Engine/Transmission (1994 - 1998) Will cold weather affect EGT & boost?

[fortunate1]

Running at constant highway speeds over the same stretch of interstate (fairly level). About 2 weeks ago (temps in the 50's) 65 mph reads 1750 rpm, 450-500 *F post-turbo, and 3-4 psi boost. 2 days ago (temp = 25 to 28) 65 mph reads 1750 rpm, 550-600 *F post-turbo, and 7-8 psi boost. The second readings are more like what I'd ordinarily see climbing a mild (3 or 4% grade) hill. Nothing in tow. Wind was very light, and these readings were the same going both directions both times.



I guess they aren't alarming, but they are different. Any thoughts about the cold temps or winter fuel. These were burning 2 different tanks of fuel, but from the same truck stop (does SE Virginia even sell winter fuel?)

 

[redram]

The difference in boost is why your EGT's increased.



The lower ambient temperature will be denser (packed with more oxygen) and therefore yields more power. Just like in the heat of the summer, enignes produce less power.



It could also be two different cetane levels of fuel but more than likely, the cooler air was the difference in the boost and thus, more work being done, more heat being created, thus the higher EGT.



redram

 

[illflem]

25 to 28 is like an April day in Montana, when it really gets cold it takes more power thus higher egts and boost just to turn the gears in tar like trans and differential fluid. You can tell when it's really cold when your truck won't coast below 10 mph, acts like the brakes are on.



I think in your case the fuel is what made the difference.

 

[The patriot]

I was thinking that you may have had a headwind. ?

I've noticed that my fuel pressure is higher in the cold weather. Guess it thickens a little.

Eric

 

[JJW_ND]

EGT Gauge probe standard

On Westachs gauges the location of the connection will read + or - from 70 degrees. So current temps here would mean it reads over 70 degrees higher.



I also notice extra fuel (be it summer with heavy foot or arctic cold and cold motor) pushes up the EGT.



jjw

ND

 

[CumminsPower98]

Interesting. My truck definitely runs higher boost and lower EGT's in the winter. I can run the same hill at the same speed and get 75º-100º lower EGT's and my boost will be at least 5 lbs higher or more.



Mark

 

[fortunate1]

Thanks for the replies. I know about the EGT's calibration to 70 deg F ambient temp. So I'd be looking at a 45 deg difference at the cold temps I mentioned and about 20 deg when warmer.



Bill, I've been to Billings, Glasgow, and points in between in the MT winter. It does indeed get cold.



Phil

 

[Ben Rumson]

Originally posted by The patriot

I was thinking that you may have had a headwind. ?

...

Even a slight difference in wind/headwind can make enough difference in wind resistance and drag to make the difference you're noting.



It's just one of the variables that makes it very hard to do an accurate/head-to-head comparison for one trip against the next.



"All things being equal" generally only exists in theory (Economics for example) and is almost non-existent in the real world of "tire hits the pavement".



Also "ditto" what Illflem said about cold fluids. I noticed a considerable difference in how much faster my truck "got rolling" in sub zero weather when I went full synthetic in the differentials, transfer case, and transmission. Cold weather can be DANG hard on stuff!