Safe?

[TRENDZ]

Is it safe to assume that with no smoke, egts are in an acceptable range?

[mprmn08]

prolly depends on how long you stay in it for. a long pull i would think they could still get up there.

[Begle1]

On a first gen, it's probably a pretty good sign that EGT's are in an acceptable range.


In general it is possible to have high EGT's with low levels of smoke or low EGT's with high levels of smoke, and it's possible to have piston temperatures higher or lower than EGT's, and smoke may cool down pistons even while increasing EGT's. There are a lot of factors and things are different from Diesel to Diesel.


But on a first gen, if you're slowly turning up the pump and have don't even have any smoke yet, your EGT's are fine. However, it is possible to have an injector dribbling fuel or popping at the wrong pressures, and that can go so far as melting a piston before smoking excessively. However, you can also wreck a piston before having excessive EGT's in those cases.

[ahale2772]

will a diesel run lean like a gas motor (longer burn even back fires) if there is too much boost and not enough fuel? i know they can run lean but what are symptoms and what dose a lean motor look like on an egt gauge?

[burnt_servo]

a diesel engine is the opposite of a gas engine , more fuel = more heat in a diesel .



there may be an exception to this rule , ever see how some of the older nissan and toyota lancrusier diesels work ? they restrict the air as well as limiting the amount of diesel to control rpm .

i'm not sure if this setup which is similar to a gas engine would cause the same reaction that a gas engine has to having a lean mix or not

[ahale2772]

yes ive actually worked on a couple british 3 cyl taxis that worked the same way once upon a time i had a 924 turbo porsche that was having a problem with excessive backfiring i narrowed it down to a bad in tank fuel pump that was restricting fuel and causing a lean condition and the little fuel that was burning burnt all the way through the ezaust and out the tip! i was just wondering if a diesel would ever do this higher temp burn if it was running lean i know in a gas motor u can burn a piston if ur too lean

[Begle1]

There are exhaust gas temperatures and piston temperatures, and the two may be directly or inversely related.

Gasoline is very well dispersed with air in the cylinder; when the mixture burns, it is possible for all of the fuel to only burn partially, and CO is created instead of CO2.

Diesel fuel disperses while it is burning, so the fuel that does burn burns completely into CO2 while the rest of the fuel doesn't burn at all. No CO is created, but the totally unburnt fuel comes out as black soot. The Diesel fuel needs more time to finish burning than gasoline since it needs time to disperse.

Black smoke can be caused by there not being enough air for the fuel to react with, or by there not being enough time for the fuel to mix and react with the air. The newer the injection system the more efficient it is and the less time it takes for it to burn a given quantity of fuel.

When fuel is injected inefficiently, it doesn't have enough time to combust on the power stroke and the combustion continues during the exhaust stroke. This causes "afterburning" in the manifold and increases exhaust gas temperatures. Afterburning does not necessarily cause an increase in piston temperatures.

When fuel is injected efficiently, more of it combusts during the power stroke and piston temperatures are therefore higher. This doesn't necessarily cause an increase in exhaust gas temperatures.

Unburnt fuel by itself is a coolant. Black smoke tends to cool the pistons, even if it afterburns and increases EGTs.

When you put more air through the cylinders, it will almost always result in cooler piston temperatures and exhaust gas temperatures, unless the turbocharger is making that air really hot.

[ahale2772]

that all makes sense i was thinking engine vs engine not fuel vs fuel thanks for clearin that up

[Oddfire]

thanks for clearin that up