[Gmecm] 7747 stumbling acceleration when cold

[Charles McDowell]

Well, I loaded up a new bin with BPW=122.  The engine isn't cold so it's not
a real big test, but it seems to run fine.  The BLMs were higher, but not
super high on my short test drive.  The range was like 123 to 140.  I'm
going to let the engine cool off and see how it works in the morning...

On Tue, Nov 30, 2010 at 6:00 PM, Charles McDowell
<charles at taildragger.info>wrote:

> 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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>
>
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