EGT Trace

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Marty Davis

Marty Davis

Well-Known Member
Joined
Sep 25, 2004
Messages
2,445
I have been working on a revision to the Engine Analysis Software and have studied this EGT Trace a lot. What is shows is several laps of my 20 hydro while logging EGT in the fat part of the pipe during laps around the course. I have removed the data that occurred before I started lapping and that data after I completed lapping. The EGT value shown is red is the time that the boat is in the turns and shows an increase in EGT due to loading of the engine. The early laps are shown first and you will see that the EGT steadily climbed as the boat ran. I was leaning the mixture control as I ran laps in getting the mixture to a perfect setting.

As far as I know, this kind of data has never been presented openly. I decided to do this so that it would spur some activity with people studying building their own pipes. This should answer the question specifically as to the EGT while running on the course.

One note that is not apparent is that as the mixture control is leaned, the segments in the turns decrease. The speed of the boat has increased to the point that it is taking only 2 segments to get through the turn rather than 4. :)

Maybe someone will do a statistical analysis and discover even more information.

Hope that you enjoy this as much as I have.

Would be interested in comments or interpretation of the data.

Marty Davis

EGT_Trace_Course.gif
 
Last edited by a moderator:
Terry Keeley said:
Very interesting data Marty!
Any idea how long the "segments" are?
Click to expand...

Terry:

I guess you could approximate by figuring what each turn is. Does the length of each segment matter??? I could probably back into the time in the turn if you think there is some reason to figure it out.

Brian Callahan timed a lot of turns as as separate item, but I don't know what they were off hand.

Marty
 
Last edited by a moderator:
Marty,

Thanks for sharing your data.

Were you still leaning the needle at the point where the last corner segment was recorded?

I'm curious to know if the cornering segment recordings eventually level out of if they continue to increase when the mixture is not altered via the 3rd channel.

Obviously with our crude fuel systems it's hard to isolate just the EGT to mixture without knowing if the fuel pressure is remaining constant, but from your initial comment about leaning the needle it throws in another factor to consider.

Wouldn't it be more useful if we could precise log rpm, fuel pressure and flow rate at the carb at the same time as logging EGT. It would help to weed out some of the variables at least.
 
Marty Davis said:
Terry Keeley said:
Very interesting data Marty!
Any idea how long the "segments" are?
Click to expand...

Terry:

I guess you could approximate by figuring what each turn is. Does the length of each segment matter??? I could probably back into the time in the turn if you think there is some reason to figure it out.

Brian Callahan timed a lot of turns as as separate item, but I don't know what they were off hand.

Marty
Click to expand...

No need, just curious.

I've seen this first hand with my little 20 mono, it was planting the nose so hard in the corners the load went way up and the needle leaned to the point of taking the plug. I had to have it so rich it 4 cycled the whole SAW just to keep a plug in the corner.

I was able to loosen the corner up which helped some, but with full cooling it would 4 cycle from 1/2 track to the corner and lean out in the corner to half track.

The solution was to cut the water down dramatically (I did it a little at a time), and richen the mixture back up till there was only a burp or two down the straight, now it would lean out in the corner and not take the plug. I ended up with an 0.020" restrictor in the back of the rudder. :eek:
 
Tim_Duggan said:
Marty,Thanks for sharing your data.

Were you still leaning the needle at the point where the last corner segment was recorded?

I'm curious to know if the cornering segment recordings eventually level out of if they continue to increase when the mixture is not altered via the 3rd channel.

Obviously with our crude fuel systems it's hard to isolate just the EGT to mixture without knowing if the fuel pressure is remaining constant, but from your initial comment about leaning the needle it throws in another factor to consider.

Wouldn't it be more useful if we could precise log rpm, fuel pressure and flow rate at the carb at the same time as logging EGT. It would help to weed out some of the variables at least.
Click to expand...
Tim:

Yes it would. This was a crude starting point.

We did build a little more complete data logger that had RPM as the other input. It was interesting as well with the efficiency of the turn fin demonstrated in each turn.

Marty Davis
 
This is great data. I've not done much with EGT since most of my testing has been on gas boats where the carb settings don't change much, even with major changes in conditions. EGT is valuable for pipe design, though. I find it useful to graph speed and rpm data from the Eagle Tree data logger in Excel. You can see how much the engine pulls down in the turns and prop to the dyno curve. With nitro boats and the Seagull telemetry system, you should to be able to set your needle right every time. It would take experience with data like yours to do this.

Lohring Miller
 
Terry Keeley said:
Marty Davis said:
Terry Keeley said:
Very interesting data Marty!
Any idea how long the "segments" are?
Click to expand...

