Engine/Transmission (1998.5 - 2002) Anyone monitoring intake air temp?

[drury]

Ah... I missed the part about his measuring the temp at the intake horn instead of on the engine. I'm wondering if something like the ZZ manifold would keep the intake air cooler?

 

[NoSeeUm]

I use a ScanGauge, so it uses the stock OEM senser and whatever the ECM thinks IAT is. I see 20 to 40 above ambient most times. With warmer OAT the difference seems to get larger. I have not chugged up while towing any good grades since I started using it though.



Jim

 

[qzilla]

The MAP and the IAT are neighbors. They both tap into the driver's side of the head towards the back. The IAT sensor is just a couple of inches farther back...

This is correct. We were just doing some testing with IAT about 1hr ago and we were seeing temps in the 118-127 deg range crusing at 60mph at 2050rpms.



Sitting with the nose of the truck parked against a structure we were able to get the IAT signal up to 167 deg with the truck off but, the key on. Starting the truck cools it pretty quickly to about 130deg at idle and then cools off some as you drive.



We were in the upper 80's outside temp.



Oh yeah, using very complicted, expensive testing equipment. Guaranteed accurate to a T.

 

[NoSeeUm]

PC12Driver;



Why is it that the smaller, AKA puddle jumpers, are hot inside until airborne?



Are they using OAT to cool the cabin air or that there is just no compressor air pressure until the turbines are spooled up while in flight?



Jim

 

[Gary - K7GLD]

I use a ScanGauge, so it uses the stock OEM senser and whatever the ECM thinks IAT is. I see 20 to 40 above ambient most times. With warmer OAT the difference seems to get larger. I have not chugged up while towing any good grades since I started using it though.



Jim

YUP - sounds FAR more reasonable than 20-40 degrees LOWER than ambient! :-laf



THEN, as you suggest, pull a good load up a steep grade, and see what the temp is in relation to outside ambient...

 

[NoSeeUm]

YUP - sounds FAR more reasonable than 20-40 degrees LOWER than ambient! :-laf



THEN, as you suggest, pull a good load up a steep grade, and see what the temp is in relation to outside ambient...

Yeah...



Just another expensive toy at this point, but that is the main reason why I bought the ScanGauge. I also wanted to get a feel for the temperatures that the timing changes occured. Although, I am beginning to think WT has a pretty significant effect on timing. My scientific method for determining timing is my eardrums and thats it.



I am going to assume the IAT does pick up some block heat, you can see it when idling. The IAT can go to OAT + 80 or so very quickly.



Jim

 

[qzilla]

Timing, especially at idle uses ECT for a major part of its mapping. This is mainly true when it is cold or when it is hot. Once it is in the sweet spot, it looks at other things.

 

[PC12Driver]

PC12Driver;



Why is it that the smaller, AKA puddle jumpers, are hot inside until airborne?



Are they using OAT to cool the cabin air or that there is just no compressor air pressure until the turbines are spooled up while in flight?



Jim

You're right on the last one. Since the engines are pretty much idling, there may not be enough extra bleed air available to run through the air conditioning packs for effective cooling. And in a nasty case of irony, on hot days they may have to turn the air conditioning off to keep the combustion temps down so they can get maximum power for take off (same idea as boost vs egts in our trucks).





Back to the intake air temp thing, is anyone else monitoring the temps in the intake horn so we can get a apples-to-apples comparison? I think we've pretty well established what the temps are doing in the head via the IAT, but it would be nice to see if someone can verify what's going on before the air hits the engine. You know, some actual data to back up or disprove Y-knot's findings, rather than temp data from a different part of the engine, speculation, or whatever sounds resonable?

 

[Gary - K7GLD]

Back to the intake air temp thing, is anyone else monitoring the temps in the intake horn so we can get a apples-to-apples comparison? I think we've pretty well established what the temps are doing in the head via the IAT, but it would be nice to see if someone can verify what's going on before the air hits the engine. You know, some actual data to back up or disprove Y-knot's findings, rather than temp data from a different part of the engine, speculation, or whatever sounds reasonable?

