Japtastic141

Ok, will keep it fairly short but essentially I had multiple issues. The original old fuel pump and FPR were well past their best. The replacement 450lph Walbro was overpowered for my setup and wiring. Wiring was replaced but the problems persisted. Out-of-sight fuel hose was leaking but seemed to be only under high load and not at idle even with the Mytivac bringing fuel pressure up to 5Bar. Once the fuel hose was replaced, the fuel pump swapped to a 255lph Walbro and FPR replaced, the problem was essentially fixed. What skewed the results after everything was fixed was that the Tomei FPR has a very bad regulation slope. @Adamw Said the typical slope is around 0.25kpa / LPH. Tomei Type S (and probably the Type L) = 0.43kpa / LPH which equates to a 47kpa loss at the high rev range. This matches what I found online and my own logs. Turbosmart FPR6 (and their other models) = 0.16kpa / LPH which equates to a 10kpa loss at the high rev range. Which again matches very closely to my logs now. I hope someday this whole thread is useful to someone in the same situation. Got to say a big thanks to everyone who helped as well. I've learnt a huge amount. Really appreciate it. Now back to tuning the car which is a lot more fun than troubleshooting this!

I'll update this later properly but swapping the Tomei Type S FPR to a Turbosmart FPR6 has fixed the problem of dropping such a big amount. It wasn't the only problem as I'll update later. The spikes now down only happen when I let the throttle off as you can see then it's back to normal. 296kpa is reported as a baseline so now only dropping 10-12kpa at a maximum while on 1 bar of boost and 7k RPM! Well happy!

@Adamw Could I check what the 0.25kpa/lph would equate to in a kpa drop please. I see some FPR’s publish this but can’t find Tomie data anywhere yet. I found some other FPR’s publish 3psi/gpm. Also what made you think the 60kpa drop was a restriction rather than normal slope? I’m seeing a few posts and comments about the Tomie and Sard FPR’s not holding 1:1 and slopes being worse than others but nothing from the manufacturer. I’m asking my supplier today if they have that data. I may have butchered this completely but if I base this on 300bhp using 108 litres per hour at full throttle / power. 0.25kpa x 108 = 27kpa. If this is correct and the Tomei FRP isn’t the greatest, it does get me in the 40kpa slope ball park I’m in and if so would that be acceptable to tune around or does is still look too far off / wrong in your opinion?

Another update. Found this little *?@**! weeping. After taking it off it was clear it was split all the way through and leaking. It's the small pipe that comes off the hard line to connect to the filter deep in the engine bay. Very hidden from view and couldn't see it leaking when doing any pressure testing with the Mytivac. Either it wasn't at idle or engine off or I didn't spot it. Not sure why it wouldn't leak at idle (or maybe only a tiny amount) but my only theory is that under load the injectors turning on and off at a much higher rate than at idle caused the little splits in the pipe to open and up and release pressure and spit fuel over the little shelf. Which is also why I couldn't see any leaks under the car when checking even after a fast run and pulling over to check. You can see that the fuel leak has caused some corrosion. Now, unfortunately, although finding that was good it still hasn't fixed my issue. I was so hopeful when I saw it and fixed it that this would finally be the issue fixed Looking at my old logs it looks like around a 10-20kpa differential fuel pressure improvement from fixing that leak..... But I've also moved the fuel pressure sensor directly attached to to the FPR rather than T'd off so it may just be the move of sensor has improved things. The signal certainly looks a lot smoother. So now looking at around 30-40kpa difference vs 40-50kpa. What's considered normal / acceptablele? Does anyone have an screenshot of a normal fuel differential log? How much does it normally drop or is it normally pretty flat?

Just the standard 8mm ID. Only running stock power at the moment so plenty big enough + return flow test comes out good.

Just a small update to this. Spent some time today testing the alternator and then the fuel pump again. Once again I can't find anything wrong lol... Fuel Pump Scope - Amps up from cruising @ 6A to 8A @ on a power run. As you can see, the voltage doesn't budge. https://ibb.co/y4s2SkH Next is the alternator on a power run. Again, all looks fine. Voltage doesn't dip whatsoever.. https://ibb.co/bLBRSH3 Still clueless as to what is causing this. Will try to figure out why ECU is seeing a voltage dip. I've checked the obvious areas and continuity/voltage drop and run a new earth to the ECU so not sure where to look next but will try.

