Smitty

iTrader: (1)

You're fuel pressure is too high !!! With your larger injectors, you will always over fuel at idle with 43 lbs pressure. I have a similar set up and have 540's with 60 lb injectors. I am at 13.8-14.2 at idle with 36 lbs pressure. Lower your pressure and remap and you will be fine.

I'm sure you have seen me out on the Chain..see avatar for pic.

yellowjacket

30 40 50 60 70 80 90 100
1000RPM: 3.05 4.09 5.37 6.53 7.63 8.61 9.83 11.41
800RPM: 2.50 3.54 4.76 5.55 6.71 7.93 9.09 10.68
600RPM: 2.50 3.30 4.33 5.37 6.23 7.39 8.54 10.31

Worked late today, will play tomorrow evening and log some data. Thanks for your help.

yellowjacket

Hmmm that makes sense for idle but won't that affect the peak flow rate? 36/43 x 50 lbs = 42 lbs like almost back to stock flow.

How much power are you making with each motor?
I probably have but I don't make it to the upper chain very often since my boat lives on a lift behind my house on the lower chain. As my handle implies it's unmistakable although I saw a similar one with one black stripe and one white stripe a couple years back at the boat races. If you make it down to Fox River Grove then don't hesitate to stop on by.

Trash

I will disagree with Smitty's recommendation to lower the fuel pressure. It is my opinion that injectors run best at a recommended pressure. When you start jacking the fuel pressure around it's a global change across the entire fuel curve. That's not where your problem lies. Your BPW/MAP tables simply need some adjustment.

I run 42lb injectors on a small block and have no problem dialing in the idle AFR at 43 psi. I don't see why you should have a problem with 50 lb injectors on a big block at 43 psi.

Looking forward to seeing the log data.

Smitty

iTrader: (1)

I'm tellin ya your pressure is too high.

Here are your options :

Lower pressure and remap all the way up

Or leave it alone and live with rich idle.

I am making 800 + per motor. My engines were tuned by Mark at Precision down in New Orleans. He is the best.

Originally they were set up by another builder at 45 psi and they ran like crap.

On my first set of motors, I had stock 42 lb injectors and ran 45 lbs pressure.


Trash-- There is no "recommended pressure" to run any injector. You set fuel pressure based on each individual set up. They can only give you a starting point.

I am sure Procharger probably said to use 43 psi, but as we all know, they suck at the set up directions.

Why don't you try a simple test at idle. Start the boat and back the pressure down slowly until it is no longer rich. I am sure as you lower it you will get to where you want to be and then go up from there re-tuning.

Griswald

Looking at the table he posted, I'm quite surprised at the high numbers in bpw at idle. Is elevation correct at 700ish feet amsl? That should be somewhere around 60-70kpa at idle? And you have 5-6ms on bpw a idle? To me, that seems extremely long, especially with 50lb injectors.

GPM

**

yellowjacket

Tried to post this late last night, was OSO down?

Logged some data at idle... BPW around 2.5 msec, 2 atm MAP, sensor 35kpa, rpm 781, iac pos 0, coolant temp 30.5C afr on MTX-L 11.0:1 Any further decrease in RUN FUEL or anything that decreases BPW to 2.4ms or below results in a stall

Here are the RUN FUEL vs MAP and RPM for this run:
30 40 50 60 70 80 90 100kpa
1000rpm 2.50 3.54 4.82 5.98 7.08 8.06 9.28 10.86
800 rpm 2.38 3.42 4.64 5.43 6.59 7.81 8.97 10.56
600 rpm 2.38 3.17 4.21 5.25 6.10 7.26 8.42 10.19

Trash

That is some good info to start with. The first thing that comes to mind is your MTX-L needs to be recalibrated. Follow the instructions and make sure you pull the wide-band sensor OUT of the exhaust and free air calibrate the sensor. Don't get lazy and calibrate it installed as it can skew the calibration.

I'm running about 2.39 BPW on a 377 at 700 rpm with a 13.5ish AFR on a warm motor. Your 2.5 value should not be giving you an 11.0 AFR at idle on a big block. My initial suspicion is your wide band is out of calibration giving you bogus numbers. The fact that you make a small change and it leans out and dies leads me to believe your 11.0 AFR at idle may actually be 14.7 or higher. Mine starts idle rough and want to die when it gets above 15.0, and usually quits when it hits the 17.0 range.

I'll crunch through some of the numbers and have a back up plan if the MTX is indeed functioning properly. My other concern is the value difference between 4 cells in the idle region.

Griswald

35kpa at idle? What is it with just the key on and what is the elevation/altitude where you are?