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13B Intake Manifolds
With that clue, I think I know my answer. Atkins
must have supplied you with the 850cc injectors that powered the 85-86 GSL-SE
13B. In that iteration of the car, Mazda used those.
In 1986-87, Mazda switched to using four 460cc
injectors in the naturally-aspirated car and using four 550cc injectors in the
Turbo II. While those had more potential for overall fuel flow, it meant that
they had them staged. I'm not positive of the exact RPM changeover to using all
four but my recollection is that it was 3800 rpm. My Turbo II has a little hicup
in acceleration when it passes through that point and the factory wrestled with
getting that right--something usually chalked up a bad ground. They worked fine
when new but sometimes developed the hicup when they got a little older and the
ground was a tad less reliable.
How many horsepower did you intend to get out of
your turbocharged rig? I think you're fine but might be near the limit at a
little over 200 HP. Any projections?
You've got 1700cc/min. The naturally-aspirated car
ran four times 460cc or 1840cc. The 87 Turbo II ran four times 550cc or 2200cc.
Somewhere around here I've got a book on fuel
injection that figures out the conversion for fuel adequacy (and helps with the
metric/min to pounds/hr conversion). I think you also have to use an 80% or 85%
duty cycle or else the injector is basically open all the time, which for some
reason isn't recommended.
The reason I asked about this is that those 850cc
injectors were some of the biggest in the auto world, at least at the time and
might be still. Other manufacturers used multiple injectors that corresponded to
the number of cylinders, so typically you find hot-rodded Mustangs, etc., using
eight, which of course could be smaller individually to sum to an even bigger
whole. When I saw your two injectors, the reason I wrote was because I thought
you might have discovered some even bigger ones than the GSL-SE.
Rumor was that Mazda had a hard time getting the
big ones like you've got to run smoothly at the bottom end, which is why they
switched in the next iteration of the car to four injectors--but remember they
were looking for a smooth 750 RPM idle speed. Aviators need neither that
smoothness nor an idle that low.
Anyhow, I was just surprised to see the two big
MONGO injectors feeding all that airflow. I think the Mazda 850cc injectors
might be on that table that Paul Lamar reprints from time to time, if you're
interested in working out the lbs/hr and then BSFC conversion to re-confirm the
top end of your fuel flow.
Barry Gardner
Wheaton, IL
----- Original Message -----
Sent: Wednesday, March 31, 2004 9:28
PM
Subject: [FlyRotary] Re: 13B Intake
Manifolds
I purchased the throttlebody, ECU and programmer
from Atkins Rotary. The throttlebody came with the injectors already
installed. Not sure what the injector flow, model, etc are. I have
that info somewhere, but it will take some searching through a lot of e-mails
to find it. Paul Conner
----- Original Message -----
Sent: Wednesday, March 31, 2004 4:23
PM
Subject: [FlyRotary] Re: 13B Intake
Manifolds
Paul Conner--
I was looking at that picture of your manifold
you enclosed. It seemed like you only had two injectors.
If true, what kind of fuel flow are they rated
for and what is the brand/model number? Those must be
big--no, MAMMOTH--injectors.
Barry Gardner
Wheaton, IL
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