Nother thought

[timsiford at hushmail.com]

Dave,

Understood.  I'm in class right now but I'll post the PWs that gave me the 
100% DC later tonight.  I wrote a convenient VB program that I use to calculate 
all sorts of Automotive data.  The DC is based on batch fire cars where 
100% DC was equivalent to an injector Pulse Width of 10.0ms at 6000RPMs. 
 I'll post the full formula later.  NOTE:  I didn't consider opening and 
closing time.  Thus, the DCs could be even higher.  I went over and over 
and over swapping out my injectors.  Everyone in MAFB said that I shouldn't 
need to go higher than 24lb injectors.  Diacom also reported AOK O2 voltages 
at WOT throughout the entire WOT run (0rpms->6500rpms).  I replaced my injectors 
SOLELY because of the DCs I was seeing.  Many people told me not to replace 
my injectors ... that the 22lb injectors would be enough.  Diacom supported 
that.  But, the DCs did not (and I was running 52psi at the rail).  I upgraded 
to 24lb SVO injectors based on everyone's recommendations.  Well, with the 
24's I was seeing almost 90% DCs at 6500rpms.  Those injectors were on my 
car for only an hour before I ordered a set of 30's.  The 30's have acceptable 
DCs ... in the order of 77% at 6500rpms ... and, the car idles great.  I 
have the injector constant set to 33lb/hr in the PROM and I am running 45psi 
at the rail.

I do remember that at 4500rpms my injector pulse width stayed pretty static 
until up to 6500rpms.  The fact that the RPMs were increasing and the IPW 
remained the same caused the DC to rise substantially.

My butt-o-meter is very inaccurate.  You're talking with someone who couldn't 
tell too much of a difference after swapping heads/cam.  But, with the new 
SVO injectors (30lb) I noticed a difference in the upper RPMs.  If I get 
to the track soon I might be able to prove it :-)

Tim

At Thu, 5 Oct 2000 10:00:52 -0400, "Dave Zug." <dzug at delanet.com> wrote:

>
>To clarify, What Pulse width (in Ms) are you calling 100% DC  at 4500 
>RPM?
>
>Were your PW's constantly INCREASING as RPM went up?
>
>My 383 CI (360hp thereabouts, almost same cam as yours- less flow above 
>5500
>though, stock lower intake) uses stock 22# and stock FP almost, hits 
>85%
>static for a BRIEF moment after the shifts. o2's still on the rich side
>according to GM sensor (093) , and plug condition backs it up.
>
>This is not meant as evidence contrary to your observations - just more 
>info
>to add to the collection.,.. mine and yours.
>
>----- Original Message -----
>From: <timsiford at hushmail.com>
>To: <gmecm at diy-efi.org>
>Sent: Thursday, October 05, 2000 9:49 AM
>Subject: Re: Nother thought
>
>
>> I was running the stock 22lb injectors on my IROC (218cam, AFR heads,
>MiniRam)
>> for about 3000 miles before swapping to 30lb injectors.  At WOT I 
>would
>> reach 100% DC by 4500rpms.  I would continue to shift at 6500.  This 
>is
>>  great example of how the stock O2 cannot be used for tuning.  The 
>O2
>volts
>> were approx 830mV and greater throughout the entire RPM range even 
>though
>> I was hitting 100% DC.  After switching to 30's I noticed significant
>improvement.
>>  The stock 22lb injectors never falterered and still function great.
>>
>> Tim
>>
>> At Wed, 4 Oct 2000 23:22:33 -0400, "Bruce Plecan" <nacelp at bright.net>
>wrote:
>>
>> >
>> >Anybody have any info., about the extended effects of running really
>> >high
>> >DCs on injector drivers?.
>> >Just thinking, out loud.
>> >Just with all the hours of running stuff here, I can't find any real
>> >reason
>> >for for the 85% DC, as applied to a street car.
>> >Just maybe do to worry about a worse case thermal situation, and
>portecting
>> >the devices?.
>> >Or maybe just a ol wifes tale....
>> >Bruce
>> >
>> >
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