Programming in Cold Weather

[Jackpine]

I don't understand what you mean when you say "timing". Is it valve timing? Can this be adjusted on diesels? As you can see, I know next to nothing about this kind of engine beyond the fact that it ignites fuel using compression only once started and that it has more power potential.

I suppose it idles at higher RPM when cold, like a gas guzzler? If so, it's getting a somewhat richer fuel mixture, and maybe the throttle is held a bit more open? Could it be that this is a normal sound at this RPM that is partially masked by road noises if the vehicle is underway?

My sister's truck has the same engine as yours. Someday, maybe I'll talk her into getting one of Bill's tunes for it. And, she's in Colorado Springs, where it gets pretty cold too.

I'd be good if someone with diesel knowledge added their thoughts here. In the meantime, I'll try to keep the thread alive.

- Jack

[Power Hungry]

Just for reference, what gassers call "timing" is called "start of injection" or SOI on a diesel. This is ROUGHLY the same comparison although spark timing on a gas is more of an instant reaction while a diesel has a small delay between the time the fuel is injected and the time it actually starts to burn. This just semantics, though.

Anyway, the reason for the extremely advanced timing in cold weather is because the diesel fuel burns SO SLOWLY at those temps that it can take as much as 20 or 30 degrees more timing just to keep the engine running. Of course, as the engine warms up, the timing will back down significantly.

Diesels also monitor Intake Air Temp since colder air needs to be heated a bit before entering the cylinder. This is what glow plugs and intake air heaters are for. Diesels also use the Intake Air Temp to advance the SOI so the engine can run properly. This is the reason that even with the engine fully warm, it is always a little "louder" in the winter than it is in the summer.

Hope this helps.

[Jackpine]

So, fuel is injected earlier in the intake stroke on a cold engine. Did I understand this correctly? And somehow the effect of that and intake heating cause the engine to be louder. It's great to learn new things!

And, since you didn't say to the contrary, a custom tune will not cause harm in cold weather.

Interesting that a tuned diesel is louder than an untuned one. My guess here is though, that it is getting more gas (so it can develop the additional power) that tunes provide. So, more gas and possibly more air too (to balance things) means a louder burn, right?

- Jack

[Power Hungry]

I tuned program can be harmful to an engine if it is too aggressive, whether it's gas or diesel, hot or cold. The reason tuned diesels are "louder" is indicative of the advanced injection timing and is normal.

In most circumstances, I don't really do much for tuning in the portions of the maps that are below 120ºF. This way it allows the engine to warm up before really putting any power to it. There might be a little timing but that's usually about it.

Diesels are odd engines to understand completely. Gas is much simpler, except for the Air/Fuel Ratio bit.

Take care.