Terry:

I guess you could approximate by figuring what each turn is. Does the length of each segment matter??? I could probably back into the time in the turn if you think there is some reason to figure it out.

Brian Callahan timed a lot of turns as as separate item, but I don't know what they were off hand.

Marty
Click to expand...
Terry:

You are VERY smart to have solved it that way - but not unexpected. :rolleyes:

Too many people just run full water cooling all the time. As you can see by the trace, the EGT (Exhaust Gas Temperature) came down after each turn and then raised again in the next turn. The water cooling was VERY balanced. Water cooling is SUPER IMPORTANT, especially in the small engines. Probably not so important in the larger engines. Most probably due to excess horsepower of the larger engines.

If I hadn't been leaning the needle to get to the perfect needle setting, the EGT trace would probably have been almost level without much heat gain. As was mentioned, my leaning the needle threw another variable into the equation. However, it also showed that getting to the best needle setting did increase heat output. What would be neat would be to show the needle change until it "went over the hill". So many people set their needle so lean that the EGT is super high and the engine will not make maximum horsepower.

There are data loggers available now that will do all of this without problem. Just have not revisited this - to many projects - not enough time. :)

Marty Davis

No need, just curious.

I've seen this first hand with my little 20 mono, it was planting the nose so hard in the corners the load went way up and the needle leaned to the point of taking the plug. I had to have it so rich it 4 cycled the whole SAW just to keep a plug in the corner.

I was able to loosen the corner up which helped some, but with full cooling it would 4 cycle from 1/2 track to the corner and lean out in the corner to half track.

The solution was to cut the water down dramatically (I did it a little at a time), and richen the mixture back up till there was only a burp or two down the straight, now it would lean out in the corner and not take the plug. I ended up with an 0.020" restrictor in the back of the rudder. :eek:
Click to expand...
 
Last edited by a moderator:
lohring said:
This is great data. I've not done much with EGT since most of my testing has been on gas boats where the carb settings don't change much, even with major changes in conditions. EGT is valuable for pipe design, though. I find it useful to graph speed and rpm data from the Eagle Tree data logger in Excel. You can see how much the engine pulls down in the turns and prop to the dyno curve. With nitro boats and the Seagull telemetry system, you should to be able to set your needle right every time. It would take experience with data like yours to do this.
Lohring Miller
Click to expand...
Lohring:

BINGO, you got it. That is the reason for the EGT revisit. That will be an important part of the new EAP.

I just sent Andy a rough draft of the Pipe Design Program since he is working so much in that area with his new CNC equipment.

Marty Davis
 
Last edited by a moderator:
Marty,

There is a group of us in nashville that have powerboats. On one particular boat we had been trying to setup big motors using egt (555 cubic inch motors). What we discovered is that we would make changes that should have made more power and the egt would go up but the boat would go slower. Drove alot of very nolagable people crazy and then they got an air fuel ratio meter and the problem became very apparent. The problem was that we were so rich that the left over fuel would burn in the headers and cuase the egt to go crazy. We started leaning the motor down and the egt went down and the power and speed would come up. Just throwing this out there as to explain why egt are not everything. Now if you could just find an wide band air fuel ratio meter that was small enough to be used in this application you could truely be over the top.

Allen
 
The EGT sensor should be in the header. Three quarters of an inch from the piston. That way there is a constant reading. Just my opion :mellow:

Bob Morton
 
G/Day Marty

As you know I'm not long back into the hobby & a big part of the reason is the tools available to understand the workings of these powerhouses. I believe the only foreseeable big gains in power that are left, is in the pipes, & too a less extent, glow plug design/metalurgy (which I can't do anything about). Nitro percentages, timings, combustion etc., have been flogged to death for years & must be close to ultimate. I still believe in ex. throttles & venturies with a remote mixture in the venturie. Trouble is, nearly everytime you make a change in the pipe, you have to change a few other parameters in the engine to maximize these gains ! All too often I have lost power with a pipe design change on the first dyno pull, but then made gains when changed combustion etc. I have been gunna,gunna post, but held back, but I feel the information being shared is too educational & important not to become involved.

Sorry for the rambling.

My graph is a run with eagle tree live. The Temp. 1 line (gray) is the thermocouple around the pipe just at the back of the silicon joiner, not clamped tight enough, so not accurate enough. The thermocouple A (green) is under the glow plug. Throttle is throttle (dark gray) & Elevator is Remote Mixture (green). Bottom scale is seconds. I was purely chasing the relationship between pipe temp & plug temp.in relation to mixture change here. When I run again I will be positioning the probe into the exhaust gas flow post throttle barrel, so it will be actual egt & not pipe temp, making it heaps faster & more accurate.

