I'm siding with the people who are saying a boost leak. Probably not in the intercooler, it's more likely in the couplers and plumbing from turbo to IC and IC to throttle body. I had a case like this once.

BIG boost leaks will give you no boost at all (or maybe 1 psi at 6000 or something like that). Teeny boost leaks are irrelevant. small-to-medium size leaks are rare, but can do this. In my case it looked like this:

http://www.codrus.com/miata/fm2r/boost-leak.jpg

--Ian

What does this mean, and what are the issues? Learn me please.

its possible the bypass valve or the bov depending on which is being used is leaking and causing the slow spool. Just a thought. They can crack open early and youll lose boost through it.

Had a few pin / slightly larger size ones in my ic pipe.
Welded them up and went from 7psi to 11.8.

So they can build up. unless i also had a leak from my tubing but hey. no idea.

Quick update since I'm drowning in work: last night I did a test run with the intercooler bridged. Using brand new silicone coupler and a 2.5" alloy tube I ran the turbo directly to the throttle body. Spool was unchanged. In the process I also did another back to back testing of the internal BOV vs the GFB DV+ -again this had no influence. 200kpa at 3850 rpm, while it took an entirety to go from 100 kpa @ 2000 rpm to 140 @ 3350. Beyond that point the spool really kicks in.

due to work I won't be able to do much more testing before the weekend.

That wacky rpm line looks like my shitty logs of the junkyard motor i threw in my car.
Im around 20-30% leak on cyl 1/3/4, cyl 2 is 40-45%. Also misfiring at times on cyl 2.

Im not burning oil, but she vents out the crankcase like crazy....
I compared all my logs on my current motor to my previous one. All logs since i threw in the motor have the jagged rpm. Prev motor was perfect smooth.

I have a feeling its caused by cyl2 not providing enough power compared to the rest, also car starting to shudder like crazy, as motors no longer balanced.

What RPMs do you mean? That jagged line at the end of the screenshot is overboost protection engaging. The spool-up RPMs are linear.

my eyes are dud.

quick look made them seem up-down slightly. considering the starting rpm jumps - which my car does.
i.e. for everyt 100rpm my car jumps it then drops 10 on 1 frame, making a slightly jagged climb.

If there are no bigger leaks in the pressure line I think it has something to do with the exhaust manifold.
I had a log type manifold at first to. Runs great with the small garrett turbo.
But with the change to the EFR 6258 it was not as good. (I have no logs and this is years ago)
Then I build a pulse-charging manifold and had 200 kPa at 3200 rpm.
But I had the air filter (open type) behind the radiator. So the intake air was very hot.
Changing this to a cold air intake pushes the spool. So I am now at 200 kPa@3200 rpm.

By the way: Your ignition is very late. Why do you run the engine with RON95 and not with RON98? I think my igintion with boost is 10° earlier... (But the later the ignition the better the spool. An earlier ignition angle will give you much more power but less spool and less exhaust temperature.)

So I checked the intercooler pipes for leaks - nothing. No visual damage, and held 1.5 bar positive pressure without any losses. So that rules out the IC system and BOV as possible causes.

two reasons: first, I completed the build 2 days before I went on a 1100 km trip hooning through the dolomites at 35 degrees. Down there they don't have any RON98 ANYWHERE. I therefore didn't want to take any chances and ran a safe map. Second, knowledgeable folks like Savington recommended to remove timing from my original map.
I built myself some det cans and will tune timing with those later on.

Did this ever get figured out?

yes. check his build thread

Well, sort of. I'll still try another manifold though. The Kraken cast manifold seems to be better flowing, similar to TSE's manifold, while being affordable for us mere Europeans.

So I finally but the bullet and bought a Kraken manifold. Installed it 2hrs ago. fuck me, this thing MOVES! It must have been the crappy log manifold as Tim said. The shorty tubular manifold offers a tremendous difference in response, spool-up and overall driveability. Since this is Miataturbo I'll soon provide catalogs to back up my subjective opinion, but this manifold is like night and day

I just installed a Kraken manifold and efr6258 and with open loop boost control set to 200-210kpa here is my spool:

4th gear pull, starting at 2700rpm

3000rpm - 8.3psi
3200rpm - 10.8 psi
3400rpm - 13.1 psi
3573rpm - hit target of 14.5 psi 201 kpa.

looks reasonable? how does yours compare now that we have the same setups?

Your welcome :skid:

Most of the data on the spool thread has runs that start at 2k. Can you do a run there for direct comparison?

Did you check spool diferences between 6258 and 6758?