Introducing the HE221 for Classic Mercedes Diesels

Back in September, we completed our HE221 kits for the Mercedes om602, om603, om604, om605, and om617 engines.  The creation of the kits was a direct result of customers asking for an easier way to utilize this particular turbo in non-OEM applications.  Here are some of the challenges our customer’s voiced:

  1. Wastegate. The turbo’s wastegate is affixed to the compressor housing and has pins inside preventing the ability to clock the turbo for proper oil drainage and compressor outlet relocation.  The pins can be removed but the wastegate still needs to be mounted somewhere with the same preload as the factory.  We solved this problem by sandwiching a bracket between the manifold and turbine housings.  The wastegate can be removed from the turbo, rotated 180 degrees, and reinstalled onto the BenzForce bracket.  We also rotated the wastegate a few degrees in an attempt to allow for more oil drain clearance and pulled it a few millimeters away from the compressor housing.  This simple solution allows full rotation of the core without obstructing the oil passages on the om60x and om617 engines.
    BenzForce HE221 Wastegate Bracket
  2. Manifold adaptation. The Holset HE221 uses a T25 flange which can be problematic for Mercedes enthusiasts looking for a simple bolt-on.  Most of the old school Mercedes turbo diesel manifold flanges on these engines are T3 but the om606 uses a KKK (triangle) flange.  While the KKK to T2 flange is a fairly straight forward adapter, some thought had to go into the T2 to T3 adapter.  A lot of the adapters out there seem to be geared toward using a T25 threaded manifold, not a T3.  The om617 and other Mercedes engines have a T3 manifold with the manifold being threaded (for studs).  This means that bolts will need to replace manifold studs and they will need to be recessed into the flange to clear the turbo which will mate to the face directly above them.  Offset was the other issue.  Some adapters move the turbos along the longest plane having two countersunk bolts into the transition from the T3 opening to the T25.  This presents a weak point and a potential point of failure as the adapter heat cycles over time.  We decided to shift the T25 face along the plane of the short side and make the adapter significantly thicker to provide enough material to ensure a long life.  Lastly, consideration was given to matching the adapter to the gaskets to ensure a seal.  We have seen cheaper adapters with recessed bolt holes that are so close to the gasket ridge that exhaust leaks were highly probable.
    BenzForce KKK to T25 turbo adapter
    BenzForce T3 to T25 turbo adapter
  3. Oil Drain. We have been asked countless times about the oil drain on the HE221 as people have a difficult time sourcing them.  BenzForce has standardized on 12AN drains for all Holset turbos.  As you can imagine, a T25 12 AN drain is not commonplace.  Because of the proximity to the compressor housing, an extended drain flange was also desirable.  In the end, there was a hole in the market for this, so our engineer was quick to design a drain for us. 
    BenzForce T25 12AN drain

    On the engine side, customers were also met with challenges.  Again our trusted engineer went to work to design a om60x drain that matched the factory angle and contours.  The shape on the om606 drain required complex machining at additional cost but was worth it.  Another unforeseen issue we ran into when bulk ordering gaskets from Mercedes, was a lack of availability so we even had an Austin, Texas-based company make our turbo drain gaskets!  By comparison, the om617 drain was an easy solution.
    BenzForce om60x 12AN block drainBenzForce 12AN drain for om617
  4. Interconnections.  I won't spend too much time on the connections to the turbine and compressor housings as BenzForce has had these in production for a while now and several hundred people are up and running with these.  These adapters have a good following in the Cummins aftermarket.  We have both the cast 90-degree elbow or the BenzForce 2.5” adapters available for the compressor.  On the exhaust side, the 79mm to 3” exhaust adapter fills the bill for a lot of people quite nicely.

A lot of time has gone into the development of these kits.  Customers can now install a HE221 on their Mercedes engine with only a few other considerations:

  1. Oil Lines. We may offer oil lines down the road.  We resell Vibrant Performance and would like to try to work with them or use off the shelf lengths of hose if possible.  Due to COVID, they have had problems meeting demand on several product lines.  As a result, this effort is just a lower priority right now.
  2. Intake Tubing. To deal with the compressor side, a complete solution is the only way to go.  This becomes problematic when you consider all the different chassis out there, all of which may present challenges on how charge pipes get to run.  We hope to get into specific solutions but, like the oil lines, it is a lower priority right now.

 So there it is.  All products are available individually or as a kit.  Overall it’s a strong solution for a trending turbo!



Leave a comment

Please note, comments must be approved before they are published

Your cart