I hope this question opens a good discussion between the heavy hitter of DP.
Can you have high IAT as long as your EGT is acceptable?

The reason why I ask this question is if as long as your EGT does not get too high, does it really matter if your IAT is higher than what is acceptable from the stock PCM?

My stock PCM on my "S" engine defuels about 210 degrees of IAT. If my
EGT is below critical (1000 degrees), it is a problem to have an IAT above 210 degrees?

I don't think so. My intake temp was getting to 304 and I never felt the wall that people talk about. So I don't think mine was defueling. The scanner never read below 68mm3 when my IAT's were at 304.

I think even if it doesn't defuel it will still lose power as the intake temps are so high and the engine is not very efficient like that.

It will help efficiency to have the IAT as low as you can get it. The diesel is a heat engine. Colder intake air will be more dense and make more oxygen available for combustion with the fuel. If two engines are running the same EGT, the one with the lower IAT will be producing more power or be getting better fuel mileage.

Jake

If its too high id look into an intercooler. Cooler air holds more oxygen molecules vs hot air, therefore burns cleaner mroe efficient.

I know the hotter the air the less dense it is. But his question was can you have hot IAT's as long as you EGT's aren't too high. And the answer is yes you can. I am sure it has a limit. But my truck has been hitting 300 degree IAT's for 110K miles. And I think CR said hit has been to 340.

I know the hotter the air the less dense it is. But his question was can you have hot IAT's as long as you EGT's aren't too high. And the answer is yes you can. I am sure it has a limit. But my truck has been hitting 300 degree IAT's for 110K miles. And I think CR said hit has been to 340.

You can have high intake temps, it will hurt power, efficiency and long term reliability. By how much who knows.

to answer your question, yes, I have seen 450+ intake air temps, performance down yes
as long as EGT's dont go over 1400 Deg F. your good
r85sub is correct.
the hotter the intake air, the less dense it is,
Meaning
if you were to have 2 boxes full of air
one was 100 deg and the other was 0 deg
the one that was colder would have more of a oxygen % in side of it.

the computer in your truck looks at the IAT exactly for this reason.
if it sees cold air ( more oxygen ) it can tell the injectors to deliver more fuel.= more power
if it sees hotter air ( less oxygen ) it will tell the injectors to deliver less fuel.= less power

same princible as airplanes and a thing called density altitude

Hope this helps

WOOOOOOO!! 1400 Deg. exhaust temps are death to a 6.5.......

Cooler IAT and intercoolers don't make power on diesels. Cooler IAT means lower EGTs which is what your shooting for. Diesels are completely different than a gassers. To get more power out of a diesel you add more fuel. The engine always takes as much air as it can and there are no air/fuel ratios to worry about like in the gas world. On a gas engine you have to add more fuel to keep your stoichiometric ratio correct or it will lean out and burn up. A diesel is just the opposite. More air means cooler engine. Cooler intake temps don't increase power unless there is more fuel.

Can anyone back me up on this one??

WOOOOOOO!! 1400 Deg. exhaust temps are death to a 6.5.......


+1

I try to never go over 1250 for even the shortest period of time and I stay below 1050 sustained.

Aluminum melts at 1,400 degrees.

For every 1 degree intake temp expect 1 degree exhaust temp.

Average exhaust temps can be deceiving. That's an average. You could have some way over that temp. No normal engine has even temps on all cylinders.

Most all of us on DP grew up on gassers(at least I did). I know that the philosophy between diesels and gassers in regards to air-fuel mixture is totally different. The real question is that we all know how inefficent all the 6.5 turbochargers are at higher boost levels with building excessive heat that if you are still getting complete combustion and your EGT's are acceptable, are the higher IAT's themselves ok for the engine, overall engine efficiency aside? Or put another way, will the high IAT's themselves damage internal engine parts if the EGT's are low enough?

I would agree so long the EGT stays below the max safe limit IATs can be high with no worrys of damage, but power might be down for the reasons others have posted, ECM defuels, lower oxygen etc, look at it this way if you lower the IAT temp that means you can add more fuel which means more po'wr, while still staying under your present or safe max EGT

Aluminum melts at 1,400 degrees.

For every 1 degree intake temp expect 1 degree exhaust temp.

Average exhaust temps can be deceiving. That's an average. You could have some way over that temp. No normal engine has even temps on all cylinders.


Maybe raw aluminium? but I've had my turbo gas EGT's as over 1700 deg's when I got pissed off and kept my foot into it, blew out the head gasket, thats it. Other too have done the same as me, :o:

Higher AIT won't hurt anything at a given EGT, but the lower you get them the more power it will make.

