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Bosio DLC 520 (ULSD RATED) - Set of 4 Nozzles 

Pricing: $289.00
5 5 2

Free Ground or Postal Service Shipping to the Continental U.S.


Bosio DLC520 - DLC Coated - Set of 4 including Copper Washers (.205mm nominal)

ULSD Rated

+10whp and 20lb-ft nozzle 

Direct replacement for the AFN / ASV Nozzle but with DLC Coatings

Great upgrade for Stock Turbo, Also works will with a level up turbo.

  • Optimized spray pattern
  • Closer tolerances
  • Hardened wear surfaces
  • DLC Coated needle for superior wear characteristics with ULSD fuel
  • More power than the OEM parts
  • More torque than OEM parts
  • Less exhaust smoke for the same power output
  • Improved economy
  • Better Throttle Response
  • Cleaner Startups

All of our Bosio VE nozzles ship with new OEM sealing washers included. 

ULSD (Ultra Low Sulfur Diesel) Rated Nozzles

ULSD aka "Ultra Low Sulfur Diesel" has brought about anew set of challenges to the Diesel Injection Systems industry. ULSD specifications more specifically "ASTM-975 1.1.4- S15".
ULSD Rated Nozzles are unique in that they are literally built around an ultra-hard "Diamond Like Carbon" coating aka "DLC". DLC provide a "Diamond like" surface with superior surface qualities in respect to smoothness and uniformity that greatly reduce sliding friction. This allows the nozzle's needle to cycle faster, with improved fuel quantity control thru better needle response.
Another key benefit of DLC is that it results in a 50% or more increase in component life when compared to a non-DLC nozzle type running ASTM 975 ULSD fuel.A nozzle is comprised of two precision made pieces, a high nickel alloy nozzle and a high carbon steel needle. A non-ULSD Rated nozzle suffers from the effects of reduced lubricity as a result of the loosely controlled lubricity specifications under ASTM 975.As a result, there is a wide range of actual fuel quality from one retailer to another.
Unfortunately, wear is greatly increased due to reduced lubricity on the internal sliding surfaces. More specifically,ULSD fuel increases the wear rates in the needle support regions which over time (3,000-4,000 running hours) leads to decreased nozzle performance. As wear increases, the gap between the needle and nozzle widens and fuel (pressure and volume)leaks back into the injector and power and efficiency are lost due to poor pressure response of the injector nozzle.
DLC increases the hardness of the needles sliding surfaces thus increasing its service life by reducing the sliding friction and increasing the hydrodynamic support that the needle utilizes to remain centered in the nozzle bore.
ULSD nozzles carry a small premium over the non-DLC types but with nearly double the service life(or more) of the nozzle your direct savings are realized not only thru greater durability but improved function of the nozzle meaning better fuel economy and lower emissions all of which translate into greater longevity of your diesel engine.
Nozzles Explained:Please click here to read the fact sheet.



ULSD Rated Nozzle

DLC (Diamond Like Carbon) coatings cover all of the internal needles sliding surfaces. The lower portion is not coated since this is a direct contact surface that requires a normal wear characteristic to generate the high pressure seal needed during pressure build up prior to and after injection.

DLC Coatings at the Nanometer level

The key advantage to a DLC coating is the superior sliding surface it creates between two moving parts. This allows significant reductions in friction, and far greater durabiltiy due to reduced reliance on the lubricity of the fuel.


Standard Needle and Nozzle

A standard needle is uncoated and relies on the end result of the precision machining. This leaves very slight imperfections in the surfaces that increase the reliance on the fuel to prevent wear. Also this slightly increases the friction and thus lowers the response time of the needle consequently lowering its overall efficiency.

Bosio nozzles from Kerma are the best option for maintenance,, or TDI performance upgrades of VW TDI injectors. kermaTDI started the TDI performance market with Power Plus 520 Bosio nozzles. This was the first breakthrough in VW Diesel performance.

Add kermaTDI VW TDI turbo upgrades, and TDI ECU or TDI Tuning upgrades with the Kerma Q Loader flash programmer ...and we can take the 90 Horsepower VW TDI to 135 , 150, or 175+ Horsepower. TDI performance with increased fuel economy , that is why kermaTDI is a leader in VW diesel performance .


Flow Data: +61% over Stock Flow (vs the 90hp Bosch DSLA 150P 706 nozzle) 

Supports Power Outputs from: 90-160hp (with supporting modifications)


ULSD Rated Nozzle - 5 year unlimited mileage warranty with Calibration Service.

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  • DLC520
  • DLC520
  • Fratelli Bosio
  • Available
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Shipping Information

  • Item Requires Shipping
  • 0.5 lbs.
  • W5.0000” x H5.0000” x L5.0000”
  • Free Ground or Postal Service Shipping to the Continental U.S.