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Texasdude74 · 11-21-2016, **(Subject: Paccar MX-13 tuning )**

Since my segments take rate for this motor over the ISX is now over 90% and climbing, a lot of my friends are asking who can tune them,work on them besides the obvious dealers.
Anyone know who deals with making these things run?
Any forums that focus on them?

Running rough · 01-10-2017, **(Subject: Paccar MX-13 tuning )**

Pm Unilevers, I believe he might know

Texasdude74 · 01-10-2017, **(Subject: Paccar MX-13 tuning )**

I've heard that he can tune them. 530-550 horsepower and 1850-1950 torque seem to be the highest recommended power levels. So far so good, it looks like a well built and durable 'lil engine. The only unreliable parts surprise, surprise seem to be the Cummins after treatment bits. But there's an easy solution for that.

I never would have believed a 13 liter engine would hold up well in a car carrier over a 15 liter. But, I do know of a stock MX with over 400k at the moment with no issues. For comparison, the C13's in their day only seemed to last 5-600k miles at best. I only know of one ISX that has gone over 400k and it's a '13 tuned by Gearhead at 230k. It currently has 510k and is still running just fine and has never been apart, although no one will believe him.

The biggest complaints with the MX are that if you run them out of fuel they are a real bitch to get started again. Heard of smoking starters and emptied ether cans! Pete 389's are notorious for sucking one fuel tank dry with 40+ gallons on the other side. (A mandate removal seems to fix this fuel balance problem somehow)
Also the jake brake isn't nearly as strong as the ISX.
Not every shop or road truck has the correct software, DAVIE to trouble shoot and clear codes. Which are almost exclusively after treatment related.
Most of the independent diesel shops aren't very familiar with them.
Guys say they completely run out of steam above 1700 rpm.
If you have to replace the camshaft the engine has to come out of the truck because it comes out the rear of the engine, they're in the block instead of the head. The cams are steel instead of cast iron and are supposed to be much tougher. Time will tell. There was a cam recall already for some of them.

On the plus side, most everyone is reporting mileage gains of .7-1.0 mpg. They seem to get best mileage at cruise rpm of 1350 vs 1450 for 2250/2350 ISX. So 3.08 vs 3.25 with 255/70/22.5 drives.
They are said to be about 380lbs lighter than ISX and the '17 models are supposed to be 50lbs lighter still. The extra was taken off the accessories.
Most importantly, I don't know anyone that's thrown a rod yet. Or blown a head gasket or had a liner sink. Or worst of all had a fuel pump (these have two) turn an entire engine into a boat anchor.

Rig Wrench · 01-10-2017, **(Subject: Paccar MX-13 tuning )**

Just took delivery of 10 579 Pete's with paccar 500s and auto shift 13s. Non are on the road yet. But I'll check back with any info. Most I talk to are relatively happy with them. Cam recall is about 65% repaired at this moment I believe. But yes, time will tell

Running rough · 01-11-2017, **(Subject: Paccar MX-13 tuning )**

Maybe I should not count the paccar out after all.....

Rig Wrench · 01-11-2017, **(Subject: Paccar MX-13 tuning )**

(01-11-2017 )Running rough Wrote: Maybe I should not count the paccar out after all.....

They seem good for a 13 liter. But they are still short in the displacement

Texasdude74 · 01-11-2017, **(Subject: Paccar MX-13 tuning )**

The 485, 500 or 510 is the way to go in my opinion. 16.5:1 compression vs 17.5:1 for the lower ratings. I think the lower compression of these things is the reason they're not having head gasket, cracked head, liner, counter bore and fretting issues like Cummins. The X15 is going to have even higher compression and IVA's. They've built their own coffin.

In turbo diesels larger displacement is all about being able to spool up a larger turbo, the displacement itself doesn't make any more power. Modern injection systems and VGT or compound turbos mean a smaller engine can still move large amounts of air at a reasonable rpm. Some of these 13 liters will blow the doors off the old 3406 a,b,c etc of yesteryear. And those were the hot rods of their day, marketed to owner ops. These little things are mega fleet engines.

The MX13 and D13 seem to be the best of the breed and are eating Cummins market share like Rosie O'Donnell at a buffet. The worst seems to be the DD13. You can't get a DD15 in a Western Star car carrier, the drop axle is too low and that engine won't fit. Only the ISX with its short deck height, but a guaranteed failure and the DD13. No one wants the ISX so everyone ordered DD13's and they're complete junk. Incapable of passing a shop or getting up a hill. It's so bad that '17 will likely be the last year of the Western Star car hauler if they don't offer a different engine. They need to figure out how to shoe horn a DD15 in there.

Running rough · 01-11-2017, **(Subject: Paccar MX-13 tuning )**

There are guys out there who somehow think that just because the red moter has a shorter deck height, that it also has a shorter rod as when compared to a c15 cat, even going as far to say as rod ratio sucks in an isx, well I have seen the c15 rod beside the isx rod and they are basicly the same lenght, in fact I would say the isx rod is a bit longer from center of piston pin to center rod journal, not defending the isx just thought people should know,

Texasdude74 · 01-11-2017, **(Subject: Paccar MX-13 tuning )**

Yeah, I've always been told the rod ratio on ISX is the lowest of the 15 liters. But I've never measured the center to center length myself and divided it by the stroke. The differences are fractions of an inch. I seem to recall the ratio being listed around 1.507 or so off the top of my head. If my memory serves from my high school readings of Smokey Yunick and other engine building guides, a rod ratio of 1.5 was considered the absolute minimum for an engine to be halfway durable and 1.7 was the sweet spot. NASCAR and Indy shoot for 1.9 to 2.2. Although that's as much for increased dwell time as durability. If you're into hot rods ask an engine builder why road racers who run small block chevys go through so much trouble with custom pistons/pins and ring packs to run a 6" rod vs the factory 5.7"? Think you could eyeball the 3/10" difference? But it increases rod ratio from 1.52 to 1.6.

The side effects of too low of a rod ratio are increased wear on the thrust side of cylinder walls/liners, pistons that rock in the bore breaking wrist pins and fretting.
These effects get exponentially greater as power levels rise.

None of this means the ISX sucks. An engine doesn't know what brand it is. It just is whatever it was designed to be, and there's no free lunch in engineering. Every design decision has consequences. The ISX works fine at moderate power levels up to around 600/2050 and it will fit in every single truck and large rv in production today. If, for some reason you want(nobody needs) 7-800+ horse and 2400+ torque it's probably not the best platform for that.