I've asked this in other threads but really haven't got a difinitive response. As you can see in my signature I run 1.7mm of advance. Main power screw in about 1 1.5 turns. High idle back out all the way. I average about 24 lbs of boost.

Before I did any mods when I would tow, I never went past half way on the coolant gauge. This was in 116 degree weather up a long mild pass with a rather heave double axle boat that weighed approx. 5900 lbs. It would need almost full throttle (truck only made 13 lbs stock before my greedy fingers got in there) but I could tug that boat up all the passes in hot weather almost floored in overdrive at 70mph running cool!

My stock timing was 1.12. Now its 1.7mm and turned up some with the cone at the deepest part. I'm wonder why going over the same pass in cooler weather with the same boat the coolant is much hotter, one full quarter of the guage! I made the run while trying to duplicate the boost at around 11-12 lbs at 70 but the truck runs much hotter.

Could someone explain if this is normal? Should I back the timimg down to a more conservative 1.4mm ? Any feedback on the same phenomenon as I've had?

brad

 

You *may* find a thread or two on this topic if you look around...the down and dirty is yes, more timing will equate to higher coolant temps. If you back down to 1.4 as you said, you should see a proportional change in average loaded coolant temps. As it turns out, Cummins really knew what they were doing when they set the specs on these engines. I've read a bunch of threads where fellas (myself most definitely included) say they used to pull like mad WOT all day long over mount olympus and never have coolant or egt troubles. Now once they got all turned up under the hood, they can't pull the same grade w/out having to get out of it. While it's true there's a bunch of free power to be had under the hood of any first gen, you really have to take a systems approach to bombing if you plan to use any of that new power for more than 10 seconds. Big pipes and BHAF's are only the beginning. What most of us lack more than anything is cool air. Sweet turbos cost big bucks, so most of us are left with the quick blast to the bermuda triangle of melted pistons and nothing more. Tuning these beasts to 'keep up' with the newer trucks is really a tricky affair---ever seen a 3rd gen radiator, or intercooler? I'd kill for half the heat dissipating capacity of either one...but I'm still gonna race him on the onramp...and if I keep up, imagine how much harder my aux systems are working at that power level...ahhh, pull your timing back a bit and throw some nitrous at it!!!
greg

 

I could see that my truck would run much hotter if I was pulling 25lbs of boost that I get now if I needed that much. I just didn't know that even taking it easy and only pullling 10 lbs of boost the truck would still run hotter than what is used to run pulling with 10 lbs before. Seems like if I ain't calling all the horses the truck should still run as cool as before at low boost?

brad

 

it's not likely, but it COULD be possible that your thermostat got stuck somewhere along the way. might want to try backing off the mods 1 at a time to see what happens. or not.

 

More advance means cooler exhaust temps for a given amount of fuel.

The heat that is not going out the exuast has to go somewhere else.

Part of that heat goes into producing more horsepower, which is why fuel efficiency increases with advanced timing.

The rest of that heat gets absorbed by the piston and cylinder and head. The piston is cooled by the engine oil, and the cylinder and head are cooled by the water jacket.

So, when you advance the timing, you increase your water and oil temperature for a given amount of fuel.