Motec tuning

[Lowell Foo]

I have not been able to find any significant difference between high
and low impedance injectors or between resistor vs. no resistor.
The Motec will run any combination quite happily so if you're
concerned about cutting the harness up just set the injector current
value to 0.  If you use a high value the box will flag an "injector
peak current not reached" error.

You can do a little experimenting yourself as the Motec box has
diagnostics that will let you fire the injectors and ignition circuits.
On the injector test you can fire each one individually and vary
RPM, PW and firing current.  By varying your battery voltage you
can generate your injector dead time comp table.

I zip tied the injectors to the rail and let them flow into their
own containers.  If by chance you have any variations in flow you
can use the Motecs individual cylinder corrections to even things
up to start with.  Later on you can do individual cylinders on the
dyno via EGT/AF/plug reading etc.  Before you install the turbo
header, TIG on some 1/8 NPT bungs or weld Swagelok 1/4"
fittings straight on.  That will let you pick up exhaust pressure,
EGT or AF ratio.

Your car should be bike killer when it's all done.  Hopefully it will
put down more than a local here with a very sad HKS twin'd
Supra making only 619rwhp.

---- Original Message ----
Date: Mon, 1 Oct 2001 10:26:37 -0500
From: Andrew Theurer <habanero at us.ibm.com>
Subject: Re: Motec tuning

Mine is not quite ready to fire yet.  I need to hook up a few more sensors.
It sounds like I am doing the same as you are, using the stock harness.  I
have a harness "extension" from Field of Japan, which is normally used to
plug between the stock harness and the stock ECU, allowing you to tap for
whatever reason without cutting the stock harness.  I am using it to serve
as
an adapter from the stock connector to the Motec connector.  I have not
really spliced my stock harness at all.  I have re-terminated some ends of
the harness for different style sensors.  For example, my stock MAP sensor
is
only a 2 bar, so I am using a delco 3 bar, which requires a different
connector.  Same for Baro (using wires from second TPS), and air temp
(probably using wires from EGR temp).  Injectors also were re-terminated
with
connectors from MSD to fit Bosch top-feed injectors.  Stock crank, cam,
throttle, and water temp sensors are used.  Only new sensors are baro, map,
and air temp.

I am using the M48Pro with ignition expander and the bosch wideband option.

One problem I am facing is injectors.  The stock harness has a "SFI
resistor"
inline with all the injectors.  I think Toyota did this to reduce the types
of injector drivers they needed for all their cars.  The Supra turbo comes
stock with low impedance injectors, while the non turbo has high impedance
injectors.  The turbo model has the resistor, while the non turbo does not.
They both measure 13.8 Ohms across the circuit.  I know my bosch injectors
are 2.5 ohm, and I can obviously find out what they are with the resistor.
My problem is, do I find out that resistance and tell the motec, leaving the
resistor in place, or do I just hack the harness, remove the resistor, and
tell motec 2.5 ohm.   I'd prefer to leave the harness alone.   I am worried
that if I give a high impedance number to the motec, it will assume
different
properties about that injector vs a low impedance injector.

Thanks for the help,

Andrew

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