Actually, to me, it's the actual temp of the air being fed into the engine vs outside ambient that is the bottom line - and while the temperature out of the turbo under boost - and how much the intercooler reduces that temp IS of interest, it's pretty hard for a layman to safely and effectively measure those temps.



I have a pair of reasonably accurate and reliable digital temperature measuring units appropriate for most tests - but haven't figured a way to safely place them directly INSIDE the intake airflow for testing that eliminates the possibility for them to become ingested into the engine - nor an I eager to butcher my intake plumbing to make the test. I'm curious as to temp changes at various points along the intake tract - but not enough to risk engine damage in the process.



If anyone has reasonable ideas as to how to make the tests safely, I'm open to suggestions...

 

[sheamc]

Without knowing every little detail that has been brought out, I seem to agree with what Gary says. Measuring the temp of air in the intake as opposed to the OAT. I believe that more than just temps need to be measured. I believe one temp pre-IC and one post along with OAT. This would give you concrete info to base theory off of. Another would be to check boost pre and post IC to obtain actual pressure drop and test PC12s idea/theory. I can understand it but don't believe the pressure drop is enough on its own. As for other variables, has any one thought of using evaporative cooling to help? Some spray water/meth INTO the engine. I prefer to use #2. Why not spray water over the IC to create evap cooling. This wouldn't create any problems that I know of, is easier on the wallet and requires only water. A washer fluid pump, reservoir, tubing, and nozzles are easy to come by in the junkyard.





As for placement of any probes, seems harder than I originally thought. Anything placed far enough into the air tract will cause a disturbance giving possible skewed results. On the boost bolt with tube, is the air possibly close enough to the actual intake temp to tee into without creating a problem. I know that isn't a good sampling point, but I don't know what else other than start butchering with holes and probes.



Shea

 

[drury]

Y-Knot's findings were with a probe in the intake horn. I don't think it needs to be more complicated than that. The GDP intake horn is already pre-plumbed with bungs suitable for the task. Certainly, if someone wants to place probes at numerous points throughout the intake tract I'd love to see the data, but let's not make the task so unnecessarily hard that no one does it.

 

[Gary - K7GLD]

Y-Knot's findings were with a probe in the intake horn. I don't think it needs to be more complicated than that. The GDP intake horn is already pre-plumbed with bungs suitable for the task. Certainly, if someone wants to place probes at numerous points throughout the intake tract I'd love to see the data, but let's not make the task so unnecessarily hard that no one does it.

And, of course, testing needs to be done in a fashion as to head off the inevitable controversy and criticism of the "armchair theory experts" who rarely ever test anything themselves, but can be counted upon to criticise EVERY detail of tests OTHERS do, :-{} regardless of how thorough and detailed the supporting data...



Been there, DONE that - MANY times - and it DOES get tiresome and annoying!

 

[NoSeeUm]

You're right on the last one. Since the engines are pretty much idling, there may not be enough extra bleed air available to run through the air conditioning packs for effective cooling. And in a nasty case of irony, on hot days they may have to turn the air conditioning off to keep the combustion temps down so they can get maximum power for take off (same idea as boost vs egts in our trucks).

Yeah Ok thanks... .



You have any any idea what stage of bleed air? If it is coming from the from the 1st - 3rd stages it could be fairly close to ambient temperature. I believe you refered to 500F combustor air? That sounds like a bit of a stretch for me, with out the use of an air to air heat exchanger, but I have absolutely no clue in actuality.

Back to the intake air temp thing, is anyone else monitoring the temps in the intake horn so we can get a apples-to-apples comparison? I think we've pretty well established what the temps are doing in the head via the IAT, but it would be nice to see if someone can verify what's going on before the air hits the engine. You know, some actual data to back up or disprove Y-knot's findings, rather than temp data from a different part of the engine, speculation, or whatever sounds resonable?

