According to my pyrometer, on my morning 6:30 am drive to work my EGT is 100-150 degrees higher than my 5:00 pm drive home. The gauge reads 550 to 600 cruising at 70. It barely drops when I let off the pedal. It reads high, 500 +, with very little pedal input. When I open up the rpm to around 2100, temp drops to 500.
At night the readings are 500 cruising. Temp drops with less pedal. 1800 rpm and 60mph are at 400 - 450. And I drive more aggressively in the PM. Are there any explanations for this?
The probe is post turbo, so I will get hammered on that, but the readings have been consistent. I've been watching closely for two weeks.

 

I'm guessing the headlights may make the difference. You don't say what type of gauges you have, perhaps if they are the type that has an powered box the place you tapped into has too small of wire size and voltage drop is causing the difference.

 

Headlights not in use this morning. Same results. Looks like the gauges came from banks. The boost is banks and the pyro is Stewart Warner. I'm still learning about this truck because I bought it in Feb. I don't really know if it still has the stock fuel plate or not. Could the grid heaters effect the voltage drop? It seems too consistent to be the grid heaters unless they are on for the whole drive +/- 30 mins.

 

Not grid heaters, unless they are staying on.

Is it uphill all the way to work.

What temp is it on the way vs going home (engine temp and outdoor temp.)

 

Temp in evening is around 60. Temp in morning is 40. Uphill grades in both directions, no difference really. There is a steep grade going North out of carson City begining the drive home in the evening. I put the pedal down and get pretty aggressive with it, Egt at 650, then it cools to around 450-500 on the freeway. Starting out in the morning everything is flat.

 

Wow..I've noticed a similar effect, just not nearly as severe as yours.. when I'm cooling down, the pyro will take a long time to drop below 400.. if I shut the lights off, it immediately increases the speed of cooling down.

Di-pricol gauge...

 

ludwick_j,
I have the exact same 'issue' with my pyro--also measured post turbo. Always hotter in the AM, not sure why. I baby the truck till the thermostat opens and it's still hotter at cruise on the pyro. The only thing I've come up with is that before the t-stat opens, there may be pockets of coolant getting pretty hot since it's not cycling. I just go easy till the t-stat opens, then let 'er rip!
greg

 

greg,
I'm really easy on the pedal in the morning. After work is when I jump on it from the get go. Maybe I am not getting the rpms high enough to start with in the morning???? It is always cooler after work.
Another thing i thought of tonight was tire pressure. i wonder if there is lower pressure (low pressure from sitting all night, higher pressure in evening after being in the sum all day) in the morning and it is creating more drag. They are Yokohama Geolander 285's. Fairly aggressive AT tire. Not an MT, just a thicker lug AT. I will check the pressure tomorrow before I leave home and again before I leave work.
It took a lot of lugging to get to 600 after the gym tonight, too. About 8:00pm

 

I think I'm reaching with the tire pressure idea.
Same situation this morning. I drove more aggressively, and I was going into the wind. No change. Still right at 600 cruising. It is 500 or below in the evening. This is weird.

 

yup, it is weird...I've given up on it I only worry about the pyro when it's pushing 900

 

Not sure but it could be increased external cooling of the exhaust system in the AM compared to PM. Hotter gasses will move through the exhaust easier (expand) than cooler. This is why some wrap the exhaust manifold to keep the gasses hot until used by the turbo. I've noticed your same question even with a pre-turbo temp probe. After the exhaust system gets warmed up, the temps will seem to come down a bit. You've talked about two things that would affect this - AM temps cooler (will affect exhaust) and in the PM you drive it harder (heats it up faster). Not sure I can explain all the physics behind this, but it has been discussed before.