Problem: My injectors are maxed out, and I need more fuel!
First, let me congratulate you. You're smarter than 80% of tuners.
The rest will happily drive at lean mixtures and wonder why they
replace pistons several times every year, and get beaten by stock
Change injectors to larger ones. Fuel curve needs to be tuned
after this. With L-jetronic type air flow meter, this is done
simply by tightening the spring tension. One notch is approximately
equal to 2% change in fuel mixture. If for examply you change to 20%
larger injectors, you should tighten the spring by 10 notches.
Verify fuel mixture by checking that oxygen sensor voltages
are right under wide open throttle and adjust if necessary.
At this point, some dyno time or using our FREE
RevTest for Amiga is a good idea.
Don't forget to make SURE your new injectors are compatible with your ECU...
to help a bit in this, see the fuel injector list.
Increase fuel pressure. To accomplish this, you need an adjustable
fuel pressure regulator. Some kind of fuel pressure meter makes it
easier to tune, your fuel pump might be maxing out at some point!
Measure the fuel delivery to be sure. K-jetronic fuel pumps operate
at a higher pressure and are therefore suitable replacements, if you
can find one! (or two). If one pump isn't enough, you can connect two
pumps in parallel if each pump has adequate maximum pressure
but not enough delivery at desired pressure. You may find that your
adjustable regulator won't give proper pressure compensation if your
fuel delivery is only barely adequate. 100% overcapacity seems to work
well with the FSE unit I have, 40% didn't.
Most Toyota fuel injection systems operate at 2.55bar pressure
difference between fuel rail and manifold. If one increases
this pressure difference to 3.3bar, fuel flow through injectors
is increased 14%; sqrt(4/2.55)=1.14. This 3.3 bar pressure I have
found to be about the reliable maximum that I can use with my old
low-resistance pintle spray injectors. Above that, the injectors
sometimes would miss (especially above 5000rpm), resulting
in a rev-limiter kind of effect. At 3.8 bar I would get constant miss
at idle. If your injectors will open reliably at higher pressures,
this may be a more useful route to take, but I'm not too happy.
The spray pattern is actually finer with higher pressure which is a
Good Thing (tm), as then less fuel will condense on the surfaces in
contact with air/fuel mixture. The possibility of fuel leaks increases,
you can almost bet that you will struggle with these for a while. Same
notes for re-tuning the mixture apply as with injector exchange.
Add more injectors. I feel that there MAY be some problems with
fuel distribution when injectors are added further upstream, usually
right after throttle body. That's why I prefer the other two choices.
These additional injectors may either be grouped to act at the same
time as the original injectors, or come into action only after a
predetermined load, usually close to the point of maxing out the
original injectors. This will require some kind of controller,
many models are available. The injectors themselves are usually
smaller in this case and therefore also cheaper.
Problem: I want to fine tune my mixture, to get that last 0.3
horsepower I feel missing at 6200rpm ;)
Water and air temperature sensors. Both sensors will cause enrichment
of mixture at higher resistance values. Therefore adding a potentiometer
gives some adjustability (5-10% for each sensor) to the overall mixture.
Usually the air temperature sensor is not used, as the intake air temperature
may vary quite a lot and tampering with it would cause unacceptable
variance in mixture.
WOT switch on throttle body. The Wide-Open-Throttle enrichment
is triggered by this switch (unless you have a potentiometer instead
working as a throttle position sensor). It can be adjusted to work
at wanted throttle opening or maybe used at some other condition by
adding some electronics, or left unused.
PE (Pressure Enrichment) sensor with 3T-GTEU. 12V signal to this
line will cause enrichment of fuel mixture. Don't know how much, maybe
5-10%. Normally this is triggered by a pressure switch at 0.15bar.
The 22R-TE might have this feature too, but I have no data on its EFI.
Toyota EFI, adjustment resistors. There is a set of lifted calibration
resistors on the analog ECU board. I have no data on which resistor adjusts what
aspect of injection. The adventurous ones may want to explore this, but
have another ECU handy as the likelyhood of frying it is around 50%,
depending on your expertise and carefulness.
Additional injector controllers and fuel computers that work
with original ECU. HKS and GReddy make these for Toyotas.
Aftermarket EFI: Hestec, Haltech, Motec, Tec III, Accel DFI, Emerald etc etc...
will be happy to accept your money ;) Prices range from $400 to $4000,
and you usually get what you pay for.