Let me start off by saying that the dyno day results were somewhat
dissapointing, yet enligtening at the same time. The weather was nice,
not too hot or humid like the last time. Regardless, intake temps
measured at the air filter (pre-turbo) were still in the 96 degree
range due to lack of airflow when the car is stationary on the dyno.
They strapped the car in and we got a baseline run. I had previously
set up the
car for about 21 PSI of boost but that was during 30 degree weather. On
this pull, with the temperatures being what they were, I peaked at
about 19 PSI. During the run the wideband O2 sensor blew out of my
exhaust so I was unable to tune the car after the first run. As shown
above, I logged about 10 knock at ~4200 RPM, which coincides with the
peak torque production. I attributed this to running too lean, so I
added a few percent of fuel to the 4500 and 5000 RPM ranges to see what
that would do. Injectors are not yet maxed out and timing advance looks
good for pump gas (93 octane Shell) peaking to over 20 during the run.
The knock falls off at the higher RPM ranges as expected. A/F ratio
(O2) looks good by me through the high RPM ranges.
Ran the car again without changing the setup beyond adding fuel to
eliminate the mid-range knock. After Run 1, the FMIC was very warm to
the touch on the inlet side and still cool on the outlet side.
Insufficient airflow to really cool it between or during runs. This
time we got a clean wideband O2 reading. The result of which was
astonishing. From 5000 rpm to redline, my car was running so pig rich
(that explains the black smoke you see) that the wideband O2 couldn't
even monitor it. It was off the chart! Funny, my stock O2 sensor reads
about ~.74v during this period, which indicates to me that everything
is okay. Not good. I took out 5% fuel across the entire 5000-redline
RPM range and we dynoed again.
By this time, the FMIC is very hot, scalding to touch. Insufficient
airflow indoors to cool it. This will adversely affect my power
production and create more heat/more knock for each succive run.
Despite this, the subtraction of fuel from the high RPM ranges yielded
an increase of 10 horses and ft lbs at the wheels! Still, during this
run, the car ran so rich over this range the wideband O2 was unable to
log it! As you can see above, injector duty cycle (in black) has fallen
off, so I'm usling a lot less of my injector now, so I figure I can
safely increase the boost again. Up to 22 PSI it goes. I lean it out an
additional 5% across the board from 5000 to redline and go for another
By this time, my FMIC is heatsoaked to death and the little airflow
provided by the fan in front can't save it. As you can see, knock
spiked to 22 at the peak torque production. This is sufficient knock to
pull back timing advance which steals your power. The combination of
heatsoak and too much boost caused this. In effect, my 16g cannot
efficiently produce 22 PSI of boost under these conditions with pump
gas. You can see the injector duty cycle is even lower now. I have
plenty of fuel left which would tend to indicate you could run more
boost, but because of the heat issues, it's just impossible today.
Regardless, the subtraction of 10% fuel across the high RPM ranges
finally yielded some noticable results and the wideband O2 graph
finally peaked into the visible range for just a second. Another 10
horses and ft lbs were gained at the wheels. Even so, the car is still
PIG rich and needs further tuning at the high end.
As you can see, the car made a paltry 231 all-wheel horsepower and 251
all-wheel torque, running pig rich at the high end. Due to the heat
issues and subsequent knock, the timing retard caused the severe drop
off of power over 4000 rpm which you can see above. When driven on the
road under non heatsoaked conditions, this power curve should peak and
smooth out without dropping off. With additional leaning out, more
power is to be gained at the top end as well. I leaned it out another
5% after I was done on the dyno. If I had more pulls (and time to cool
the FMIC down) I could have tuned it a lot better. But hey, four pulls
for $43 is a pretty durn good place to start. At least now I know I
can't tune by the stock narrowband O2s anymore. They are misleading and
caused my tuning to be crappy going into the event. You can see how at
5500 rpm the wideband O2s started showing themselves at long last.
Still too rich though.
My car makes significantly more torque than horsepower. This seems to
be the case for other DSMs that dynoed that day. The EVOs I watched
were opposite, they made more horsepower than torque. In fact, my car
made as much torque as one modified EVO that day.
On compression ratio, my 16g is about maxxed out with my current set up
even though I have extra fuel to offer, it is running out of breath. A
lot of people are making well over 300AWHP with their 16gs, but my
motor is too old and beat up and my 7.8:1 compression pistons are
holding me back. The car would benefit significantly from a rebuild and
to use some 2g pistons (8.5:1) or even higher ratio aftermarket. That
would really unleash the power of the 16g. For now, though, the car
makes more than enough power for what I use it for (namely autox and
rallyx) so I'm perfectly content to run it like this for now. I am
pleased with the amount of torque it makes (over 330 ft lbs at the
crank) which will be great for pulling out of turns in rallyx this
year. I had been hoping for higher numbers but this is to be expected
on a motor with 170k miles on it. I shouldn't be too upset I guess.