge in, and pay attention to it as I play with the tuning. Maybe some day I will go for the sequential setup, which really only needs the right ignition triggers to work. Thanks.

Sam

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I read about a guy in mopar muscle that was running a turbo Ply Acclaim in drag races and was really kicking butt(low 14's in the 1/4 IIRC). He was using EGT to regulate how much boost to allow from his turbo. He said to keep the EGT below a specific temp(I dont remember what it was since I dont run a turbo) so you dont melt pistons. Again he was looking at max power not economy.

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Sam,

What kind of mileage are you getting now?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Me Dale Rose, and Norm all use autometer pyromnters or egt temp for our tune up. This on race cars and wide open throtle is what we look at. I use to look at plugs ect to see rich or lean settings. The pryo is more accurate and is instant response. They burn methanol I use 110 oct racing fuel. Thanks Ron Parker








It Aint Over Until I Win

So far I have not been driving it in conditions that make mileage checks very meaningful. Most of the driving falls into two catagories: Either driving to work 4 miles, in which it just barely gets warm, or out tuning on it. It spends a fair amount of time when I get back from work, idling as I tinker with the timing and fuel maps. I have calculated as low as 15 MPG and as high as 29, but feel both those numbers aren't very real. I think tomorrow morning I am going to fill it up and take a long drive just to get a baseline figure.

Right now it has gotten suddenly cold, and it would not start after work because the pre-start fuel is not tuned yet in that temp range. Until I have a couple of weeks of cold weather, I will not be able to dial it in for the really cold start tune. It did start finally. With the Accel, you can actually give it a shot of fuel by pumping the pedal twice real fast before turning the key, just like with a carb. I was afraid to do that since I thought maybe I had flooded it already.

Sam

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I use EGT's for my snowmobiles. The thing to keep in mind is, the temp alone means nothing. You must tune first then associate the EGT temp to a proper tune. Chek you plugs first then record the temp. Higher octaine fuel burns colder then cheap gas.Compression, timing,and octaine go hand and hand. Placement will matter only when you compair with someone else. It is just a referance mark, other than knowing when aluminum melts
excample: sled tune right on- 11-1 comp 89oct = aprox 1226'
14-1 comp 114oct= aprox 1045'