Over the weekend I drove my 05 over Fremont Pass. Coming and going I saw EGT's easily over 1300 very easily. Is the altitude a factor in this? My truck is an 05 that has the airbox drilled and the muffler gone. Otherwise stock..at least the PCM has the stock 05 Bullydog program....So plenty of "stock" power and boost, just high EGT's. My guess is that the program is not leaning the fuel curve and at high altitude and temperature it is over fueling and causing the EGT's??? Thoughts?

 

My truck ran up there easily under heavy loads stock.I've seen 1100* POST TURBO.& that was at about 3500ft.The stock truck will give high egt's easily.

 

I believe if the motor was running in a rich condition it would LOWER your EGT's.

 

For every 1000' of altitude your turbo must spin 3000 more RPM to achieve the same boost as sea level. The problem with this is that at some altitude the stock turbo will lose it's efficiency and will lose the ability to burn the excess fuel at that point causing higher EGT's. This is my opinion of why I see higher EGT's in our mountains here.

 

It's my understanding that there is no "rich" nor "lean" condition with a diesel (like on a gas engine). Even with a turbo, the air is less dense at altitude and your EGTs run hotter. You control the fuel with your right foot, not the computer. The unthrottled engine will take whatever air it can gulp. There is no optimal ratio (like a gasser).

Someone else will be able to explain it better than me I'm sure

 

Coming up over Eisenhower and then Fremont (both over 11K) with high ambient temps (about 70-75 F) my truck touched 1350 easy and on the way back over Fremont the outlook actually defueled and I saw 1400 for about 2 seconds....Had to pass that stupid gasser that wouldn't get out of my way. I agree with Staarma that the stock turbo has a limited ability to feed enough air for the fuel and that is what is causing the high EGT's. I wish instead of a boost gauge we could have an manifold pressure gauge. Like the turbo Arrow that I fly. The Arrow will maintain 41 inches of manifold pressure to about 11-12K altitude after that it falls off pretty quickly.

 

Your Turbo Arrow starts dropping off quickly because it has a ratio controller controlling your boost, higher the Altitude the harder the turbo has to work and to prevent detonation it reads the ambient and boost pressure. your Manifold pressure gauge is no different from the Boost gauge in your truck , just one read in p.s.i. and other in in.hg. So when your reading 41 in. on your manifold gauge, that is 20 p.s.i. on a boost gauge, one reason its called a manifold press. gauge is because you are reading what is between the throttle plate and intake valves. there are some aircraft that read in p.s.i also.

 

Your going to have higher EGT at altitude, especially with a chip or tuner that adds fuel. Less charged air to push those hot gasses out, and you heat up, especially with a load. Your also going to see more black smoke at elevation.
It works opposite with a gasoline motor, as higher altitude and more fuel will cause a rich condition, and lower your EGT.
DK

 

That said, I guess you high altitude folks have a good excuse to go with Twins, Bombs away!

 

Well, I guess I will have to convince the better half of that. Wish me luck!!!!