Thanks Adam, that’s the info I didn’t know about FPR’s. But if it looks abnormal and more than it should be I’m back to square one. The voltage dropping at the ECU so much and in conjunction with this happening does bother me and it’s the only thing now that I haven’t really spent a huge amount of time on. I feel like it needs sorting either way. I’ll do another run with the Picoscope attached to the pump to check Voltage and Current just to be sure nothing has changed there. Next, I’ll spend some time looking at the ECU voltage drop, as quite frankly there is nothing else I can think of to try or test…

Well yes, that was a theory a couple of days ago but now seeing that fuel pressure drops without any boost reference attached makes me think again. I need to think it all over. Been a long day juggling work, family and car bits!

Spent some time today changing out the last two fuel hoses to the hat from the hard lines under the car and then putting the the cam belt cover on. This has cleaned up the RPM a fair bit. These logs are with no filtering applied. The CAS definitely likes those rubber gaskets for vibration it seems! I thought I'd do a test with boost reference removed from FPR and set to 400 kpa. Still dips by nearly 60 kpa. With no reference shouldn't the FPR keep the same pressure it's set to? This is it set back to normal 300kpa and boost reference back on. [url=https://ibb.co/80HsSK0][img]https://i.ibb.co/xDNLRCD/image.png[/img][/url]

GReddy so should be quite decent.

The more I think about this the more it confuses me. I've learnt a lot over the last few months and am fairly sure I have a decent grip on what is supposed to happen with a 1:1 referenced FPR and all my tests while the car is on or off and stationary confirm that everything looks perfect. When used live it doesn't follow what I see stationary as you know from the logs. 3 Different Fuel Pumps - same issue 2 Different FPR's - same issue Return flow test at various pressure has always returned the correct amount and bang on what Walbro publish. Mytivac to FPR reference port - Perfect 1:1 pressure increase and decrease and holds it. Line to FPR tried on it's own port at the front of the balance tube and T'd into the MAP sensor line at the rear of the balance tube. New AWG4 wire to new relay for fuel pump and even bypassed relay and ECU control as a test. Picoscoped voltage and amps at the pump and all looks good. Surely this is now some kind of weird mechanical issue rather than ECU, config, wiring etc? It's like there is not enough pressure on the FPR reference line to hold open/closed the spring/diaphragm but there is enough to supply the MAP sensor and boost gauge with the correct figures. Does this theory make any sense at all and if so what are the likely culprits? On a slightly separate note, adjusted the calibration table. Should be bang on now. FP on the gauge and ECU match perfectly. On that theory and maybe not important at all but thought worth mentioning, I have noticed that my 'plumbing' is not factory for the vacuum lines. AC = Air Chamber BC = Mac 3 Port Green are rubber lines, black is hard lines.

It's a GReddy one. The ECU reports the same as the in-car gauge. I didn't put the lower and higher values in yet. I know the calibration is not bang on perfect but it's pretty close. I'll work on this but still doesn't help or explain the massive fuel differential.

Sure, here it is: https://drive.google.com/file/d/1mQtrxLFBgl6IUbwO945mr6Lz9PK1QaWj/view?usp=sharing I'll double-check this but pretty sure it does. Report back later. Yes, it's been mentioned a few times in this and other groups how bad it is. Not sure why. After speaking to Mark he kindly offered to lend me an NZ one to test but I think it's just better to upgrade to the NZ trigger kit either way. This CAS is 32 years old (with AEM disc) so has probably seen better days. After thinking about it overnight I was also under the impression that it probably won't fix my FP issue as this is mechanical rather than ECU-controlled but maybe I'm wrong..?

Ahh ok, good tip. Did the logs tell you anything? I'll try to get the ECU log of the engine off with the fuel pump on shortly.

Hi, All these logs are from a laptop so far. I think I have ECU logging setup correctly now. I've upped the trigger filtering to see if that helps also. I'm having trouble getting the ECU to log with the ignition on and not started so here is a PC log of ignition on and the fuel pump activated by test output and then an ECU log of the car running with boost ID removed. Let me know if this is correct and what you wanted. https://drive.google.com/file/d/1mJn5RO5SuzN2F3IRp28r3LUACWWhKNJO/view?usp=sharing https://drive.google.com/file/d/177C7uUiZP9Au9B7Bu4d8_o7jh4rG2iO-/view?usp=sharing