If you’re adding a turbocharger to a naturally
aspirated engine you will inevitably have some concerns regarding engine
management. In the first part of this series (see
Engine Management for Turbo Conversions - Part One
)
we examined ways to sneak through with zero or minimal changes to the engine
management system. Now it’s time to look at more expensive solutions that,
arguably, provide a better result...
Approaches to Engine
Management
According to Lachlan Riddel, the head of
ChipTorque, the most all-round attractive way to optimize engine management with
a bolt-on turbocharger is a custom ECU reprogram. Using dedicated programming
software, the tuner is able to tailor fuel and ignition maps to provide the best
balance of power, reliability and fuel economy. You can also control a host of
other functions including the closed-loop switch-over point, intake air
temperature correction and knock retard. It’s these functions which really make
this approach attractive. In most instances, the management can be
recalibrated to work with a turbo-compatible MAP sensor (which is rated at 2 Bar
absolute or higher), a bigger airflow meter and bigger injectors. All this while
retaining factory cold-start qualities, air conditioning compensation and
failsafe strategies... Perfect for a street car.
Mr Riddel says a custom remap to suit a turbo
fitment typically costs around AUD$1900 including any necessary MAP sensor
swaps. A popular vehicle where there’s lots of existing tuning information
available – such as a Holden Commodore – costs a few hundred dollars less.
The most expensive option is an aftermarket
programmable management system.
An aftermarket system gives total tuning
flexibility – you can change the type of ignition system, upgrade injectors, add
extra injectors, customize fuel and ignition timing and associated correction
factors (such as inlet air temperature). This approach is arguably the most
sophisticated solution to your management woes – but it’s important to recognize
the drawbacks...
“The biggest issue with most programmable
management systems is the lack of closed-loop fuel control and knock sensing,”
Mr Riddel says.
“This makes it difficult to meet emission
standards and to compensate for the variations in fuel.
“And, in later model cars, there’s also the
problem of working with electronic controlled automatic transmissions and other
car systems.”
Depending on the vehicle, switching to aftermarket
programmable management may mean that you lose the factory trip computer,
stability control, electronic throttle control and more. However, as seen in
this Nizpro modified Ford XR6 Turbo, it is possible to use a stand-alone
programmable management system in a piggy-back configuration with the standard
management system. In this arrangement, everything remains under the control of
the factory management except for the injectors and ignition which are
controlled by the programmable ECU. Inevitably, though, you will lose some
functionality – for example, it’s impossible maintain proper operation of the
trip computer.
Expect a tuned aftermarket management system to
set you back at least AUD$2000, depending largely on the brand of management
system and the extent of tuning. Some installations may run closer to AUD$4000.
Fuel System
Once you’ve fitted a turbocharger and commenced
tuning, it’s likely you’ll need some extra fuel delivery.
In the first part of this series we discussed
modifications to the fuel tank return line, adding an aftermarket fuel pressure
regulator and increasing the voltage supplied to the fuel pump. Each of these
approaches can perform well, but a more elegant result can be achieved if you’re
prepared to spend some extra...
Ideally, the engine should be fitted with
injectors that are rated for your target power output. This might seem simple
but, of course, there’s more to it. According to Mr Riddel, an injector that’s
rated at X pounds of fuel per hour is not necessarily the same as another
injector with the same rating.
“If you took a Mazda 13B Turbo injector and a new
Siemens injector of the same rating, I know which I’d prefer,” he says.
Apparently, most of the latest high-grade
injectors offer far better fuel injection linearity. In other words, doubling
injector duty cycle will virtually double the fuel flow whereas lower grade
injectors often have a non-linear fuel delivery. This makes tuning more
difficult and you’re more likely to end up with small glitches in the tune.
Bigger injectors can be used without any changes
to the rest of the fuel system but often they should be fitted in conjunction with
an upgrade fuel pump. This is necessary where, when the bigger injectors are
fitted, the fuel pump can’t maintain adequate pressure at full noise. An upgrade
pump typically costs a few hundred dollars and helps ensure there is no drop-off
in pressure as the injectors near maximum flow. In some instances, you can use
two fuel pumps in parallel or in series to achieve the necessary fuel flow –
this depends largely on your desired power output.
Combined, a set of bigger and injectors and an
upgrade fuel pump might set you back well over AUD$1000.
If all this sounds too expensive, refer back to
Part One of this series...
Contacts:
ChipTorque +61 7 5596 4204
http://www.chiptorque.com.au/
Nizpro +61 3 9761 1522
www.nizpro.com.au
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