ECMlink Stumble at max boost

[bmxfelon420]

1). Any boost, vac, or exhaust leaks?
Tested to 20psi, only leaks when I wiggle the throttle shaft

2). Verified mechanical timing?
It's a 2g, doesnt have that
3). Verified base timing?
It's fixed
4). Ignition system
COP or Stock Coil: Stock coil
Wire brand and Age: MSD Superconductor, very few miles
Spark Plug brand, type and Gap: NGK BPR7ES .30

5). Motor health (Compression Test)
Cylinder 1: Havent done but runs fine with little blowby. No oil blowby at all.
Cylinder 2:
Cylinder 3:
Cylinder 4:

6). Performed basic throttle body adjustments?
Idle Switch: Yes
Throttle Cable:Yes
TPS:Yes
BISS:Yes

7). Compression ratio
9.3:1
8). Any known bad sensors or brittle wiring?
Knock sensor is going but has issues whether it sees knock or not
9). Any DTC/CEL codes?
For knock sensor as mentioned above
10). Electrical system
Car off (not running): 13.6v
Car running: 13.4v or so

11). Base fuel pressure and injector values
Base Fuel Pressure: 43.5PSI
Injector Size (cc/min): 800cc

12). Properly calibrated and configured wideband sensor
Sensor Brand:Innovate LC1
Calibration Date: Early June

13). Type of fuel
Type: E85
Percent of Ethanol: 83% (set in global

14). Watched ECMlink how-to videos? Yes


Hey all, I have already ordered a replacement alternator since it is suspect, but I wanted to ask opinions on the following behavior:
When running/driving not in boost, car runs fine/normal. Running o2 simulation from wideband and switch point is calibrated to around 15.5:1 in closed loop.

However, when under boost, around 10-12psi or so the car starts stumbling/cutting out. As seen in the log, voltage to the ECU itself seems to be OK when it does this, but I'm wondering if the ignition coils arent getting enough current or something. It seems to me that it just cant produce a spark at higher cylinder pressures/loads or something. If I only let it build 5-8psi or so to accelerate, it will do so just fine. AFRs in Open loop under boost conditions are between 12:1 and 11:1 or so. Could the alternator cause this even though the voltage the ECU is seeing is OK?

Things i've tried to fix it:

-Checked plugs. Light tan, normal looking
-Replaced battery terminals as they were very poor and didnt clamp properly
-Experimented with injector deadtimes. I dont suspect this as it seems to only happen under load, idle/cruising are fine and my understanding of deadtime is that idle/cruise are where I'd see issues if the deadtime was incorrect
-Removed boost controller. I thought that perhaps it was an issue with the controller itself but the issue persists
-Checked for boost leaks up to 20psi. Since I only had it set to 12 before I ran it up to 20 and fixed a leak at the MAP sensor, which would have been behind the MAF.

At this point I have formulated the following plan to get the problem resolved
1. Replace alternator which sometimes doesnt charge upon startup. The three lights on the dash come on and the voltage reads around 12.1v until it kicks on.
2. Replace fuel filter and feed line. I already have these ready to go, and will probably do so when the alternator goes in.
3. Failing both of those, I have a set of PTE 780cc injectors I planned on putting in for testing purposes. The 800's I have are of unknown manufacture. Since the PTE's are pretty popular I have a latency table for them so I can be sure my settings are correct.
4. Rewire fuel pump. I also have the kit for this sitting. I'd still think the car could get over 3000rpm though.

 

[bizie]

What is the targeted afr? If your combft isn't adjusting much and you're at 12.0 at wot I would say maybe try a richer mixture. Maybe the boost kicking in is making you go too lean? Was this car ever running right? How is your bov set up? Recirculated with stock maf right? I don't think its your alternator, injectors, or fuel pump. Alternator problems will cause issues to be more at idle or when the engine is spinning slower. Post a pic of the engine bay just for poops and giggles. Maybe a vacuum line error somewhere? Just throwing ideas out there...

 

[Dsmkauai]

You don't understand what ? 2 and 3 are bro! You really need to stop and learn these 2 things before you destroy somthing. Yes you have a timing belt therefore you have mechanical timing. Check and verify all the timing marks are lined up correctly. Then verify base timing not just say it's fixed it's either right or wrong.

 

[bmxfelon420]

You don't understand what ? 2 and 3 are bro! You really need to stop and learn these 2 things before you destroy somthing. Yes you have a timing belt therefore you have mechanical timing. Check and verify all the timing marks are lined up correctly. Then verify base timing not just say it's fixed it's either right or wrong.

I thought the questions meant the adjustment, which I dont have. Of course the mechanical timing is correct, I'm not sure who wouldnt check that 17 times when putting the timing belt on. I know we did.

Oh and I forgot to put I have a GM MAF set for blowthrough, non recirc BOV. It was running good for quite awhile, just seems to have started doing this since I swapped transmissions. The PCV is bad too though, so I'm gonna replace that this afternoon and see if it helps. Didnt know those could suddenly go bad though.

 

[bizie]

Of course the mechanical timing is correct, I'm not sure who wouldnt check that 17 times when putting the timing belt on.

hahahahaha I know the feeling on that. Easiest way for that is to line all marks up with dowl pins up yea yea we all know that, but for me when I read the manual I learned it helped to use the top of the cylinder head as the point to align the marks. This makes it so I don't have to check it a bunch. Top of cylinder head IE where the valve cover meets the top of the head.

Still, it would stumble throughout the rpm range if it were timing. Stumbles at boost are usually vacuum issues. I would go with PCV on the guess list. Its cheap and easy to replace. It wont throw a check engine light, it is vacuum related so I would fix that asap

Can a brother get his first like(s) eh eh??

 

[bmxfelon420]

hahahahaha I know the feeling on that. Easiest way for that is to line all marks up with dowl pins up yea yea we all know that, but for me when I read the manual I learned it helped to use the top of the cylinder head as the point to align the marks. This makes it so I don't have to check it a bunch. Top of cylinder head IE where the valve cover meets the top of the head.

Still, it would stumble throughout the rpm range if it were timing. Stumbles at boost are usually vacuum issues. I would go with PCV on the guess list. Its cheap and easy to replace. It wont throw a check engine light, it is vacuum related so I would fix that asap

Can a brother get his first like(s) eh eh??

Yeah I hear you there, I got a PCV waiting when I get home. We'll see what it does. If I can go back to the knock sensor just being a bastard again i'll be happy with that. I have a new one ready to go in anyways, just trying to cross off problems. Even if the stumble isnt caused by the alternator I'm tired of wondering whether today is gonna be the day it just stops charging forever, so it's going. For 80 bucks it'd be stupid not to replace it. I'll report back tonight whether the PCV worked. If not, I have all the other stuff to try, and another set of ignition coils to try that I didnt originally use because they're from some JDM engine and dont fit under the intake.