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John S
09-19-2007, 06:29 PM
Hi All, i am working on a theory that thermal imaging can be used as a tool for tuning and troubleshooting 4 stroke engines. I am in the beginning stages of my research but I wanted to try and get the opinions of others that are most likely more knowlegable then me in engine theory.
My goal is to determine if thermal imaging could be a usefull tool especially during dyno tuning of fuel injected engines and I am basing this on exhaust gas temperatures (EGT) in particular.
It is my belief that there are two things that will affect exhaust gat temperatures;
Timing
A/F ratioWith many of the modern engine management computers both of these units can be controlled either globaly (all 8 cylinders) or individually. This would also only work with a Sequential MPFI system since there is no direct way to control fuel metering into an individual cylinder with a TBI or batch fire system.
It is also my belief that a lean mixture will cause a higher EGT and conversly a rich mixture will show lower EGT's.
What i am unsure of at this point is what role timing plays in both cylinder temp and EGT so if someone can elaborate on that it would be a good start.
Here is an image I took today of the right bank of my engine at operating temperature. This engine has only seen one dyno tuning session but from what I see it appears that there is a lot of room for improvement to balance all the cylinders. Another question is what would be a good baseline? For example, there is a Delta T ( temp difference) of 206.2* between cyl 4 & 6. Would it be safe to assume that the hottest/leanest a cylinder can run without any detonation is going to derive the most useable power?

https://static1.pt-content.com/images/pt/2007/09/CHE20070919_0076-1.jpg

In the image above it is quite apparent that there is a huge difference between the hottest and coolest cylinders. All things being equal and timing remaining constant would adjustments to the pulswidth of the cylinder injectors bring the cylinders into a more uniform heat pattern and increase or at least optimize power in the process?


Obviously since this is only an idle test, data would have to be gathered at various rpm and loads. This is where a dyno comes in but I have been unable to get any dyno time donated to do some testing. But I am still working on that.

Sorry about the long post but I am still gathering my thoughts and working out some details on this whole thing.
And in case anyone is wondering about the equipment I am using the IR camera I have is a very high quality ($35k) industrial camera.

HsvToolFool
09-20-2007, 05:20 PM
How fast is the response time of that thermal imager? Are we
seeing the instantaneous effect of hot exhaust gases in the
header tubes? Perhaps your photo indicates the heat of the
exhaust gases at one random moment. At another time, perhaps
the other two tubes are hotter.

It's very neat regardless.

John S
09-20-2007, 07:27 PM
How fast is the response time of that thermal imager? Are we
seeing the instantaneous effect of hot exhaust gases in the
header tubes? Perhaps your photo indicates the heat of the
exhaust gases at one random moment. At another time, perhaps
the other two tubes are hotter.

It's very neat regardless.

The camera sees in "real time" and the image represents more of a "specific moment" and not a "random moment". Any changes in the heat signature are evident as they happen.
My next step is to set the camera up to record video and record the engine heating up from ambient (cold) to stable operating temperature. Once I do that I'll try to post the video and you will get a good idea of how responsive the camera is and also what the heat characteristic of the engine is.

aggressive male
09-22-2007, 03:06 AM
Ineresting pic. Where I work we have one of those things which you point at something ant it will give you the surface temperature of whatever you point it at. I'm curious about tuning a motor this way too. What kind of engine is this? Is it carbed, throttle body injection or is each cylinder injected? You should have tried to take a picture of the other side about the same time.

Do you have the radiator filled all the way? Maybe there is an air pocket in the front of the motor since they are usually tilted up a little. If your radiator isn't filled all the way maybe that would cause it. I can't remember but I have a book called "how to tune and modify engine management systems" I think it actually does say what a exhaust temperature baseline should be. I'll see if I can find it.

HsvToolFool
09-22-2007, 09:00 AM
The camera sees in "real time" and the image represents more of a "specific moment" and not a "random moment".

Sorry, I meant a random moment in the engine's combustion cycle.
Is it possible that the image captures hot exhaust gases as they exit
certain cyclinders? That might explain the 250-degree difference
between header tubes. In other words, the cool cylinders are on
their intake cycle while the hot ones are on their exhaust cycle.

A video will be extremely neat. That's a cool toy I'd love to have.

David Pozzi
09-24-2007, 08:48 AM
In the combustion chamber leaner mixtures are hotter.

But I have seen a way too-rich mixture create horrible amounts of header heat. My theory is the extra fuel is not burned, so it enters the exhaust and burns there, perhaps aided by oxygen from excessive overlap of the cam. This was on a race car with roller camshaft and Weber carbs.

So much heat was generated at idle (1200rpm) that a coolant hose 1.5 foot away was smoldering! It radiated heat like a furnace.

Individual header temp probes or wideband oxygen sensors would tell a lot.
David

dipren443
09-24-2007, 09:42 AM
Ineresting pic. Where I work we have one of those things which you point at something ant it will give you the surface temperature of whatever you point it at.


