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Droppin Fuel Pressure Too Rich

Don Dada

By Don Dada,
in Engines & Forced Induction

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Don Dada Mentor

Don Dada

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today i fitted a jap tuned ecu an dynoed to see the results.The dreaded drop in hp and tq with the stock ecu (11psi) between 5-6000rpm is no longer there but the curve falls flat over 6000rpm with a loss of hp from 229 to 208 an afr's in the 9's at peak rpm.Now it gets intresting! Fuel pressure was set at 37psi through an adj aeromotive fpr (with vac hose on) On dropping the fp to 25psi (with vac hose on) there is more power an tq through out the entire mid range and an increase to a peak of 233hp with afr's in the high 10'S at peak rpm(7400)

My question is this--- Is it safe to run this amt of fuel pressure?It seems kinda low to me! I hav'nt heard any pingin an as i said afr's are about 12's from about 4000rpm droppin to high 10's to the limiter

The car feels much smoother on the road too!

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chrissso Proficient

chrissso

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AFR of 9 is just too rich. That why when you drop the pressure, your ratios are getting closer to what they need to be.

You mentioned that you fitted an ECU, but did you tune it? Sounds like the injectors are too big for the program. Retune should do it.

The higher fuel pressure will atomize the fuel more, creating an even air/fuel mixture, therefore a cleaner,better fuel burn.

Don Dada Mentor

Don Dada

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AFR of 9 is just too rich. That why when you drop the pressure, your ratios are getting closer to what they need to be.

You mentioned that you fitted an ECU, but did you tune it? Sounds like the injectors are too big for the program. Retune should do it.

The higher fuel pressure will atomize the fuel more, creating an even air/fuel mixture, therefore a cleaner,better fuel burn.

The ecu is an upgraded stock ecu not tuneable an my injectors are stock 370's. My friend goes japan to bring in used parts 4 sale an the 33 he got it from also had stock inj an air flo not sure what boost they wererunin tho.

So is this fuel pressure safe for everyday use?

With out vac it reads bout 33psi - hav searched but found no definate ans about fp

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