Fuel pressure / Flow rate formula

Bruce Plecan nacelp at bright.net
Wed Nov 18 00:15:46 GMT 1998


-----Original Message-----
From: d houlton x0710 <tc75918 at hpr357.msc.az.boeing.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Tuesday, November 17, 1998 6:48 PM
Subject: Re: Fuel pressure / Flow rate formula


>Bruce Plecan wrote:
>>
>>
>> > It quotes RC Engineering and they
>> >apparently swear by the Lucas disk type injectors.
>>
>> I just wonder if they just happen to sell them.
>
>Yup.  It does have the ring of marketing hype except that this isn't >the
first I've read about the Lucas disk type injectors and their >advantages so
I just more or less believed what they were saying.
>
>Some other things were that the metering hole of the pintle types is >at
the end of the injector whereas the disk type is more towards the >center of
the injector surrounded by the injector's mass.  When you >shut down an
engine, at least some of the exhaust and intake >valves are open on the same
cylinder letting the heat of the exhaust >manifold back up and through the
cylinder to the injector in the >port.  Pintle type tend to fry and boil the
fuel at the tip gumming it >up.  Disk type are recessed in the injector
which also acts as a big >heat sink so the effect isn't nearly as bad.  They
also pointed out it's >much worse on turbo'd "V" engines.

Just to play devil's advocate, Gee someone call General Motors,
and tell em there is a cure for their injector problem.  If it was a
really big deal, every one would be using them.  With all the
detergent packages, I don't really see that justifing the added
expense.  If it really mattered to the turbo'd V crowd the GN list
would all be running by now, again not the case.
>
>>  They say they can run
>> >at 85% - 95% duty cycle with no ill effects and can handle higher >>
>pressure much better than the pintle type.  They can also run a >> >much
shorter pulse at idle than a pintle type because of the
>> > smaller lift needed for a disk type.  Something like a .8 - .9 ms >>
>opening time for the disk vs 2 ms or so for the pintle.
>>
>> They mention if they were Peak+Hold?.
>
>Hmm, don't remember if they did or not.  I don't think so, but they >may
have mentioned the impedence so I'll check for that.


Also, they were/are big into motorcycles.  A "normal V-8" at
6,000 rpm gives ya 10 msec for an injector event if batch mode
so 85% is  8.5 msec which is just fine for a Saturated injector.
However if a 12,000 ya got 4.25.
  According to an old post, 1-5msec for P+H, and 2-10
for saturated, so it kinda falls into place why they sell what they do.
Bruce
>
>
>--Dan
>




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