'Lazy" Maf or Static Injector questions

[RI lx]

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.

[paluka21]

Just as a comparison, I am running a GT40X, cobra, E303 combo with a pro-m75, 50# injectors, walbro 255 w/ ati external. The car ran and dynoed fine with 10psi @464 to the wheels. Since I added more boost to 13psi and it was still fine at this level, although I haven't had the car dynoed to prove the meter isn't peggings. I've seen several guys use the 75 bullet over 500rwhp.

later
DAN

[WA2FAST]

This is the exact reason that Pro-M came out with the Univer. People were having a lot of problems tuning with blow through setups period. Pro-M came out with the blow through meters which were bullet meters with the lip to prevent blowing a tube off and a richer callibration. Speaking with a few tuners, they are very difficult to work with still and ever since the Univer came out, they will either only tune cars with them (to save waisting their time and the customers money) or STRONGLY pressing the Univer on customers and if they don't get one, warning them that the tune won't be nearly as good and it will be quite a bit more probibly. I wouldn't doubt that if you got it re-called and cleaned up that it would read better, but at the same time if I remember correctly, blow through meters don't neccessarily have to hit 4.7 to 'peg' or act like they are pegging. If you are going to go through getting it re-callibrated, I would just ditch it and get the Univer.

[RI lx]

When I was on the Pro M site the other day, the page for the Optimiser meter wouldn't load.

Turns out it can only handle injector size changes up to 4 sizes from its base calibration. Since mine is calibrated for 19's, its out of range. 19-36 or 24-42 is the ranges they listed.

Hopefully a recalibration will clear up my A/F problem, improve milage, drivability, power and all that good stuff.

[SnakeIs]

I have to agree, if you are going to go to all that trouble I would get the Univer at your power level you will need it. I would not chance my motor making that kinda power on an unreliable/insufficient meter. BTW- the stock A9L EEC only allows a maximum of 4.5 volts from the MAF so unless you get the eec tuned and the voltage limit raised, you will peg the bullet at 4.7v. I have heard bad things about the optimizer, I'm sure its fine for a 13 second N/A car that wants to run 24 or 30 pounders but you are playing with the some serious injector/power here. You will be much better off getting the correct meter and having them calibrate it for your combo ( I speak from much experience and a nice cracked shortblock...)