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Discussion Starter #1
Been running my 347 stroker,EFI, with 30# inj.,89 Mustang computer,since last Sept. Runs great except at W.O.T.,it blows black smoke, most likely too rich. I know that the computer goes out of closed loop ( O2 sensors in loop), and uses stored tables. So with the stored tables thinking I have 19# Inj, I'm probably 50% rich.
Proble solution is to go to a dyno., and have a custom chip burned.
Does any one know of a chip that can be purchased to accomodate 30# inj., without having to do the dyno. thing? Appreciate any help, Randy Richards
 

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FFCobra Craftsman
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Pardon my ignorance to all the EFI particulars, but don't you just need to match the #30 injectors with a new Air Meter calibrated to the injectors?

I also thought that Mass Air would "re-learn" new curves based on the new equipment installed. I think you need to power down the ECU for awhile so it can learn all over again.

I hope someone else can help you with this as well.

Raymond
 

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Is your MAF calibrated for 30s? If not, this could be your problem. Get one that is calibrated for the 30s or get a chip to change the MAF function and possibly WOT functions.

You can buy a mail order chip from numerous companys ( www.jmschip.com ). I recommend going to a dyno and getting it done for your needs.. every engine has differences.
 

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If it weren't calibrated for the 30's it would run like dog stink and you'd know it, especially while cruising.

What kind of fuel pressure are you running?
 

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What size MAF and TB are you running? along with feeding it to much fuel, you might be starving the other half on top of everything. If you are still using the stock 55mm MAF get a 70mm to 75mm calibrated for your injectors and a 65mm or bigger TB. Without it you are beating a dead horse. All the dyno tunning and chip burning isn't going to really cure the problem.
 

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If the MAF isn't calibrated for 30s OR fuel pressure is off, an a9l will "learn" to reduce or increase the injected fuel in closed loop and then it will use these settings in open loop, (start-up). It however does not use these changes during WOT. The computer uses the WOT breakpoint indication to start using functions (fuel multipliers and spark adders) against the uncorrected open loop tables. So you would only see this at WOT.

I agree that high fuel pressure could cause this... But wouldn't discount the MAF calibration. :)
 

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FFCobra Fanatic
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I have a 347 with the 30 lbs injectors and stock 89 computer, it doesnt show any signs of being rich at wop, although I may be a tiny bit rich throughout the complete rpm range according to the plug readings.
 

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Discussion Starter #8
Thanks for the inputs guys. I have a Pro-M 77M/M MAF, calib. for the 30# inj's. also using a 70 M/M T.B. I've got the fuel press set at 40# with the vac line disconnected and plugged.
As I said, it runs great, except for the black smoke at WOT. Seems to me that with a fixed set of tables for WOT operation,based on 19# inj's,with 30# inj's ,I must be getting too much fuel at WOT.
I guess the answer is a dyno tune and a custom chip.
thanks all, Randy
 
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