Acceptable fuel pressure range?
Hi all. I have a brand new, freshly installed 30012 1200hp Power Adder system on top of 4/71 blown 360 mopar. Car has Holley in-tank 340lph pump and Fitechs internal regulator is still in use. AN8 feed and return, and mechanical fuel pressure gauge on one of the inlet ports. 10 micron in-line filter on feed line.
On initial prime pressure gauge shows 60 psi. After start up it first settles on 58 and then slowly drops to 52-54. I have only driven the car couple times around the block, and it seems to run ok except when coming to a stop, AFR reads quite high, around 16 - 17 and car hesitates for a moment.
I have been reading about the fuel pressure and some posts are saying that anything under 58 indicates issue (most likely glogged filter), but then some posts say that since regulator has vacuum attached it intentionally drops pressure when it's not needed. So which is it? Should I replace the filter, or just keep driving some more and let the system learn and calibrate itself?
Edit:
I have external relay providing power for the pump. Fitech controls the relay so PWM is disabled, and pump is running full speed all the time.
The 1200 unit is designed to run on 58psi. The on board regulator is a 4 bar / 58psi regulator. At idle, fuel pressure will be a few pounds lower, if the vacuum line is attached to the regulator. Under load, vacuum drops and pressure goes back up.
If you a producing much more than 800hp, your fuel system is inadequate. An external regulator and more pump flow is required.
As for your high AFR, I need more information. A datalog would be helpful.
Thanks for the info! The pump is in fact dual 340lph unit, second pump has it's own relay and it's controlled by Hobbs switchs to turn on at 5 psi of boost. Since I have only been tiptoeing around the block few times I did not mention it, since it shouldn't be relevant for this case.
I tried to record logs, but now I had slightly sticking throttle which prevented the engine from falling back to idle, and the car didn't stutter or die. I try to get the throttle fixed tomorrow, and record the logs then.
Okay, I got the throttle link fixed, and recorded couple stops. For some reason two of the logs failed (file content were foobar) but one seems to be ok, you can find it here:
https://drive.google.com/file/d/1gmcmiJdsKeDCEY75hN8-LJwW3ANaUF6_/view?usp=sharing
It also feels like the harder I brake, the worse the engine stutters. Like if I have to abruptly stop at red light, the issue happens every time, but if I can slowly ease into a stop, it might not happen at all. I do have a full tank of fuel (filled her up just before recording logs) so it shouldn't be a starvation issue.
Your log is showing fault code 36. That rpm noise/electrical interference.
Thanks for noticing! Apparently it's so intermittent it does not end up in the permanent codes, and I have missed it myself. I'll try to solve that next. I'm using the Fitech to control spark, so I don't have the blue wire connected, but instead Fitech is connected directly to distributor with the two-wire connector. Since Fitech is sitting on top of a blower, there is not much room to play with the wire location, it goes pretty much straight up from the distributor into the Fitech. I'll see if I can shield the wire, and maybe move the spark plug wires little further away. The spark plug wires are MSD Streetfire wires so they should have some kind of RFI shielding in them.
Make sure nothing is grounded to the engine, except the battery. No frame to engine or firewall to engine.
Well, it took some time but I got rid of the rpm noise error. I had to replace distributor cap and reroute some wires. I logged few short runs, and the hesitation (when coming to stop) is sadly still there. There are still high AFR readings when the rpm's drop.
Before recording the logs I already checked the Dfco settings and put the temp limit to 299 so it shouldn't be causing the issue. Also, the map limits are still default and the lowest map values I see on the logs are hair under 40, so they are not even near the cut limit.
Here are the latest log files, if you could check them out to see if you can make anything out of them:
Short run
Superchargers can be fun!!!!
I looked at your logs. I haven't seen data that looks like any stumble or hesitation. Could you pinpoint the data lines where the symptom occurred. Just let me know which lines to look at
It happens every time when I lift the gas rapidly, and after that rpm's start to come down. If you look for example few dozen lines after 280 on the longer log, TPS first drops from around 10 to zero. Then when rpm's start to drop, it goes extremely rich for a second (afr 11.9) and then computer starts to correct it and then it goes lean (afr over 16).
I'm very much beginner here, but I think that similar pattern is visible all around the logs:
TPS comes quickly down -> rpm's start to come down -> rich -> lean