joshuaho96

For a single throttle body there's no real need for a MAF. Haltech Elite supports both. If you want to keep the MAF in place to help you tune though that can help quite a lot with part throttle setup. At steady state in a load cell you can empirically derive volumetric efficiency with a MAF. GM's ECUs can use this data to help with transient throttle too.

Check the battery voltage and compare with the number you get in Nissan Datascan. If it's substantially different you got problems. Look up the factory wiring diagram for the power feed to the ECU and check for voltage drop across the wires/relays. I bet your ECU is browning out when you try to crank. Try running Nissan Datascan logging while cranking. If the data stream dies you have a problem. When I try doing this on my car as long as the battery is charged it won't brown out and I will see all consult parameters during crank and the moment it kicks over.

Only pull the turbos for service if there's shaft play or obvious oil/coolant leaks coming from it. Ball bearing turbos should have basically zero shaft play. Journal bearing may have a bit of shaft play but only for oil clearances. If you have a boost leak you should test for it first instead of just guessing.

Sits somewhere between the GTIII-RS and GTIII-SS, one thing a dyno chart can't show you is the effect of bearing drag on transient response.

That will definitely be part of your problem. Did you pull any plugs after cranking to see if they were wet?

Definitely at least better than the ARMS M7655, totally worth it.

Who would ever pay 3k for a set of journal bearing turbos because they might be miraculously better than an older ball bearing turbo for mid-range torque? Definitely not me. I would never buy snake oil like that.

The price is nuts if you want them to do it end to end: https://www.organizedgaragestatus.com/product-page/4nr33prcfqprde

You could retrofit some rectangular Mini D2S if you have the appropriate brackets, end result looks something like this, just ignore the weird carbon fiber stuff they added to the housing:

Your battery voltage is super low, should be more like 12V. Take some logs while cranking the engine and post them here.

DSport calling out the difference between Tomei JP and Tomei USA head gaskets is pretty interesting, I already heard about differences but I didn't know to what extent.

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.