Effect on Exhaust Gas Temperature (EGT)

what is the +- max EGT you have to keep in mind? High EGT wil kill first turbo and other parts from the exhaust system? Or wil like 1000degree celcius kil first the pistons etc?

thankyou!

Exhaust Valves usually bear the brunt of the damage from high EGT's.

Are you talking Peak or sustained EGT's? Peak you can get away with 1100 degrees for a very short period of time, but normally you would want to max out around 900 degrees, or even less if it is going to be sustained.

Depends - as Stephen said, the exhaust valves are directly in the firing line nd will usually be one of, if not "the" hottest parts of the engine, and while it's importan to use materials that are stable at such high temperatures, they are also cooled by their seats and via their valve guides.

The next critical thing in line is normally the exhaust manifold, which is going to have a constant, very hot gas heating it, but at least is can dissipate some to the surrounding air and components by physical interactions.

However, the turbo' turbine just sits in the path of these hot gases, and is largely surrounded by them, with the only real way of losing the heat being through the shaft to the bearings, the oil passing through them, and the impellor at the other end. Different turbine wheel materials have different tolerances for high temperatures, and this is why it's important to know what the "safe" limits are* for the specific turbine - the manufacturers should have that info', if not provided with the turbo'. As Stephen also said, some will give different "recommended" maximums for instntaneous, for a second or two, and a lower rating for sustained! THIS is ESPECIALLY important to bear in mind when "tuning" on inertial dyno's, and doubly so for diesels and other vehicles that will be under power for more tha a couple of seconds, or so, as many "tuners" don't take into account the heat-soak and other factors that can increase sustained temperatures by as much as 100C, or more, over a ramp-run.

As for the pistons, as you surmise, they will get hotter, and aluminium weakens as it heats, which could lead to crown collapse. Some alloys are better than others, and sometimes thicker crowns are used to add mechanical strength, and oil squirters are used to try and cool the underside of the pistons to help retains strength.

*For waranty, and other reasons, that may be a little lower than what it will actually tolerate, but you're rolling the dice going above their numbers.

Personally I'm not thinking about the pistons when thinking about EGT, instead to name a few I want oil temps and combustion pressure under control.

Please remember not to advance ignition timing to the point of detonation for the purpose of reducing EGT. I'll take brief high EGT over brief detonation or pre-ignition because they'll tear things up very quickly.

Some turbo manufacturers will tell you a specific exhaust temperature to avoid, and I do heed that at least in terms of not sustaining that temperature for very long.

Duration at temperature is a huge factor, and the temperature you see is hugely impacted by where you measure, and how slow the sensor is, so keep that in mind.

If we had to throw numbers out, mine would be similar to Stephen's, and the time allowed towards the high end of that temp range would be extremely short. There are lots of factors at play, for example material properties, quality, thickness/mass, etc. so the max temp, max time, at each spot form combustion chamber to tailpipe varies quite a lot.

Hey guys!

thankyou for the details! @stephen, i just wanted this to know for knowing as an extra information point. i understand what it does, and how it works. But i wanted to know what is the moment you have to watch out.