Howzit going All ?! -- Welcome to the fifth instalment the TurboDirect

Howzit going All ?! -- Welcome to the fifth instalment the TurboDirect Technical instalment – this is
the first of a number of “Know what you’re buying” articles. The intention of these articles are to
inform you, the public, about what you are purchasing to enable you to make an educated decision
about where and what you are spending your money on. As you are aware there are many, many
alternative products on the market and sometimes simply choosing the right product from the
massive volume of options can be the most confusing part of your performance car build.
The reason for these articles are simple –
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To educate you, the consumer, about what it is exactly that you are buying.
To protect you, the consumer, from the sometimes uninformed retailers who themselves
may be unaware that they are selling you an inferior product for a premium price.
To provide a general knowledge about products and their alternatives on the market today,
as well as their pros and cons.
We hope to educate both retailers as well as the public about what should be looked for in a
quality product, which is not going to have a negative impact on the car builders pocket or
the cars performance.
We will be addressing many different automotive components from the turbocharger, to pistons, to
engine management systems, clutches and the list goes on. For this first article we strip down a
Precision6262 Ball Bearing turbocharger, and provide you with an inside view into what makes this
turbo tick. Please note that this is in no way an attack on the Precision product, the product is not
terrible and certainly holds a place in the performance market. This Turbocharger is simply being
used as an example of what can be noted from a number of branded, reputable products on the
market. Let’s begin.
Some background information into this specific test turbocharger, this was a brand new
turbocharger which failed due to a lubrication failure, which is no weakness of the product in any
way, the cause of the failure was a result of installation error, we simply chose this to strip down as
it had already failed and we were requested to do an assessment on the failure, as a result you will
see the failed components as we progress through the strip down procedure.
Let’s take a look at the compressor housing, this housing uses a design based on the Garrett A/R 70
compressor housing from a GT3582R turbocharger. This design has proved to be very efficient for
Garrett and for this reason it has been copied and rebranded by many turbocharger manufacturers
of which Precision is but one. As Garrett did not issue any patents on this housing the copying of the
design is 100% legal and should in no way effect ones decision to purchase these products. If
anything it merely proves that the Garrett design is one to be proud of.
Now let’s look at the compressor wheel – this unit is a billet machined wheel and is a downscaled
version of the original Garrett GTX billet compressor wheel which was manufactured by Garrett for
large turbo sizes for the U.S. drag racing applications. There is little difference in design or
technology when compared to the similar Garrett GT35R unit apart from the Precision unit being
billet, in fact the two wheels are identical except for the diameter of the root or hub of the
compressor wheel. This difference is there for two reasons, one was to insure copyright and patent
laws are adhered to and the second is to allow for a larger blade area. This narrowed hub and larger
blade area offers both pros and cons, as a pro it should theoretically offer greater air flow for
improved efficiency, as a con however it weakens the strength of the compressor wheel at its
highest stress point.
Facts show that the highest stress area on a compressor wheel is in the root itself. Here’s a picture
to illustrate:-
Here is the Original Garrett GT35R comp wheel next to the Precision 6262 compressor wheel –
notice the massive size difference in the root/hub of the two compressor wheels
Below is what happens with a compressor wheel during high speed operation. Keep in mind that Ball
Bearing turbochargers are used mainly in race engines and high performance street car applications,
these turbochargers rotate at very high speeds, higher than the journal bearing counterparts, the
potential for similar failure is a concern with turbochargers with narrow compressor wheel hubs. As
mentioned before this should not be an indication that the precision product is flawed this merely
indicates an area where there may be potential for failure, it is advisable to assess the root diameter
sizes of any turbocharger which uses variations of researched designs.
Next let’s look at the bearing housing, this specific unit uses an air cooled unit, we would however
advise the use of water cooled housings wherever possible, especially for ball bearing units due to
their higher operating loads and temperatures. The cooler housing helps guard against carbonisation
of the lubricant and will insure the maximum life out of your turbocharger bearings.
The flange face of the bearing housing along with many other aspects of this housing resemble that
of the original Garrett T04 bearing housing – here they are next to one-another for you to clearly see
the similarities.
1) The Precision unit, as with most precision turbos, uses the exact same o-ring position and
size as the original Garrett unit, allowing the unit to be serviced with Garrett components.
2) The PCD of the mounting holes in the Precision bearing housing that hold the backplate also
match the dimensions of the Garrett unit.
3) The overall physical size of the Precision bearing housing is almost identical to an equivalent
Garrett unit, with small cosmetic changes, this allows these units to be interchangeable with
very little modification.
Next let’s look at the flange face of the two housings below – this is the oil drain of the turbocharger
– note the Precision unit uses the same size and pattern as a Garrett unit.
Now we move further into the rotating assembly of the units, and we take a closer look at the
internals of the Precision turbocharger.
Below
From left to right—the original Garrett thrust collar from an old design Garrett T04B/E series journal
bearing turbocharger and the Precision thrust collar - again these items are identical and
interchangeable.
We remain sceptical about Precision’s methods of using somewhat out dated Garrett journal bearing
designed thrust collar with ‘modern’ ball bearing technology, ball bearing turbochargers were
introduced, in part, to cope with the high thrust loads generated by high performance applications,
with the ball bearing itself carrying the thrust load as well as the rotational load. Our best educated
guess would be that it was a suitable solution to an otherwise expensive engineering exercise.
Let’s look at the ball bearing design that Precision have adopted for their rotating assembly, the
bearing design in the Precision is very similar to the Garrett design except that it is made slightly
larger and uses ‘ceramic’ balls.
