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Due to interest in our Z1 Motorsports AshSpec ECU upgrades the following article was prepared to explain the benefits and advantages. The 300ZX engine, the VG30DE and TT, use a computer to monitor all of
the engine sensors and appropriately control systems such as fuel
delivery and ignition timing. This computer is a 3MHz computer that
has its own 'operating system'; like the Windows of your PC. This
'operating system software' contains the instructions that the computer
follows and it is all contained in a device called an EPROM. It is the
'chip' that people commonly refer to in aftermarket performance
vehicles. By modifying the information within the chip we can
effectively tune the car. From the factory, the ECU is mapped in an unsafe manner for running
boost levels above 12psi or so. It primarily has to do with the
ignition timing being too far advanced. To safely run higher levels of
boost, one must modify these settings to keep from damaging the engine
from detonating it to pieces. This is done through painstaking hours of
running the engine, monitoring sensor data, changing the fuel delivery
and ignition timing and then re-running and verifying the results. By
doing this one psi at a time, a complete map can be constructed that
will cover any upgrade up to a specific airflow range. This allows you
to run boost levels up to the limits of your upgrade stage without
worrying about the timing being too advanced or running lean. It would fall short of a good product to engineer an engine control
system without implementing fail safe functions, so, the ECU also has
safety features to handle situations when something isn't right. The
system employs a knock sensor, which is basically a microphone attached
to the engine block and it monitors for the frequency of detonation.
When that noise is detected, the ECU then reverts to the secondary fuel
and timing maps. These secondary maps have less advanced ignition timing
and greater fuel delivery to try and ward off the detonation. If for
whatever reason the engine continues to knock even after this point, the
ECU will continue to use these low octane maps AND it will trigger
safety boost. Safety boost is when the turbochargers will limit
manifold pressure to 7psi (down from 9.5psi or whatever your boost jets
were making it run). This is done to protect the engine and the driver
will certainly notice the decrease in performance and either take it in
to a shop for troubleshooting or take care of it themselves. They even went a step further. There are actually fuel maps
specifically for 5th gear. These maps introduce a little more fuel
because 5th gear WOT runs generally pull for very long times at very
high speed. This introduces heatsoak of the engine and without
introducing additional fuel to keep the cylinder temperatures down, the
engine could exceed reasonable exhaust gas temperatures.
Another parameter in the ECU's software that is designed for engine
safety is called a fuel-cut. This part of the software is designed to
interrupt the flow of fuel when too much air is flowing into the engine.
This condition can occur with runaway boost such as one would see if the
wastegate actuator hoses popped loose or the actuators failed. This has
good points as well as bad points though. For the daily driver who
doesn't care about high performance, its good because it will keep them
from blowing up their engine with a stock ECU when the boost runs
rampant. Without a fuel cut in place, the engine would certainly meet a
catrastrophic death to the unknowing of drivers. However, for
performance tuning, this fuel-cut presents an airflow barrier that WILL
cause problems. Since we will be raising the bar on manifold pressure,
we are introducing much more air into the system than was being pumped
in before. However, we are doing this intentionally and controllably.
If the fuel cut points are not altered, you will certainly bump into
this nasty bugger. So, the datapoints for the fuel cut cannot be
removed, however, to get around it, all we do is set them to impossibly
high values and therefore will never experience 'fuel cut'. The same
method is used for the vehicle speed limiter. At its highest possible
value in the ECU, the speed limiter is 510km/h, which is roughly 315MPH.
What all this means is that Nissan deployed a good deal of effort in
designing a system that will do its best to keep you from destroying
your engine. As long as proper oil changes are made, proper grade fuel
is run, cooldown period is observed, and other mechanical preventive
maintenance is done, a VG30DETT will (and many many have) get years of
reliable service even when run hard frequently. These safety features that Nissan has built into the ECU can (and
should) be taken advantage of when tuning for performance on a daily
driver. While remapping of the primary maps is necessary to allow a
daily driver to run 16psi of boost safely, the secondary maps must also
be addressed properly. Increasing fuel delivery by 8-10% and retarding
ignition timing by 3-5 degrees will maintain that same level of safety
that Nissan deployed in the original design. It will also become very
apparent to the driver when knock is being detected (above and beyond
the audible aspect, some detonation isn't easily heard) as engine
performance will notably suffer with ignition timing dropping back so
much. This is indication that either something is wrong or they are
simply overboosting the system for the environmental conditions that
exist. Unfortunately, no aftermarket ECU tuner for the Z32 take advantage of
ANY of the additional maps. All of their maps are the same as the
primary map. What this means is that when you start to detonate,
perhaps your girlfriend put bad gas in your car and she's out with her
girlfriend showing off with all the power, the ECU will revert to the
secondary maps, but since they are the same, it will not correct the
condition. So it will continue to knock and knock until the ECU finally
kicks into safety boost. If you have a boost controller, god help your
engine in this case. Additionally, on long 5th gear runs, although the
timing and fuel delivery *may* not be too advanced or lean, it begs the
question: Did they tune the car for long high speed 5th gear pulls or
did they tune it for all the other gears? I would be inclined to say
they tuned it for 4th gear pulls on a dyno, then backed off a degree or
two and bumped the fuel up for sake when the driver is in 5th gear, but
that's not performance tuning in my book. Performance tuning is taking
everything into account and tuning for safe power, but also for the
maximum power. Not taking advantage of the low octane maps or the 5th
gear fuel maps specifically for their intended use is very
unprofessional and lackluster, especially for the money paid for one of
these 'other' ECU upgrades. You cannot go on the assumption that
everything in all cars is working 100%, you have to tune for these
circumstances and you do that by taking advantage of the secondary
mapping. Performance and safety are the two key elements kept in mind when
remapping this ECU. Although they almost seem like opposites at first
glance, this document demonstrates how it is actually achieved. The
simple fact is, the ECU's original design has this same idea in mind.
The Z32 is very reliable in stock form and very forgiving when something
is wrong because of this programming ethic. Properly setting ignition
timing and fuel delivery while maintaining the safety by properly
mapping secondary maps is key to producing a safe and powerful program. Thanks,
Z1 motorsports 1990+ Nissan Z specialists
Used parts (50+ parts cars), New Parts, Service, Performance
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22:00:25 11/12/03
