First question - I notice the boost up around 200lbs when I accelerate on to the highway most of the time. I have a light foot and drive for mileage but at the point where I stop accelerating up to cruising speed and flip the cruise control on the boost gauge reads up around 200?

Second topic - I notice a sucking noise from the truck, like a vaccum cleaner, every time the boost is between 100 and 180lbs or so. Closer to 200lbs the typical turbo whine kicks in over the vaccum. What is the vaccum sound and why does it take the boost pressure to go up so much before the "normal" turbo whine kicks in? Like if I am in 5th gear and push the petal down to accelerate, but not to the point where it down shifts, I hear the turbo spool up with the whine up around 200lbs boost and the truck pushes you back in the seat. I haven't pushed it past 75mph so I don't know how high the boost pressure will go, not really a concern, but I would like to understand it a little better.

Third topic - My last tank I was well over 17mpg. I don't have my receipt in front of me where I wrote it all down, but the calculated was something like 17.5 and the meter was 16.8. Is that "pretty close" or are some of yours even closer? I know some people's are way off (calculated vs. meter). I re-set my mpg with each fill-up, as well as one of my trip meters. I do only go to 1/4 to get around the $75 pre-pay limit. Otherwise its a pain in the butt.

This next tank should be even better than my last one - I spent a lot of time on the highway for the first 1/4 tank. The meter is showing 17.4 as of when I pulled in the driveway.

 

eh... my boost gauge is 10, 20, 30, 40..

my LOM is usually high as compared to calculated..

Sam

 

That is some PSI going on there...ready for take off. No wonder it sounds like an airplane....just harassing you.

I think with the DPF is does not sound as normal exhaust would sound.

You have a sequencial turbo, smaller to get bigger going.

 

Sam - Isn't the boost gauge x10? I am referencing the 1/2 way mark as 200lbs - 20 x10.

Scott - Does the smaller turbo make the sucking noise rather than the whine then?

Another question - why is there the lag? Does the engine just need to build some RPM's before the turbos can catch up and thus the time delay in petal-down vs. take-off-and-go? Thats an extra "sense"/"skill" I need to add to my driving enncyclopedia - factoring in the pickup time in manuvering decisions.

 

It's 1x10, 2x10, 3x10 and 4x10.

I'm in no way an expert but I think it's the other way around.
The engine is ready but the turbo takes a second or two to spool up and aid the engine in accleration. Just give yourself extra time when pulling out although I do realize you can't always apply that logic. There has to be enough exaust pressure to spin the small turbine at a useful speed.

 

some of the lag is the exhaust is needed to turn the turbo's..spooling. But there is a little more than should be because of the emissions programming built into the programming of the truck.

That is why you will see some off the line with black smoke.

Ours will not have that because of the emissions will not allow an overfueling to occur.

Each mark on the boost guage is 10 psi for a max of 40.

Max this motor can take is 41 psi. More than that and it would blow its top.

 

Gotcha on the pressure. Im about to head out so I'll take another look at it