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Idle question

 
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killa



Joined: 19 Feb 2008
Posts: 4

PostPosted: Tue Feb 19, 2008 3:43 pm    Post subject: Idle question Reply with quote

Hello guys, having trouble dialing in the idle on my C950, motor specs are as following:

2032cc 9:1 high duration/ovelap cams 16v head and 83lb injectors, 14in/HG@idle which in my case is 800rpm

It won't idle good unless i give it some decent fuel, any thoughts.
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cutlassefi



Joined: 21 Apr 2008
Posts: 176
Location: Central florida

PostPosted: Tue Apr 22, 2008 5:12 pm    Post subject: Won't idle Reply with quote

Remember the Holley only fires in total batch, all injectors at once. Makes sense that you have to throw more fuel at it. Half of it is going out the tailpipe. Does it run o.k. off idle? If so then not out of the ordinary.
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killa



Joined: 19 Feb 2008
Posts: 4

PostPosted: Wed Nov 26, 2008 6:34 pm    Post subject: Reply with quote

I was able to get it to idle better by throwing 20 degrees of timing at idle and playing with the enrichments.
Thanks
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Danny Cabral



Joined: 03 Jan 2007
Posts: 3
Location: Connecticut

PostPosted: Sun Dec 14, 2008 4:48 am    Post subject: Re: Won't idle Reply with quote

cutlassefi wrote:
Remember the Holley only fires in total batch, all injectors at once. Makes sense that you have to throw more fuel at it. Half of it is going out the tailpipe.

Wrong.
Batch fired EFI (bank-to-bank) sprays 4 injectors on one bank, then 180 crankshaft degrees later, the other 4 spray on the opposite bank. The C950 ECU has 4 drivers and each one pulses the ground on 2 injectors. On the C950 MPI harness, the injector connectors with the same color ground wires are pulsed together.

If you want to minimize the 'fuel pressure drop' at the fuel rails/injectors, you can wire the harness to 'batch fire' a pair of injectors on each bank. This is an improved strategy for batch fired (bank-to-bank) EFI so each bank doesn't fire at the same time, which can possibly disrupt the 'fuel pressure stability/distribution' (especially with large injectors and a single fuel feed line).
In other words, wire the injector harness like this (Chevy):
A - #1 & #3
C - #6 & #8
B - #2 & #4
D - #5 & #7

http://www.boxwrench.net/specs/chevy_bb.htm

C950 manual (pg. 96) wrote:
Batch or Group Fuel Injection System. The injectors are divided into two or more groups that are activated separately. Each group meters fuel once per each cycle of a 4 stroke engine. Each group or pair of group is offset by one crankshaft revolution. This arrangement allows for an injector timing selection that eliminates metering the fuel into an open intake valve. Holley uses this type of system.

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cutlassefi



Joined: 21 Apr 2008
Posts: 176
Location: Central florida

PostPosted: Sun Dec 14, 2008 5:48 am    Post subject: Holley Idle Reply with quote

Hey Danny,

You may want to tell Holley that they don't fire all at once, because if you ask their tech guys that's what they'll tell you! Read their explanation. They contradict themselves. "Each group meters fuel once per each cycle (they didn't say revolution, they said cycle, meaning two revolutions) of a 4 stroke engine". Sounds to me like their firing them once per cycle being all eight in the "group". Wouldn't a true "staggered" or "bank -to-bank" batch fire system meter or fire them twice in a cycle? I'm sorry, this is double talk to me. Especially considering my experience with their system.

The Holley is 80's technology done by the infamous John Meaney. To some degree it mirrored the GM/Motorola systems in that era. Guess what, they fired in total batch as well.

Not sure where you're getting your info. Holley just donated a C950 to Univ. of N. C. Charlotte. They have a pretty sophistcated dyno. Guess what? Their C950 fires all eight at once too! Their eight individual O2's reflect a significant imbalance, no matter how you arrange the wiring. It always follows a pattern. And if you call Holley they'll offer you the "Pro" version which fires all eight every TWO revolutions! Go figure!

Double check your info. Unless they've changed something very recently I believe I'm correct.
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Danny Cabral



Joined: 03 Jan 2007
Posts: 3
Location: Connecticut

PostPosted: Sun Dec 14, 2008 6:45 am    Post subject: Re: Holley Idle Reply with quote

These two quotes from Doug_F should substantiate things:
http://www.chevytalk.org/fusionbb/showpost.php?post/1383341/
http://www.chevytalk.org/fusionbb/showpost.php?post/1251981/



cutlassefi wrote:
And if you call Holley they'll offer you the "Pro" version which fires all eight every TWO revolutions! Go figure!

What you're referring to here is just one of the "PRO" features (MPI-1 PW per 2 rev.). The 'one pulse per two revolutions' strategy is primarily used when very large port injectors are used. Again, it doesn't simultaneously fire all eight injectors.
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'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI, DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, 4" lift, 35" tires
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cutlassefi



Joined: 21 Apr 2008
Posts: 176
Location: Central florida

PostPosted: Sun Dec 14, 2008 6:51 am    Post subject: C950 Reply with quote

Then Doug needs the tell the Holley tech guys as well as the guys at UNCC. Plus he'll need to explain the imbalanced that follows the change in "stagger"
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cutlassefi



Joined: 21 Apr 2008
Posts: 176
Location: Central florida

PostPosted: Wed Jan 07, 2009 5:56 pm    Post subject: Holley idle problem Reply with quote

Just an update. Talked to Holley tech today because I have a C950 SBC project. Guess what? Woody at Holley confirmed that it is a total batch fire system, not bank to bank or staggered batch. That will cause a probelm at idle, especially if have a bit of a cam in it.
Plus some versions of their software won't work with XP, has to be 2000 or lower.
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