tuning question

[Rawze]

(05-14-2022 )ptlogan77 Wrote:  ...
The max boost is about 36-37 lbs, and since I still have the VGT turbo I have great engine braking with boost up to 38lbs on stage 3.

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THAT IS ABSOLUTE ENGINE TORTURE!!!..... It is over-boosting.. and the engine brake .. if it is able to get to 38 psi... has been most likely jacked up too and is eventually going to destroy that engine. I.E.> crack the head, maybe bend a vale, or send a piston thru the block with absolutely zero warning.

(with no more egr gas going into the intake) The x15 only needs about 30-31 psi or so to make 600+ HP 32 being the upper limit before causing harm ... and engine brake set to more than about 28~ish lbs of boost or so is going to eventually cause it to drop a valve. - those numbers that you describe so far point directly towards a possible bad delete where someone jacked with the engine brake settings and did not have a clue how to correctly re-program the turbo to make a proper fuel-air-mix. - You should be worried.. REALLY worried!.

also, it seems like most of what you are saying makes little to no sense. You have been led down some kind of rabbit hole by a bunch of engine and truck abusing collection of morons at some point.

That is not a direct-drive tranny at all... it is a 0.73 over tranny.

YOUR TRUCK IS GEARED TOO TALL FOR THAT TRANNY!

here is the reality of how that truck is spec'd...
http://rawze.com/forums/showthread.php?t...4#pid71474

How about you go rent a truck with the same make/model, engine, tranny, and everything with a proper set of 4:36's in it and see how much better it drives and gets out of its own way IN EVERY SINGLE GEAR YOU PUT IT IN. See how much easier that truck gets up and going with heavy freight behind it, etc... - and when driven right ... how much better fuel mileage it can make with exactly the same loads simply because it is not geared too tall for the application.

As someone who knows how to drive a truck properly.. and has test driven hundreds and hundreds of trucks with every kind of gear ratios out there .. it becomes obvious real fast.

Your only fooling yourself at this point by continuing to disagree, because your not going to fool me. I have been there and done that over and over with too many people and trucks to know better.

Also, even when simply test driving a truck.. immediately, when the truck has a decent set of rears in it,.. you can simply feel it.. it accelerates like it was designed to pull that 80,000 lbs.. and every single time I get into a truck with those tall arsse rears that are not fit for a pick-up truck... the damn thing always feels sluggish because EVEN THE LOWEST GEARS IN THE TYRANNY ARE TOO TALL FOR THOSE TALL REAR ENDS) .. the person driving it is always pushing the pedal a lot harder because IT just does not want to get out of its own way compared to something that was geared right, once the truck is loaded heavy. - It is terrible, and the engine has to work a whole lot harder just to sling it around.. in every single gear range.. you can just tell something is wrong with it compared to something that was actually geared for its intended application.

so if I were given that truck, I would be saving up for a decent set of rear ends to put in it and get rid of those tall garbage engine killing rear ends, unless all it was going to do was haul around a bunch of flowers that don't weigh anything.

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last but not least... higher RPM in the ISX does not mean less fuel mileage once the engine is loaded down. There are days where we don't even use 10'th gear (we have a 10 speed)..and the engine is always up at 1500-1900+ all day long .. and we still break 9+ mpg with it grossing 80,000lbs with water totes, big paper rolls, coils of wire, wood pulp, etc. kinds of loads. people's logic has gotten severely flawed somewhere if they think that higher rpm = lower fuel mileage on a loaded truck.

Those numbers that you posted clearly shows that it is over-boosting .. and it is most likely that the engine is labouring against its own exhaust gasses all the time due to an over-spooled turbo when in higher rpm ranges. An engine that does this will have significantly lowered fuel efficiency because the turbo is choking the exhaust all the time unnecessarily.