joshuaho96

Isn't the whole line of GTIII turbos from HKS period-correct?

Can the N55 manifold swap over? That would be the way to go IMO for a single turbo swap.

Did you change the DCT shift aggressiveness? It's a nondescript button next to the shifter, if you leave it in the least aggressive mode it slurs all the shifts and will optimize for fuel economy. If you put it up to max aggression it'll shift hard and fast and be willing to downshift and hold low gears for quite a long time. I do agree that the F80 is a very sterile experience. Put your foot down and you go incredibly fast with very little drama. The S55 also sounds awful and BMW has gone well out of their way to engineer out all the induction and turbo noise from the engine. If you leave it in efficient mode and push the accelerator pedal down just enough to keep the exhaust valves closed while still getting the engine into boost you will hear the slightest hint of turbo spooling but that's it. The suspension in comfort mode is actually very, very soft if you put a tire with a soft sidewall unlike the factory PSS or BMW spec PS4S. I got an R33 because of my experiences with that car knowing that R-chassis cars have all kinds of technical deficiencies relative to something like an F80.

I agree that you should make sure you have no other leaks before pointing the finger at the AAC valve.

Isn't this at least partially due to the way the dyno run was done? I'm used to seeing runs where they start as low as 1500 rpm to see how boost develops over the 2000-3000 rpm range. Seeing the torque curve fall on its face by 6000 RPM similar to this chart gives me some confidence that this run wasn't just entirely make-believe:

They're pretty mediocre but I figured someone would be interested if they ever dug this thread up. Personally all I'm hoping for is to get results on par with -7s, any more than that I'd consider a win. Every time I look at the twin turbo piping it's pretty cringeworthy how many twists and turns and right angle merges occur.

Mega thread bump I know, but a tuning shop in Kentucky managed these results with VCAM step 1 and the GTIII-SS turbos: https://www.facebook.com/Dynosty/videos/528591662283860/ I'm not really interested in the numbers themselves which seem a little overstated IMO but this seems to vaguely corroborate UP Garage's results seen here where peak torque happens at 5500 rpm: https://www.facebook.com/upgarage/photos/a.2754286177933791/2756172981078444 I'm still not sure if 0.54 a/r on the exhaust is the right thing for midrange power but shape of the curve especially with E85 seems pretty decent for a bolt-on turbo.

You have to figure out what the ECU wants. If the AAC valve is going to maximum opening because it's commanding it to be that way then replacing the AAC valve or fixing the wiring is not going to fix it. Also, keep in mind that for engine stability reasons I'll often see the AAC valve hang open in cases where you would expect it to close. The ECU is doing this by design. So one possible explanation for what you're seeing is the ECU sees the idle switch is off because the TPS is improperly adjusted and advances timing with what it believes is a sane value for the AAC valve causing the idle to race up like crazy when you plug the AAC connector in. Try a multimeter on the AAC valve pins to rule out the 100% duty cycle theory.

https://nissan.epc-data.com/skyline/dr30/3732-fj20t/engine/G2730/27061/ Looks to me like it's attached to a strut tower.

As far as I could tell at 280,000 km the RB26 I got was fine except for all the leaks. To BMW's credit though an F80 M3 will survive a track day on modern track rubber without breathing a quart per lap through the PCV and possibly ventilating the block, an RB probably won't in stock form.

True, but BMW started taking reliability more seriously circa N55/S55 era.

Scope the signal the ECU sees during cranking. This sounds like it could be a signal integrity issue.

F80s are pretty reliable in stock form, they only start breaking weird parts once you start pushing the power past 500 crank hp.

That sounds horrific and unrelated to any booster. Like Duncan my first instinct is that the clutch may have be pushing on the thrust bearing hard enough to cause serious friction and slow the engine down. The other possibility is a clutch bearing has failed. Or maybe the transmission and engine aren't actually bolted together properly and operating the clutch is causing the input shaft/crankshaft/clutch to touch something it shouldn't. Don't keep trying it until something more catastrophic occurs. I would check for crank walk and if that's not your problem it's time to pull the transmission and inspect the clutch.

It's maybe plausible in some regards, but the pictures show some pretty obvious modifications that wouldn't have been how Nismo does things. The missing fan shroud is a weird one.

I'm pretty sure that what you're seeing there is just Nismo parts made for the GTS25t, it's not a complete car by Omori Factory like the 400R/270R/Z-Tune/etc:

I'm just quoting book spec but yes.

If you have an FCon V-Pro you can't use the factory ECU documentation as a reference. These are details that you have to mention if you want useful advice as the ECU controls the check engine light. The ECU can be used in both piggyback and standalone mode so it's hard to say what exactly is happening in your ECU.

Error code 12 is MAF: https://www.importavehicle.com/blog/check-engine-light-diagnostic-trouble-codes-for-1989-to-1994-nissan-skyline-gt-r

Can't you snoop the TC lockup solenoid to determine this too?

I recommend reviewing this picture:

https://blog.garage-yoshida.net/archives/14252 Anyone see this post? Pretty impressive how 3D scanning is being used to create replicas of discontinued body panels.

I recommend connecting a diagnostic cable to the ECU and figuring out why it won't fire the injectors.

I would not trust any used engine with "40k km mileage" without opening it up and measuring everything and inspecting for damage in critical regions and a major overhaul. Your battery can't cause a bottom-end knock. RBs in general seem to attract a lot of questionable mechanics at least in the US that are used to doing sloppy work. There's a reason why YouTubers are able to buy two cars with RB26s that snap a cam and start crank walking an engine that is not known for such issues. Any new car design within the last 20 years is going to be even more sensitive to improper maintenance/repair than an R-chassis. Use a stethoscope or something similar to narrow down where the noise is coming from. If you know it's from the bottom-end shut it down and stop doing damage to the engine. If you've spun a bearing every second the engine runs raises the risk that it's beyond saving. Don't waste your time buying a new battery to see if that changes anything. The only way it could be the battery is if you somehow flipped the terminals and destroyed the electronics but it somehow still barely runs. I know this is tough to hear but unfortunately this is just how it goes with cars.

Have you considered buying the OEM part? Seems to be pretty cheap.