Congratulations! You own a vehicle with a GM LNF engine. This engine
offers some advanced features that can enable power increases. It can also
be frustrating to understand and tune. Most engines have electronic
ignition, fuel injection and other computer controlled functions. With
most of these engines minor increases in torque and power can be attained
by the tried and true additions of cold air intakes (CAI), high flow air
filters, freer flowing exhausts systems, timing chips, etc. Turbo charged
engines also permit significant power increases by increasing the turbo boost
pressure.
The LNF engine is complex and the Electronic Control
Module (ECM) controls many functions. Of significance is its control of boost
pressure and the electronic throttle to achieve, maintain, and limit
engine torque to specified values as related to accelerator pedal position
and engine rpm. It does this by measuring the incoming air through a Mass
Air Sensor (MAS), air temp and barometric pressure sensors, then compares
it to values in its program tables and sets turbo boost and throttle to
get more or less. By this process it learns and adjusts for conditions or
devices that would normally be used to increase power. Without a change to
the tune, the result is no
power gain or loss regardless of how much money you spend on aftermarket
products or the claims of their manufacturers.
So what can we do? Put simply, the ECM program must first be modified.
We and other vendors offer revised tunes to change the torque tables,
limits, and error code generators. You can find our offerings on the “Fuel
& Electronics” page. We offer several paths to tuning.
The best and simplest is the
TRIFECTA Tune capable
of 330hp/360ft-lbs with stock turbo. We send you a cable and
electronics module. Trifecta sends you a web link to download their
software and emails you a tune specific for your VIN and list of mods.
You connect your notebook PC or MAC (with windows) to the cable and to
your OBDII port (under the steering column). Download the new tune,
test drive your car and datalog with Trifecta's software. Then email
him the datalog. Trifecta analyzes it and emails you a tweaked tune
which gets you the best performance for your location and gas quality.
If you are
comfortable working with computers and want to tune yourself, then
purchase HP Tuners VCM suite and download a copy of your car’s tune
program. If you simply want to upload a tune, we offer our own
DEJON tune
300hp/340ft-lb, or
one by Wester’s Garage. If you want to experiment yourself, there is
much info available on the car and HP Tuners forums.
These results compare to the GM Performance tune 280hp/340ft-lbs!
There are also hardware limits to torque and hp. The factory intercooler
restricts air flow to the equivalent of a 2”dia tube. This causes pressure
drop across the IC which increases exponentially with air flow. At high
rpm’s this pressure drop requires the turbo to run faster, reaching a
higher pressure than manifold pressure. Higher pressure results in higher
air temperature as well. We offer an
intercooler that has the equivalent
airflow of a 3” tube and is rated at 600hp capability. We offer mandrel
bent intercooler piping made from 2.5” tubing with no area reductions like
the factory pipes.
The stock air filter has a paper element that is restrictive at high
air flows. We offer an intake pipe that pulls air from in front of the fan
before it’s heated by the engine and flows 44% more than stock at the same
pressure drop.
The exhaust system is another restrictive component. However the
factory turbo itself is much more restrictive than either the catalytic
converter or muffler, but at the higher power levels of performance tunes,
the exhaust system becomes a noticeable factor. We supply
Magnaflow’s 3”
exhaust system which bolts right up.
Finally the stock turbo itself is small. Designed to supply max torque
at low rpm’s, this turbo is limited in its top end horsepower capability.
Pushing it too hard takes it out of its efficiency range, resulting in
very hot air and shortens the life of its bearings. We offer several
turbo
upgrades, starting with the turbo used on the Mitsubishi EVO. Larger
Garrett turbos offer even more power. As size increases, so does exhaust flow capacity, horsepower
and the rpm required to spin the turbine wheel up to speed. You can’t have
both low rpm torque and high horsepower, so a realistic assessment of your
driving style will result in the most driver satisfaction.
Larger turbos have different wastegate control dynamics. Trifecta supplies
the best tune for larger turbos in our opinion. Although not as good,
we can supply HP Tuner compatible tune tables to control boost.
We also offer inexpensive manual boost controllers for setting precise
boost. But limits in the stock tune program trigger “limp mode” when
boost exceeds 23psi for 3 seconds.
As turbo size increases, exhaust flow restriction from the catalytic
converter and muffler limit top end horsepower, and high-flow components
are required. We offer down-pipes with both high-flow converters and
without converter (off-road use)
Hopefully this summary will help you chart a path for improved
performance.
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MORE PERFORMANCE - What to buy, and when for
your Solstice GXP or Sky Redline
Stage 1. Get an ECM tune like Trifecta's
Stage 2. In order of performance effectiveness, replace the Intercooler, Intake Pipe
to replace the Air Box, Intercooler Pipes, and Catback Exhaust
Stage 3. Larger turbo kit. (the stock turbo is rated at 280hp) Select from the
Mitsubishi 16g :375hp, FP68: 425hp, Precision 5557 :480hp, or
5857:530hp
The engine internals and
drive train will support the factory turbo to its limits and larger turbos
to about 400hp
For Info on Turbos go to the following (Garrett) links Turbo Tech
101
102
103
WHAT SIZE TURBO UPGRADE SHOULD I GET?
That depends on your driving style and goals for your car. Be honest
with yourself or you'll be disappointed.
If your driving is 25-70mph street, twisties, or
auto-crossing: Mitsu16g or FP68 because they spool up quickly giving lots of low
rpm torque for the power you want when you stomp the pedal at any rpm.
With this engine, it will run 25+psi all the way to 7000rpm
For freeway or high speed driving or if you like
to go drag racing occasionally: FP68 or Precision 5557 because they will handle
27-30psi with
race gas and additional fuel or methanol, and make good midrange-hi rpm power. Spool up
for the 5557is
at noticeably
higher rpm than stock, but still fun to drive on the street.
High speed driving, frequent drag racing, and beating up
on most street cars: Precision 5857. You'll spool up about 1500rpm later
than stock, but have massive power available over 5000rpm. However
you'll be downshifting a lot to get the torque you need when passing cars
on the road. Twisties will have you shifting a lot to stay in boost.
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