My original plan was to install a T/C in the air horn, but I got lazy and bought the ScanGauge.



The number I have heard tossed around is 1F drop in IAT is roughly 1. 5F drop in EGT, but I may have that axe backwards. And that is probably at WOT, which is almost always never the condition in my case. I believe that the IAT sensor is fairly close with the engine running at load, same as the EGT, until the flow decreases and the surrounding metal temperatures have an effect. The placement of the IAT sensor might also lead to some difference, it should be located closer to the air horn outlet center line. Probably a purpose for that. Consequently; a T/C in the air horn, would suffer some differences also just the other way around.



At one time I was actively researching the pros and cons of a more efficient IC to drop my IAT. But once again I got lazy and just added twins. I feel it was easier get more pounds of air in the cylinder with higher pressure higher temperature vice raising the air density with a lower temperature same pressure. The offset is that the air is hotter and I have cylinder pressure issues. End result is the same as my EGT's are manageable and that was my goal.



Thanks for the info,

Good discussion fellas;

Jim

 

[DMcPherson]

Without knowing every little detail that has been brought out, I seem to agree with what Gary says. Measuring the temp of air in the intake as opposed to the OAT. I believe that more than just temps need to be measured. I believe one temp pre-IC and one post along with OAT. This would give you concrete info to base theory off of. Another would be to check boost pre and post IC to obtain actual pressure drop and test PC12s idea/theory. I can understand it but don't believe the pressure drop is enough on its own. As for other variables, has any one thought of using evaporative cooling to help? Some spray water/meth INTO the engine. I prefer to use #2. Why not spray water over the IC to create evap cooling. This wouldn't create any problems that I know of, is easier on the wallet and requires only water. A washer fluid pump, reservoir, tubing, and nozzles are easy to come by in the junkyard.





As for placement of any probes, seems harder than I originally thought. Anything placed far enough into the air tract will cause a disturbance giving possible skewed results. On the boost bolt with tube, is the air possibly close enough to the actual intake temp to tee into without creating a problem. I know that isn't a good sampling point, but I don't know what else other than start butchering with holes and probes.



Shea

your absolutely right and I dont understand why there isnt anyone doing this. evaporative cooling works very well, look at a new subaru they come with a water mist over the intercooler stock, this is no new concept, there are nitrous, c02 and water spray systems, and I think its a much better alternative to an expensive intercooler, although you still have the pressure drop.

Im not sure about diesel aplications but in automotive aplications we have seen lower temps than ambient. I measured right before the throttle body on my drift car, I could see lower than ambient temps, under full boost 30-40 degrees hotter than ambient air.

I have also seen air to water intercoolers bring a charge down to 32 degrees, which is not relevant here but something to think about.

 

[Gary - K7GLD]

your absolutely right and I dont understand why there isnt anyone doing this. evaporative cooling works very well, look at a new subaru they come with a water mist over the intercooler stock, this is no new concept

This has been discussed in related threads on this board before - but a bit of investigation and "real world" testing has shown that spraying various solutions EXTERNALLY to the radiator or intercooler leads to eventual buildup of deposits on the surfaces being sprayed - either directly from contaminants in the solution used itself (hard water, various trace chemicals or contaminants, etc. ) - or else from airborne dust and other similar junk that is attracted to the surface being sprayed - and that stuff CAN be extremely difficult or impossible to remove once deposited and hardened.

 

[Gary - K7GLD]

I've piddled around and gathered all the stuff needed to adapt one of my digital temp gauges for installation directly into the intake system - probably at the air horn as others have described. Problem is, doing so will require the permanent modification of the temp sensor itself, if I am to provide maximum safety against the sensor coming loose and getting sucked into the engine - I'll have to actually epoxy it into/onto a plug, and drill and thread the airhorn for the testing - and the sensor will then be worthless for other uses.



