[Gmecm] 7747 stumbling acceleration when cold

[Charles McDowell]

Interesting.  Somehow I got myself to 132.  The standard ASDU is 135, so I'm
a little confused,  I'm sure I originally scaled it like 135*(55/65), but
maybe I found the BLMs to be running away or something....  I think I'll try
again and double check.

On Tue, Nov 30, 2010 at 3:14 PM, Scott Peitzsch <jlg-sep at comcast.net> wrote:

> The 9C1 Caprice TBI injectors (aka Cop injectors) are nominally
> rated to flow 68#/hr @ (I believe) 12PSI.  The correct BPWs for
> them are:
>
> BPW on a 305 = 107
> BPW on a 350 = 122
>
>
>
> ----- Original Message -----
> From: "Aaron" <aaron at creativeoverdrive.com>
> To: <gmecm at diy-efi.org>
> Sent: Tuesday, November 30, 2010 3:11 PM
> Subject: Re: [Gmecm] 7747 stumbling acceleration when cold
>
>
> I've not seen "cop" injectors, but a quick search shows them to be 65
> lbs/h.
> But to calculate a correct BPW you MUST know what they flow.
> And the rated flow is based on a steady fuel pressure, so you'll need that
> as well.
>
> It's been so long since I've looked at the hack for the 7747, I can't
> remember what you should check next.
> I've always started with a bin that was close.
> Maybe Allen will pipe up soon. He's better at this than me.
>
> From: cmcdowell12 at gmail.com [mailto:cmcdowell12 at gmail.com] On Behalf Of
> Charles McDowell
> Sent: Tuesday, November 30, 2010 12:02 PM
> To: Aaron
> Cc: gmecm at diy-efi.org
> Subject: Re: [Gmecm] 7747 stumbling acceleration when cold
>
> I can check in the log file tonight for the items you asked about. I was
> having major grief when I first installed this because I was given 305
> injectors by mistake. I examined every tiny detail of the install so I'm
> pretty sure I don't have any air leaks. Also bear in mind that it all works
> fine when warm. I know things expand when they warm up, but it sure can't
> be anything major. The thing idles and cruises fine when cold too. It
> really seems like an acceleration thing.
>
> Does anyone know for sure what things need to be changed when using a
> larger
> injector size? All I changed was the BPW to account for "cop car"
> injectors. Are there other things too?
>
> Thanks.
> On Tue, Nov 30, 2010 at 9:19 AM, Aaron <aaron at creativeoverdrive.com>
> wrote:
> We have discussed the adapter plates before.
> They are notorious for creating a vacuum leak were the TB and IAC gasket go
> over one of the bolts.
> The IAC sometimes even hangs over the adapter plate, so there is no seal to
> the gasket.
>
> What is the IAC position at idle open loop and closed?
> Map voltage?
> TPS voltage?
> Fuel Pressure on the supply side?
> Fuel Pressure on the return side?
> Have you looked at the fuel spray pattern from the injectors?
> I like using a dial back timing light to strobe the spray to see it
> more clearly.
>
> From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On
> Behalf
> Of Charles McDowell
> Sent: Monday, November 29, 2010 3:09 PM
> To: Eck, Joel
> Cc: gmecm at diy-efi.org
> Subject: Re: [Gmecm] 7747 stumbling acceleration when cold
> I'll double check my logs, but I think my temp is good. Bear in mind that
> it's not like this thing ran well once and stopped. It never worked well
> since I installed it. I have an Edelbrock performer quadrajet carb manifold
> with an adapter for the TBI. Thanks.
>
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