CAT C15 6NZ Straight Pipe Sound for American Truck Simulator
The Caterpillar C15 6NZ from 435 to 625 hp with a straight pipe, two engine brake variants and an automatic fan. Free, by Slav Jerry; version 5.5 for ATS 1.58.
Download CAT C15 6NZ Straight Pipe Sound
More screenshots on TruckyMods (verified creator), SCS forum and Steam Workshop ↗
What this mod does
CAT C15 6NZ Straight Pipe Sound is one of Slav Jerry‘s most downloaded sound mods: it turns the Caterpillar C15 6NZ into a straight pipe engine, with no muffler and the deep rumble associated with classic American trucks. Its thread on the SCS forum has been open since 2021.
What it includes
- C15 6NZ engines with 435, 500, 550, 595 and 625 hp and open exhaust.
- Two engine brake variants; 5.5 debuts a new one for the main variant.
- An engine fan that kicks in on its own, exhaust stack effects and sound attenuation with distance.
- CAST system to add modded trucks that aren’t on the list.
Where the sound comes from
The author starts from SCS Software’s engine samples and thanks Louisiana Truckspotting for its recordings of a real truck. It uses no audio from other games.
Compatibility
It works on some SCS trucks (not on those that never had this engine) and on many modded trucks. The idle engine brake isn’t compatible with mods that change the cab switch sounds.
Version
Version 5.5 (April 1, 2026) is tagged for ATS 1.58. It renames the engine files, so you’ll have to pick the engine again at the service shop.
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It's in Documents › American Truck Simulator › game.log.txt. It's read in your browser: the file is never uploaded.
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User rating
Mod video
Highlights and things to keep in mind
- Carefully crafted straight pipe sound, with two engine brakes
- Recording sources declared by the author
- Works on many modded trucks and lets you add more
- Tagged only up to ATS 1.58
- Doesn't work on every SCS truck
- After updating you have to fit the engine again
Requirements
- American Truck Simulator 1.58 (compatible from 1.56 to 1.58 according to the author)
- No DLC required
- An SCS or modded truck that supports the CAT C15 engine
How to install it
- Open the mod's page on TruckyMods (it's also in the author's thread on the SCS forum and on Steam Workshop).
- Download version 5.5.
- Copy the .scs file to Documents/American Truck Simulator/mod.
- In the Mod Manager, enable it and place it above modded trucks and other sound mods.
- Go to a service shop and fit the CAT C15 6NZ engine again: 5.5 renames the files and the previous engine is lost.
- If a modded truck doesn't support it, use the CAST system the author explains in his thread.
Version history
-
5.51 Apr 2026Current
Engine names matched to the stock 6NZ, new engine brake and minor tweaks
Common problems
Why did the engine disappear from my truck after updating?
Version 5.5 renames the engine files to match the stock 6NZ. Pick it again at the service shop.
Does it work in ATS 1.61?
The author tags it up to 1.58. It may load, but the game will show it as an outdated mod until he updates it.
Where does the sound come from?
From SCS Software samples processed by the author and real recordings provided by Louisiana Truckspotting.
Is there a stock version, without the straight pipe?
Not for this engine. The same author does have the Cummins ISX with a stock sound.
More mods for ATS
ATS 1.57 
ATS 1.58 
✓ ATS 1.61 
ATS 1.60 
✓ ATS 1.61Multiplayer 
✓ ATS 1.61Requires DLC