Spot radiometers are good for reference only. Most of them have a fixed emissivity setting and will only return accurate temperature readings when directed at a dull object with minimal reflectivity. The ones I have seen usually have a fixed emissivity of 0.95, which is indicative of a near perfect emitter (e=1.0). Infrared imagers, like the one the OP is using, can account for changes in emissivity to return accurate temp. readings on even shiny surfaces.

To the OP, what infrared imager are you using to capture your stills and video? I work with both Flir and Indigo systems at my place of work.

John S
09-24-2007, 05:58 PM
I'll try to answer several questions here;
Agressive; if you could fine that baseline information it may provide a great starting point, thanks.
HSV: I monitored the the engine for over 5 minutes taking several images. What you are seeing in the image is a very accurate representation of the header tubes at max temp ( at idle). This will be validated once I take a video of the engine. I believe that that there is not enough time for header heat to dissipate during the intake or compression cycle of the engine.
David; Thermal imaging will provide the same information as individual exhaust temp probes except without intruding in the exhaust pipe and at a much higher resolution. And you get the added benefit of seeing just where your thermal displlacement is.
dipren; Your assesments are right on! you obviously have some type of thermography experience. Care to share a little more? As far as my camera I have an Infra Red Solutions FlexCam Pro which would be the equivelant of a Fluke TI45 (Fluke bought InfraRed Solutions) and I am using Flukes Smart View software for image interpretation. I am an ASNT level II thermagrapher but hold the level III Title at the company I work for. I should add at this time that my Camera settings were for an E of 0.96 and the headers are very dull black. there was no air movement in the engine bay and ambient air temp was 68*.

silver69camaro
09-25-2007, 11:19 AM
That might explain the 250-degree difference
between header tubes. In other words, the cool cylinders are on
their intake cycle while the hot ones are on their exhaust cycle.


I'd venture to guess than such a rapid (and extreme!) thermal cycle would eventually crack the HREW tubing. The tubes can't radiate heat that fast, anyway.

Fuelie Fan
09-25-2007, 03:27 PM
In the combustion chamber leaner mixtures are hotter.

But I have seen a way too-rich mixture create horrible amounts of header heat. My theory is the extra fuel is not burned, so it enters the exhaust and burns there, perhaps aided by oxygen from excessive overlap of the cam. This was on a race car with roller camshaft and Weber carbs.

So much heat was generated at idle (1200rpm) that a coolant hose 1.5 foot away was smoldering! It radiated heat like a furnace.

Individual header temp probes or wideband oxygen sensors would tell a lot.
David

1. Hottest in-cylinder temps are at stoichiometric, not lean.
2. Sounds totally plausible. It's not too far removed from an anti-lag system, when you think about it.

dipren443
09-25-2007, 04:05 PM
1. Hottest in-cylinder temps are at stoichiometric, not lean.
2. Sounds totally plausible. It's not too far removed from an anti-lag system, when you think about it.

My doubt's about #1 led me to pull out my ICE design book and do some reading on a physics forum. Boy is my head spinning. :rolleyes:

Anyhow, what I have gathered is neither contradictory to #1 nor complementary. It really just depends on how you look at the situation. It seems that peak flame temps occur at stoich, but not necessarily peak cylinder temps. The fuel has a higher SFC and serves to soak up a good majority of the heat at stoich. Lean mixtures cause pre detonation and therefore have a tendency to increase component temperatures, that is until you lean the mixture so much that the increased air has a cooling effect. Hence why lean mixtures and detonation are what cause pistons to melt.

Enriching has a similar inverse effect. Just rich of stoich has a slight cooling effect, but way rich of stoich will spike the cylinder temps.

I do feel pretty dumb after reading through pages and pages of engineering and physics curriculum though... :hand:

HsvToolFool
09-25-2007, 04:18 PM
The tubes can't radiate heat that fast, anyway.

I didn't think so either, but it was worth asking. It's incredible that
a 220-degree difference exists between cyclinders at idle. That can't
be good.

dipren443
09-25-2007, 04:34 PM
dipren; Your assesments are right on! you obviously have some type of thermography experience. Care to share a little more? As far as my camera I have an Infra Red Solutions FlexCam Pro which would be the equivelant of a Fluke TI45 (Fluke bought InfraRed Solutions) and I am using Flukes Smart View software for image interpretation. I am an ASNT level II thermagrapher but hold the level III Title at the company I work for. I should add at this time that my Camera settings were for an E of 0.96 and the headers are very dull black. there was no air movement in the engine bay and ambient air temp was 68*.

My thermography experience/exposure is quite similar to yours. I am certified Level II in IR with enough hours to take the Level III exam. I just need to go do it one of these days. We don't use IR in a conventional manner, however. Our applications are a little more experimental. We inspect gas and steam turbine components with a twist. The parts are excited in one of three ways and the whole process is imaged with IR. Flaws are then viewed on the resulting thermograph. Unfortunately we use laboratory grade instruments for extremely high frame rates and are not necessarily worried about temp. measurement. We are only looking for temp. differentials. Therefore, none of our cameras are radiometric, nor are they handheld standalone units.

