afc closed loop questions

[bbilly]

when I use my afc2 am I ever running in closed loop operation, like while cruising on the freeway. My turbo pushes alot of air right around 3200 rpms, even at low throttle(35%) so I richened it since their is so much air so quickly. Its at -%5 but my cruising rpm is 3200 as well and I want to have -%12 on my afc but I cant have both so...? Is it ignoring the afc and using close looped?

Ok at LOW throttle and 3200 rpms, my boost hits 17psi i get detonation so I richened it, but at WOT wouldnt i need to Lean out my AFC settings since the throttle is already letting alot of air AND fuel in at 3200rpms?

Most setting say to richen it at high throttle but I get a ton of boost even at low throttle so I think I should only richen it at low throttle. Am I right?

[kjewer1]

You dont add fuel in proportion to boost necessarily. Remember that these are mass airflow cars, so any added flow from more boost is automatically seen and compensated for by the ECU. Below about 70-80% throttle and 4 or 5k rpms you are going to be in closed loop (I wish I could remember the actual numbers, but if you have an AF guage/blinky light guage you can EASILY see when it switches to open loop (no more cycling). In closed loop there is nothing you can do to AFR with the AFC unless you have the trims maxed out, which is obviously not recomended. Just tune the low throttle map for centering the fuel trims (0% on 2Gs, 100 on 1Gs).

I'm assuming you have the other thread about low throttle/high boost, I still dont see how you are getting 17 psi at "low throttle." I think you also have a few misconceptions about how this works, which is fine too. Just post a mod list including what logger you are using and your current AFC settings, and I'll try to help if I can. I've been tuning AFC cars for about 5 years now, hopefully I can help.

[bbilly]

ok first I dont have a data logger, and my cars automatic which makes this harder. ANyway my mods are... k/n intake, nkgwires plugs, 16g turbo, dejon BC, greddy s bov, upper lower ic piping, 190 fuel pump, 550 injectors, safc2

my problem is the car stutters at 3500 to 4500 rpm when in high boost. maybe because im going past the fuel trim limit? and also i moded my mas so it lets in a little more air on the bottom so what does the ecu do to fix this if it cant see this air? dont I need to add more fuel via the afc?

right now i have my afc at for low throttle at
-12 at 1k
-10 at 2k to 3k
-8 at 3.2k to 4.2k
-6 at 4.4k to 5.4k

high throttle is about 2% higher throughtout the range

[spyderturbo007]

Originally Posted by bbilly

ok first I dont have a data logger,

Go buy one before you blow something up or melt a piston.

Tuning with your "butt dyno" is bad!

[kjewer1]

Tuning without a logger isnt even tuning Its called shooting in the dark. Those settings are way off for 550s though I can tell you that. I'm surprised it runs well enough to "tune" at all. www.pocketlogger.com is a popular choice, but there are others as well.

[bbilly]

Originally Posted by 95 GSXracer

Tuning without a logger isnt even tuning Its called shooting in the dark. Those settings are way off for 550s though I can tell you that. I'm surprised it runs well enough to "tune" at all. www.pocketlogger.com is a popular choice, but there are others as well.

what are some normal settings for 550s? I paid this guy to do it but I would like to see how they measure up to yours

[kjewer1]

The best place to start is to calculate basic injector compensation values. Divide the expected injector size by the new injectors size, and subtract 1. So in this case, 450/550-1, should be -18%. Lows will vary from this number a bit as you dial in the LTFTs. Highs should generally be leaner since the ECU shoots for a relatively rich AFR from the factory. How much leaner depends on several factors, to be prevent this from becoming a novel, if airflow at the ECU is over 2.1 g/rev I almost invariably go another 14% leaner beyonf injector compensation which provides an AFR of 11:1, but there are too many disclaimers to list here. Just for a reference.