enhanced boost chips for the Elan
interest in tinkering with the Elan's engine management programming
started back when I wrote ElanScan. Understanding the ALDL (assembly
line diagnostic link) required much raking around websites with
information concerning the modification of GM P4 ECUs. It is possible
to download the contents of the Elan's 32kb PROM 63 bytes at a time via
an ALDL command and so an algorithm was written into ElanScan to do
After lot of
work reverse engineering
the PROM the boost control code was been identified and the ability to
reprogram the boost control
Boost from the
limited by a wastegate, when this is open exhaust gases bypass the
turbo so drive is removed from it. The wastegate is opened by an
actuator that operates
when the pressure in the output side of the turbo exceeds around 0.5bar
(curiously a bit higher than the 0.4bar quoted in the Lotus manuals).
In the Elan the ECU can actively control the boost above the passive
limit, up to 0.65 in factory configuration. The extra boost is gained
by limiting the
pressure the wastegate actuator receives. A solenoid valve is installed
in the wastegate acuator's feed line and by varying the proportion of
time the valve is open (the duty cycle) the size of the leak, and
therefore the boost achieved, can be varied. The ECU looks up a target
boost, the value
of which depends on engine RPM and throttle opening and varies the duty
cycle of the solenoid
valve to meet the target.
In this upgrade
the tables have been modified to allow higher boost values to be
employed – up to 0.9 bar. Two
boost maps are offered here.
characteristics of the
chip are different to the original. First
and foremost the boost targets are higher.
characteristics are listed here:
The ECU solution
leaves all the
safety features enabled:
- Stock Turbo Elan
- Maximum programmed boost 0.65bar
- Fuel cut limit 0.92bar
- Boost pickup rate quite slow (boost lags
behind target value
under heavy throttle)
- Nominal power 165bhp (flywheel)
- Maximum programmed boost 0.8bar
- Fuel cut limit 0.96bar
- Boost pickup rate enhanced
- Dyno power 180bhp (flywheel estimated)
- Maximum programmed boost 0.9bar
- Fuel cut limit 0.98bar
- Boost pickup rate enhanced
- Dyno power 200bhp (flywheel estimated)
- Boost is limited to 0.5bar when:
- the coolant temperature is below 50°C
- any fault code is set
- The boost is progressively reduced if knock
Why not use
a cheap MBC (with optional
FCD) or an Expensive BBR kit
An MBC puts a
fixed leak in the
air line to the wastegate this
increases the pressure required to open the wastegate and gives higher
boost as a result. Its primitive but it works with a few caveats:
- With an MBC the leak is always on
so the engine will be exposed to high boost even when the engine is
cold or faults are detected.
- An MBC cannot react to changes in atmospheric
maximum absolute pressure will vary by 0.1bar depending on the weather.
This can mean overboost fuel cut some days but not others.
- With an MBC the knock control strategy in the
only partially, spark retardation remains but boost reduction (via the
BSV) is disabled.
- The boost attained varies with RPM (due to
in turbo & wastegate efficiency with RPM) so the boost will vary
over the rev range, the peak boost will occur at around 4500RPM.
- An FCD removes all the protection against
uncontrolled boost caused by a stuck wastegate.
- An FCD fools ECU into believing the boost is
lower than it
and all table lookups that use manifold pressure (mixture & spark
advance included) are compromised as a result -
for example the engine will run progressively leaner and more advanced
in the ECU above the clipping threshold (generally around 0.75-0.8bar).
Good for power, bad for engine life. Its a good thing the ECU also
includes knock control!
if you don't like it
If you send an
back within 30 days, for any reason,
you'll get a full refund minus postage & packing costs. All UK
orders are sent recorded delivery.