Even with dyno tune Car starts to run lean after 4800

KenneBell

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Apr 14, 2005
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San Jose California
I have kennebell at 8psi, 30# injectors and C&L Maf with 30# calib. tube. I was having my car tuned on the dyno and the guy opened my injectors all the way past 3000 and it ran richer and richer like it should until 4800 when it just starts leaning out from 11:1 at 4800rpm all the way to 14:1 by 5200rpm, the fuel curve is smooth and flat from 2000 all the way to 4800 then starts arcing up. He didn't take it past 5200rpm because it was leaning out. He said my 190lph fuel pump wasn't big enough that I needed a 255 pump and also the C&L using the stock MAF sensor could be the problem and I should get a true aftermarket meter like a granatelli. Has anyone ever had this problem? Is it the MAF, fuel pump, or both? By the way I made 289rwhp at 5200 and 340ft.lb. torque at 3500. I think if I get this lean situation figured out and take it to 6000 I should see around 300rwhp, perhaps? Thanks for all the help.
 
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HUNTED

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Aug 2, 2005
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do u have a fuel pressure guage my dad had the same problem and he added more fuel to through his pressure regulator and that cured it all and he runs 14 psi. If that doesnt cure it you might need a bigger fuel pump
 

bjl95mustang

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Jan 18, 2000
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Get a Lightning maf, 42 lb injectors, and a 255 high pressure pump. You can find the lightning mafs for about $100 and you will need a new maf plug. You will also not beable to use it with out a chip/ or tweecer becuase you have to have the maf tables loaded into the comp.
 

MattZ281LE

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Feb 6, 2000
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Yup I maxed 38# at 5500 on my KB at 8# That was with a 255 intank pump, I pegged the voltage on the Pro-M77 I had at the time. Put down 385 rwhp 420 rwtq at 5400.

New combo I did a complete fuel system with 60# injectors and a lightning MAF.
16# on the KB.
 

CManT1914

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Feb 5, 2004
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I think those 30's are too small, and so is that fuel pump. The C&L's are known to be pieces of crap, mine was, so I had my Pro-M recalibrated. Bumping the fuel pressure up is only a bandaid cure and I would not recommend it. Try some 42's or something, with a 255 pump, and get a better (Pro-M) maf and see what happens.
 
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