GTSBoy

That would likely be a dead time issue and also related to the very short pulse widths required to idle it. The short pulse width will be badly affected by the dead time. Effectively you need "less scaling" at the low end (effectively giving you the ~75% that's working for you) and "more scaling" (which is actually "correct scaling") at larger loads. I know this sounds like it contradicts what my first post said, but it doesn't really. The problem of older slower ECUs managing short pulsewidths is still a thing.

If it was tuned by someone who knows what they're doing, it wouldn't have to be a risky tune. It would just (probably) be too rich at very low loads & idle.

In a simple control system, yes. But once you go electronic you have the option to put in all sorts of things that were unimaginable before. So they might have specific strategies around starting to open the wastegate as shaft speed reaches a certain point, or closing the wastegate if shaft speed falls under certain circumstances, all coupled in with throttle control, cam timing etc etc. The possibilities are really quite wide. I'm sure that there are a dozen things that OEM engineers have been wanting to be able to do but were prevented by not having the tools available. They're now reaching that capability.....just as the IC engine is reaching its last gasp.

Let's take this apart piece by piece. First though, I have an R32, which I suspect is different in the central locking area from an R34 - I haven't paid any attention to the R34 in that way, so I don't know. So my advice will be a bit general and maybe not 100% on target for the 34. 1. R32s had central locking, but not remote central locking. So only the passenger door (on coupes) had a solenoid. The driver's door was actuated by key or the internal lock at the door handle. When fitting an alarm to provide remote central locking, a typical aftermarket solenoid is installed in the driver's door. The alarm/central locking box drives that solenoid. The passenger door is a slave to the driver's door from factory anyway, and just follows the driver's door after the solenoid moves the driver's side lock on/off. 2. R34s have what? The same, or remote central? If the same as R32, then the paragraph above applies. If they have remote central already, then there is no need to fit aftermarket solenoids. Well, maybe there is. It was reasonably common back in the day to have central locking only on the front doors in cheaper sedans - and an NA Skyline probably fits that description. 3. So the question for you is, "how much central locking did you have before it was stolen?" 4. Changing lock barrels and keys will have no effect on the central locking, whatever and however much of it you have. 5. "When I put in my alarm system"...... Does that imply that you never had an alarm on a Skyline? That's an unexpected situation. How did you get it insured? 6. Any aftermarket alarm/central locking system (in old cars like this - not modern cars with body control computers) will just send a trigger pulse to whatever solenoid is in the driver's door. See points 1 and 2 above for what this means for you installing a solenoid to go with your alarm. 7. The R34 workshop manual is freely downloadable off the 'net and has the wiring diagrams in it. But if, as you say, you have no idea what you're doing, you're probably better off just throwing the car at a good alarm installer, who will be able to decide if you need extra solenoids and put it all in in a couple of hours, and do it properly. There is nothing worse than a bodgily installed alarm/immobiliser, which you could be at some peril of leaving yourself with if you install yourself. You could get stranded on a freeway on-ramp or 300km out into the bush in the middle of the night, or just put up with random glitches like doors not opening, car starting only after performing a strange dance with key on-off-on sort of crap, etc.

The problem with older/cruder standalones is not that you can't set the ECU to know what their flow data is, it is that they struggle to control the injectors to really short pulsewidths, which is what is required to idle (and possibly even light cruise/trasnsient) on very big injectors. The PowerFC is old and crude. So it's not ideal for large injectors. But the evidence does show that plenty of people have successfully run ~1000cc injectors on FCs. They just probably have fat idle mixtures (because the alternative is lean idle, which is terrible).

Serious? More wire, soldering iron, heat shrink.

Suffice to say that sucking air and oil out the back of the head and then trying to jam the froth into the pressure pump is not going to end well.

7163 is the interesting turbo in that size range.

They could hardly not be the same shape. There's only one shape that is correct.

~600 - 650 in drive. Maybe 700 at a pinch. Look for vacuum leaks, or for your idle/throttle to be dirty/sticky and staying a little too far open.

Spray carby cleaner around every place where air could leak in until you find it.

@Duncan is being a grumpy old man. He's not wrong, but if you want to get more power and make it nicer to drive, put a single on it. Having seen your intro thread now though, I would suggest perhaps not bastardising the car.

Yes. It's probably dirty and jammed so that it can't close down far enough. Block off the air pipe that goes to the IACV and see if the idle speed crashes. Otherwise just do the usual clean it out thoroughly thing.

Switch globes, use multi-meter. All the things you should do to diagnose minor electrical problems.

Perhaps that's not the question to ask. For any given power level the single will smack the twins senseless. More response, more area under the curve (from the single). So you could put a "smaller" single on and shoot to max it out at less than 400rwkW (say, aim for 350) and enjoy life a lot more. No. See 1. First question though would be "what fuel?" You can push smaller turbos to more power using E85 than you can on 98. E85 allows higher boost, which causes higher air temps at the same compressor efficiency and pushing the boost higher usually reduces efficiency when you're aiming for the top of the compressor map. The recommendation will be for a T3 or T4 twin scroll housing and proper divided manifold and wastegate arrangement. Have a look at the various RB25 & 26 turbo upgrade threads stickied on here to see what people are achieving. The options range from GTX3076, through GT3576 or GT3582, to G30-550 or 660, and BW EFRs like the 7670. There's a lot of size difference across those ones I've listed, and not all are available with divided housings, etc. And that's ignoring Precisions and all the off-brand stuff.

The timing is likely at zero because the ECU is (probably) pulling al the timing out to control idle speed, which would imply a problem with the IACV. 875 rpm is too fast for 81°C coolant temp, which tends to support the theory.

Didn't you ask this question in another thread yesterday and get told "most likely no"?

Put it in the cooler pipe. In a 4" inlet it is worth HUUUUUGE power (in terms of how much air mass flow it will take to saturate it) and even though the card type AFMs are more resistant to reversion, hectic flutter will make tuning harder.

I think the largest RB30 is either 3.6 or 3.8, but it really doesn't matter because you are talking pure drug money at that point and would be better off with a Barra.

Yeah, nah sweetheart. We'd be talking about $20+k of work here and it still probably wouldn't work.

Oh, and the 2nd one appears to be the solenoid on the idle control valve.

The first one is a solenoid valve for switching a vacuum source on and off. It may or may not be supposed to be connected to the FPR vac source. It probably shouldn't. You should look at the RB30 engine manual's relevant page for the vaccum line system.

I wasn't aware of that one.

I would say that that is a hard no. The shapes and sizes of the intake and exhaust ports are quite different, and you don't necessarily have the room to hog out the (small) exhaust ports to approach the size of the intake ports because the water jackets are quite close to the exhaust port walls. Then you would have to look at whether it would be possible to fit intake sized valves where the little exhaust valves come from (which would require removing a lot of metal and you'd probably face a similar problem with water jacketing there) and then you'd have to close up the inlet valve holes to take smaller valves. Just use a 1JZ.

If that means <2500rpm and no load at all, then you could get away with it. Still not a great idea.