Finally dug into the tune a bit on the car. I started with the PE table.... gawd it was a mess, not at all a smooth curve like the 07 one GMRedline posted a pic of. I also have some personal opinions on the COT tables. With N/A cars that don't have nearly the enrichment we have...the COT table is much more important. The driving style is also influential to this as well I believe. GM had to ensure that if Joe Shmoe decided to bury his foot for 5 minutes on a long highway pull the cat wasn't going to melt down.... but I don't drive like that. Maybe a squirt or two up to 100-110mph is good for me. That being said, with PE set and the COT adder lowered slightly, I moved the limiter for now to 6700 to log some more. A few tweaks to PE delay and other PE enable settings were in order. When logging, the commanded AFR (and delivered) are 10.8AFR at the top instead of 10.4 as it was stock. At 6700rpm and 191-192kpa MAP I saw 106% duty cycle on the stock injectors. Debating if its worth taking the commanded to 11.0 (including PE and COT adder) to see if we can get to 67-6800rpm at 100% Duty cycle. I know ideally we want to avoid hitting 100%, and I will be installing my injectors in the spring, but I just wanted to see what can be done on the stock car without any bolt-on mods. Call me crazy. Thoughts?
Last edited by Papa C 2000; 11-11-2012 at 06:31 PM.
Yeah, ideally with any component in an EFI system, its best to have some headroom. In my experience, on any boosted cars I have tuned, there has been marginal if any gain from about 11.5AFR up to 12AFR. Depending on boost level, static compression and how good the fuel is you use....I guess that determines how agressive you get. I realized 10.8 and even 11.0 was pretty damn rich, but I am creeping up on this to be safe. Also good to get feedback from the community to see what has been tried and tested on this little LSJ. I love it so far! I'll log some more today with a bit less commanded fuel to see what we can squeeze out.
Thanks armclure. I always tread lightly when doing this sort of thing. My motto has become "leave some on the table so theres none on the floor". I take this approach on everyones car I tune...and on mine since I don't wanna replace or be fixing it. Today I did some more logging with total PE at 1.31 ( PE plus COT). Theres not alot of COT being added, but I didn't want to remove it altogether. Now the inj DC hits 100% at 6500RPM. Keep in mind the boost solenoid is 100% all the way up now. I think this is pretty good. I am sure that its not too often people bother to invest in a tune when the car is stock like mine, so I am experimenting with it. At this point I will be putting it back on the dyno this week to verify things before going ANY further. Although its bad practice and I know it, I have made these subtle changes with logging only ATM without the wideband since firstly it met commanded on the dyno and secondly if its off a bit the conservative AFR I've stopped at leaves room for error. FWIW the O2 senor voltage as useless as it might seem never dropped all the way to 6800 so I think we're fine. Proof will be coming soon.
In my experience, on any boosted cars I have tuned, there has been marginal if any gain from about 11.5AFR up to 12AFR.
Exactly. I think the suggestions was intended to help you lower the IDC a little.
Originally Posted by Papa C 2000
Thanks armclure. I always tread lightly when doing this sort of thing. My motto has become "leave some on the table so theres none on the floor".
Yes. Yes. Yes.
11.2 will work but you will experience a faster carbon build up on your spark plugs and rear bumper. Plugs are cheap so its really not that big of a deal. If you can lean it out to 11.7-11.8 you won't have to worry about cleaning your bumper after a couple of pulls.
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