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RE: Considering Injector Change..



Ok so you guys are saying I am right in that their duty cycles will be
reduced but I understand the problem with the low limit on the injectors..
Sounds like good quality injectors will help alot.


-----Original Message-----
From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
Of the Fredericks
Sent: Sunday, July 23, 2000 6:04 PM
To: gmecm@diy-efi.org
Subject: RE: Considering Injector Change..


I'll give you a little personal experience...I am running 55 lb/hr injectors
in my GN, up from the original 28 lb/hr units.  I suffer absolutely no
driveability or mileage problems with these and the stock ECM (I of course
have matching chips for the bigger injectors).

I agree that their idle stability in theory should have some problems as
pulse width decreases, but we don't seem to have hit it yet.  I don't recall
off-hand what my idle pulse-width is.

I have a friend with a batch fire DFI who recently went up to 72 lb/hr
injectors, and his idle quality, cruise, etc. are good as well.  We had been
told by some people that we'd need to go to a sequential ECM for better idle
stability to run the 72s, but they seem to do OK.  I know of several street
(well, sorta street) cars running 96s with sequential ECMs with no real
driveability problems.

Good luck!
Kendall Frederick

> -----Original Message-----
> From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
>
>
> Well, are you sure that you will eventually need bigger injectors???
>
> One of the cons of running big injectors is that the flow rates at very
> low PW values are questionable.  There is a physical limit to the minimal
> open time where the injectors are no longer that accurate.  The value is
> around 1.3ms (or so I've read and heard).  Thus, idle quality can suffer.
>  But - you can tune your car yourself!  That's a big plus.  You can tune
> your idle A/F ratio and alleviate the con that I mentioned above.
>
> If you are never going to add heads and cam then I say stick with
> 24lb SVOs
> (which are really 26lb injectors when looking at GM standards).  If you
> will definitely do heads and cam then I would consider 30lb injectors.
> But, you need to be 100% sure :-)  Hey, now that I think about it
> - that's
> a great excuse!  ... ...
> 'But honey, I have to buy a new set of heads and a cam because my
> injectors
> need them!'
>
> Hahahhaaa.
>
> Cya
> tim
>
> At Sun, 23 Jul 2000 16:40:37 -0400, "Rodney Fulk" <elixir@pathwaynet.com>
> wrote:
>
> >
> >I have a currently stock '94 LT1.
> >I am considering changing out my injectors for larger ones. The ones
> >I have
> >have over 140,000 miles on them and are likely due to be changed. I
> >am
> >flowing a little more air then stock and I figured being able to throw
> >more
> >fuel at the engine would be good. Especially if I decide to go with
> >a NOS
> >system I want the injectors to be able to handle the pressure.
> >
> >I understand I have 24lb injectors now. If I go to 30# or 36# injectors
> >I
> >won't be hurting anything will I? I AM using LT1 edit and can change
> >the
> >program to reflect the added injection.
> >
> >I am guessing my duty cycle will be less that way.
> >But can someone tell me the pros and cons to doing this change before
> >the
> >engine really needs it?
> >
> >I figure though that if I am going to buy injectors I only want to buy
> >them
> >once.

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