Not real sure I'm interested enough to "sacrifice" a good instrument on a project that is sorta controversial, and likely to provide results that will only be challenged and criticised anyway, if it comes out the way I suspect it would.



For the time being, I remain curious and interested - but will hold off for a bit to see if any other "backyard experimenters" step forward...

 

[PC12Driver]

Yeah Ok thanks... .



You have any any idea what stage of bleed air? If it is coming from the from the 1st - 3rd stages it could be fairly close to ambient temperature. I believe you refered to 500F combustor air? That sounds like a bit of a stretch for me, with out the use of an air to air heat exchanger, but I have absolutely no clue in actuality.

In our engine (P&WC PT6A-67B) we have two axial compressors and one centrifugal, and we'll either pull from 2. 5 (between the last axial and the centrifugal) or 3 (after the centrifugal). Below 83% RPM the 2. 5 air is used to bleed off some of the air charge entering the centrifugal compressor to prevent surge. And yep, that's about the temp after the final stage of compressed air at 100% rpm. Our combustion temps (ITT) are around 720*C for cuise/takeoff.



It does sound like PFM, but it works!

 

[TAbbott]

I have an 18 wheeler with a 60 Series Detroit Diesel. Its electronic control package is called "DDEC" with its particular iteration being "DDEC IV". This particular engine is an 855 cubic inch, 575 hp, turbocharged and aftercooled, inline six cylinder, 4 stroke diesel --- much like our 5. 9 liter engines, only everything is bigger.



Anyway, I also have what is called a "DDEC Reader" that plugs into the system much like any other scan tool plugs into the electronics of any electronically controlled engine. One of the many monitored parameters of this system is "Intake Air Temp", another is "Ambient Air Temp" and I have operated this truck with the scanner plugged into the system and monitored the intake air temp under lightly loaded and fully loaded conditions. The inlet air temp. sensor is located in the intake manifold. Never have I seen cooler intake air temps than ambient, and under heavy load for prolonged periods it will climb 20 - 30 degrees F. or even more above ambient even at highway speeds. And this is with a huge charge air cooler swinging a 31" fan.



I understand there is no such thing as cold, only a relative absence of heat. I know that dumping a cup of boiling water into the ocean isn't going to raise the ocean's temperature. I also understand how compressing a gas, cooling it to ambient and then allowing the compressed gas to expand will produce relatively colder temperatures by removing heat from the gas. (Its exactly what happens in an air conditioning system). But, there is also something in that system called an expansion valve that prevents the compressed gas (compressed to the point of being a liquid) from travelling though the system too fast and that also causes a dramatic pressure drop from one side of that valve to the other (changing phase back from a liquid to a gas, with extremely rapid expansion and cooling effect).



That, or anything similar, doesn't exist in the charge air cooling system of a truck -- big truck or little truck making no difference whatsoever.



I reiterate my opinion that there is no operating condition or circumstance likely to be encountered that would result in colder air entering the intake manifold than the ambient air temp at the engines air inlet excluding a water/meth ingestion or other rapidly expanding gas entering the inlet air stream (propane or nitrous) excepting perhaps on older Cummins engines using "optimized aftercooling" where the cooling system liquid was used as the cooling medium for the charge air system. In that event it would be possible on a cold engine that had not yet warmed to the surrounding ambient temperature. Obviously that circumstance would not exist if the engine were warmed to operating temperature prior to measuring the temps.

 

[Gary - K7GLD]

I have an 18 wheeler with a 60 Series Detroit Diesel. Its electronic control package is called "DDEC" with its particular iteration being "DDEC IV". This particular engine is an 855 cubic inch, 575 hp, turbocharged and aftercooled, inline six cylinder, 4 stroke diesel --- much like our 5. 9 liter engines, only everything is bigger.



