>1- there were a couple of Midgets and Spitfires with what looked like
>"distributorless ignition systems".
AKA crank-fire ignition systems. The benefits are absolute
rock-steady firing and reliability even at high RPM (how
high? Try pushing 9000 in your Spridget), because there is
no mechanical element to go out of alignment, no backlash in
the drive gears, no distributor wobble as it wears out. There
might also be a minor performance enhancement in the lack of
drag on the camshaft from driving the distributor, but I doubt
that this is much more than a quarter of a BHP or so.
How it works: You place sensors on the flywheel and a pickup on
the bellhousing. When the sensors pass the pickup, you get spark.
The advance curve is determined by the electronics, how I don't
know. (My race car had used a crank-fire but it had been removed,
along with the engine, when I bought the car a year ago. So all
I have is this dummy switch on the master switch box. Next time
I get my hands on a Dymo I think I'll make a label for it reading
"NITROUS" or maybe "JATO.")
With individual sensors for each cylinder, distributed around
the flywheel, you have the best possible degree of accuracy in
ignition because you've got the largest circle possible in the
car to use as the base. In the last such system that I read
about, which was several years ago, there were also individual
coils for each cylinder as well, which meant a fatter spark at
each plug. Each coil is fired independently in sequence by the
master box, again at a time determined by the advance curve
programming which counts the time it takes each sensor to pass
the pickup, determines the engine's speed, compares it to previous
speeds and adjusts the advance accordingly. Again, I don't know
if this is the way they're doing them now.
Where to get them: The Winner's Circle sells them for A-series
cars at least; in theory they should work for most any car as
long as you tell the electronics how many pistons you have.
How much: Expensive. I vaguely remember them costing in the
range of many hundreds of dollars six or seven years ago, but
I didn't pay that much attention to it since I didn't need it.
>2- I looked at the rear-end (:-) of a couple of the Midgets and
>noticed that they did not have leaf-springs.
Yup. Coil-over rear suspensions are legal in Production. They
typically consist of a number of brackets that you weld to the
chassis, another number of brackets that you weld to the axle,
and adjustable radius arms that you use to connect the two. The
spring is typically mounted to an adjustable perch threaded onto
the shock absorber so that you can adjust ride height to get
the car balanced. The front end of my race car has such a coil-
shock mechanism in place, the rear is still leaf-sprung but modified
to avoid the stock roll-understeer provided by the MGB's designers.
The main purposes of going to coil-overs are to improve the spring
rates, give clearance for wider rear tires, and reduce weight, as
well as control the suspension geometry. Also, by replacing the
bushings at the rear with spherical rod-ends (Rose joints to our
UK readers), you lose any deflection from the soft bushings and the
car is less prone to bump-steer at the rear. The back end of a race
car at speed is the wrong place to conduct experiments in Brownian
motion.
>3- All of the Spitfires had steel bars with sphericals ends going
>from the top of the shock towers to the fire wall. Is this to stiffen
>the front suspension[...] ?
It sounds just like the Monte Carlo brace used by Shelby on his
GT-350 cars, and first developed by Ford for use on the Falcon
Sprint (which is why they called it the Monte Carlo brace). On
the Fords, the brace was a pair of gusseted sheet-metal brackets
welded to the tops of the shock towers and the firewall, forming
a V above the engine with the apex toward the rear. I would guess
that the purpose of these bars on the Spitfires is to help stiffen
the front suspension by transmitting loads into the roll cage,
which is inside the firewall.
You can't make a race car chassis too stiff. (Which reminds me,
everyone should rush out and get this month's Road & Track and
read Peter Egan's article. "Critics of the Seven say that Colin
Chapman started taking bars out of the chassis until it collapsed,
then he put one back." It's really about stripping paint off an
old English chassis, the good ways, the bad ways, and the True
Way. Great stuff.) If the chassis deflects under loads (as
opposed to under impact, of course), all your careful work with
the suspension geometry will be pointless, like building a freeway
on alluvial sand (hello Oakland!).
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