Bosio DLC 520 Nozzles (Set of 4) — ULSD Rated, VW AFN/ASV Direct Replacement

What it is
This is a set of 4 Bosio DLC 520 performance injector nozzles, a direct replacement for the stock AFN/ASV VE-pump nozzle, upgraded with DLC (Diamond-Like Carbon) coating. Includes new OEM sealing washers (0.205mm nominal, copper).

Performance specs

• +10 hp, +20 lb-ft (over stock)
• 61% more fuel flow than the stock 90hp Bosch DSLA 150P 706 nozzle
• Supports total power outputs of 90–160 hp, with supporting modifications
• Works well with both the stock turbo and a step-up turbo upgrade

What ULSD rating and DLC coating actually mean
Ultra-low-sulfur diesel (ASTM 975 spec) has looser lubricity control than older diesel fuel, which increases wear on standard nozzle needles over time — typically noticeable after 3,000–4,000 running hours, as the needle-to-nozzle gap widens and pressure leaks back into the injector, costing power and efficiency. DLC coating on the needle's sliding surfaces reduces friction and increases service life by 50% or more compared to a non-DLC nozzle running the same ULSD fuel. The coating covers the needle's sliding surfaces but not the lower direct-contact sealing surface, which needs normal wear characteristics to seal properly under pressure.

Design features

• Optimized spray pattern
• Tighter manufacturing tolerances
• Hardened wear surfaces
• Reduces exhaust smoke at equivalent power output versus stock
• Improved fuel economy
• Improves throttle response
• Cleaner cold starts

Warranty — requires calibration
5-year unlimited-mileage warranty, but only when installed with KermaTDI's Injector Calibration Service (sold separately). Installing without calibration falls outside this warranty term.

Fitment
1996–2003 VW Golf, Jetta, Jetta Wagon, New Beetle, and Passat, on AFN/ASV-equivalent VE-pump engines.

Common questions

How is this different from the DLC 764 nozzle KermaTDI also sells? The DLC 520 is a lower-flow option (+10hp/+20lb-ft, 61% more flow than stock) built as a direct AFN/ASV replacement, positioned for stock-to-mildly-modified builds. Higher-flow nozzle options in Bosio's lineup, like the DLC 764, are built for more aggressive power targets — check KermaTDI's nozzle comparison or call to confirm which fits your power goal.

Do these come with sealing washers? Yes, new OEM copper sealing washers (0.205mm nominal) are included with the set.

How much longer do DLC-coated nozzles last than standard ones on ULSD fuel? At least 50% longer service life compared to a non-DLC nozzle running the same ULSD fuel, according to Bosio's DLC coating data.

Do I need calibration for the warranty to apply? Yes — the 5-year unlimited-mileage warranty requires installation with KermaTDI's Injector Calibration Service.

Will this work with just my stock turbo, or do I need an upgraded turbo? Works well with either — it's suitable for a stock turbo setup and also compatible with a turbo upgrade.