Ever notice how strong the truck feels on a cold day vs a hot dry summer (other than the chopper blade being locked up on your LLY:()

Same principle of using water injection, it cools the ait, more dense air, more power. Goes up even further if you shoot the water INTO the turbo compressor, keeps the air far more dense during compression and is good for about a 10% gain in compressor flow and efficiency. Just have to super atomize the water before it hits the wheel.

I'd say IT DEPENDS. Great answer huh. Everything is relative. IAT is another measure of the heat that has to be dissappated. As long as ECT and EGT are in check then hotter IAT is ok to a point. IF ECT climbs then IAT is more harmful. IF all three are high then its more prone to melt something with a lower reading of any of the three. If 2 are low then 1 can get a bit higher and be ok.

Think about the IP in an oven with the heads and intake the heating elements. IF ECT and heads get really hot and intake is really hot then the IP is going to get hot. Probably will shorten life but won't kill the IP but probably will kill a PMD.

A thought of mine more and more I think oil temperature could be an unkown that has big influence. Cooler oil will HELP piston survive hotter IAT and EGT at least a little.

Cooler IAT and intercoolers don't make power on diesels. Cooler IAT means lower EGTs which is what your shooting for. Diesels are completely different than a gassers. To get more power out of a diesel you add more fuel. The engine always takes as much air as it can and there are no air/fuel ratios to worry about like in the gas world. On a gas engine you have to add more fuel to keep your stoichiometric ratio correct or it will lean out and burn up. A diesel is just the opposite. More air means cooler engine. Cooler intake temps don't increase power unless there is more fuel.

Can anyone back me up on this one??

not quite right, cooler air means more air in the chamber to expand with heat therefore more power;), why do you think a vehicle gains more power with a intercooler even with the same amount of fuel.

my question is: why in the hell would you want to run high iat's:rolleyes:, that like sayin your gonna run 50 degrees below max egts:rolleyes:, thinkin "hey im still below max i should be fine" wrongo

my question is: why in the hell would you want to run high iat's:rolleyes:, that like sayin your gonna run 50 degrees below max egts:rolleyes:, thinkin "hey im still below max i should be fine" wrongo

I not saying that I WANT to run high IAT's, but until I can get some sort of intercooler, I am kinda stuck. The sort of high IAT's that I am talking about is for a short WOT blast when necessary. The main reason I questioned the whole high IAT thing is the difference in defueling setpoints between the F and S engines. 210 for the S and 250 for the F. One can only guess that they are calibrated that way because of the idea that the S intake will naturally be hotter due to the EGR gasses in it?

I not saying that I WANT to run high IAT's, but until I can get some sort of intercooler, I am kinda stuck. The sort of high IAT's that I am talking about is for a short WOT blast when necessary. The main reason I questioned the whole high IAT thing is the difference in defueling setpoints between the F and S engines. 210 for the S and 250 for the F. One can only guess that they are calibrated that way because of the idea that the S intake will naturally be hotter due to the EGR gasses in it?

Think of it like this: that heat has to go somewhere, it doesn't just disappear. If it isn't showing up in the EGT, it's going into the cooling system and the oil. Those don't react as fast so for the short bursts you're describing you'll be okay. It's the long momentum play that you can't do and you can really get into some heat-soak problems when your ECT and oil temp is rolling past 230 or 260.

When I'm pulling the horse trailer I can sustain the boost at about 12 psi pulling a long gradual climb. The IAT is running 300+, EGT can be 1200, but, the engine temp gauge is going up and the oil pressure is dropping (oil is getting hot and thinning out). Pretty soon I'm pulling over and getting out the garden sprayer to cool it down. This is where I really need the intake charge cooler.

Regarding the S vs F intakes, those numbers make sense because the IAT sensor is upstream from the EGR. The factory engineers programmed in the margin required to accomodate the extra heat coming in with the EGR down stream of the IAT sensor. Ideally the IAT sensor should be downstream of the EGR and the program would be the same but that probably was not considered practical.

Mike

not quite right, cooler air means more air in the chamber to expand with heat therefore more power;), why do you think a vehicle gains more power with a intercooler even with the same amount of fuel.

Yeah I completely agree if your talking about a gasser, A diesel engine is a completely different concept. In a diesel, More air or cooler IAT = cooler engine. By adding an intercooler you are not increasing the fuel so you will not make more power. Basically if the same amount of fuel is injected, cooler air doesn't make more power, you must add fuel. Until you can put your gas engine thinking aside, the diesel engine will never make sense to you!!

