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529 Posts
keep the engine in rpm.
I think I'm tracking with you, as in don't lug it at low rpm's, and take advantage of the fact that this is an oversquare V-8 with a redline of 4000 rpm that actually likes to rev and maintains torque all the way to 4000. That keeps oil pressure higher too of course.

It does resemble a gas v-8 more than it does the other diesel v-8's out there. In the valve train for sure. No one else is using a quad-cam design for an engine this small...in fact the Duramax 6.6 and Powerstroke 6.7 are OHV designs. A more traditional approach. Looking at the pic below, at a quick glance observer would prabably say "this is a nice looking quad cam v-8...what is the redline?...." The glow plugs do stand out though ;)

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2019 Titan XD Pro4x Cummins
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My feeling is the engine starts to defuel around 3900 but will allow up to 4250rpm before complete defuel.

I think peak volumetric efficiency is somewhere around 2600-2800rpm. These engines can make way too much torque at low rpm due to the turbocharger arrangement. 15psig at 1100rpm is a lot of power.

Lower rpms at high torque are the most likely candidate the hammer out the bearings. With such a low friction design it should be driven more like a big block. Not revved out all the time, but not lugging it either.

My other observation has been you can run much less boost for the same power by letting the engine spin faster. I’d rather do 2200 rpm at 5psig than 1600 at 15psig.
 

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I can't imagine it is anywhere close to 50/50. Yes there have been a number of posts here about broken crankshafts and such but not dozens. I would think (just wild speculation from being on the forum for a while) it is much closer to you 95/5 threshold.

One member on here (who sadly has since left) had 2 XD's....one he bought at auction post flood a few years back. Completely underwater and he rebuilt the whole thing and had it on the road. Wrecked trucks are out there, but the engines go pretty fast and are expensive. The underwater thing was probably a different story....

I think there have been a number of spun bearings as stated earlier in this thread. (e.g. problems start with knocking before the crank lets go or it just gets shut off and metal is in the pan...) Normally that is an oil starvation root cause--but not in these cases. Well cared for engines have let go for no apparent reason-so that is the worry. Bearing surfaces are not as wide at a straight six and heat is an issues. Quality oil and regular changes are really important. I have never gone over 5K for the interval on mine. It is not deleted so not taking chances on TBN dropping low and soot building up to crazy levels.
Thanks Vann. That makes me feel a lot better. I really love this truck and I hope I get many many years out of it.
 
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