EFI Please????

[Chris Conlon]

So here's my attempt to add some actual EFI content, with some
pointless replies to other stuff below.

Since my Toyota ECU is effectively untweakable, my current
(and long-delayed project) is an overkill intercept box.
It's supposed to replace the AFM with a speed-density system,
ala the HKS VPC, except be tunable via maps in EEPROM. It has
a bunch of channels of data logging, incl some undedicated
ones, serial io, etc. In the second phase it'll also get some
injector drivers, and do an end-run around the stock ECU, at
least as far as fuel delivery. I will need this after a point,
the stock injectors max out around ~225HP and I don't plan to
stop there. If I get really amibitious, I may eventually
include spark control as well, but this is a thorny issue for
several reasons.

The other data-logging duties will include monitoring of
various temperatures, accelerometers (Analog Dev has some very
nice 2nd generation units out now), O2 sensor, etc.

The box is based on an $80 68hc11 from New Micros, an external 8
channel A/D chip, and the usual collection of op amps, etc. I
have a Motorola MAP sensor (mpx4250ap), but you could use pretty
much any common one. I don't like any of my temperature measuring
options so far, and am using thermistors for now.

(I started the project on a PIC chip but got off that platform
for the moment.)

I don't see this as a commercial project (been there, done that,
left for a reason), plus the HKS VPC is available for most of the
vehicles where there is a real market. (Not mine though.) I do
expect to sell 4-5 of them to friends and MR2 list members, just
the hardcore tweakers though. So, I have no problem sharing any
and all info, and would actively welcome collaboration with
anyone doing similar work. I have several years of experience
in embedded systems, data acquisition, and process control, but
this is my first automotive project. (These days it's software
that pays the bills, and I get to missing hardware projects :)


Ok my $0.02 on another thread:

> >> Toyota engines on the other hand can take 225% of the stock power on bone
> >> stock internals, easily. I do not know many makes that can claim the same.
> >
> So the Toy engineers have not let their bean counters get at the next
> 75%!--Sorry but I am not impressed. If you want to talk about overbuilt
> engines, lets talk about Harvesters or Cummins or that old 302 CID GMC
> in-line six, or even Hudson Hornets or Packards!! 225% would be just
> another day at the office for any of these!!

Well to be somewhat fair you might also consider the specific
output of each motor in stock form. I don't have to use as big a
multiplier over stock when my starting point is 75HP/liter than
when it's 50HP/liter.  Except for one engine, there will always
be some other engine more overbuilt than yours. So what? Unless
you're on the ragged edge of blowing it up, the extra weight's
likely slowing you down. Personally I'm impressed by tractor pull
tractors running what, 75-100psi of boost? But that's just me.

> > From a technical standpoint, designing something to a 125% safety factor is
> > FAR more of an engineering challenge--that is, if you do not want a lot of

And Honda is really good at this; and in the long run it is a
win to go this way. How many car owners will ever modify the
engine? 1%? If that many? Especially as emissions laws get
tougher and tougher. Luckily us power freaks do still have a
few sturdy toys to play with... for the time being.

   Chris C.