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tree98 · 03-22-2018, **(Subject: Most reliable hp & torque for x15 )**

Spec'ing a new truck with an X15. I know I read somewhere on this forum what the best rating is for an x15. To high and it's prone to liner fretting. This truck is 80k-90k gross and goes off-road. Peterbilt says get the 565 hp 1850 torque because it's only a few hundred dollars more than the 525hp and can easily be turned up to 605hp. I wouldn't want to go to 605, originally I just wanted 525. What would be most reliable? Gonna have 4.10 and an 18 speed 24.5 rubber

schISM · 03-22-2018, **(Subject: Most reliable hp & torque for x15 )**

I haven't researched the cpl's on any of the X15's but I'm gonna guess 500 through 605 is the same so save your money and go with the 500 and turn it up after warranty is up.
As far as reliability your guess is as good as the next guys but obviously less hp = less stress on components and lower operating costs(fuel and def)
Keep us updated and enjoy that "new truck smell".

Hammerhead · 03-22-2018, **(Subject: Most reliable hp & torque for x15 )**

I don't know squat about the new X-series, so take this for what it's worth...

With the 871 I do know that any engine with factory HP rating EXCEEDING 500hp had an ST Block.
You can't see anything different externally, but when they're tore down side by side you can see differences internally.
Just something to keep in mind, it's always simpler & safer to turn something down than it is to turn it up...

dhirocz · 03-23-2018, **(Subject: Most reliable hp & torque for x15 )**

Agreed.

I tend to think, however, the more important part of the equation is how it's driven, not so much the power is set at.

I would think having the engine set at a decent rating combined with driving more conservatively would do the most...that and getting rid of the soot problem.

tree98 · 03-23-2018, **(Subject: Most reliable hp & torque for x15 )**

(03-23-2018 )dhirocz Wrote: Agreed.

I tend to think, however, the more important part of the equation is how it's driven, not so much the power is set at.

I would think having the engine set at a decent rating combined with driving more conservatively would do the most...that and getting rid of the soot problem.

I hear you about the soot problem. These trucks are driven by employees so driving habits can be pretty poor, Not much I can do about that......... unfortunately.

Brock · 03-23-2018, **(Subject: Most reliable hp & torque for x15 )**

525 and up is x15 performance
500 and down is x15 economy

My ISX 15 small cpl 500 is almost at 2 million km on original engine and still running strong, 4:11 gears 100,000lbs+ it's whole life.

525 and higher motors don't last as long but here's the kicker....... they usually haul more weight which is why the guys get the higher HP engine's so we're not comparing Apple's to apples.. ....

dhirocz · 03-23-2018, **(Subject: Most reliable hp & torque for x15 )**

(03-23-2018 )tree98 Wrote:
(03-23-2018 )dhirocz Wrote: Agreed.

I tend to think, however, the more important part of the equation is how it's driven, not so much the power is set at.

I would think having the engine set at a decent rating combined with driving more conservatively would do the most...that and getting rid of the soot problem.

I hear you about the soot problem. These trucks are driven by employees so driving habits can be pretty poor, Not much I can do about that......... unfortunately.

Maybe, maybe not. You might not be able to fend off the drivers driving style, but a tune and bypass filter will still help out alot, even if it's not demandated. Have you also considered talking to the tuners here about limiting maximum boost, speed or other potential safeguards in the ecm to protect yourself against abuse?

That's an awful lot to spend on a truck...it makes sense to spend just a tad more to protect it.

Mikiisx09 · 03-31-2018, **(Subject: Most reliable hp & torque for x15 )**

I have Kenworth T 680 with X15. 525HP 1850Tq. Pulling Reefers on West Coast.There is no reason to go more then 525HP unless you pulling something really heavy.

the missing link · 04-03-2018, **(Subject: Most reliable hp & torque for x15 )**

(03-31-2018 )Mikiisx09 Wrote: I have Kenworth T 680 with X15. 525HP 1850Tq. Pulling Reefers on West Coast.There is no reason to go more then 525HP unless you pulling something really heavy.

I am running 525 and 1650, ( maybe a touch more then 1650, not buy much ) pulling 140,000 lbs on alot softer roads then alot of guys are used to . she does just for fine . ,I will also out pull a 600 down in low range if I want to . it's a 871.
It all depends on what you want and are comfortable with. It was not long ago we were pulling the same weight with 400//425 . there is no reason you can't , except for your ego .