Anyway, I also have what is called a "DDEC Reader" that plugs into the system much like any other scan tool plugs into the electronics of any electronically controlled engine. One of the many monitored parameters of this system is "Intake Air Temp", another is "Ambient Air Temp" and I have operated this truck with the scanner plugged into the system and monitored the intake air temp under lightly loaded and fully loaded conditions. The inlet air temp. sensor is located in the intake manifold. Never have I seen cooler intake air temps than ambient, and under heavy load for prolonged periods it will climb 20 - 30 degrees F. or even more above ambient even at highway speeds. And this is with a huge charge air cooler swinging a 31" fan.



I understand there is no such thing as cold, only a relative absence of heat. I know that dumping a cup of boiling water into the ocean isn't going to raise the ocean's temperature. I also understand how compressing a gas, cooling it to ambient and then allowing the compressed gas to expand will produce relatively colder temperatures by removing heat from the gas. (Its exactly what happens in an air conditioning system). But, there is also something in that system called an expansion valve that prevents the compressed gas (compressed to the point of being a liquid) from travelling though the system too fast and that also causes a dramatic pressure drop from one side of that valve to the other (changing phase back from a liquid to a gas, with extremely rapid expansion and cooling effect).



That, or anything similar, doesn't exist in the charge air cooling system of a truck -- big truck or little truck making no difference whatsoever.



I reiterate my opinion that there is no operating condition or circumstance likely to be encountered that would result in colder air entering the intake manifold than the ambient air temp at the engines air inlet excluding a water/meth ingestion or other rapidly expanding gas entering the inlet air stream (propane or nitrous) excepting perhaps on older Cummins engines using "optimized aftercooling" where the cooling system liquid was used as the cooling medium for the charge air system. In that event it would be possible on a cold engine that had not yet warmed to the surrounding ambient temperature. Obviously that circumstance would not exist if the engine were warmed to operating temperature prior to measuring the temps.

THANK YOU!



My position and expectation exactly - and you saved me the trouble of severely modifying my own stuff to "prove" what you have already seen yourself.



SURE, under situations and installations that vary RADICALLY from the systems used on our trucks, differing results CAN be obtained - but I expect precious FEW here could, or would even WANT to duplicate those conditions - so what's the point, other than plain old curiosity?

 

[NoSeeUm]

At one time I had a wireless, "Garden Style" thermometer taped to my air horn. It did not update rapidly, but I could exeed the 150F range of the instrument, and eventually melted the sensor wire insulation.



Running the math using some Ideal Gas Laws...



T1 = Ambient

T2 = Compressor Outlet

T3 = Intercooler Outlet



P1 = Ambient

P2 = Compressor Outlet

P3 = Intercooler Outlet



CE = Compressor Efficientcy

IE = Intercooler Efficientcy



Case 1

T1 = 85F

P2 = 50psia

CE = 75%

IE = 73%



T2 = 374F

T3 = 163F



This is more or less typical at 35psi boost. I am cutting a wide swath through the numbers for illustration only.



At any rate, IAT - OAT = about 80F, which still seems a high from the actual numbers taken from the IAT sensor, but the calculation assumes running pretty hard and under steady state. This would be hard for me to duplicate in the real world as it would require complete heat soaking of all components.



Suppose the pressure drop in the manifold or maybe actually cooling from the manifold itself? There is always the remote possibility that I am completely out to lunch



Case 2

T1 = 85F

P2 = 50psia

CE = 100%

IE = 100%



T2 = 302F

T3 = 85F



This is a perfect system.



Case 3

T1 = 85F

P2 = 50psia

CE = 75%

IE = 73%



T2 = 374F

T3 = 75F

P3 = 11psia



Running the numbers backwards. In order to drop T3 to 75F then the manifold pressure would have to be close to 11psia or about 4psi of vacuum. (Hopefully )



However, running at a CE >75% would make this easier as would a IE > 73%.



I am starting to think that one must start with much higher pressures, like from an aero turbine, than typical the boost pressures to make this work. And even at that would require some cooling prior to the pressure / temperature drop to provide cabin cooling / pressurization air that PC12 describes.



Jim