Back to your process. About the only thing you could do, and this all depends on how accurate you want to get, is to determine the emissivity of the target components and adjust your camera appropriately. Depending on access, its not always that easy, but in your case, it should be a no brainer as long you have access to some thermocouple wire and a DRO for them. Not sure how necessary that would be, since your really only looking for large temperature variations and the 0.96 e value is probably close enough though.

Nick

John S
09-25-2007, 05:34 PM
Thanks for all the inpt guys and please keep it coming. You've all got me thinking overtime about all this.
Unfortunately with all the input also comes some realizations;
1) it may be next to impossible to baseline any engine under the conditions that I currently have.
2) It is going to take way more dyno time then I can afford to come up with any realistic numbers.
3) Even if I could afford the dyno time more instrumentation will be necessary.
4) Narrow band O2 sensors on each cylinder would be the best way to balance an engine where you can trim timing and fuel curves for each cylinder. Done in conjunction with an Infra Red camera you could probably gather enough information to set baseline information for future tuning without the addition of the O2 sensors.

if anyone in the TriState area is willing to donate dyno time I would be willing to travel to do more testing.

silver69camaro
09-26-2007, 11:02 AM
4) Narrow band O2 sensors on each cylinder would be the best way to balance an engine where you can trim timing and fuel curves for each cylinder.

Why narrow band sensors? Or do you mean wide band?

John S
09-26-2007, 11:25 AM
Why narrow band sensors? Or do you mean wide band?
I mean Narrow band when tuning if you can adjust fuel and timing such as in a Sequential fire MPFI system. The sensors would only be installed during the tuning process then removed for normal engine operation. The use of a permanment Wide band sensor would still be required for normal engine operation.

By using the O2 sensors while tuning you can monitor cylinder A/F ratios and adjust to achieve as close to Stoich as possible. Once set a baseline thermal image could be obtained and any future changes could be analyzed by taking another thermal image and comparing it to the baseline.

The use of the thermal camera during the tuning process would also enable you to trend EGT changes during adjustments and this way you would know what adjustments to make (Richen/lean) to obtain Stoich during tuning based on EGT alone.

Once again, the use of these NB O2 sensors would not pre-empt the need of a permanment WB sensor for normal engine operation.

silver69camaro
09-26-2007, 12:13 PM
Maybe I'm missing something.

Narrow band sensors are good only regarding a stoichiometric burn. Nothing more, nothing less (right?). Why limit your abilities to gathering such a narrow range of data, when a wide band sensor can be used for reading data at other air/fuel ratios?

Personally, I'd be more interested how EGTs change for air/fuel ratios that produce maximum economy (which is often leaner than stoich), and maximum power. But that's just me.

John S
09-26-2007, 06:48 PM
it's my belief that narrow band can read between ~12.2 - ~15.6 (hence narrow band) and the wide band reads a higher range especially for boosted engines while also providing a feedback to the ECU. Am I mistaken in this?

But I agree with you on your second point, after all that is the whole purpose of this thread. I want to learn what EGT's are using a thermal Imaging Camera instead of thermocouple probes for best A/f ratio, power and economy.

Fuelie Fan
09-27-2007, 11:21 AM
narrowbands CANNOT read over such a wide range. However, they are more repeatable and precise in measuring 14.7 than say two widebands are at measuring 12.6 for instance. So, actually, I kind of like the idea of using narrowbands for cylinder equalization tuning under part load conditions. Plus, it'd be a lot more cost-effective than using 4 or 8 widebands simultaneously.

Keep in mind that throughout this discussion, one cannot ignore spark advance.

In reference to my earlier post and dipren443 's response, i don't think detonation should really be considered as part of the determination of the general temperature dependence on A/F ratio, as detonation is a phenomena heavily dependent on a multitude of other factors and can be eliminated through test design. Also, by what mechanism does excessive fuel-rich conditions spike in-cylinder temps?

gt1guy
10-08-2007, 08:13 AM
When the image above was taken, was the fan turning? It looks to me that if the fan was moving air from front to rear it would cool the headers in the exact order that the temp variances show. Cyl #1 is in the direct path right in front, and has the lowest temp. Cyl #3 is next in line, but with a space between #1, and has the second lowest temp. Cyl #5 is right behind #3 and therefore the airflow to it is somewhat blocked. It has the highest temp. Cyl #7 has a gap between #5 and more airflow to it. It's temp is lower than #5.

I may be way off base here, but it makes sense to me.

Kevin

Helmantel
10-12-2007, 06:42 AM
Keep in mind that there is a difference between flame temperature and average gas temperature.

Maximum flame temperature will usually occur at close to stoichiometric mixtures (depends a little on the type of fuel). This is a local temperature, just behind the very thin flame sheet and has not much to do with the exhaust gas temperature.

When the mixture is enriched, more fuel is burned for a given amount of air. Assuming the mixture is not too rich (A/F set at maximum torque), more thermal energy will be added mass in the cylinder, so the maximum average (meaning average temp of the gas in the cylinder) gas temperature will be higher, and so will the exhaust temperature.