I tried to get my car tuned last summer/Fall to run 42's with no FMU.
When first on the dyno with a chip with base tune, the A/F ratio wouldn't maintain its set point till redline.
I was told it was likely a fuel presure problem, and to replace the inline pump to support flow at the increased FP caused by the boost load, and to replace the stock regulator with a quality adjustable.
After replacing the inline (with an MSD 190) and adding a Mallory regulator, I went back to the dyno.
This time it was confirmed that the fuel presure was rising steadily with boost, but that the A/F curve remained the same or slightly worse. I was told the injectors are going static.
the power is 460 at 5900, and tq is 469 at 4600. I see lots of guys running much more power with the same injector/pump combo. The intank pump is a walbro GS 340, and I see people making more power with just this pump.
The Meter is a Pro M 75 optimiser. When i first got it, it needed to be recalibrated at 19 lbs. BT for an ATI. I'm wondering if the built in transfer function of this MAF gets 'lazy' at high flow, when set for 42 lbs injectors, and with the better flowing head cam intake the car has now, higher boost, etc. and starts under reading the amount of air being flowed. I was told the meter is not pegging (more than 4.7 volts) But I am wondering if its possible that the curve for fuel inrichment is too flat with the calibration set at 42 lbs. so it stops calling for more fuel at some level below 4.7 volts and does not acurately track increasing air flow after about 5000 RPMs.
If set at less than 42 lbs. It fattens the mid range, but still curves lean up top. This is why I was told it was the injectors, but I'm wondering if this meter needs to be sent back to Pro M and reset for the new airflow the engine sees. I just don't want to keep replacing parts if its a simple problem. I have seen the enrichment curves posted on Pro M.com and I could see how a curve that flattens out up top could mimick the injectors going static. Its been almost 4 years since the meter was last calibrated. I have raised the base F.P. to keep it safe up top, but that sort of defeats the purpose of the chip, and caused a loss of tq and HP, and a decrease in milage.
The combo is a 306 with SRP flat top and eagle rods, p600b 2 core, 14 lbs 2.75 pulley, 75 mm tbody, cobra intake, Edlebrock RPM heads (58 cc), A small Lunati/Bennet blower cam, 42 lbs injectors, stock pickup lines and rails, gs340 and MSD inline, mallory regulator. The blower has a 4" elbow on it, with a 4" filter, up from the ATI 3.5" intake, and its venting to atmosphere. THe exhaust is also probably restrictive. MAC 1 5/8 shorties, A 2 1/2 off road H with catco cats, and 2 1/4 turbo mufflers with dumps. The ignition is a MSD 6al. and plugs are gapped at .025.
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