| Garrett's
new GT3071R Dual Ball Bearing offers the perfect balance for
a street/track SRT-4! |
In an application where redline
hits just after 6000 rpm, the powerband must be kept broad
and fat. There is no time to "wait for boost." Couple
that with the requirement to make 400-450 peak HP...enter
the new GT3071R... the turbo the Garrett Engineers built to
address these very requirements. We are now happy...not only
with the performance and power delivery, but with the manner
in which the power is delivered. Now
available!
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Application
Notes: Since the SRT-4's powerplant introduction in
2002, SRT-4 owners asked for no less than 400 HP while still
maintaining a stock-like torque band. After trying over a
dozen potential turbo trims and combinations over the course
of 15 months, we were not happy with any of them. While peak
HP was not a problem, we were not satisfied with the overall
power delivery of any of the existing turbos.
We asked for it and now we have it: a combination that is
both powerful and fun to drive all around. Full boost is seen
at just over 3000RPM, and the GT3071R ball bearing's transient
response and boost recovery means boost and power is available
all the time. There is no wait for boost between gears, and
no more downshifting to pass.
Of course the turbocharger unit alone cannot work to deliver
all this additional power. There are many other components
involved.
The GT3071R has been integrated into a kit that allows the
user to easily implement the turbo upgrade as a system.
In building this kit (we call Stage 3), we have built and
used only the finest components to insure ease of installation,
proper fitment, and product quality! |
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The
kit components:
-High Flow Cast Exhaust manifold (guaranteed for life against
cracking)
-GT3071R Ball Bearing Turbocharger
-Custom Cast Turbine Housing (additional fine tuning item
to enhance the GT3071R on the SRT4 engine)
-Tial 38mm External Wastegate
-Stainless Steel 3" 02 Housing with V-band connections
(For easy installation)
-Stainless recirculated dump tube for wastegate discharge
-Steel Braided oil feed and return lines
-Steel Braided coolant lines
-CNC machine fittings and flanges
-Turbo grade Silicone connectors and T-bolt clamps
Kit Price: $2499 |
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The
dyno data:
Stock Dyno on a typical SRT-4 is 225 HP @ the wheels
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| With boost set @ 20 psi, net HP
is 400 @ the crank and 350 @ the wheels on pump gas through
our own 3.0" downpipe and stock exhaust. |
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Without touching
the boost, we install an exhaust diverter to overcome the
restrictions in our stock exhaust and added a mix of 100 octane
fuel.
Fuel pressure is also turned up to ensure that we don't lean
out the engine. |
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Notes
about tuning options for the SRT-4 engine:
There is no easy way to remap ("chip")
the SRT-4 ECU. The manufacturer of this vehicle has made it
impossible for the aftermarket to disassemble and retune the
stock ECU to accomodate the hardware changes in the engine
(ie. turbo upgrades). As a result, there are several tuning
solutions that are being developed that can be used in conjunction
with the turbo upgrade to ensure proper fueling control once
the above components are installed.
Some available systems are:
-FPR - Fuel Pressure Regulator. The SRT-4 comes with a "returnless"
fuel system. One popular upgrade is to install a complete
return line system and adjustable fuel pressure regulator.
These systems work by extracting more fuel out of the stock
injectors simply by raising the fuel pressure while under
boost.
-Piggybacks - Typically a "wired-in" system that
has its own brain/ECU and works concurrently with the stock
ECU, often manipulating signals going in/out of the ECU.
-Stand-Alone Engine Management - Often the most expensive,
but the most effective. This method deletes the engine control
functions of the stock ECU and provides a new, fully programmable
environment (usually via laptop).
In our turbo testing and development, we used the FPR method
to extract more fuel out of the stock (Mopar Stage I) injectors
by raising the fuel pressure under boost. The biggest drawback
to this method is a sloppy fuel curve and not being able to
have control at different RPM points resulting in a less than
perfect power curve. In our 100 octane run, we delibritely
turned up the fuel pressure even higher in an effort to protect
the engine from leaning out. The side effect of this was way
too much fuel at the onset of boost causing the engine "break-up"
on the lower RPM spectrum.
Our tuning solution for this kit
will consist of the following:
750cc injectors
High flow fuel pump
SRT-4 specific plug-in piggyback with auto-tune to control
the larger injectors
(This fueling package
will be offered at an additional cost, above and beyond the
cost of the hardware only kit.)
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