Injector Scoop Technology
by Jim Hill - 12/10/1998
The Scott "Slot" featured a cast aluminum, futuristic-looking
scoop that was removable. The "hat" itself was a long, narrow, rectangular
shaped venturi, hence the "slot" name.
Like a Hilborn, these units used a return jet system that could be enlarged (drilled out,
the crude way!) or changed to a larger orifice jet from the factory (the correct way).
Several guys in the South Florida area used them with success. I do remember
that the pumps Scott supplied were less than terrific. Most guys merely called up
Gene Adams at Hilborn and got a PG-150-A pump for gas or a PG-150 pump for fuel having a
greater "specific gravity".
Having done some electronic fuel injection work, I can only look back at the
Hilborn, Enderle, Algon (!) Scott and even the more advanced concept of the Orner Injectors (Dr.
Pete Orner, Akron, OH) and note that they were all quite crude.
First "real" FI system I saw for racing was when I visited the McLaren Engines
operation in Livonia, Michigan. McLaren was then the series champs (pre-turbo
Porsche) in Can Am with their 494", aluminum motor big-block Chevys. These
engines used a Lucas-Bosch electronically timed FI system running through magnesium
injector bodies. Jim Kinsler did a lot of the fuel systems work for
McLaren,
including set-up and tuning of the systems as well as porting and flow work. Fuel
metering was extremely precise and McLaren was using the timing to "tune" their
way out of the unequal fuel distribution problems produced by the different runner lengths
problem inherent to BBC motors. (Sig Erson's old "Tri-Flow" cam designs -
different valve timing for each cylinder - were another approach, as was the
"twisted" carburetor pad location of the early single-plane BBC 1x4 intakes made
by Edelbrock in the early 70's)
One detail I noted (incredulously!) was these systems used extremely
high fuel pressure at the nozzles - like 100 PSI! Although they were running
relatively easily atomized gasoline, this extreme pressure helped to prevent the vapor
from dropping out of suspension, thus producing a better burn. If you read the Hot
Rod Magazine articles on The Surfers, (tip of the cap to Adam Sorokin!) you'll note that
they
were running very small diameter lines with a high pressure pump. Results: Better
atomization of a dense fuel (nitromethane, 98%) and reduced liquification of the fuel/air
mixture. Sounds like those old drag racers were onto something!
These Lucas-Bosch systems worked very well for the McLaren program, were state-of-the-art
and vastly advanced over what drag racers and sprint racers were using then.
Hmmm... all modern computer controlled FI systems today use high pressure, submersible,
in-tank electric pumps. Ford runs around 75 PSI. Just try and change a fuel filter
without letting the pressure dissipate and you'll see what I mean!
Jim Hill
Crane Cams
