Homebrew EFI box

[Kenneth Bailey]

Alex, Where is this web site you seek and found. Also have you done any work
with a mazda RZ-7 rotary ?

I would like to learn to build hobby boxes ...


Ken









Alex Samson wrote:

> Hi to All,
> After more than 4 years I finally found this site that I have been
> looking for!  I build EFI boxes for a hobby and every time I start a
> project, it is always one big massive guessing game.  I always wondered
> if there exists a website or reflector for this activity to help make
> the guesses a little less wilder.
>
> My last project was a complete engine management box for a Subaru 2.2L
> flat-4.  This engine went into an early 80's VW Vanagon which had that
> famous engine commonly known as a "grenade with a short fuse".  The box
> I made was based on an 80C31 for the EFI, another 80C31 for the
> distributorless ignition system, and a PIC for the idle stabilizer.  Man
> this was a wild project for about 6 months! I did a lot of guessing
> because we never had access to a Subaru with the same engine. I had 8k
> bytes of scratchpad RAM to log sensor readings to help in developing the
> software written in assembler. At present, the van has done over 30K
> miles already and I havent made any more changes the last 2 years.  Its
> a daily driver owned by a shop mechanic who simply loves the novelty of
> his engine setup.   Exhaust has the usual stuff and an O2 sensor which
> the box reads for mixture control.  Softwares and look-up tables for the
> 80C31's are stored in individual SRAMs with  a small backup battery to
> allow easy upgrade downloading from a laptop. Naturally, a default setup
> is in Eprom.  I used the original Subaru air flow sensor, Cam & Crank
> sensors and other peripherals.  Fuel injectors were quite rare in that
> they didnt need a step-start scheme, they were merely turned completey
> ON or OFF with a straight FET switch (no modulation). The power output
> of this new engine is way outside the league of the original aircooled
> VW.  The owner once had damaged a pinion gear bearing, then obliterated
> a clutch, and the last repair was the transmission getting stuck in 1st
> gear.  Unfortunately, the engine has proven to be too strong for the
> tranny but otherwise it is very smooth and more appropriate for the van.
> One just has to learn to be easy on the throttle to preserve the drive
> train.  Would I do it again?  YES!  It was a lot of fun. Kenedy
> Engineering in Palmdale made the adapter plate.
>
> I have started a new project, this time for an old Bosch D-jetronic in a
> 73 Mercedes 450SLC.  This one is for myself.  At the present, I just
> finished installation of an O2 sensor in the exhaust, and I finished a
> small box based on the AT89C2051 that processes the EFI points from the
> distributor.  The problem with the original system design is that the 4
> EFI trigger points are located at the bottom of the distributor and the
> lower pair of points get fouled by oil sling.   So my small box
> "synthesizes" the action of the lower pair of points by just reading the
> upper pair of points.  I will start on the main box next.  The main box
> will allow mixture correction with the O2 sensor and will implement a
> more positive step-start injector control instead of the weak original
> Bosch circuit.  This should hopefully improve emissions, power, and fuel
> mileage when I am done.  We use the Atmel AVR at work so I am tempted to
> use the AVR for this project this time.  I want to keep the distributor
> original with regards to suggestions from others in the past to install
> a GM magnetic trigger scheme to the Mercedes distributor.  I want to
> maintain full compatibility with the original box so its easy to go back
> to stock.
>
> By the way, I was recently at a junque yard because I needed a connector
> for a D-Jetronic computer.  I found an old 1972 (or older?) Mercedes 280
> SE 3.5 thats been sitting out in the open for probably many years.  The
> D-jetronic box was still there although exposed to the rain etc in the
> exposed engine compartment.  I picked up the box (and connectors) and
> ran it in my bench simulator back home (for which I needed the connector
> for in the first place).  I wanted to see what kind of failure this
> junque yard box  had acquired after all the exposure.  Would you
> believe, this box still works?  I was amazed. This was the first
> generation of Bosch EFI and they certainly must have made sure that the
> boxes are dependable!
>
> I can go on and on with this subject but I would first like to get
> feedback from the members of the list if my topics are appropriate.
>
> regards to all,
> alex samson