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Amateur Tuning Questions


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So I have an 05 LGT Limited 5-speedMT. I just started tuning not too long ago(via COBB tuner) because I absolutely love DIYing and saving money is a big plus. Starting off and making the car run smoothly wasn't that much of an issue but the more I get into refining stuff the more barriers I hit. I wanted to start off with my build list before I explain my main issue:


Bottom end:

Manley H-TUFF rods

JE Pistons 99.75 8.5:1 comp ratio

King bearings(rod+main)

Brand new STI Nitrated Crank("430")


Other relevant mods/maintenance:

DW 1000cc injectors w/ 07-09 top feed rails

AEM 340lph fuel pump

Tomei Type L FPR

Kinugawa IWG actuator(14psi spring)

Grimmspeed EBCS

DIY tgv deletes(fully gutted)


Heads resurfaced, vac tested, and had 1 exh valve job done.


Okay now to the issues I'm having which I have tried looking up but had no luck. During normal driving with the AC off, I have the AFR set up to where I like it. The issue is when I have the AC on, especially at idle, AFR is extremely rich. I don't have a WBO2 sensor, which is on the list, but the AFR O2 sensor reads 11 at idle and the highest I'm seeing is 12-13. My question is why exactly is it dumping fuel with the AC on? Another question I have is, what else would cause boost to kick in during normal driving? My wastegate Duty cycle is almost zeroed out and I'm still seeing 2-6psi of boost at around 20-30% throttle. is I will have pics of some of the tables attached below


The last issue I have that probably isn't tuning-related, is the infamous 2-3k rpm stumble. Maybe there is something I missed but I've tried all the methods that I've found on these forums to negate it but had no luck. Those methods are:

- Reroute AFR vacuum and Tee'd off the BPV vacuum

- Different Fuel Pressure Regulator

- Richen the loads for that rpm range(13.5-13.9 afr)

- Raised the Fuel injector Latency(0.85ms to 1ms, this actually made it stumble a bit less but that's the best it gets.)

- BUILT ENGINE! (this wasn't why I built the engine though haha)


NOTE: CL to OL Delays are zeroed out


P.S. I feel like my ignition seems extremely low based on looking at other peoples and stock vs cobb stg2. Any higher and it picks up knock.







Edited by WillYang
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  • 1 month later...
Thanks for the bump haha. I should prob update that reason for it running rich with ac on was because I was stuck in open loop. Overlooked all the closed loop transition tables and forgot that there's like 2-3 tables in the open loop folder that also plays a role. The stumble was solved by adding timing. I keep picking up small amounts of knock and thought it was actually knocking so I kept pulling timing as you can tell the values are extremely low. Though I still pickup knock around that range and sometimes it would cause my DAM to drop and sometimes to very low values. But would always return back to 1.000 after some driving and stop picking up knock for a few hours of driving then repeat. It's been doing this since my stock block but a lot less noticeable with the built block.
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