galimim wrote: 15 Feb 2024 21:12
I am aware. I just need to find the motivation to create a whole new set of engines with the 2024 specs.
Hey galimim,
Yeah, uhm, I’m also super into the tech behind truck drivetrains and I’m always checking out what the big players are up to—like Cummins, Mercedes/Detroit, Volvo, MAN, you name it.
So, I’m always tweaking files in your mods (only the engines I use) to try to get that real shifting/driving behavior. The buzzword for modern drivetrains is keeping those RPMs low while cruising. Like, Scania engines can chill in overdrive at under 1,000 RPM when they’re rolling at 85 km/h, and that’s becoming more and more the norm in the U.S. for company drivers—not so much for owner-ops yet. Usually, those engines cruise around 1,150 RPM.
To give you a solid example for dropping those EPA 2024 engine versions in your mods, I added the Cummins X15 450 EX-rating to the Paccar drivetrain mod. The EX-rating is basically Cummins’ version of the Detroit integrated drivetrain. Cummins efficiency series coupled with Eaton Endurant. Those EX engines got in with just 1650 lb-ft of torque (2237 Nm) in the lower 9 gears, then they flaunt the engine rating in the top 3. It’s kinda like a multitorque setup but with heavy torque in the upper three gears. Other than a few Paccar engines, Multitorque is still kinda rare in the U.S., but Cummins is definitely heading in the right direction. They just have it in the EX version with the top 3 gears instead of the usual 2 like in Europe. By the way, for Cummins' ST ratings, only the upper 2 gears benefit from that higher torque. Cummins is saying it’s got a solid 200 lb-ft more torque, so like 1550/1750 or 1650/1850 lb-ft.
For this one, I used the 1850 lb-ft / 2508 Nm / X15 450 hp EX-rating EPA 2024 model. Cummins is leveling up with high torque at low RPMs too, especially with their modern Efficiency engines and the EX-rating. Their brochures say they’ve got max torque ready around 900 RPM. Here are the specs I put together:
Code: Select all
SiiNunit
{
/**
* By Galimim
*/
accessory_engine_data : x15_450ex.kenworth.t680_2022.engine
{
name: "2024 X15 450 EX"
price: 42000 # Engine price
unlock: 0 # Unlocks @ Level
# Engine display info
info[]: "450 @@hp@@ (416@@kw@@)"
info[]: "1@@dg@@650 @@lb_ft@@ (2@@dg@@237 @@nm@@)"
info[]: "1@@dg@@150 @@rpm@@"
icon: "x15"
# Engine Specs
torque: 2237 # Engine power in Newton-metres
secondary_torque: 2508 # Secondary Torque in Newton-metress
resistance_torque: 68
volume: 14.9 # Engine size in liters. Used for Realistic Fuel Consumption settings
# Torque Curves
torque_curve[]: (300, 0)
torque_curve[]: (870, 1)
torque_curve[]: (1150, 1)
torque_curve[]: (1330, 0.9892)
torque_curve[]: (1420, 0.9520)
torque_curve[]: (1520, 0.866)
torque_curve[]: (2100, 0)
# Secondary Torque Curves
torque_curve[]: (300, 0)
torque_curve[]: (910, 1)
torque_curve[]: (1270, 1)
torque_curve[]: (1350, 0.9297)
torque_curve[]: (1500, 0.8135)
torque_curve[]: (1700, 0.6940)
torque_curve[]: (2100, 0)
# RPM Data
rpm_idle: 600 # RPM at idle
rpm_limit: 1700 # Governed RPM limit
rpm_limit_neutral: 1900 # RPM limit in neutral gear
rpm_range_low_gear: (870, 1060)
rpm_range_high_gear: (890, 1130)
rpm_range_power: (1300, 1600)
rpm_range_engine_brake: (1500, 2000)
secondary_torque_gear_ratio: 1.31 # This defines the transmission gear ratio below which secondary_torque is used
# Engine Brake data
engine_brake: 2.5 # Engine Brake Strength
engine_brake_downshift: 1 # Enable automatic downshift for Engine Brake
engine_brake_positions: 3 # The number of engine brake intensities
# Adblue / Fuel consumption Settings
consumption_coef: 0.92
adblue_consumption: 0.05
no_adblue_power_limit: 0.6
# Sound Data
@include "z_x15_sound.sui"
# Overrides
#overrides[]: "/def/vehicle/truck/kenworth.t680/badge/cummins.sii"
overrides[]: "/def/vehicle/truck/kenworth.t680/accessory/badge/cummins.sii"
