[MidwayMuller]

Hey 2ers, I just upgraded my FMIC to a CTS turbo stepped unit to match the CTS chargepipe. The car still pulls good, but feels almost like it's holding back. I finally had some time to get out and do some pulls.

These are my logs with Stage 1 91 OTS:
https://www.bootmod3.net/log?id=5f99...0b43028e1fa1a2
https://www.bootmod3.net/log?id=5f99...90c67183eba593

Does anything look off in these? It performs pretty consistently like the FMIC is doing its job, but I noticed it says "stock tune" (definitely doesn't feel like it) and the boost plate PSI isn't reaching target

Appreciate anyone that can chime in.

[lmb.m3]

IAT is relatively low so the FMIC seems to be working properly there. Boost seems a little off - you might have a boost leak. I'd probably check the charge pipe to begin with.
Also, I'm not too familiar with the N55 OTS tune, but 14psi target seems a bit low for Stage 1 tune (again, not 100% sure). Are you sure you flashed it to stage 1?

[Ericm235]

Target of 14 is about right for stage 1 91.

Pre throttle boost is way down. Looks like a boost leak.

[mike@x-ph.com]

double-check the install, you might have a boost leak

[MidwayMuller]

Thanks for all your responses, I think you're right about it being a leak. It was warmer outside so I had the windows all the way down, and it sounds more like air escaping than an induction noise (I only have the K&N drop in for an intake).

Double checked the tune and fittings this morning before work. It was definitely flashed right yesterday and drives the same- the car only holds 9-10lb of boost with a target of 14. All the upper vacuum lines I messed with seemed solid with no play, methanol bung screw is tight and MAP sensor is clean and pointing to the right. Upper clamp for the charge pipe feels rock solid and sits all the way in the groove, too.

Right now I'm thinking the silicone coupler clamps might not be seated right, or a gasket got pinched at the CP/throttle or CP/FMIC ends. I can try spraying soapy water on these and have a buddy rev the car if you all think it'll help find the culprit. Anything else I could be missing before I hit the lift?

[dalderks]

Agree with boost leak (boost never reaches the target and WGDC is 90+ through each pull). I think you're already on the right track. I would suggest creating the pressure tester in the thread below. I didn't get the coupler tight enough on my chargepipe which created a leak. It was extremely easy to diagnose even with minimal pressure (try to avoid blowing up your inlet pipe like I did...). If the leak is bad enough, you might be able to do the propane test while the engine idles (i.e. while the intake is operating under a vacuum). I haven't done that myself, but might be easy if you have the tools on hand.

https://f30.bimmerpost.com/forums/sh....php?t=1621695

[OldCrow7xx]

My car is FBO stage 2 93 and I still think it feels like its holding back- I tried the accelerator pedal reset and it did not seem to make much difference. Converted to RWD and the steering got a bit better but it still hesitates. Did the BM3 tranny tune as well, still not as responsive as I would like.

Sometimes I think its just the way a car feels when you force it to make ~150% of its original power ratings. It will do it, but it may not do it happily or perfectly.

I did notice on your graphs and wonder why sometimes one cylinders timing is off from the others when they are all the same exact value? Not sure if its relevant or not, I know very little about tuning IC engines yet.