I have noticed that when the truck is at operating temp, but cold outside (like 20 or lower) that when I am at a part throttle almost coast situation that the the turbo quit whistling entirely and then spools up every few seconds.

Also at an idle it does this after the engine is warmed up, but cold outside.

Is this normal? The truck runs great, and have no problems with it except ball joints and I guess that is what ford calls normal.


BTW, thanks to whoever fixed my username!!

 

I'm not sure what you mean by the turbo "spooling up"...

At idle when parked, in cold weather, the computer will speed up the idle to 1000 RPMs or so to try to keep the engine heat up. It will drop the revs back down again, and speed them up again, as necessary, to maintain the engine parameters where it wants them. I find that the speed it puts the idle to is enough to start hearing the turbo whistle, if that's what you mean.

Also as part of its cold-weather strategy, it will use the turbo as a subsitute for the 7.3s EBPV, using the variable vanes to present a bigger load in the exhaust path, to make the engine work harder and produce more heat. It does this wayyyyy more nicely than the annoying EBPV of the 7.3 but it can similarly result in the turbo whistling more than you would normally be used to under that load or RPMs.

When coasting, it *also* puts the vanes of the turbo in a position to provide more backpressure, to help with engine braking. And under some coast-down conditions the computer will also turn off the injectors, making the engine vary silent, which allows you to hear the spinning-faster-because-you're-engine-braking turbo whistle more than usual.

Does that help? I'm not sure I answered your questions.

Duncan

 

No, what I mean is it stops whistling entirely.

Like when you first start it and then the turbo winds up after a couple seconds and starts the whistle, it goes back to where it just sounds like a big-block idling with no whistle.

But this only happens after the engine is to operating temp and the outside temp is below 20.

 

The turbo only whistles when it's being asked to work hard and provide boost. My '97s turbo only whistles if I have a lot of weight in the bed and am going up a big hill. With its variable vanes, the 6.0s turbo can provide better-matched boost at more times, so it whistles a lot more often. But when it's not being asked to provide boost, it's not going to whistle. That would be at idle, while coasting, etc. (With the exceptions I noted above, where they play games with the vanes to perform other functions and a side-effect is more turbo whistle.)

Keep in mind, with your new giant free-flow exhaust, you're probably going to be better able to hear both the whistle and the lack of whistle. It's also possible you'll hear things like flutter that those of us with stock exhaust systems will never hear.

Duncan

 

I could hear this before I got the new exhaust.

When it is warm outside +30 degrees the turbo nevr stops whistling even at an idle ever. On days when it is cold it stops entirely.

 

I dont know exactly why, but I will offer a possible explanation.

The basic function of a turbo is to increase the amount of air per any volume of air...hence the reason for boost to be measured as a pressure, pounds per square inch. When the air outside is cold, it is naturally more dense, effectively reducing the work load on the turbocharger (one of the reasons for the advent of an intercooler). So, under low load, light acceleration, or idle conditions, sensors may manipulate the vanes in the turbo so that it is not in use, due to the already high density of air entering the engine. Furthermore, this hinders the production of white exhaust smoke, a side effect of haveing a air to fuel ratio that is higher than engine specifications require (again, more likely to occurr at colder temps).

Again, not sure if this is the reason, but it might be....