why is there a diff between being cold and warm?

[97powerstroker]

im just curious to why my truck is much slower and sluggish when its cold.i have to give it more gas when i let the clutch out,it doesnt accelerate nearly as quick and also sounds different.everything works the same whether it be cold or warm,so why the difference in performance? somebody take me to school real quick.thanks

 

[DaveBen]

Diesels are "heat" engines and like to run at their operating temperature. When they are cold they are sluggish, just the nature of the beast. Compression is what generates the heat, and when it is cold they don't perform up to expectations. Let your truck warm up for a few minutes and treat it kindly for the first 5 miles. It will make a difference.

Dave

 

[Sawboy]

stroker.......you live in Florida! Your truck don't know nuthin' bout no cold weather!

Try starting it on a Chicago morning when it's 0 outside. I can actually see the headlight beams "rattling" across the street here!

And it's only "cold" here, let alone the guys the live in the U.P. and Canada.

 

[MBRPCrazyford]

Yeah, that's how they are, but I know a guy that has a 97 OBS and said that it actually run better when the ambient temp. outside is around 40-55.

 

[bbressler]

I think the real reason you see a difference is because the computer is adjusting the timing based on the engine oil temp. When you start off, and it's cold, the engine is advancing the timing just a little bit. After you get it up to operating temps, it's just like any other warm day..

 

[bushpilot]

I think the real reason you see a difference is because the computer is adjusting the timing based on the engine oil temp. When you start off, and it's cold, the engine is advancing the timing just a little bit. After you get it up to operating temps, it's just like any other warm day..

REALLY....i thought advance/retard had to do w/ SPARK

 

[hheynow]

REALLY....i thought advance/retard had to do w/ SPARK

Diesel fuel injection timing

 

[bbressler]

Here's an excerpt from a write-up regarding the EOT mod:

The 1995 Powertrain Diagnostics Manual confirmed my suspicions that the PCM uses the EOT (Engine Oil Temp) sensor to adjust fuel, timing, and initial idle speed based on oil temperature. The sensor has a resistance of about 1k ohm at 250 degrees F, and resistance increases to about 330kohm at -30F. The change is not linear, but is gradual at the high and low ends, with the bulk of the change occuring from 50 to 0 degrees (approx from 60-300kohms).

 

[strokin'_tatsch]

i believe the cold performance has a lot to do with oil temperature. cold oil is very thick oil. your powerstroke's injectors are run from the oil pressure right? the oil can flow as easily when it's cold and thick right? resulting in less oil pressure until the oil gets up to temperature. advanced injection timing actually helps performance. i believe they advance timing when oil temp is cold to try to compensate for the cold oil and lower pressures the injectors are seeing.

 

[97powerstroker]

yea,i think its all about oil myself,but i also do think it runs better in the cold after its warmed up,few days back it got down to 32 degrees,thats cold here in fl,im from michigan so i know about cold and 32 is pretty cold.