# Attachments
defaults[]: "/def/vehicle/truck/kenworth.t680_2022/transmission/eeo18f112cr.270.sii"
}
}
The data is as close as possible, I grabbed the torque curves from both the 450 hp/1650 lb-ft and the 450 hp/1850 lb-ft EPA 2024 X15 efficiency engines, and I did some recalculating (like, 1850 lb-ft at 1600 RPM and 450 hp isn’t possible) and factored in typical RPM-related friction losses for modern 15-liter engines (kinda rough estimates, although backed up by AI). SCS usually calculates friction losses at 2000 RPM using the formula 20 times displacement (20*15 l = 300 Nm @ 2000 rpm), which gives about 300 Nm for a 15-liter engine, way above what we see these days in modern truck engines. So I asked the AI and learned that Scania, Paccar, Detroit, etc., are looking at around 70 Nm at 2000 RPM for resistance torque when simulating 15-liter engines. But hey, these are just ballpark figures from various sources online that the AI pieced together. But still better than nothing
As for the drivetrain behavior: The numbers hold up pretty well in ATS (and also ETS 2). At about half load, the engines chill in the lower gears around 950 to 1200 or 1250 RPM (the values in the files aren’t carved in stone, the game still does some work in the background - the drivetrain doesnt shift up at 1060 revs
). When you push it harder up to max power, the engines rev between 1150 to 1450 RPM. This totally matches what you see in YouTube videos of folks driving modern trucks as company drivers. So it seems pretty spot on. On hills, the engines rev higher or delay shifts in auto mode or downshift sooner. When cruising, the trans drops from around 1200 RPM to about 980 RPM. But if there’s even a slight incline, the trans stays at 1200 RPM and holds off on shifting up until it’s past the hill—again, pretty realistic. As for modern transmissions, AI suggests shifting times between 300 ms to 500 ms at low load and up to a second for high load. So I did 0,6 seconds
. Again, quite realistic if compaired to POV driving vids of modern trucks.
By the way, I’m testing that engine in a 2022 Kenworth T680—it’s wild to see how many people in the resale market are going with the Cummins X15 instead of Paccar (which isn’t super popular in the U.S. but is slowly getting better). My fuel economy’s sitting at 9.1 mpg after about 3000 miles (driving from Portland to Iowa and back, with quite a bit of mountain driving, for sure), with an average load of around 38,000 lbs. I usually cruise at 65 mph on the highway (which is quite realistic, given the fact that company trucks are governed at 65 mph), and when it’s rainy, foggy, or night driving on smaller roads, I slow down to like 50 to 58 mph. The transmission is the Endurant HD from Cummins/Eaton (Eaton is now a part of Cummins company), with a rear axle ratio of 2.85/0.77, which is standard now. The gearing drops from around 1200 RPM in 11th to about 970 RPM in 12th at around 57 mph when cruising flat terrain—quite realistic. So yeah, overall it’s looking pretty real. Especially with those adjusted numbers for friction losses, those lower-speced engines ain’t just bouncing around like jelly anymore. I mean, honestly, the behavior feels pretty on point with reality, especially since SCS hasn’t even accounted for idle cruising yet. But at least those adjusted friction losses kinda make up for it, you know?
Also, I’ve adapted similar parameters for other modern engines, like the Cascadia Gen 5 with Detroit’s newer drivetrains of the DD13 and DD15, and also for ETS 2 (Volvo, MAN, etc.), based on their data sheets and YouTube POV videos to see how they shift. One little bummer though: When you let it idle and give it some gas, it takes a sec for the engine to bounce back to idle RPM. A bit of a flaw for sure, but it doesn’t mess up with the driving itself.
