Re: [AMC-list] Adding TBI fuel injection to a...

[tom jennings <tomj@xxxxxxx>]

OK, I just went through Tedd Brown's Corvair TBI conversion page. I'm sold.
He did a great thing, and it's about 95% right for Rambler sixes (and v8's,
for that matter). I've only got two unknowns at this point:

* precisely which throttle body to use, that's easiest to adapt physically.

This is just junkyard hunting, there's the '87 Ford Tempo body, but I have
to figure out if the throttle position sensor is directly GM compatible. The
same GM body Tedd used is actually pretty close to right for a 1 bbl
downdraft carb. Adapter required, but it's just a flat plate at each end of
a tube.

* details on how Tedd handled the reluctor for the crank position.

First, DIS (GM's wasted-spark) system is overwhelmingly the way to go. I
won't bore you with the details, but it's 40KV at all speeds, zero timing
jitter, donors are all GM V6's from 87 - 00, all parts are CHEAP (Rambler
Mentality). Absolutely no distributor needed, for the 195.6, just plug the
hole, it doesn't drive the oil pump. THe catch is of course you need that
ECM to control it.

THe catch here is that it reads crank position with a notched wheel that is
of critical precision. Tedd Brown did a very clever job -- onto the harmonic
balancer, he bolted a saw blade that was notched to drive the DIS crank
sensor. He then ran the engine with his normal ignition, but used a timing
light connected to the DIS system to adjust the crank sensor to the precise
location, then using marks made with that test, drilled holes in the face of
the harmonic balancer to drive the sensor.

He didn't describe the process, or how many holes he had to drill, on or off
the car (I suspect on-car, as he was avoiding engine disassembly all along).
It's a sweet trick, and the only complication in the whole thing.


The clever thing about wasted-spark ignitions (which fire six cylinders with
three coils -- two cylinders fire at the same time, the two that are at
top-dead-center, one compression stroke, one exhaust stroke). THe "wasted"
spark does nothing... but because of this scheme, the ignition doesn't need
CAM timing, just CRANK timing! Because for a given pair of cylinders, one of
them is at TDC at the same crank position... for a given rotation of the
crank, the ignition can't tell which one is at the power stroke, but it
doesn't matter -- both get fired.

OK the whole world knew this, but I wasn't paying attention until just
recently :-)
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