Holley TBI Injectors VS Pressure

[Walter Sherwin]

>
>Date: Mon, 14 Feb 2000 22:09:28 -0600
>From: "Shane Buss" <shaneb at ev1.net>
>Subject: Re: Holley TBI Injectors VS Pressure
>
>What's the lowest effective pressure these injectors work well with? I
>should have the 80#ers  tommorrow..
>
>Shane



Shane, I think I covered this info in a previous DIY post directed your way,
but in the event that the message did not get to you I will include a copy
below.  Technically, you can operate these injectors at pressures well below
12psig and still have "flow", but,  the cone shape/spray pattern/atomization
characteristics all become really messy and begin to really affect the
overall performance!  Not something you really want to do.  Stay around
12-15psig.  Good luck with your new injectors.  Stay in touch if any more
questions.

Walt.

_____________________________________________
The #85 injector that I mentioned below is in fact the same thing as what is
oft referred to as the "#80" injector.  In either case this is the injector
which comes standard from Holley in the 900 CFM 4bbl TBI, injector P/N
250R-51A, service P/N 522-26.

The #85 actually flows about 85 pounds per hour of fuel @ 15psig (Holley's
rated pressure).  It will slip into your smaller TBI injector housing pod.
When four of these injectors are housed and fed via the pod passages, and
driven via four 4/1 amp P&H drivers, you can usually get about 310 pounds
per hour of maximum fuel flow.

I would aim to calibrate your setup at a pressure somewhere between
12-15psig.  Any less pressure, and the injector spray quality is really
"globbery".  15-18psig will get you more volume, which in your case you
don't need.  Over 18psig, and you risk hydraulic shut down of the injectors.

I don't know if you intend to purchase new or used injectors, but here's a
tip that will save a lot of headaches when either buying used,  or
performing regular maintenance at a later date.  Measure the resistance of
each of the four injectors, from the very tip of one terminal post to the
very tip of the other terminal post.  The spec is 1.3 ohms +/1 0.1 ohms.
Now measure the resistance of the same injector, from the cylindrical collar
that appears to sheath the terminal post to the other collar around the
other terminal post.  The resistance should be identical to what you just
measured above.  If not, there is an electrical resistance and/or break
between the collar and the terminal post somewhere.  If you look at the
mating connector, you will see that the connector terminals engage over the
outsides of the collars, and that current must flow through the collars in
order to enter the terminal posts and windings of the solenoid.  I've been
caught by this a couple of times myself.  Sometimes a dab of solder at the
collar/post interface will fix this problem.  Sometimes not.
_____________________________________________


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