Interceptors have earned a worthy position in the
aftermarket tuning scene. When you’ve treated your car’s engine to a few
breathing mods, you’ll probably want to maximise performance by altering engine
management to suit – and, if it weren’t for interceptors, we’d all be shelling
out for stand-alone management systems or trying to hack into increasingly
complex factory management systems. Fortunately, interceptors are available
cheaply, are relatively easy to install and, by retaining the logic
of the factory management system, the tuning effort is much easier than starting
from scratch. No wonder interceptors have become a popular approach for the
average streeter.
In this two-part series we’ll examine
the interceptors that are currently on the market.
Interceptors
– the Basics
Before
we get stuck into the nitty-gritty detail, we should first establish how an
interceptor works and its pros and cons.
As
its name implies, an interceptor is an electronic device which is used to
intercept and change the input and/or output signals of your car’s ECU. Most
interceptors work on the principle of modifying the engine load input signal to
the ECU (the signal derived from an airflow meter or MAP sensor). By altering
the load signal, the ECU can be fooled into thinking there is more or less
engine airflow than actual and so it will give different fuel
mixtures and ignition timing.
In
addition to this relatively basic function, some interceptors have the ability
to control fuel and ignition timing separately. This typically involves the
interception of an rpm/engine position signal or ignition output. Some
interceptors also offer the ability to control turbo boost pressure, extra
injectors, water injection and other accessories.
So
what are the pluses and minuses associated with interceptors?
Well,
an interceptor is generally cheaper to purchase and install than an aftermarket stand-alone ECU. But the biggest attraction is that there’s much
less tuning involved. The vehicle manufacturer has spent countless hours
fine-tuning hot and cold start characteristics, idle quality, closed-loop
control and various other tasks that are easy to take for granted – with an interceptor, all you need do is change the input and/or output signals in the specific load/rpm zones that you want modified.
But
an interceptor is not a total solution.
In
comparison to a comprehensive ECU reprogramming software (such as EcuTeK or LS1
Edit), an interceptor offers a limited range of adjustment. You usually can’t alter
knock sensor sensitivity, intake air temperature correction maps, idle
strategies or prerequisites for closed-loop. However, engine management
reprogramming software is not available to suit all vehicles and might not be an
option.
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Haltech
Haltech – an Australian company most widely
recognised for its stand-alone programmable management systems – now offers an
interceptor unit to augment your standard management system.
The Haltech product allows separate fuel and
ignition timing tuning over 16 load and 16 rpm sites (with both axes
user-adjustable). The user also has up to +/- 100 percent injector duty cycle
adjustment while ignition timing can be altered up to +/- 16 degrees with 0.25
degrees resolution.
In addition, the unit has some extra analogue and
digital inputs/outputs that can be put to use in different applications
depending on the type of engine. In turbocharged vehicles, you can use the
Haltech Interceptor’s boost control capability (which lets you map boost against
rpm), trigger a water injection system or control a variable cam timing system.
The unit can also clamp any existing boost or speed cut.
Interestingly, the Haltech Interceptor
incorporates a switch which allows the user to select between two operating
modes. These modes can be programmed with different fuel, ignition timing and
(where relevant) boost pressure maps. A flexible, high-speed data logging
function is also included.
Buyers can spend extra on an optional boost
control solenoid, 1, 2 or 3 Bar MAP sensor, multi LED shift light and a user
trim module. The trim module allows the user to ‘fine tune’ mixtures, ignition
timing and boost pressure while on-the-move.
The interceptor is installed using a universal
type wiring loom and tuning is performed via laptop using Haltech’s
user-friendly Interceptor Windows software. The unit can be tuned by a workshop
or an educated backyard tuner using suitable air-fuel ratio and detonation
monitoring equipment.
The product is currently available to suit the post VT Series 2 LS1 V8, VN
- VT V6 and V8, current Ford 6 and 8-cylinder engines, EL - AU 6 and
8-cylinders, performance Subarus, Nissan 350Z, R32/R33 Skyline, S14 200SX,
Pulsar SR20, Mitsubishi Lancer Evo 6 - 8, Lancer CC, Magna/Verada, Honda
Jazz, Mini, Toyota 1J and Land Cruiser. The list of supported vehicles is
growing rapidly. Retail price is AUD$1050.
Digital Fuel Adjuster (DFA)
Designed by Silicon Chip electronics magazine, the
Digital Fuel Adjuster (DFA) is currently the cheapest interceptor available in
Australia.
Available in assemble-it-yourself guise for just
AUD$79.95 plus AUD$59.95 for the necessary hand-controller, the DFA is perfect
for the home tuner. Why? Because it is ultra simple to install and tune, there’s
no special programming software required and you don’t need a lap-top – data is
entered by using the hand-controller. The controller
can then be removed once the DFA is programmed.
The DFA is different to other interceptors because
it has only one-dimensional map adjustment – you can alter the engine load
signal but there is no rpm input. This might seem like a major disadvantage but because the system is primarily designed to be used with an airflow meter (which automatically takes into account engine rpm, intake air temp and throttle position in its output), numerous people using the DFA have tuned vehicles with
great success. However, the DFA’s lack of
rpm input means it isn’t ideally suited to cars which rely on a MAP sensor load
input. In these applications, the DFA will see the same load signal when you
floor the throttle at 2000 rpm as it will when the engine is running at maximum
power – and it’s quite likely you’ll want different fuelling adjustment at each
end of the spectrum.
The DFA offers 128 points of adjustment (typically
across a 0 – 5V signal range, but it can also work with 5-0V, 0-12V, etc) with interpolation incorporated to smooth the
curve of adjustment. The DFA’s output signal can also be adjusted in +/- 127
steps for extremely fine tuning. DFA adjustment can be performed in real-time,
which makes it quick and easy to tune for maximum power when using a chassis
dyno – simply hold the engine at specific load/rpm zones and adjust the DFA
until you see the highest power reading.
Note that the DFA must be used on engines with a
voltage output load sensor – either an airflow meter or MAP sensor. It is not
compatible with a frequency output airflow meter as used on LS1s and many
Mitsubishis.
See http://autospeed.drive.com.au/cms/A_2418/article.html for
full details of the DFA.
Stick around for the second and final
part of the series – we’ll look at the rest of the interceptors on the market.
Contacts:
Haltech +61 2 9525 2400
http://www.haltech.com.au/interceptor.htm
DFA (AutoSpeed Shop)
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