nate704

Okay!
whenever the car decelerates, EGT drops.
Why?
please let me know.

DTN

Because EGT is Exhaust Gas Temperature. When you accelerate it goes up because there's more fuel being burned. It goes down when you decellerate because there is less fuel being burned.

dddude55

Lol I was gonna say that but I wasn't positive that I had the right acronym laugh.gif

J3R0MY

^^^^ dang smart word.... lol, im dumb.

nate704

one more question!
why the temperature drops below 800 degrees ( 300-400 degrees) when the car decelerates?
800 degrees is my idling temperature.

dddude55

wahts it even mater, where are you getting these reading o_O

nate704

from my EGT gauge probe which is located in the exhaust manifold, and it is on the second cylinder from the driver's side. (1 inch from the head)
why does it matter? Because I want to know something that I don't know. And it is helpful to understand how my car functions.

DTN

Because the EGT is reading the temperature of the exhaust. When you rev past 4Krpm and then let it fall, you will get fuel cutoff. This means there's none or little fuel being burned in your engine. It's just hot air. Without fire, the gas temp will lower. Your car's exhaust temp gauge was probly set up for nitrous at one time... Nitrous is the best reason to have a EGT. You don't want to exceed temps of 1400 or you will have a danger to your manifold.

The exhaust gas temp will go up when you burn fuel and down when you're not burning fuel. That's the simplest explanation. There's other varriables like how much fuel you're burning and your fuel/air ratio, but in your case... Just know that temp goes up when the fuel usage goes up and down when it goes down.

radu_rd2

Yes, when you are decelerating there's no (or very little) fuel burnt (the wheels/inertia are keeping the engine spinning). When you are idling, there is some fuel burnt, as much as necessary to keep the engine and all accessories spinning.

tanc

Thats not the simplest explanation, that is the wrong explanation.

Richer than peak EGT cooling occurs because there is excess fuel, and leaner than peak, cooling occurs because there is excess air. So you must have a basic idea of where you are starting from regarding combustion gas temperatures and rich or lean condition of the fuel system.

There are so many factors when it comes to EGT readings, than just your explanation.

The distance of the probe from the edge of the piston as well as the location of the tip of the probe relative to the center of the pipe both have a major effect on what the temperature value is that his displayed.

The exhaust gases exit the cylinder in a conical shape. If you've ever looked at the flame on your gas grill or a brazing torch you may have noticed the conical shape to it. The tip of the conical shape (called the "flame point") is the hottest temperature in the flame. The exact location of the "flame point" in your manifold runners is effected by ANY modifications to the engine or manifold.