Regarding the S vs F intakes, those numbers make sense because the IAT sensor is upstream from the EGR. The factory engineers programmed in the margin required to accomodate the extra heat coming in with the EGR down stream of the IAT sensor. Ideally the IAT sensor should be downstream of the EGR and the program would be the same but that probably was not considered practical.

Mike

That is why I installed the old style F engine intake gasket that have the metal EGR block off plates to keep that heat out of the air intake charge area completely.

Might be a little off subject, but I seem to remember ????? gas mixture is 14 to 1 for best cumbustion and diesel can be from 30 to 1 all the way up to 70 to one.

Might be a little off subject, but I seem to remember ????? gas mixture is 14 to 1 for best cumbustion and diesel can be from 30 to 1 all the way up to 70 to one.

Idle ratio can be 100:1 on OTR engines

Yeah I completely agree if your talking about a gasser, A diesel engine is a completely different concept. In a diesel, More air or cooler IAT = cooler engine. By adding an intercooler you are not increasing the fuel so you will not make more power. Basically if the same amount of fuel is injected, cooler air doesn't make more power, you must add fuel. Until you can put your gas engine thinking aside, the diesel engine will never make sense to you!!

I can seperate gas and diesel very well thank you. answer me this: why did my intercooler make more with same fuel?? more air (cooler air=more air) in the cylinder will produce more power. Diesels are different from gassers in the fact that they excellerate from fuel not air, gassers are vice versa. However, cramming more air in will create more power to the point of running it too lean. Add a turbo to a n/a 6.5 without juicin pump and you still get more power. Ill give you the fact that it also helps keep the engine cool with cool air comin into it;).

Maybe raw aluminium? but I've had my turbo gas EGT's as over 1700 deg's when I got pissed off and kept my foot into it, blew out the head gasket, thats it. Other too have done the same as me, :o:

I was off a little. (Imagine that)
Aluminum Melting Point: 660.37 °C or 933.52 K or 1220.666 °F)


1,400`F Steel turns cherry red. I use to calibrate pyrometers for dyno runs. I made a fixture out of an acetylene torch and a long length of pipe. The torch was placed in the bottom of the pipe and turned wide open. At the point where the pipe turned cherry red I had a hole drilled. I would place the probe in the hole and verify the pyrometer was correct with the rest of the pyrometers. Kinda of a comparison chamber I guess you would call it.

1,350`F flakes of piston would start fouling the plugs.

1,200~ degrees the piston start loosing it's strength. Sustained runs at that temp will weaken the molecular structure.

I like to think of it this way as far as the high IATs go, just cause when you go to the bathroom it comes out warm doesn't mean you'd want to drink warm or boiling water. Not that the warm would do any damage, just wouldn't be enjoyable (to me at least). Boiling... Now that would hurt.

Also, take 2 stock trucks, run one with the airbox intact, and with an IC, the other, take away the airbox, and don't run an IC.

The one getting the cooler air into the combustion chamber will out perform the other one. Not to say it'll be a one sided test in favour of the IC truck, but It'll keep the EGTs, IATs, ECTs, engine oil and the rest of the engine cooler.

With heads and mains that can potentially crack, I'd like to keep my opperating temps as low as I reasonably can.

I was off a little. (Imagine that)
Aluminum Melting Point: 660.37 °C or 933.52 K or 1220.666 °F)


1,400`F Steel turns cherry red. I use to calibrate pyrometers for dyno runs. I made a fixture out of an acetylene torch and a long length of pipe. The torch was placed in the bottom of the pipe and turned wide open. At the point where the pipe turned cherry red I had a hole drilled. I would place the probe in the hole and verify the pyrometer was correct with the rest of the pyrometers. Kinda of a comparison chamber I guess you would call it.

1,350`F flakes of piston would start fouling the plugs.

1,200~ degrees the piston start loosing it's strength. Sustained runs at that temp will weaken the molecular structure.
Would carbon deposits on the pistons help protect against heat as carbon melts at Approx. 6300*F? Leo

Might be a little off subject, but I seem to remember ????? gas mixture is 14 to 1 for best cumbustion and diesel can be from 30 to 1 all the way up to 70 to one.

for gas ideal stochiometric ratio is 14.7 (generally) though this is not the peak power number. That is greatly dependent on the engine setup, fuel etc. Most of the time peak power is made in the high 11, low 12:1 ratio, and light load cruising in the mid 15's, just goign to 20's under very high vac, zero load decel fueling.

Diesels are a completely different animal. They can get up in the 100:1 ratio without an issue, it's part of their inherent design. But that's not really part of the discussion here at all.

Would carbon deposits on the pistons help protect against heat as carbon melts at Approx. 6300*F? Leo

Yes and no, it can also cause hotspots than can burn thru as well.