SoCalDMAX
06-29-2002, 01:25
I found an interesting thread discussing EGTs, basically asking what EGTs people were seeing. These guys get into some in depth diesel performance discussions and I learn a lot.
There was a very wide range of responses, from under 1100* towing heavy to 1800* just running empty. A lot of the stock engines were seeing 1300* towing.
One post in particular was a real eye opener, quoted from jimnance:
"Although my pre-turbo EGT never goes above 1100 degrees I suspect that as high as 1500 degrees could be sustained if all other temps are in the green. I'll tell you why I think this.
I operate an aircraft with a turbocharged aircooled 310 HP engine. Being all aluminum except for the cylinder barrels, crank, cam, etc. these engines require great care with respect to operating temps. Surprisingly, the allowable values given the aluminum heads are quite high:
Cylinder head temp - 460 degrees max. Normal 350-380 degrees
Tubine inlet temperature (pre-turbo EGT) - 1650 degrees max
Normal operating EGT runs about 1500 degrees.
Anything above 1650 degrees and you are at the point where the metal begins to literally sag. You don't want to go there.
I realize there are some differences between a Turbo charged liquid cooled diesel and a gasoline powered aircraft engine, but the basic metalurgy of the turbocahrgers is the same.
Personally, I subscribe to the theory that cooler is better. Engine components will last longer. If you want to get 300,000 miles out of your Cummins I would suggest that the 1250 degree EGT limit is a safe conservative limit."
__________________________________________________ ___
I'm not familiar with aircraft maintenance procedures at all. It's obvious that the mfr feels it's safe to fly all the time at 1500*, even though it's very close to the limit for the metal. I can understand the author's feeling that cooler is better.
So do these aircraft engines undergo some sort of periodic inspections that would ensure the engine is undamaged from heat, or do they not expect to get 300,000mi out of them? I thought aircraft were always operated with more safety margin than autos, since you can't exactly just pull over and wait for a tow truck.
The entire thread is here:
http://www.turbodieselregister.com/forums/showthread.php?s=fff98af08bb81df10e63c6871f2b3737&threadid=48525&perpage=15&pagenumber=2
What do you guys think? We've had some discussions about EGTs while towing with the Juice. My theory is EGTs are controllable thru judicious throttle application for the conditions and increased airflow. Does anyone have any theories on relationship between EGTs and:
1. method of increasing fuel flow.
2. Timing
3. Load.
4. Restrictions to airflow.
5. Driving style.
6. Ambient air temp.
Regards, Steve
[ 06-29-2002: Message edited by: SoCalDMAX ]</p>
There was a very wide range of responses, from under 1100* towing heavy to 1800* just running empty. A lot of the stock engines were seeing 1300* towing.
One post in particular was a real eye opener, quoted from jimnance:
"Although my pre-turbo EGT never goes above 1100 degrees I suspect that as high as 1500 degrees could be sustained if all other temps are in the green. I'll tell you why I think this.
I operate an aircraft with a turbocharged aircooled 310 HP engine. Being all aluminum except for the cylinder barrels, crank, cam, etc. these engines require great care with respect to operating temps. Surprisingly, the allowable values given the aluminum heads are quite high:
Cylinder head temp - 460 degrees max. Normal 350-380 degrees
Tubine inlet temperature (pre-turbo EGT) - 1650 degrees max
Normal operating EGT runs about 1500 degrees.
Anything above 1650 degrees and you are at the point where the metal begins to literally sag. You don't want to go there.
I realize there are some differences between a Turbo charged liquid cooled diesel and a gasoline powered aircraft engine, but the basic metalurgy of the turbocahrgers is the same.
Personally, I subscribe to the theory that cooler is better. Engine components will last longer. If you want to get 300,000 miles out of your Cummins I would suggest that the 1250 degree EGT limit is a safe conservative limit."
__________________________________________________ ___
I'm not familiar with aircraft maintenance procedures at all. It's obvious that the mfr feels it's safe to fly all the time at 1500*, even though it's very close to the limit for the metal. I can understand the author's feeling that cooler is better.
So do these aircraft engines undergo some sort of periodic inspections that would ensure the engine is undamaged from heat, or do they not expect to get 300,000mi out of them? I thought aircraft were always operated with more safety margin than autos, since you can't exactly just pull over and wait for a tow truck.
The entire thread is here:
http://www.turbodieselregister.com/forums/showthread.php?s=fff98af08bb81df10e63c6871f2b3737&threadid=48525&perpage=15&pagenumber=2
What do you guys think? We've had some discussions about EGTs while towing with the Juice. My theory is EGTs are controllable thru judicious throttle application for the conditions and increased airflow. Does anyone have any theories on relationship between EGTs and:
1. method of increasing fuel flow.
2. Timing
3. Load.
4. Restrictions to airflow.
5. Driving style.
6. Ambient air temp.
Regards, Steve
[ 06-29-2002: Message edited by: SoCalDMAX ]</p>