The Garret Design has been flawless in operation for many years and there is little doubt as to why it
has been copied by so many turbocharger manufacturers worldwide. It would be difficult to dismiss
the similarities as coincidental; the assumption would be that the size differences were merely a
method of overcoming copyrights. Hey the Garrett design is generally the yardstick everyone
measures against, so why wouldn’t it be copied? It’s like blaming Bridgestone for copying the tyre!
Should we be concerned about the design changes made by Precision? Let’s check?
The above picture is the perfect illustration of the differences between the use of steel balls and
ceramic balls in turbocharger applications. Where the benefits are realized are during extreme
operation, or on the brink of failure – the above picture shows the Steel ball versus the Ceramic ball
– during high thermal and thrust loading which exceed operational conditions.
The Ceramic ball (silicon nitride) on the right hand side has much less thrust loading capacity in the
presence of high thermal ceilings. The ball just does not cope with high temperatures and high loads
at the same time. The Ceramic ball will not last as long as a steel ball – this is why Garrett use Steel
balls in their ball bearing designs, for both heavy duty commercial aswell as performance
applications.
Let’s move onto the most concerning part of this strip down, the turbine wheel. This again seems to
be a direct copy of a Garrett turbine wheel. However there is an obvious difference in the thickness
of the blades. A Garrett wheel has a blade thickness of 0.6mm and is made from a super-alloy known
as Inconel 713LC and has a Chrome-Moly shaft electron beam welded to it.
This specific Precision shaftwheel’s blades measure 1.4mm thick and this component is made in
China by a company called Worldturbocharger, this company is well known for manufacturing
“copy” products of OEM original Garrett, KKK, IHI, Holset etc – this company uses a material called
K18 for the turbine head, which is a steel derivative with a high thermal ceiling, but by no means
anywhere near the same quality as the Inconel 713LC material used by Garrett, KKK or Holset, hence
the thicker blades on the Precision turbine, thicker blades simply mean more weight, and for any
component which relies on its ability to accelerate, weight is not great. The shaft also appears to
have been friction welded onto the turbine head.
What is also interesting is that Precision and TurboneticsINC both use this component in their
turbochargers, in fact the shaft in this Precision turbo still has the Turbonetics logo cast into the back
of the shaftwheel which an be seen in the pictures below.
This picture was taken in the Chinese factory of the Turbonetics shaftwheel used in the Precision
turbocharger.
As a matter of interest we measured the running face of the Garrett T04E Journal Bearing shaft
wheel known as a T4 Stage2 – Garrett Part# 446905-0501 next to the Precision 6262 ball bearing
shaft(Pictures below) and this is what we found.
1. The Garrett shaft face where the journal bearings run measured 10.16mm and
2. The Precision shaft measured at the same point on the shaft measured 10.18mm
These two shafts are within 2 hundredths of a millimeter from one another. Put simply you will be
able to use this Precision shaft inside a Garrett Journal Bearing turbocharger using the Garrett
journal bearings with a 360 degree thrust collar.
Lastly let’s look at the oil supply to the bearing cartridge. Aside from the basic shape and the fact
that it screws into the bearing housing, the functional design of this unit is again duplicated from the
Garrett turbocharger unit.
Precision locator and oil restrictor on the left and the Garrett unit on the right – both perform the
same function in almost identical bearing housings.
Now let’s put the design comparisons behind us and concentrate on performance. As it’s been made
fairly obvious by our investigation, the Precision turbocharger is for all intents and purposes
manufactured with components copied from the designs used by Garrett turbochargers. So it seems
only fair that we draw performance comparisons with a competitive Garrett unit.
It has been said that the ceramic ball bearing turbocharger are better and spool up faster aswell as
handle higher heat than the steel ball bearing units, this is not entirely true, since these features do
not rely only on the ball bearing cartridge alone, it is a combination of many things – for example.
The Precision turbocharger has the same physical dimensions in terms of the turbine wheel and
compressor wheel outside diameters, but the turbo has tested to be laggier than the comparative
Garrett unit. The reason for this is threefold –
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The bearing cartridge from Garrett is smaller and has less rotational drag, and less weight –
therefore better transient response (less lag)
The Garrett turbine wheel blades are lighter and thinner than the Precision, allowing it to
accelerate faster and therefore once again allow for less lag
Lastly the turbine housing designs differ in Air Ratio – the Garrett unit has an Air Ratio of
0.63, and the Precision unit has an Air Ratio of 0.64, although this is very slight in terms of
the number itself, the facts remain that the Garrett housing outflows and out-spools the
Precision unit by approximately 500rpm
When we set out to investigate comparative product for this “know what you’re buying” series we
were not expecting to discover the somewhat controversial evidence that we did. We were led to
believe that Precision Turbochargers manufactured their turbochargers in house, and there can be
no doubt that Precision have made a mark on the South African and international Performance
markets. They certainly enjoy a loyal following and deserve credit for what they have achieved and
will, no doubt, continue to achieve. That being said we did discover, at least for this particular turbo,
that it consisted of components from many unrecognised manufacturers, and copied technologies
long being used by Garrett. Yes we do have concerns about materials used and subsequent
longevity, and some hesitations when it comes to performance efficiencies but in the most part the
turbocharger works and those that have purchased them seem happy with their purchase.
Personally I don’t believe the price is justified when compared to a genuine Garrett turbocharger,
but it would certainly be an option if the alternative is a very poor quality ‘FongKong’ fake. The first
rule when buying a turbocharger should always be: Buy only recognised brands from legitimate
authorised dealers. If you have any doubt about a dealer’s credentials visit the websites of the turbo
Manufacturers for a list of authorised distributors. We would also like to extend an invitation to
submit products for evaluation and comparison should it be for personal interest or possible
marketing reasons.
I hope this first edition of “Know what you’re buying” was informative. We will see you next time,
when we will be moving toward the engine internals, taking a closer look at Con-Rods and what the
differences are between some of the models available locally.