As an aside, at a later date I will be logging rudder servo travel, to corner speed, to egt., which I hope will help optimize turn fin/rudder shapes sizes & position. I can not speak highly enough of the Eagle Tree as a tuning tool, but it's allot of hard work.

Regards Richard

2run1stdaym.jpg
 
GrePower said:
G/Day MartyAs you know I'm not long back into the hobby & a big part of the reason is the tools available to understand the workings of these powerhouses. I believe the only foreseeable big gains in power that are left, is in the pipes, & too a less extent, glow plug design/metalurgy (which I can't do anything about). Nitro percentages, timings, combustion etc., have been flogged to death for years & must be close to ultimate. I still believe in ex. throttles & venturies with a remote mixture in the venturie. Trouble is, nearly everytime you make a change in the pipe, you have to change a few other parameters in the engine to maximize these gains ! All too often I have lost power with a pipe design change on the first dyno pull, but then made gains when changed combustion etc. I have been gunna,gunna post, but held back, but I feel the information being shared is too educational & important not to become involved.

Sorry for the rambling.

My graph is a run with eagle tree live. The Temp. 1 line (gray) is the thermocouple around the pipe just at the back of the silicon joiner, not clamped tight enough, so not accurate enough. The thermocouple A (green) is under the glow plug. Throttle is throttle (dark gray) & Elevator is Remote Mixture (green). Bottom scale is seconds. I was purely chasing the relationship between pipe temp & plug temp.in relation to mixture change here. When I run again I will be positioning the probe into the exhaust gas flow post throttle barrel, so it will be actual egt & not pipe temp, making it heaps faster & more accurate.

As an aside, at a later date I will be logging rudder servo travel, to corner speed, to egt., which I hope will help optimize turn fin/rudder shapes sizes & position. I can not speak highly enough of the Eagle Tree as a tuning tool, but it's allot of hard work.

Regards Richard
Click to expand...

Richard:

Nice to see you posting. Your data is very interesting in all of the different type data collected.

Maybe sometime you can do an analysis running laps to see what is happening throughout several laps on the course.

Marty Davis
 
G/day again Marty

There's 7 odd laps recorded there. With the live dashboard, max. recording rate is 4 times a second (from memory) where as if I download from the boat it's 10 times a second (think), so I would have to do it that way. The throttle & mixture (elevator) are read in degrees of servo travel, on the right hand axis, so I started out rich @ 170 deg. & leaned it off 5 times to finish @ 118 degrees. To get the speed & accuracy needed, I've got to position the probe into the exhaust gas flow, & I'm working on that now & will hopefully test in a weeks time.

Regards Richard
 
That is really useful data and illustrates the relation between the needle setting and EGT. If you calibrate your needle with a flow meter, you get closer to absolute needle settings for that engine/pipe combination. I like to use Excel to display the data. You can even plot the latitude vs the longitude and see what the shape of your lap or the course through the traps really looked like. You can plot rpm against the time in the turn,but I'm still trying to tag the course points with rpm data for a better picture. If you expand the data using Excel you will find that the GPS speed lags the rpm. Since rpm should be a good speed indicator, that is peak rpm should equal peak speed, you can correct the GPS speed for this. I'm not sure this amounts to much for lap data, but when a boat is accelerating from 50 to 100 mpg in under 2 seconds this is significant. Below are two graphs from last years SAW at Legg Lake where Mike Bontoft upped the GX2 Hydro record by more than 20 mph.
 
G/day Lohring

I try not too look at the 3D data, it shows how much my driving needs to improve !! At present I am trying to determine the best heat measurement pickup points & stay with them - water outlet temp too. You're right, when I get back to the bank, I reset the mixture servo to the best power setting & read the mixture, I then go a couple clicks (or degrees) either side & can tell how critical (touchy) this combination is - a good pointer for trying to finish a race.

Regards Richard
 
You notice that I didn't show you a plot of a circuit around the buoys. The one I have illustrates how much less the engine pulls down if you take a nice round turn compared to a square one. The big weakness of the Eagle Tree software is the inability to plot sections of data like one lap of a race. That's why I started using Excel. There is a learning period, but the data is clearer.

Lohring Miller
 
Talk about me being "late to the party!" - I have been using the Eagletree data-recorder for 3 years after I found that I enjoyed the testing and tuning more than the heat racing (maybe because I am an engineer ?!? :rolleyes: ). After some health issues, I am back and am working on using what I have learned to develop an on-board microprocessor to take the sensor input for control output. Have any of you gone this route already or, if not, be interested in collaborating?
 

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