joshuaho96

The shorter the wiring run the less resistance there is but you'd have to actually measure the voltage drop to be sure. If you've confirmed that the fuel pump is running at 100% flow all the time then your problem is almost certainly related to the regulator then. Every other part of the system is running like it would be at full throttle.

If you want the long explanation, you need a fast-reacting IAT because in alpha-N or speed density you want to be able to know roughly the temperature of the air in the cylinder the instant the intake valve closes. This feeds into the ideal gas law equation which is then used to estimate the air mass in grams in the cylinder. The reason why the stock ECU doesn't need to use a fast-reacting IAT is because air mass is not calculated but measured directly at the MAFs. So it doesn't matter what the IAT is downstream, you already know the air mass directly. This applies to any MAF-based system.

Pretty sure the base map is a weird one, one of the tables is TPS vs RPM only, another is MAP vs RPM only. I'd have to check to be sure but it's one of those things where even though a lot of bad things were done the holes in the system definitely maybe probably didn't all line up to cause a catastrophic failure. I would be nervous if this was a rotary engine though, those can die from a single knock event.

It's fine, main concern with a big pump is you overwhelm the pressure regulator but if you fit an aftermarket high flow one it shouldn't be a problem until you're really flowing a ton of fuel.

Could also be this. It's still a circuit, just a really simple one. The metal cup is technically an inductor.

I can still think of a number of weird things that can cause what you saw. It's basically just an inductor at the end of the day. RF interference might do it if nothing is wrong with the circuit. If something is wrong with the circuit flipping an inductor off and on with a smoothing capacitor connected to a load is basically a classic boost converter. The flipping of the inductor off and on to ground is usually supposed to be controlled by a transistor but in this case it could be literally anything. Tin whiskers, that kind of thing. Only way to verify is to get it on a bench and see if you can reproduce with known input signals.

Don't the R33 tachometers have a tendency to go completely crazy with age? Capacitors can lose their dielectric and basically turn themselves into a short circuit, dry joints intermittently making contact on inductive paths can pump up voltages beyond what's normal, etc. It's hard to say exactly what is causing it without really getting into the guts of it and reproducing/testing it but it's nothing beyond belief IMO.

It’s probably fine unless you actively tried to get it deep into boost and hold it just short of where it started misfiring. The danger is when you get deep into boost and it’s rich enough to ignite reliably but lean enough to get dangerously hot and knock-happy. If you just floored it and let it sit at the misfire limit you probably didn’t blow up your engine. The stock Haltech base map has even less timing than the stock ECU tune.

https://www.gtrusablog.com/2020/01/fuel-pump-control-module-fpcm-on-nissan.html It's a switched resistor on the ground that slows down the pump at idle. It's possible that this module isn't behaving and is a source of your fuel pump problems. You can check this by seeing fuel pump voltage at idle and seeing how it transitions. In the ECU map if your FPCM is still hooked up you should have a map for determining which of the 3 distinct fuel pump speeds should be commanded depending on fuel flow requirements.

I'm not an expert on fuel systems but a 0.2 bar drop in fuel pressure just from the return lines not flowing enough sounds like a lot, especially if you haven't bypassed the FPCM. Have you bypassed the FPCM btw?

I was just going by the book value mentioned earlier. Wouldn't this depend on the particular slope/response of the fuel pressure regulator? I figure the goal at idle is to drop fuel pressure so you stay deeper in the linear regime of the injectors.

Isn't there a delta in temperature across the turbine housing? Some of that heat has to go into generating KE for the turbine no? It's probably a second order effect compared to the delta in pressure so I doubt it'll be a huge benefit for performance but it's probably not entirely make believe.

Yeah I was hoping to learn more about the finer points of trying to make this pump fit some kind of R33 fuel pump hanger. Does the 6mm aux jet need to be used? Are the inlet/outlet vaguely in the right place? Stuff like that.

I want the car to survive extended track use but it's not the intended use, this is mostly just for fun on the street.

That's the correct port, not sure why your fuel pressure is behaving weirdly then. You sure it only changed by 0.05 bar and not 0.5 bar?

I agree that something is wrong if pulling the vac line only changes the fuel pressure by 0.05 bar. Look at your manifold pressure in absolute pressure. If your idle is -20 inHg then assuming your base pressure is 4 bar it should drop to 3.32 bar with the vacuum line plugged in. Are you sure your vacuum line is plugged in at the front of the balance tube? I have heard of people mixing up the charcoal canister vacuum line for the FPR vacuum line.

Isn't the stock RB26 fuel damper in the return line? That's how I read it here:

Upgrade to the 49614? I strongly doubt I'll ever need to though. 300 kW to the wheels at best is what I'm trying to engineer the whole system around.

Properly designed water-cooled turbos should have a self-siphoning ability that keeps coolant circulating through the CHRA so oil shouldn't coke even without the water pump going:

Pull the return line where it goes to the chassis rail from the plenum. Get a bucket to catch the raw gasoline that will be coming out of it. Get someone to start the engine, make sure it's safe to do so before you catch your hand in the radiator fan or something like that. Check to see that fuel is coming out in a steady stream. A bad fuel damper can block the return line so only tiny little spurts will come out. Then verify that with the return line open to a bucket your fuel pressure is still the same pressure as when you put the line back on. To try and eliminate the impact of engine idle tuning you want to do this test with the FPR vacuum line disconnected. If there is a downstream restriction there will be more fuel pressure with the return line connected properly vs draining into a bucket. If there is a restriction you're going to have to measure fuel pressure in various sections of the line to find where the blockage is. It will be the source of pressure drop so somewhere downstream of high fuel pressure but upstream of low/zero pressure. Diagnosing this stuff is just how it goes with any significantly modified engine. This is likely not the first time this engine has needed this kind of work, nor will it be the last. Everything you're saying is pointing to a fuel system issue as others have mentioned.

Surely it's not just stop-start as a concept that causes problems no? Otherwise decades of Priuses would show excessive bearing wear as those things are constantly turning the engine on and off. From what I've heard the MG1 spools the ICE up to ~1000 rpm with fuel/spark off until it builds oil pressure. Not sure how much that helps vs a conventional 12V starter spinning an engine at ~150 rpm with fuel and spark on.

Curious to know what people's thoughts are on this fuel pump. 350 lph is closer to what I'm looking for and it comes with integral check valve. Also has a 6mm hose barb to run the venturi to pump the other half of the tank. There's also a 500 lph variant that draws less than 15 amps which is pretty impressive IMO.

High fuel pressure means even higher demands on the fuel pump. 600 whp with what sounds like small fuel lines and a lot of fuel pump sounds like it could easily cause the pressure relief valve on the pump to be permanently damaged and not flow properly anymore. Had this happen in the past so I recommend being careful with it.

You probably have a few different issues. The first is that an RB25DET NEO will require a ton of work the moment you change airflow beyond stock limits as the stock ECU tune has protections built in. This is part of the reason why your fuel economy is aggressively awful. Your fuel pressure regulator may have been modified as well in the past, not unusual for people to tap the top of one with a punch to adjust the spring pressure. Or to drop it on accident. The spec is likely a standard 3 bar regulator, the tolerance there isn't going to be 0.4 bar either way but you can check the factory service manual to be sure. Even older ECUs like what runs on the RB25DET for R33 they're still going to drop like 5 degrees of timing at least if you flow more air than what is expected as a reasonable max for the stock turbos. I can pull up Nistune to be sure but that's my experience with the RB26.

https://www.nismo.co.jp/news_list/2022/news_flash/22012.html That's not a real price, that part number is discontinued. Those clusters sold out instantly as well, presumably some people plan on scalping them.